US20140137570A1 - Variable thermal resistance mounting system - Google Patents
Variable thermal resistance mounting system Download PDFInfo
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- US20140137570A1 US20140137570A1 US14/084,587 US201314084587A US2014137570A1 US 20140137570 A1 US20140137570 A1 US 20140137570A1 US 201314084587 A US201314084587 A US 201314084587A US 2014137570 A1 US2014137570 A1 US 2014137570A1
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- Prior art keywords
- cylinder
- rod
- heat
- thermal
- heat source
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
- F28F9/007—Auxiliary supports for elements
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B21/00—Machines, plants or systems, using electric or magnetic effects
- F25B21/02—Machines, plants or systems, using electric or magnetic effects using Peltier effect; using Nernst-Ettinghausen effect
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/10—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects operating with only the Peltier or Seebeck effects
- H10N10/13—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects operating with only the Peltier or Seebeck effects characterised by the heat-exchanging means at the junction
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
- F28F2013/005—Thermal joints
- F28F2013/008—Variable conductance materials; Thermal switches
Definitions
- the present disclosure relates generally to mounting systems for thermal platforms and, more particularly, to systems for optimizing heat flow to a heat load such as a thermoelectric generator.
- thermoelectric energy harvesting systems such as thermoelectric generators convert thermal energy into electrical energy in response to a thermal gradient across the thermoelectric generator.
- the thermal gradient may occur as a result of heat flow from a heat source that is thermally coupled to one side of the thermoelectric generator to a heat sink that is thermally coupled to the other side of the thermoelectric generator.
- the thermoelectric generator may have an optimal temperature or an optimal temperature range within which the thermoelectric generator operates at maximum efficiency.
- the thermoelectric generator may be coupled to electronic components for conditioning the voltage produced by the thermoelectric generator prior to delivery to a device (e.g., a sensor) to be powered by the thermoelectric generator.
- Electronic components typically have a maximum rated temperature up to which the electronic components may operate on a nominal basis. Approaching the maximum rated temperature of the electronic components may result in a reduction in the performance of the electronic components. Exceeding the maximum rated temperature of the electronic components may result in damage or failure of the electronic components. A failure of the electronic components may compromise the capability of the thermoelectric generator to power the device.
- thermoelectric generator may be installed in an environment where the temperature of the heat source fluctuates.
- the thermoelectric generator may be thermally coupled to the surface of a heated pipe in an industrial facility. Process variations may result in fluctuations in the surface temperature of the heated pipe such that heat flow to the thermoelectric generator may fall outside of the range for maximum operating efficiency of the thermoelectric generator. Heat flow from the heated pipe may also result in exceeding the maximum rated temperature of the electronic components that may be coupled to the thermoelectric generator.
- thermoelectric generator may operate at maximum efficiency and is thermally protected from overheating.
- thermoelectric generator may operate at maximum efficiency and is thermally protected from overheating.
- thermoelectric generator may operate at maximum efficiency and is thermally protected from overheating.
- thermoelectric generator may operate at maximum efficiency and is thermally protected from overheating.
- a system and method for adjusting heat flow from a heat source such that electronic components are maintained below their maximum rated temperature and are therefore thermally protected from overheating, and also such that the electronic components may operate at maximum efficiency.
- variable-thermal-resistance mounting system may include a cylinder coupled to a heat source or a heat load.
- the heat source may have an optimal warm-side temperature.
- the variable-thermal-resistance mounting system also may include a rod movably engaged to the cylinder. The rod may be coupled to the remaining one of the heat source or heat load.
- the rod may be axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in heat flow between the heat source and the heat load in a manner such that the warm-side temperature of the heat load is set at a substantially optimal value.
- a variable-thermal-resistance mounting system including a cylinder and a rod movably engaged to the cylinder.
- a heat source may be mounted to an end of the cylinder.
- the rod may be coupled to a thermoelectric generator which may be mounted on an end of the rod.
- the thermoelectric generator may have an optimal warm-side temperature.
- the rod may be axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in thermal resistance between the heat source and the thermoelectric generator in a manner such that the warm-side temperature of the thermoelectric generator is initially set at a substantially optimal value.
- the method may include coupling a rod to one of a heat source and a heat load, and coupling a cylinder to a remaining one of the heat source and the heat load.
- the method may additionally include axially moving the rod relative to the cylinder between a collapsed position and an extended position.
- the method may include changing a heat flow between the heat source and the heat load in response to moving the rod between the collapsed position and the extended position, and adjusting a warm-side temperature of the heat load in response to changing the heat flow.
- FIG. 1A is a schematic diagram of a heat source coupled to a thermal device (e.g., a heat load mounted on a thermal platform) via a variable-thermal-resistance mounting system comprising a rod engaged to a cylinder and which is shown in a collapsed position;
- a thermal device e.g., a heat load mounted on a thermal platform
- a variable-thermal-resistance mounting system comprising a rod engaged to a cylinder and which is shown in a collapsed position
- FIG. 1B is a schematic cross-sectional diagram of the variable-thermal-resistance mounting system in an extended position
- FIG. 1C is a schematic cross-sectional diagram of a cross sectional view of a mechanical clamp locking the axial position of the rod relative the cylinder;
- FIG. 2 is a schematic cross-sectional diagram of the variable-thermal-resistance mounting system wherein the heat load is configured as a thermoelectric generator;
- FIG. 3A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system wherein the cylinder contains a cylinder fluid that expands and contracts when respectively heated and cooled;
- FIG. 3B is a schematic cross-sectional diagram of the variable-thermal-resistance mounting system of FIG. 3A wherein the mounting system is in an extended position;
- FIG. 4A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system having a bellows containing a bellows fluid;
- FIG. 4B is a schematic cross-sectional diagram of the variable-thermal-resistance mounting system of FIG. 4A in an extended position as a result of expansion of the bellows fluid;
- FIG. 5A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system wherein the bellows is thermally isolated from a thermally low-conductive shaft that is axially slidable within a shaft guide mounted in the cylinder;
- FIG. 5B is a schematic cross-sectional diagram of the embodiment of the variable-thermal-resistance mounting system of FIG. 5A in an extended position as a result of expansion of the bellows fluid;
- FIG. 6A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system wherein the cylinder and the rod have a vernier-type structure;
- FIG. 6B is a schematic cross-sectional diagram of the embodiment of the variable-thermal-resistance mounting system of FIG. 6A in an extended position as a result of expansion of the bellows fluid;
- FIG. 7A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system wherein the vernier-type structure of the cylinder and the rod have a linear configuration and showing the rod in a collapsed position;
- FIG. 7B is a schematic cross-sectional diagram of the embodiment of the variable-thermal-resistance mounting system of FIG. 7A showing the rod in an extended position;
- FIG. 7C is a schematic cross-sectional diagram of an embodiment of the vernier-type structure having a non-linear configuration and showing the rod in a collapsed position;
- FIG. 7D is a schematic cross-sectional diagram of an embodiment of the vernier-type structure having a non-linear configuration and showing the rod in an extended position;
- FIG. 8 is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system having a chimney for drawing cool air into the chimney for convective cooling of a heat load mounted within the chimney such as a thermoelectric generator and/or an electronics enclosure;
- FIG. 9A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system having a motor for actively controlling the extension of the rod relative to the cylinder;
- FIG. 9B is a schematic cross-sectional diagram of the embodiment of the variable-thermal-resistance mounting system of FIG. 9A showing the rod in an extended position;
- FIG. 10 is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system having a thermal divider positioned between the thermal device (e.g., a heat load) and the heat source;
- the thermal device e.g., a heat load
- FIG. 11 is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system having the thermal divider positioned between a thermoelectric generator and the heat source;
- FIG. 12 is a flow chart illustrating one or more operations that may be included in a method of regulating heat flow between a heat source and a heat load.
- FIG. 13 is a schematic diagram of a thermal path from a heat source to a heat load and wherein the thermal path includes the variable (e.g., adjustable) thermal resistance of the presently-disclosed variable-thermal-resistance mounting system and the thermal resistance of a thermal load such as a thermoelectric generator.
- the variable e.g., adjustable
- FIG. 1A shown in FIG. 1A is a schematic illustration of a heat source 100 thermally coupled to a heat load 106 (e.g., a thermal device 102 ) by means of a manually-adjustable variable-thermal-resistance mounting system 130 .
- a heat load 106 such as for example, a thermoelectric generator 110 , has a heat capacity and possesses structural elements to collect heat energy from the heat source 100 , as well as dissipate all or a portion of the collected heat energy.
- variable-thermal-resistance mounting system 130 provides a means for adjusting or regulating (e.g., optimizing) heat flow from the heat source 100 to a thermal device 102 or heat load 106 .
- the heat source 100 may comprise a structure having a surface temperature than is higher than the ambient temperature.
- the heat source 100 may comprise a heated pipe having a surface temperature that is higher than ambient temperature of the surrounding environment.
- the heat source 100 may comprise any type of system, subsystem, assembly, or structure from which heat may flow from the heat source 100 to the heat load 106 or thermal device 102 .
- the thermal device 102 or heat load 106 may comprise any type of device having a desired or predetermined warm-side temperature 114 or warm-side temperature range.
- the heat load 106 may also have a maximum temperature such as a maximum operating temperature.
- the thermal device 102 may include one or more temperature-sensitive components 108 such as a sensor, an imaging device, or any device having a maximum rated operating temperature.
- the thermal device 102 may be a thermoelectric generator 110 .
- the thermoelectric generator 110 may have an optimal temperature range within which the thermoelectric generator operates at maximum efficiency.
- the thermoelectric generator 110 may have an optimal warm-side temperature 114 similar to the T Warm temperture of the thermal load (designated by R Load ) in the schematic diagram of FIG. 13 and described below.
- the thermoelectric generator 110 may be coupled to electronic components 112 such as conditioning electronics for conditioning the voltage produced by the thermoelectric generator 110 prior to delivery to a device (e.g., a sensor) to be powered by the thermoelectric generator 110 .
- the efficiency of the conditioning electronics may be at a maximum at an optimal voltage generated by the thermoelectric generator 110 . Due to the dependency of the thermoelectric voltage on the temperature gradient across the thermoelectric generator 110 , the generated voltage may change if the temperature of the heat source 100 changes resulting in reduced conversion efficiency.
- thermoelectric generator 110 initially setting or maintaining a substantially constant optimal temperature on one side (e.g., the warm-side temperature 114 ) of the thermoelectric generator 110 may ensure maximum operating efficiency of the conditioning electronics (e.g., electronic components 112 ) for conditioning the voltage produced by the thermoelectric generator 110 .
- conditioning electronics e.g., electronic components 112
- variable-thermal-resistance mounting system 130 operates to adjust heat flow from a heat source 100 such that the thermoelectric generator 110 may operate at maximum efficiency by maintaining the warm-side temperature 114 at a substantially constant value or within a temperature range.
- the variable-thermal-resistance mounting system 130 may adjust heat flow in a manner such that the thermal load is thermally protected from overheating.
- the variable-thermal-resistance mounting system 130 operates to adjust heat flow from a heat source 100 such that electronic components 112 are maintained below their maximum rated temperature and are therefore thermally protected from overheating, and may operate at maximum efficiency.
- FIG. 13 shown is a schematic diagram of a thermal path for heat flow from a heat source to a heat load.
- the thermal path includes a series of thermal resistances arranged in series and including the variable (e.g., adjustable) thermal resistance of the presently-disclosed variable-thermal-resistance mounting system and the thermal resistance of a thermal load such as a thermoelectric generator.
- T Source may be described as the surface temperature of the heat source. Thermal resistance of the heat source is neglected in the diagram.
- T Sink may be described as the temperature of the ambient environment.
- T Warm may be described as the warm-side temperature of the thermal load such as a warm-side temperature of a thermoelectric generator.
- ⁇ T Var may be described as the temperature gradient across the variable-thermal-resistance mounting system.
- ⁇ T Load may be described as the temperature gradient across the thermal load (e.g., across the thermoelectric generator).
- ⁇ T Ext may be described as the external temperature gradient.
- R Var may be described as the variable thermal resistance of variable-thermal-resistance mounting system (e.g., the cylinder-rod configuration and mechanical mount with adjustable thermal interface—see FIGS. 1A-6B and 8 - 11 ).
- R Load may be described as the thermal resistance of the thermal load which may be a thermoelectric generator or other device.
- thermoelectric generator may be described as a system containing a series of thermal resistances such as of a heat collector (e.g., thermal platform), the thermoelectric generator itself, and a heat exchanger (e.g., a heat sink such as ambient environment).
- a heat collector e.g., thermal platform
- thermoelectric generator itself e.g., the thermoelectric generator itself
- heat exchanger e.g., a heat sink such as ambient environment
- variable-thermal-resistance mounting system allows for maintaining T Warm at a substantially constant (e.g., optimal) temperature.
- the variable-thermal-resistance mounting system may prevent T Warm from exceeding a maximum rated temperuare which may otherwise result in overheating of the thermoelectric generator. If T Source increases, then the variable-thermal-resistance mounting system may be manually, passively, and/or actively adjusted to increase R Var , in a manner as described below, such that T Warm is maintained at a substantially constant (e.g., optimal) temperature.
- variable-thermal-resistance mounting system may be manually, passively, and/or actively adjusted to reduce R Var , in a manner as described below, such that T Warm is maintained at the substantially constant (e.g., optimal) temperature
- the thermal device 102 may include a thermal platform 104 .
- the thermal platform 104 may provide a stable mechanical support for coupling the heat load 106 (e.g., thermoelectric generator) to the thermal interface 134 comprising a rod 140 slidably coupled to a cylinder 136 as described below.
- the thermal platform 104 may have a larger cross-sectional area than the rod 140 to distribute the heat from the rod and spread out the heat across the cross sectional area of the heat load 106 and thereby avoid temperature concentrations in localized areas of the heat load 106 .
- the thermal platform 104 may be comprised of one or more layers of materials each having individual predetermined thermal conductivity values and selected geometries (e.g., cross-sectional geometry and thicknesses).
- the thermal conductivity values and the geometry (e.g., thicknesses) of the one or more layers of the thermal platform 104 may be selected to provide a desired temperature range for the thermal device 102 or heat load 106 .
- selection of the materials for the thermal platform 104 may provide a means for tuning the system to provide a desired amount of heat to the thermal device 102 (e.g., heat load 106 ) within an optimum temperature range.
- the thermal platform 104 may include one more metallic or non-metallic layers such as at least one layer of aluminum having a relatively high thermal conductivity of approximately 230 Watts/meter-Kelvin as a high end of range.
- the thermal platform 104 may include at least one layer of polytetrafluoroethylene (TeflonTM) having a relatively low thermal conductivity of approximately 0.25 Watts/meter-Kelvin which is approximately 100 times lower than the thermal conductivity of aluminum.
- TeflonTM polytetrafluoroethylene
- the thermal platform 104 may include other layers of material to provide a relatively narrow working range for the warm-side temperature of the heat load 106 .
- the thermal platform 104 may be comprised of two metallic layers having an insulting layer sandwiched therebetween. The metallic layers may provide mechanical stability to the connection of the heat load 160 to the rod 140 .
- the thermal platform 104 may assist in spreading the heat from the rod 140 and thereby provide substantially uniform heat flow into the cross-sectional area of the thermal device 102 or heat load 106 .
- the heat load 106 may be coupled to the thermal platform 104 using mechanical fasteners and/or adhesive or other means.
- the thermal device 102 may comprise an energy harvesting system such as a thermoelectric generator 110 as illustrated in FIG. 2 and described below.
- the thermoelectric generator 110 may receive heat flow from the heat source 100 for providing a temperature gradient across the thermoelectric generator 110 such that the thermoelectric generator 110 may generate a voltage.
- the thermal platform 104 may be configured to mechanically couple the thermoelectric generator 110 to the variable-thermal-resistance mounting system 130 disclosed herein.
- the thermal platform 104 may allow for substantially uniform heat distribution into the thermoelectric generator 110 and provide a relatively narrow working range for the warm-side temperature 114 of the thermoelectric generator 110 .
- the thermal platform 104 may integrate several layers each having a different thermal conductivity in order to tailor the thermal resistance of the thermal platform 104 .
- the materials of the thermal platform 104 may be selected to provide a desired level of thermal resistance between the heat source 100 and the cylinder 136 to achieve a relatively narrow working range for the warm-side temperature 114 .
- the materials of the thermal platform 104 may be selected considering the working fluid 194 in the bellows ( FIG. 4A-6B ) as discussed below wherein a relatively high temperature may be required to expand the bellow fluids 194 .
- variable-thermal-resistance mounting system 130 may include a thermal interface 134 comprising a rod 140 that may be slidably coupled to a generally hollow cylinder 136 .
- the cylinder 136 may be mechanically coupled at one end to the heat source 100 via a mechanical mount 132 .
- the mechanical mount 132 may be fastened to the cylinder 136 such as by using mechanical fasteners.
- the torque of the mechanical thrusters may influence the heat transfer capability between the heat source 100 and the mechanical mount 132 .
- the mechanical mount 132 may include an arrangement of one or more materials that may be selected in consideration of the temperature range of the heat source 100 such that a desired temperature range is provided at the location where the cylinder 136 is mechanically coupled to the mechanical mount 132 .
- the materials of the mechanical mount 132 may be selected to provide a desired level of thermal resistance between the heat source 100 and the cylinder 136 similar to that which is described above with regard to the thermal platform 104 .
- a heat shield 158 may be provided between the thermal device 102 and the heat source 100 to minimize radiative heat transfer to the thermal device 102 .
- the heat shield 158 may be formed of relatively thin-gauge metal or non-metallic material and may be provided in a size that is larger (e.g., wider) than the thermal device 102 (e.g. heat load 106 ) and/or other components (e.g., temperature-sensitive electronics) that may be mounted adjacent to the heat load 106 .
- the rod 140 may have a cross sectional shape that is complementary to the cross sectional shape of the interior of the cylinder 136 .
- the rod 140 may have a rod outer surface 142 sized and configured to provide a sliding fit with the interior surface of the cylinder 136 .
- the overlap in contact between the rod outer surface 142 and the cylinder inner surface 138 may define a contact surface area 144 between the rod 140 and cylinder 136 .
- the amount of contact surface area 144 may correspond to the axial position of the rod 140 relative to the cylinder.
- the rod 140 and the cylinder 136 may be provided in any cross-sectional shape, without limitation and are not limited to a cylindrical shape.
- the rod 140 and the cylinder 136 may be sized and configured to provide an annular gap between the rod 140 and the cylinder 136 as shown in FIGS. 3A-3B as described below.
- the mounting system 130 may include a mechanical clamp 146 that may be sized and configured complementary to the rod 140 .
- the rod 140 may extend out of the end of the cylinder 136 opposite the heat source 100 .
- the thermal device 102 may be coupled to the rod end.
- the thermal resistance of the mounting system 130 may be adjusted by adjusting the amount by which the rod 140 is axially pushed or extended out of the cylinder 136 to thereby adjust the amount of contact surface area 144 between the rod 140 and the cylinder 136 .
- the rod 140 may be axially moved relative to the cylinder 136 to any position between and including a collapsed position 152 and an extended position 154 .
- FIG. 1A illustrates the thermal interface 134 of the rod 140 and cylinder 136 in the collapsed position 152 providing a minimum or reduced amount of thermal resistance to heat flow from the heat source 100 to the heat load 106 .
- a maximum portion of the rod 140 may be axially positioned within the cylinder 136 to provide an increased contact surface area 144 for increased heat flow from the heat source 100 to the thermal device 102 (e.g., the heat load 106 ).
- FIG. 1B illustrates the thermal interface 134 of the rod 140 and cylinder 136 in one of a variety of different extended position 154 at which the rod 140 may be positioned relative to the cylinder 136 .
- the rod 140 may be axially displaced to an extended position 154 to at least initially set the warm-side temperature 114 of the heat load 106 .
- the system 130 may adjust the warm-side temperature to a substantially constant value or to be maintained within a temperature range.
- the thermal interface 134 of the rod 140 and cylinder 136 may provide a reduced amount of thermal resistance to the heat flow from the heat source 100 to the heat load 106 relative to the thermal resistance provided by the rod 140 and cylinder 136 in the collapsed position 152 .
- a relatively larger portion of the rod 140 is axially extended outside of the cylinder 136 to provide a relatively small amount of contact surface area 144 between the rod 140 and the cylinder 136 .
- a small amount of contact surface area 144 may minimize or reduce the amount of heat flow passing from the cylinder 136 into the rod 140 and into the thermal device 102 .
- the axial position of the rod 140 relative to the cylinder 136 may be manually adjusted to provide any level of heat resistance.
- the amount of rod 140 extension and the amount of contact surface area 144 between the rod 140 and cylinder 136 may be defined based on the extension length 156 as shown in FIG. 1B .
- the axial position of the rod 140 relative to the cylinder 136 may be adjusted to a desired extension length 156 to regulate the heat flow from the cylinder 136 into the rod 140 and thereby maintain the thermal device 102 (e.g., heat load 106 ) at a desired warm-side temperature 114 or within a desired temperature range.
- the thermal device 102 e.g., heat load 106
- FIG. 1C is a sectional illustration of the cylinder 136 and rod 140 taken along line 1 C of FIG. 1B and illustrating a mechanical clamp 146 that may be included with the variable-thermal-resistance mounting system 130 .
- the mechanical clamp 146 may be mounted to the cylinder 136 such as on an end of the cylinder 136 or in any other suitable location.
- the mechanical clamp 146 may facilitate the coupling or locking of the axial position of the rod 140 relative to the cylinder 136 .
- the mechanical clamp 146 may include a set screw ring 148 that may be coupled to the end of the silver.
- the set screw ring 148 may have an inner diameter that may be complementary to the rod 140 outer diameter.
- the set screw ring 148 may include a set screw 150 for engaging or locking the rod 140 to the cylinder 136 to prevent relative movement therebetween.
- the set screw 150 may be engaged after adjusting the axial position of the rod 140 relative to the cylinder 136 .
- FIG. 2 illustrates an embodiment of the variable-thermal-resistance mounting system 130 configured similar to the system illustrated in FIGS. 1A-1C except in FIG. 2 , the thermal load may be a thermoelectric generator 110 .
- An electronics enclosure 112 may be mounted adjacent to the thermoelectric generator 110 .
- the electronics enclosure 112 may contain electronics for power management or power conditioning for the thermoelectric generator 110 .
- the electronics may be contained or integrated within the thermoelectric generator 110 .
- FIGS. 3A-3B illustrate an embodiment of a passively-adjusted variable-thermal-resistance mounting system 130 wherein the cylinder 136 contains a cylinder fluid 172 that expands and contracts when respectively heated and cooled.
- the fluid may comprise a gas, a liquid, or a two-phase gas/liquid composition that alternates between gas and liquid depending upon the temperature.
- the rod 140 may be a hollow rod 170 to provide increased volume within the cylinder 136 for the cylinder fluid 172 .
- a seal 174 may be included at the end of the cylinder 136 to provide a seal 174 between the rod outer surface 142 and the cylinder inner surface 138 to prevent the cylinder fluid 172 from escaping from the cylinder 136 .
- the cylinder fluid 172 may be trapped or contained within the volume of the cylinder 136 such that an increase in temperature of the cylinder fluid 172 due to heat from the heat source 100 and resulting in an increase in cylinder fluid pressure 176 within the cylinder 136 .
- the increase in cylinder fluid pressure 176 may push or extend the rod 140 out of the cylinder 136 (see FIG. 3B ) thereby increasing the extension length 156 between the thermal platform 104 /heat load 106 and the end of the cylinder 136 .
- the increase in extension length 156 corresponds to a reduced length of the rod 140 within the cylinder 136 .
- the reduced length of the rod 140 within the cylinder 136 corresponds to a reduction in the heat flow transfer from the cylinder 136 wall into the cylinder fluid 172 and into the rod 140 and thereby resulting in an increase in thermal resistance between the heat source 100 to heat load 106 .
- the increase in thermal resistance may reduce heat flow and thereby protect the heat load 106 and related components from over-temperature.
- variable-thermal-resistance mounting system 130 may operate in a manner such that a relatively small increase in heat source 100 temperature will result in a relatively small increase in the cylinder fluid 172 temperature causing a correspondingly small extension length 156 of the rod 140 out of the cylinder 136 and a relatively small increase in thermal resistance to heat flow from the heat source 100 to the heat load 106 .
- a relatively large increase in the heat source 100 temperature may result in a relatively large increase in the cylinder fluid 172 temperature causing a correspondingly large extension length 156 of the rod 140 out of the cylinder 136 and a relatively large increase in thermal resistance to heat flow from the heat source 100 to the heat load 106 .
- the variable-thermal-resistance mounting system 130 may include an extension spring 178 (e.g., a tension spring) which may be mounted between the rod 140 and the heat source 100 .
- the extension spring 178 may be configured to bias the rod 140 from an extended position 154 ( FIG. 3B ) back toward a collapsed position 152 ( FIG. 3A ). In this manner, the extension spring 178 may allow the variable-thermal-resistance mounting system 130 to operate in a passive manner to maintain the warm-side temperature 114 at a substantially constant value or within a temperature range.
- the extension spring 178 may provide a means for tuning the thermal resistance of the system.
- the extension spring 178 may be preloaded when the rod 140 is in a fully retracted position.
- the preloading of the extension spring 178 may provide a means for controlling (e.g., increasing) the temperature at which the rod 140 starts to axially displace or extend out of the cylinder 136 .
- FIGS. 4A-4B illustrate a further embodiment of a passively-adjusted variable-thermal-resistance mounting system 130 having a bellows 192 or a bladder filled with bellows fluid 194 .
- the bellows fluid 194 may comprise a gas, a liquid, or a two-phase gas/liquid combination.
- the bellows 192 may be mechanically coupled to the rod 140 and the cylinder 136 and may be located between the thermal device 102 and the cylinder 136 end.
- the rod 140 may be configured as a relatively highly-thermally conductive rod 140 . Heat from the heat source 100 may be conducted along the rod 140 and into the bellows fluid 194 .
- the bellows fluid 194 may expand from heat from the heat source 100 causing the bellows 192 to increase in length and resulting in an increase in the extension length 156 (e.g., axial displacement) of the rod 140 from the retracted position ( FIG. 4A ) to an extended position 154 ( FIG. 4B ). In this manner, the bellows 192 in FIGS. 4A-4B may provide indirect control of the thermal resistance.
- an increase in the extension length 156 of the rod 140 may result in a reduction in the heat resistance of the thermal interface 134 between the rod 140 and the cylinder 136 .
- a reduction in heat resistance may result in a decrease in heat flow from the heat source 100 to the thermal device 102 and may protect heat load 106 components from over-temperature.
- the bellows fluid 194 may contract when cooled which may result in the bellows 192 decreasing in length and the rod 140 retracting into the cylinder 136 as shown in FIG. 4A and which may decrease the heat resistance between the rod 140 and the cylinder 136 resulting in an increase in heat flow from the heat source 100 to the thermal device 102 .
- the expansion and contraction of the bellows fluid 194 may provide a means to passively maintain the warm-side temperature 114 of the heat load 106 (e.g., thermoelectric generator) at a substantially constant value or within a temperature range.
- a retraction spring may be included to retract the bellows 192 toward the collapsed position 152 and causing the rod to retract into the cylinder 136 .
- the bellows 192 may also be constructed of material having a memory (e.g., stainless steel) which, when the temperature drops, may act as a return mechanism for biasing the rod 140 from an extended position 154 toward the collapsed position 152 .
- the bellows 192 may also provide structural support to the thermal device 102 on an exterior of the cylinder 136 .
- the bellows 192 may mechanically stabilize the connection between the thermal device 102 and the cylinder 136 .
- the bellows material, the bellows geometry, and the bellows fluid 194 may also provide for a wide range of adjustability for altering the thermal resistance of the variable-thermal-resistance mounting system 130 .
- the bellows fluid 194 may be provided as a liquid that boils at a predetermined temperature to increase the bellows fluid pressure 196 and cause displacement of the rod 140 .
- the bellows fluid 194 may comprise an inert gas.
- the mechanical mount 132 , the rod 140 , the cylinder 136 , the bellows fluid 194 , and the thermal platform 104 may be selected to provide a relatively narrow working temperature range at the heat load 106 .
- the bellows 192 may be replaced with a bi-metallic spring/lever for axially displacing or extending the rod 140 out of the cylinder 136 .
- the bi-metallic spring may be comprised of two components (e.g., two different metals) fastened together and having different coefficients of thermal expansion. Heat flow from the heat source 100 may be thermally transferred along the cylinder 136 and/or rod 140 and into the bi-metallic spring result in mechanical displacement (e.g., curvature) of the bi-metallic spring due to the differences in coefficients of thermal expansion and causing the heat load 106 to be moved the axially away from the heat source 100 and thereby increasing the thermal resistance to heat flow from the heat source 100 to the head load.
- FIGS. 5A-5B illustrate a further embodiment of the variable-thermal-resistance mounting system 130 configured in a manner similar to the embodiment of FIGS. 4A-4B and wherein the bellows 192 may provide for direct control of the thermal resistance.
- the bellows 192 may be directly coupled to the cylinder 136 end and the heat load 106 or thermal device 102 .
- the bellows 192 may be thermally isolated from a thermally low-conductive shaft 190 that may be slidable within a shaft guide 198 mounted within the cylinder 136 .
- the shaft guide 198 may be formed of material having a relatively low thermal conductivity to minimize heat flow from the cylinder 136 into the rod 140 .
- Heat from the heat source 100 may flow along the cylinder 136 walls and into the bellows fluid 194 .
- the heating of the bellows fluid 194 may cause axial displacement of the rod 140 from a retracted position ( FIG. 5A ) to any one of a variety of different extended positions 154 ( FIG. 5B ) as described above.
- the bellows fluid 194 may have a composition that becomes less thermally conductive with an increase in the temperature of the bellows fluid 194 . In this manner, the system may provide a non-linear change in thermal resistance in response to increases in temperature at the heat source 100 .
- FIGS. 6A-6B illustrate an embodiment of the variable-thermal-resistance mounting system 130 configured similar to the embodiment of FIGS. 5A-5B and wherein the cylinder 136 and the rod 140 have a vernier-type structure 212 .
- the cylinder 136 and/or the rod 140 may each include one or more axially-spaced, segmented thermal contacts 210 .
- the segmented thermal contacts 210 may provide a further means for tailoring the rate of change of the thermal resistance of the system with changes in the temperature of the heat source 100 .
- the thermal contacts 210 may have defined thermal resistances.
- the thermal contacts 210 in FIGS. 6A-6B are of unequal length which may result in a non-linear change in heat resistance with changes in extension length 156 of the rod 140 relative to the cylinder 136 .
- the vernier-type structure 212 disclosed herein may provide a means for significantly changing the thermal resistance of the mounting system with minimal displacements (e.g., several millimeters) of the rod 140 .
- FIGS. 7A-7B illustrate an embodiment of the variable-thermal-resistance mounting system 130 with the vernier-type structure 212 of the rod 140 and cylinder 136 having a linear configuration 216 .
- the rod 140 and the cylinder 136 may each include axially-spaced thermal contacts 210 that may be substantially equal in length.
- the segmented thermal contacts 210 of the rod 140 may be sized to provide a sliding fit with the segmented thermal contacts 210 of the cylinder 136 .
- the thermal contacts 210 in any embodiment disclosed herein may preferably have a relatively high surface hardness to minimize wear of the thermal contacts 210 during sliding movement.
- the thermal contacts 210 may be formed of nickel-plated copper, aluminum, steel, or other material.
- the thermal contacts 210 may optionally be provided with an oxidized or anodized surface.
- the substantially equal lengths of the axially-spaced thermal contacts 210 may result in a linear decrease in the contact surface area 144 between the thermal contacts 210 when the rod 140 is axially displaced relative to the cylinder 136 . In this manner, the substantially equal lengths of the axially-spaced thermal contacts 210 may result in a linear change in thermal resistance upon axial displacement of the rod 140 .
- FIGS. 7C-7D illustrate an embodiment of the variable-thermal-resistance mounting system 130 with the vernier-type structure 212 having a non-linear configuration 214 .
- the axially-spaced thermal contacts 210 for each one of the rod 140 and the cylinder 136 may be of unequal lengths.
- the unequal lengths of the axially-spaced thermal contacts 210 may result in a non-linear decrease in contact surface area 144 between the thermal contacts 210 when the rod 140 is axially displaced relative to the cylinder 136 .
- the unequal lengths of the thermal contacts 210 may provide a non-linear change in thermal resistance between the heat source 100 and the heat load 106 .
- the vernier-type structure 212 arrangement for the rod 140 and the cylinder 136 may advantageously provides a means for adjusting the thermal resistance of the system independent of axial displacement of the rod 140 relative to the cylinder 136 .
- the total contact surface area between the thermal contacts 210 at any given axial position of the rod 140 relative to the cylinder 136 may be determined by the quantity of thermal contacts 210 , the geometry at the interface between the thermal contacts 210 , the thermal contact length, the thermal contact width, and the thickness of the thermal contacts 210 .
- the relative thermal resistance at a given axial displacement of the rod 140 may be determined by a combination of the thermal contact sizes, shapes, and configurations, the material of the thermal contacts 210 , and other parameters which may collectively provide a wide range of capability for adjusting the thermal resistance of the system 130 .
- FIG. 8 illustrates an embodiment of a variable-thermal-resistance mounting system 130 that may include a chimney 230 arrangement for convective cooling of a heat load, 106 , an electronics enclosure 112 , a thermoelectric generator 110 , or any thermal device 102 that may be included with a heat load 106 or which may be thermally coupled to the heat load 106 or located adjacent to the heat load 106 .
- the chimney 230 may be applied to any of the above-described mounting system 130 embodiments.
- the heat shield 158 may be configured to form a shaft or chimney 230 having an open bottom end 232 and an open top end 234 .
- the heating of the thermal device 102 may cause cool air 236 to be drawn into the bottom end of the chimney 230 .
- the cool air 236 may pass over the electronics enclosure 112 and/or the thermoelectric generator 110 for convective cooling thereof.
- the air may exit out of the top end of the chimney 230 .
- FIGS. 9A-9B illustrates an embodiment of an actively-controlled variable-thermal-resistance mounting system 130 and which may include a motor 160 for controlling the extension or axial displacement of the rod 140 relative to the cylinder 136 .
- the motor 160 may comprise a direct current (DC) motor 160 although any type of motor may be used.
- the motor 160 may be powered by a thermoelectric generator 110 although the motor 160 may be powered by other means such as a battery.
- the motor 160 may be coupled to a drive mechanism such as a screw drive mechanism 162 .
- the motor 160 may receive a signal from the thermal device 102 (e.g., heat load 106 ) such as when the heat load 106 reaches a predetermined temperature.
- the thermal device 102 e.g., heat load 106
- a signal may be provided to the motor 160 when the heat load 106 reaches an upper limit temperature or when the warm-side temperature 114 or range is exceeded causing activation of the motor 160 to axially extend the rod 140 further out of the cylinder 136 from a retracted position ( FIG. 9A ) toward an extended position 154 ( FIG. 9B ). In this manner, the motor 160 may move the heat load 106 away from the heat source 100 and thereby decrease heat flow into the heat load 106 .
- a signal may activate the motor 160 to retract the rod 140 into the cylinder 136 to move the heat load 106 toward the heat source 100 .
- the motor 160 may actively control the displacement of the rod 140 relative to the cylinder 136 to adjust the thermal resistance therebetween and thereby control heat flow from the heat source 100 to the heat load 106 .
- FIGS. 10-11 illustrate embodiments of a variable-thermal-resistance mounting system 130 having a thermal divider 250 positioned between the thermal device 102 (e.g., heat load 106 ) and the heat source 100 .
- the thermal device 102 may be configured as a thermoelectric generator 110 which may have a separate electronics enclosure 112 or which may integrate the electronics components within the thermoelectric generator 110 .
- the thermal divider 250 may be included in applications where the heat source 100 operates at a relatively high upper temperature.
- the embodiment may further include a heat shield 158 as described above and located between the heat load 106 and the thermal divider 250 to further minimize radiative heating of the thermal device 102 .
- the thermal divider 250 may include radiator fins 252 for rejecting heat to the ambient environment.
- the thermal device 102 e.g., thermoelectric generator 110
- the ratio of heat flow through the radiator to heat flow through the heat load 106 may be adjustable by adjusting the displacement of the rod 140 .
- the arrangement of the rod 140 and cylinder 136 may be configured such that the rod 140 is connected to the heat source 100 and the cylinder 136 is connected to the thermal device 102 (e.g., heat load 106 , thermoelectric generator 110 , etc.).
- the rod 140 may be fixedly coupled on one end to the heat source 100
- the cylinder 136 may be fixedly coupled on an opposite end to the thermal device 102 .
- the cylinder 136 may be displaced relative to the rod 140 by any one of the above-described embodiments including by manual means, passive means (e.g., with a fluid-filled cylinder or fluid-filled bellow), or active means (e.g., with a motor).
- a temperature-indicating device such as a strip may be provided on an exterior of the cylinder 136 or the thermal device 102 to provide an indication of the temperature of the system.
- a liquid crystal strip may be mounted on an exterior of the thermal platform 104 of the heat load 106 or on an exterior of a thermoelectric generator 110 .
- the strip may change color corresponding to changes in temperature and may provide a visual indication to an observer as to whether the thermal platform 104 is in the desired temperature range.
- Step 302 of the method 300 may include coupling a rod 140 to a heat source 100 or a heat load 106 , and coupling a cylinder 136 to the remaining heat source 100 or the heat load 106 .
- the heat source 100 may be coupled to an end of the cylinder 136 and the heat load 106 may be coupled to an end of the rod 140 .
- variable-thermal-resistance mounting system 130 may be configured with the heat source 100 may be coupled to an end of the rod 140 and the heat load 106 coupled to an end of the cylinder 136 .
- the heat source 100 may be coupled to the rod 140 or the cylinder 136 using a mechanical mount 132 formed of material providing a desired level of thermal resistance between the heat source 100 and the cylinder 136 or rod 140 .
- the heat load 106 may be coupled to the rod 140 or the cylinder 136 using a thermal platform 104 comprised of one or more materials or layers of material each having predetermined thermal conductivity value as discussed above, and/or a selected geometry (e.g., cross-sectional geometries and/or thicknesses) selected in consideration of a desired operating temperature range of the heat load 106 or the electronics.
- a thermal platform 104 comprised of one or more materials or layers of material each having predetermined thermal conductivity value as discussed above, and/or a selected geometry (e.g., cross-sectional geometries and/or thicknesses) selected in consideration of a desired operating temperature range of the heat load 106 or the electronics.
- Step 304 of the method 300 may include axially moving the rod 140 relative to the cylinder 136 between a collapsed position 152 and an extended position 154 as shown in FIGS. 1A-1B .
- the heat load 106 may be manually pulled away from the heat source 100 which may result in the rod 140 being extended at least partially out of the cylinder 136 .
- the rod 140 may be axially moved to any position between the collapsed position 152 and the extended position 154 . Extending the rod 140 at least partially out of the cylinder 136 may result in changing (e.g., decreasing) the contact surface area 144 between the rod 140 and cylinder 136 .
- Step 306 of the method 300 may include changing a heat flow between the heat source 100 and the heat load 106 in response to moving the rod 140 between the collapsed position 152 and the extended position 154 .
- the change e.g., decrease
- the change in contact surface area 144 may result in altering (e.g., decreasing) heat flow between the heat source 100 and the heat load 106 as a means to at least initially set or adjust the warm-side temperature 114 of the heat load 106 .
- the method 300 may optionally include mounting a heat shield 158 ( FIGS. 1A-1B ) and/or a thermal divider 250 ( FIG. 10 ) between the heat load 106 and the heat source 100 as shown in FIGS. 1A , 1 B, and 2 , for reducing radiative heat transfer to the heat load 106 .
- Step 308 of the method 300 may include adjusting the warm-side temperature 114 of the heat load 106 in response to changing the heat flow.
- the warm-side temperature 114 may be initially adjusted to a substantially optimal value which, in the present disclosure, may be described as within a relatively small range of the optimal value.
- the warm-side temperature 114 may be initially adjusted by manually pulling the rod 140 out of the cylinder 136 to a position that initially results in substantially achieving the optimal warm-side temperature 140 or relatively small range based on a given temperature of the heat source 100 . If the heat source temperature changes, then further adjustment of the position of the rod 140 may be required to accordingly adjust the warm-side temperature 114 .
- the method may include clamping or fixing the position of the rod 140 relative to the cylinder 136 after the warm-side temperature 114 has been adjusted.
- the rod 140 may be clamped to the cylinder 136 such as by using a mechanical clamp 146 , an embodiment of which is shown in FIG. 1C described above.
- variable-thermal-resistance mounting system 130 may be operated in a passive manner without manually or actively displacing (e.g., manually or actively pulling) the rod 140 axially outwardly from the cylinder 136 or manually or actively (e.g., with a motor— FIGS. 9A-9B ) pushing the rod 140 inwardly back into the cylinder 136 .
- certain passive embodiments of the variable-thermal-resistance mounting system 130 may include a cylinder 136 containing a cylinder fluid 172 such as a gas, a liquid, or a 2-phase fluid as shown in FIGS. 3A-3B and described above.
- the method 300 may further include heating the cylinder fluid 172 with heat from the heat source 100 , and expanding the cylinder fluid 172 when heated causing an increase in cylinder fluid pressure 176 within the cylinder 136 .
- the increase in cylinder fluid pressure 176 may cause the rod 140 to at least partially extend out of the cylinder 136 , resulting in an increase in thermal resistance between the rod 140 and cylinder 136 .
- the increase in thermal resistance may result in a reduction in heat flow between the heat source 100 and the heat load 106 .
- the method 300 of varying the thermal resistance between a heat load 106 and a heat source 100 may also be implemented in a passive manner using a variable-thermal-resistance mounting system 130 having a bellows 192 containing a bellows fluid 194 .
- the bellows 192 may be mounted between the heat load 106 and the cylinder 136 as shown in FIGS. 3A-7D .
- the method 300 may include heating the bellows fluid 194 with the heat flow from the heat source 100 , expanding the bellows fluid 194 when heated causing the bellows 192 to increase in length, and extending the rod 140 out of the cylinder 136 due to the increasing length of the bellows 192 .
- the method 300 may further include increasing the thermal resistance between the rod 140 and the cylinder 136 due to the extension of the rod 140 , and reducing the heat flow between the heat source 100 and the heat load 106 as a result of the increase in the thermal resistance.
- the bellows 192 may be thermally isolated from the rod 140 in a manner such that the heat flow from the heat source 100 may be conducted along the cylinder 136 and directly into the bellows fluid 194 as shown in FIGS. 4A-6B and described above.
- the cylinder 136 and the rod 140 may each include at least two axially-spaced segmented thermal contacts 210 forming a vernier-type structure 212 .
- the thermal contacts 210 of the rod 140 may be slidably engaged to the thermal contacts 210 of the cylinder 136 .
- the vernier-type structure 212 may have a linear configuration 216 with substantially equal length thermal contacts 210 for each of the rod 140 and cylinder 136 as shown in FIGS. 7A-7B .
- the method 300 of varying the thermal resistance between the heat source 100 and heat load 106 may include axially moving the rod 140 , and linearly changing the thermal resistance of the cylinder 136 and rod 140 in response to axially moving the rod 140 .
- axially moving the rod 140 relative to the cylinder 136 may result in linearly changing the thermal resistance of the cylinder 136 and rod 140 .
- variable-thermal-resistance mounting system 130 may be actively operated to vary the thermal resistance between the heat source 100 and heat load 106 .
- the method 300 may include actively displacing or axially moving the rod 140 relative to the cylinder 136 .
- the method 300 may include using a motor 160 (e.g., a D.C. motor) coupled to the rod 140 with a screw drive mechanism 162 to actively axially displace the rod 140 relative to the cylinder 136 .
- the method may include powering the motor 160 using the thermoelectric generator 110 which may be the heat load 106 for which the temperature is being regulated using the variable-thermal-resistance mounting system 130 .
- the motor 160 may be powered using one or more batteries or another power source.
- the method 300 may include mounting the heat load 106 within a chimney 230 as shown in FIG. 8 .
- the chimney 230 may be formed using one or more heat shields 158 .
- the chimney 230 may further facilitate controlling the temperature of the heat load 106 .
- the method 300 may include drawing cool air 236 into the open bottom end 232 of the chimney 230 , passing the cool air 236 over a heat load such as a thermoelectric generator 110 and/or electronics enclosure 112 to convectively cool the thermoelectric generator 110 and/or electronics enclosure 112 , and discharging the air out of a top end of the chimney 230 .
Abstract
A variable-thermal-resistance mounting system may include a cylinder coupled to a heat source, or heat load and a rod movably engaged to the cylinder and coupled to a remaining one of the heat source and heat load. The rod may be coupled to a heat load. The rod may be axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in heat flow between the heat source and the heat load such that the warm-side temperature of the heat load is initially set at a substantially optimal value.
Description
- The present application claims priority to pending U.S. Provisional Application No. 61/728,233 filed on Nov. 19, 2013, and entitled VARIABLE THERMAL RESISTANCE MOUNTING SYSTEM, the entire contents of which is expressly incorporated herein by reference.
- The present disclosure relates generally to mounting systems for thermal platforms and, more particularly, to systems for optimizing heat flow to a heat load such as a thermoelectric generator.
- Thermoelectric energy harvesting systems such as thermoelectric generators convert thermal energy into electrical energy in response to a thermal gradient across the thermoelectric generator. The thermal gradient may occur as a result of heat flow from a heat source that is thermally coupled to one side of the thermoelectric generator to a heat sink that is thermally coupled to the other side of the thermoelectric generator. The thermoelectric generator may have an optimal temperature or an optimal temperature range within which the thermoelectric generator operates at maximum efficiency. The thermoelectric generator may be coupled to electronic components for conditioning the voltage produced by the thermoelectric generator prior to delivery to a device (e.g., a sensor) to be powered by the thermoelectric generator.
- Electronic components typically have a maximum rated temperature up to which the electronic components may operate on a nominal basis. Approaching the maximum rated temperature of the electronic components may result in a reduction in the performance of the electronic components. Exceeding the maximum rated temperature of the electronic components may result in damage or failure of the electronic components. A failure of the electronic components may compromise the capability of the thermoelectric generator to power the device.
- A thermoelectric generator may be installed in an environment where the temperature of the heat source fluctuates. For example, the thermoelectric generator may be thermally coupled to the surface of a heated pipe in an industrial facility. Process variations may result in fluctuations in the surface temperature of the heated pipe such that heat flow to the thermoelectric generator may fall outside of the range for maximum operating efficiency of the thermoelectric generator. Heat flow from the heated pipe may also result in exceeding the maximum rated temperature of the electronic components that may be coupled to the thermoelectric generator.
- As can be seen, there exists a need in the art for a system and method for adjusting heat flow from a heat source such that the thermoelectric generator may operate at maximum efficiency and is thermally protected from overheating. In addition, there exists a need in the art for a system and method for adjusting heat flow from a heat source such that electronic components are maintained below their maximum rated temperature and are therefore thermally protected from overheating, and also such that the electronic components may operate at maximum efficiency.
- The above-described needs associated with adjusting heat flow from a heat source are specifically addressed and alleviated by the present disclosure which, in an embodiment, provides a variable-thermal-resistance mounting system. The variable-thermal-resistance mounting system may include a cylinder coupled to a heat source or a heat load. The heat source may have an optimal warm-side temperature. The variable-thermal-resistance mounting system also may include a rod movably engaged to the cylinder. The rod may be coupled to the remaining one of the heat source or heat load. The rod may be axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in heat flow between the heat source and the heat load in a manner such that the warm-side temperature of the heat load is set at a substantially optimal value.
- In a further embodiment, disclosed is a variable-thermal-resistance mounting system including a cylinder and a rod movably engaged to the cylinder. A heat source may be mounted to an end of the cylinder. The rod may be coupled to a thermoelectric generator which may be mounted on an end of the rod. The thermoelectric generator may have an optimal warm-side temperature. The rod may be axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in thermal resistance between the heat source and the thermoelectric generator in a manner such that the warm-side temperature of the thermoelectric generator is initially set at a substantially optimal value.
- Also disclosed is a method of regulating heat flow between a heat source and a heat load. The method may include coupling a rod to one of a heat source and a heat load, and coupling a cylinder to a remaining one of the heat source and the heat load. The method may additionally include axially moving the rod relative to the cylinder between a collapsed position and an extended position. Furthermore, the method may include changing a heat flow between the heat source and the heat load in response to moving the rod between the collapsed position and the extended position, and adjusting a warm-side temperature of the heat load in response to changing the heat flow.
- The features, functions and advantages that have been discussed can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings below.
- These and other features of the present disclosure will become more apparent upon reference to the drawings wherein like numbers refer to like parts throughout and wherein:
-
FIG. 1A is a schematic diagram of a heat source coupled to a thermal device (e.g., a heat load mounted on a thermal platform) via a variable-thermal-resistance mounting system comprising a rod engaged to a cylinder and which is shown in a collapsed position; -
FIG. 1B is a schematic cross-sectional diagram of the variable-thermal-resistance mounting system in an extended position; -
FIG. 1C is a schematic cross-sectional diagram of a cross sectional view of a mechanical clamp locking the axial position of the rod relative the cylinder; -
FIG. 2 is a schematic cross-sectional diagram of the variable-thermal-resistance mounting system wherein the heat load is configured as a thermoelectric generator; -
FIG. 3A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system wherein the cylinder contains a cylinder fluid that expands and contracts when respectively heated and cooled; -
FIG. 3B is a schematic cross-sectional diagram of the variable-thermal-resistance mounting system ofFIG. 3A wherein the mounting system is in an extended position; -
FIG. 4A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system having a bellows containing a bellows fluid; -
FIG. 4B is a schematic cross-sectional diagram of the variable-thermal-resistance mounting system ofFIG. 4A in an extended position as a result of expansion of the bellows fluid; -
FIG. 5A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system wherein the bellows is thermally isolated from a thermally low-conductive shaft that is axially slidable within a shaft guide mounted in the cylinder; -
FIG. 5B is a schematic cross-sectional diagram of the embodiment of the variable-thermal-resistance mounting system ofFIG. 5A in an extended position as a result of expansion of the bellows fluid; -
FIG. 6A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system wherein the cylinder and the rod have a vernier-type structure; -
FIG. 6B is a schematic cross-sectional diagram of the embodiment of the variable-thermal-resistance mounting system ofFIG. 6A in an extended position as a result of expansion of the bellows fluid; -
FIG. 7A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system wherein the vernier-type structure of the cylinder and the rod have a linear configuration and showing the rod in a collapsed position; -
FIG. 7B is a schematic cross-sectional diagram of the embodiment of the variable-thermal-resistance mounting system ofFIG. 7A showing the rod in an extended position; -
FIG. 7C is a schematic cross-sectional diagram of an embodiment of the vernier-type structure having a non-linear configuration and showing the rod in a collapsed position; -
FIG. 7D is a schematic cross-sectional diagram of an embodiment of the vernier-type structure having a non-linear configuration and showing the rod in an extended position; -
FIG. 8 is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system having a chimney for drawing cool air into the chimney for convective cooling of a heat load mounted within the chimney such as a thermoelectric generator and/or an electronics enclosure; -
FIG. 9A is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system having a motor for actively controlling the extension of the rod relative to the cylinder; -
FIG. 9B is a schematic cross-sectional diagram of the embodiment of the variable-thermal-resistance mounting system ofFIG. 9A showing the rod in an extended position; -
FIG. 10 is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system having a thermal divider positioned between the thermal device (e.g., a heat load) and the heat source; -
FIG. 11 is a schematic cross-sectional diagram of an embodiment of the variable-thermal-resistance mounting system having the thermal divider positioned between a thermoelectric generator and the heat source; -
FIG. 12 is a flow chart illustrating one or more operations that may be included in a method of regulating heat flow between a heat source and a heat load; and -
FIG. 13 is a schematic diagram of a thermal path from a heat source to a heat load and wherein the thermal path includes the variable (e.g., adjustable) thermal resistance of the presently-disclosed variable-thermal-resistance mounting system and the thermal resistance of a thermal load such as a thermoelectric generator. - Referring now to the drawings wherein the showings are for purposes of illustrating various embodiments of the present disclosure, shown in
FIG. 1A is a schematic illustration of aheat source 100 thermally coupled to a heat load 106 (e.g., a thermal device 102) by means of a manually-adjustable variable-thermal-resistance mounting system 130. Aheat load 106, such as for example, athermoelectric generator 110, has a heat capacity and possesses structural elements to collect heat energy from theheat source 100, as well as dissipate all or a portion of the collected heat energy. Advantageously, the variable-thermal-resistance mounting system 130 provides a means for adjusting or regulating (e.g., optimizing) heat flow from theheat source 100 to athermal device 102 orheat load 106. Theheat source 100 may comprise a structure having a surface temperature than is higher than the ambient temperature. In a non-limiting embodiment, theheat source 100 may comprise a heated pipe having a surface temperature that is higher than ambient temperature of the surrounding environment. However, theheat source 100 may comprise any type of system, subsystem, assembly, or structure from which heat may flow from theheat source 100 to theheat load 106 orthermal device 102. - The
thermal device 102 orheat load 106 may comprise any type of device having a desired or predetermined warm-side temperature 114 or warm-side temperature range. Theheat load 106 may also have a maximum temperature such as a maximum operating temperature. For example, thethermal device 102 may include one or more temperature-sensitive components 108 such as a sensor, an imaging device, or any device having a maximum rated operating temperature. In an embodiment, thethermal device 102 may be athermoelectric generator 110. Thethermoelectric generator 110 may have an optimal temperature range within which the thermoelectric generator operates at maximum efficiency. For example, thethermoelectric generator 110 may have an optimal warm-side temperature 114 similar to the TWarm temperture of the thermal load (designated by RLoad) in the schematic diagram ofFIG. 13 and described below. - The
thermoelectric generator 110 may be coupled toelectronic components 112 such as conditioning electronics for conditioning the voltage produced by thethermoelectric generator 110 prior to delivery to a device (e.g., a sensor) to be powered by thethermoelectric generator 110. The efficiency of the conditioning electronics may be at a maximum at an optimal voltage generated by thethermoelectric generator 110. Due to the dependency of the thermoelectric voltage on the temperature gradient across thethermoelectric generator 110, the generated voltage may change if the temperature of theheat source 100 changes resulting in reduced conversion efficiency. In this regard, initially setting or maintaining a substantially constant optimal temperature on one side (e.g., the warm-side temperature 114) of thethermoelectric generator 110 may ensure maximum operating efficiency of the conditioning electronics (e.g., electronic components 112) for conditioning the voltage produced by thethermoelectric generator 110. - Advantageously, any one of the presently-disclosed embodiments of the variable-thermal-
resistance mounting system 130 operates to adjust heat flow from aheat source 100 such that thethermoelectric generator 110 may operate at maximum efficiency by maintaining the warm-side temperature 114 at a substantially constant value or within a temperature range. In addition, the variable-thermal-resistance mounting system 130 may adjust heat flow in a manner such that the thermal load is thermally protected from overheating. In addition, the variable-thermal-resistance mounting system 130 operates to adjust heat flow from aheat source 100 such thatelectronic components 112 are maintained below their maximum rated temperature and are therefore thermally protected from overheating, and may operate at maximum efficiency. - Referring briefly to
FIG. 13 , shown is a schematic diagram of a thermal path for heat flow from a heat source to a heat load. The thermal path includes a series of thermal resistances arranged in series and including the variable (e.g., adjustable) thermal resistance of the presently-disclosed variable-thermal-resistance mounting system and the thermal resistance of a thermal load such as a thermoelectric generator. InFIG. 13 , TSource may be described as the surface temperature of the heat source. Thermal resistance of the heat source is neglected in the diagram. TSink may be described as the temperature of the ambient environment. TWarm may be described as the warm-side temperature of the thermal load such as a warm-side temperature of a thermoelectric generator. ΔTVar may be described as the temperature gradient across the variable-thermal-resistance mounting system. ΔTLoad may be described as the temperature gradient across the thermal load (e.g., across the thermoelectric generator). ΔTExt may be described as the external temperature gradient. RVar may be described as the variable thermal resistance of variable-thermal-resistance mounting system (e.g., the cylinder-rod configuration and mechanical mount with adjustable thermal interface—seeFIGS. 1A-6B and 8-11). RLoad may be described as the thermal resistance of the thermal load which may be a thermoelectric generator or other device. In the case where the thermal load is a thermoelectric generator, the thermoelectric generator may be described as a system containing a series of thermal resistances such as of a heat collector (e.g., thermal platform), the thermoelectric generator itself, and a heat exchanger (e.g., a heat sink such as ambient environment). - Refering to
FIG. 13 , the variable-thermal-resistance mounting system allows for maintaining TWarm at a substantially constant (e.g., optimal) temperature. In addition, the variable-thermal-resistance mounting system may prevent TWarm from exceeding a maximum rated temperuare which may otherwise result in overheating of the thermoelectric generator. If TSource increases, then the variable-thermal-resistance mounting system may be manually, passively, and/or actively adjusted to increase RVar, in a manner as described below, such that TWarm is maintained at a substantially constant (e.g., optimal) temperature. If TSource decreases, then the variable-thermal-resistance mounting system may be manually, passively, and/or actively adjusted to reduce RVar, in a manner as described below, such that TWarm is maintained at the substantially constant (e.g., optimal) temperature - The
thermal device 102 may include athermal platform 104. Thethermal platform 104 may provide a stable mechanical support for coupling the heat load 106 (e.g., thermoelectric generator) to thethermal interface 134 comprising arod 140 slidably coupled to acylinder 136 as described below. In addition, thethermal platform 104 may have a larger cross-sectional area than therod 140 to distribute the heat from the rod and spread out the heat across the cross sectional area of theheat load 106 and thereby avoid temperature concentrations in localized areas of theheat load 106. In an embodiment, thethermal platform 104 may be comprised of one or more layers of materials each having individual predetermined thermal conductivity values and selected geometries (e.g., cross-sectional geometry and thicknesses). The thermal conductivity values and the geometry (e.g., thicknesses) of the one or more layers of thethermal platform 104 may be selected to provide a desired temperature range for thethermal device 102 orheat load 106. In this manner, selection of the materials for thethermal platform 104 may provide a means for tuning the system to provide a desired amount of heat to the thermal device 102 (e.g., heat load 106) within an optimum temperature range. For example, thethermal platform 104 may include one more metallic or non-metallic layers such as at least one layer of aluminum having a relatively high thermal conductivity of approximately 230 Watts/meter-Kelvin as a high end of range. On the opposite end of the thermal conductivity spectrum, thethermal platform 104 may include at least one layer of polytetrafluoroethylene (Teflon™) having a relatively low thermal conductivity of approximately 0.25 Watts/meter-Kelvin which is approximately 100 times lower than the thermal conductivity of aluminum. Thethermal platform 104 may include other layers of material to provide a relatively narrow working range for the warm-side temperature of theheat load 106. In some embodiments, thethermal platform 104 may be comprised of two metallic layers having an insulting layer sandwiched therebetween. The metallic layers may provide mechanical stability to the connection of theheat load 160 to therod 140. Thethermal platform 104 may assist in spreading the heat from therod 140 and thereby provide substantially uniform heat flow into the cross-sectional area of thethermal device 102 orheat load 106. Theheat load 106 may be coupled to thethermal platform 104 using mechanical fasteners and/or adhesive or other means. - In an embodiment, the
thermal device 102 may comprise an energy harvesting system such as athermoelectric generator 110 as illustrated inFIG. 2 and described below. Thethermoelectric generator 110 may receive heat flow from theheat source 100 for providing a temperature gradient across thethermoelectric generator 110 such that thethermoelectric generator 110 may generate a voltage. Thethermal platform 104 may be configured to mechanically couple thethermoelectric generator 110 to the variable-thermal-resistance mounting system 130 disclosed herein. In addition, thethermal platform 104 may allow for substantially uniform heat distribution into thethermoelectric generator 110 and provide a relatively narrow working range for the warm-side temperature 114 of thethermoelectric generator 110. In addition, thethermal platform 104 may integrate several layers each having a different thermal conductivity in order to tailor the thermal resistance of thethermal platform 104. In this regard, the materials of thethermal platform 104 may be selected to provide a desired level of thermal resistance between theheat source 100 and thecylinder 136 to achieve a relatively narrow working range for the warm-side temperature 114. In some embodiment, the materials of thethermal platform 104 may be selected considering the workingfluid 194 in the bellows (FIG. 4A-6B ) as discussed below wherein a relatively high temperature may be required to expand thebellow fluids 194. - As indicated above, the variable-thermal-
resistance mounting system 130 may include athermal interface 134 comprising arod 140 that may be slidably coupled to a generallyhollow cylinder 136. Thecylinder 136 may be mechanically coupled at one end to theheat source 100 via amechanical mount 132. Themechanical mount 132 may be fastened to thecylinder 136 such as by using mechanical fasteners. The torque of the mechanical thrusters may influence the heat transfer capability between theheat source 100 and themechanical mount 132. Themechanical mount 132 may include an arrangement of one or more materials that may be selected in consideration of the temperature range of theheat source 100 such that a desired temperature range is provided at the location where thecylinder 136 is mechanically coupled to themechanical mount 132. In this regard, the materials of themechanical mount 132 may be selected to provide a desired level of thermal resistance between theheat source 100 and thecylinder 136 similar to that which is described above with regard to thethermal platform 104. Aheat shield 158 may be provided between thethermal device 102 and theheat source 100 to minimize radiative heat transfer to thethermal device 102. Theheat shield 158 may be formed of relatively thin-gauge metal or non-metallic material and may be provided in a size that is larger (e.g., wider) than the thermal device 102 (e.g. heat load 106) and/or other components (e.g., temperature-sensitive electronics) that may be mounted adjacent to theheat load 106. - In
FIG. 1A , therod 140 may have a cross sectional shape that is complementary to the cross sectional shape of the interior of thecylinder 136. For example, therod 140 may have a rodouter surface 142 sized and configured to provide a sliding fit with the interior surface of thecylinder 136. The overlap in contact between the rodouter surface 142 and the cylinderinner surface 138 may define acontact surface area 144 between therod 140 andcylinder 136. The amount ofcontact surface area 144 may correspond to the axial position of therod 140 relative to the cylinder. Therod 140 and thecylinder 136 may be provided in any cross-sectional shape, without limitation and are not limited to a cylindrical shape. In some embodiments, therod 140 and thecylinder 136 may be sized and configured to provide an annular gap between therod 140 and thecylinder 136 as shown inFIGS. 3A-3B as described below. - In certain embodiments (e.g.,
FIGS. 1A-1B ), the mountingsystem 130 may include amechanical clamp 146 that may be sized and configured complementary to therod 140. Therod 140 may extend out of the end of thecylinder 136 opposite theheat source 100. Thethermal device 102 may be coupled to the rod end. The thermal resistance of the mountingsystem 130 may be adjusted by adjusting the amount by which therod 140 is axially pushed or extended out of thecylinder 136 to thereby adjust the amount ofcontact surface area 144 between therod 140 and thecylinder 136. In any of the embodiments disclosed herein, therod 140 may be axially moved relative to thecylinder 136 to any position between and including acollapsed position 152 and anextended position 154.FIG. 1A illustrates thethermal interface 134 of therod 140 andcylinder 136 in thecollapsed position 152 providing a minimum or reduced amount of thermal resistance to heat flow from theheat source 100 to theheat load 106. In thecollapsed position 152, a maximum portion of therod 140 may be axially positioned within thecylinder 136 to provide an increasedcontact surface area 144 for increased heat flow from theheat source 100 to the thermal device 102 (e.g., the heat load 106). -
FIG. 1B illustrates thethermal interface 134 of therod 140 andcylinder 136 in one of a variety of differentextended position 154 at which therod 140 may be positioned relative to thecylinder 136. Therod 140 may be axially displaced to anextended position 154 to at least initially set the warm-side temperature 114 of theheat load 106. In some passive or active embodiments described below, thesystem 130 may adjust the warm-side temperature to a substantially constant value or to be maintained within a temperature range. In anextended position 154, thethermal interface 134 of therod 140 andcylinder 136 may provide a reduced amount of thermal resistance to the heat flow from theheat source 100 to theheat load 106 relative to the thermal resistance provided by therod 140 andcylinder 136 in thecollapsed position 152. In theextended position 154, a relatively larger portion of therod 140 is axially extended outside of thecylinder 136 to provide a relatively small amount ofcontact surface area 144 between therod 140 and thecylinder 136. A small amount ofcontact surface area 144 may minimize or reduce the amount of heat flow passing from thecylinder 136 into therod 140 and into thethermal device 102. In some embodiments, the axial position of therod 140 relative to thecylinder 136 may be manually adjusted to provide any level of heat resistance. The amount ofrod 140 extension and the amount ofcontact surface area 144 between therod 140 andcylinder 136 may be defined based on theextension length 156 as shown inFIG. 1B . In this regard, the axial position of therod 140 relative to thecylinder 136 may be adjusted to a desiredextension length 156 to regulate the heat flow from thecylinder 136 into therod 140 and thereby maintain the thermal device 102 (e.g., heat load 106) at a desired warm-side temperature 114 or within a desired temperature range. -
FIG. 1C is a sectional illustration of thecylinder 136 androd 140 taken alongline 1C ofFIG. 1B and illustrating amechanical clamp 146 that may be included with the variable-thermal-resistance mounting system 130. In an embodiment, themechanical clamp 146 may be mounted to thecylinder 136 such as on an end of thecylinder 136 or in any other suitable location. Themechanical clamp 146 may facilitate the coupling or locking of the axial position of therod 140 relative to thecylinder 136. In one example, themechanical clamp 146 may include aset screw ring 148 that may be coupled to the end of the silver. Theset screw ring 148 may have an inner diameter that may be complementary to therod 140 outer diameter. Theset screw ring 148 may include aset screw 150 for engaging or locking therod 140 to thecylinder 136 to prevent relative movement therebetween. Theset screw 150 may be engaged after adjusting the axial position of therod 140 relative to thecylinder 136. -
FIG. 2 illustrates an embodiment of the variable-thermal-resistance mounting system 130 configured similar to the system illustrated inFIGS. 1A-1C except inFIG. 2 , the thermal load may be athermoelectric generator 110. Anelectronics enclosure 112 may be mounted adjacent to thethermoelectric generator 110. Theelectronics enclosure 112 may contain electronics for power management or power conditioning for thethermoelectric generator 110. In an embodiment not shown, the electronics may be contained or integrated within thethermoelectric generator 110. -
FIGS. 3A-3B illustrate an embodiment of a passively-adjusted variable-thermal-resistance mounting system 130 wherein thecylinder 136 contains acylinder fluid 172 that expands and contracts when respectively heated and cooled. The fluid may comprise a gas, a liquid, or a two-phase gas/liquid composition that alternates between gas and liquid depending upon the temperature. Therod 140 may be ahollow rod 170 to provide increased volume within thecylinder 136 for thecylinder fluid 172. Aseal 174 may be included at the end of thecylinder 136 to provide aseal 174 between the rodouter surface 142 and the cylinderinner surface 138 to prevent thecylinder fluid 172 from escaping from thecylinder 136. - In
FIG. 3A , thecylinder fluid 172 may be trapped or contained within the volume of thecylinder 136 such that an increase in temperature of thecylinder fluid 172 due to heat from theheat source 100 and resulting in an increase incylinder fluid pressure 176 within thecylinder 136. The increase incylinder fluid pressure 176 may push or extend therod 140 out of the cylinder 136 (seeFIG. 3B ) thereby increasing theextension length 156 between thethermal platform 104/heat load 106 and the end of thecylinder 136. The increase inextension length 156 corresponds to a reduced length of therod 140 within thecylinder 136. The reduced length of therod 140 within thecylinder 136 corresponds to a reduction in the heat flow transfer from thecylinder 136 wall into thecylinder fluid 172 and into therod 140 and thereby resulting in an increase in thermal resistance between theheat source 100 to heatload 106. The increase in thermal resistance may reduce heat flow and thereby protect theheat load 106 and related components from over-temperature. - In some embodiments, the variable-thermal-
resistance mounting system 130 may operate in a manner such that a relatively small increase inheat source 100 temperature will result in a relatively small increase in thecylinder fluid 172 temperature causing a correspondinglysmall extension length 156 of therod 140 out of thecylinder 136 and a relatively small increase in thermal resistance to heat flow from theheat source 100 to theheat load 106. Conversely, a relatively large increase in theheat source 100 temperature may result in a relatively large increase in thecylinder fluid 172 temperature causing a correspondinglylarge extension length 156 of therod 140 out of thecylinder 136 and a relatively large increase in thermal resistance to heat flow from theheat source 100 to theheat load 106. - As shown in
FIG. 3B , in an embodiment, the variable-thermal-resistance mounting system 130 may include an extension spring 178 (e.g., a tension spring) which may be mounted between therod 140 and theheat source 100. In an embodiment, theextension spring 178 may be configured to bias therod 140 from an extended position 154 (FIG. 3B ) back toward a collapsed position 152 (FIG. 3A ). In this manner, theextension spring 178 may allow the variable-thermal-resistance mounting system 130 to operate in a passive manner to maintain the warm-side temperature 114 at a substantially constant value or within a temperature range. In addition, theextension spring 178 may provide a means for tuning the thermal resistance of the system. For example, theextension spring 178 may be preloaded when therod 140 is in a fully retracted position. The preloading of theextension spring 178 may provide a means for controlling (e.g., increasing) the temperature at which therod 140 starts to axially displace or extend out of thecylinder 136. -
FIGS. 4A-4B illustrate a further embodiment of a passively-adjusted variable-thermal-resistance mounting system 130 having abellows 192 or a bladder filled with bellows fluid 194. The bellows fluid 194 may comprise a gas, a liquid, or a two-phase gas/liquid combination. Thebellows 192 may be mechanically coupled to therod 140 and thecylinder 136 and may be located between thethermal device 102 and thecylinder 136 end. In an embodiment, therod 140 may be configured as a relatively highly-thermallyconductive rod 140. Heat from theheat source 100 may be conducted along therod 140 and into the bellows fluid 194. The bellows fluid 194 may expand from heat from theheat source 100 causing thebellows 192 to increase in length and resulting in an increase in the extension length 156 (e.g., axial displacement) of therod 140 from the retracted position (FIG. 4A ) to an extended position 154 (FIG. 4B ). In this manner, thebellows 192 inFIGS. 4A-4B may provide indirect control of the thermal resistance. - As indicated above, an increase in the
extension length 156 of therod 140 may result in a reduction in the heat resistance of thethermal interface 134 between therod 140 and thecylinder 136. A reduction in heat resistance may result in a decrease in heat flow from theheat source 100 to thethermal device 102 and may protectheat load 106 components from over-temperature. The bellows fluid 194 may contract when cooled which may result in thebellows 192 decreasing in length and therod 140 retracting into thecylinder 136 as shown inFIG. 4A and which may decrease the heat resistance between therod 140 and thecylinder 136 resulting in an increase in heat flow from theheat source 100 to thethermal device 102. The expansion and contraction of the bellows fluid 194 may provide a means to passively maintain the warm-side temperature 114 of the heat load 106 (e.g., thermoelectric generator) at a substantially constant value or within a temperature range. Although not shown, a retraction spring may be included to retract thebellows 192 toward thecollapsed position 152 and causing the rod to retract into thecylinder 136. Thebellows 192 may also be constructed of material having a memory (e.g., stainless steel) which, when the temperature drops, may act as a return mechanism for biasing therod 140 from anextended position 154 toward thecollapsed position 152. - Advantageously, in an embodiment, the
bellows 192 may also provide structural support to thethermal device 102 on an exterior of thecylinder 136. In this regard, thebellows 192 may mechanically stabilize the connection between thethermal device 102 and thecylinder 136. The bellows material, the bellows geometry, and the bellows fluid 194 may also provide for a wide range of adjustability for altering the thermal resistance of the variable-thermal-resistance mounting system 130. The bellows fluid 194 may be provided as a liquid that boils at a predetermined temperature to increase the bellowsfluid pressure 196 and cause displacement of therod 140. Alternatively, the bellows fluid 194 may comprise an inert gas. Themechanical mount 132, therod 140, thecylinder 136, the bellows fluid 194, and thethermal platform 104 may be selected to provide a relatively narrow working temperature range at theheat load 106. - Although not shown, the
bellows 192 may be replaced with a bi-metallic spring/lever for axially displacing or extending therod 140 out of thecylinder 136. In an embodiment, the bi-metallic spring may be comprised of two components (e.g., two different metals) fastened together and having different coefficients of thermal expansion. Heat flow from theheat source 100 may be thermally transferred along thecylinder 136 and/orrod 140 and into the bi-metallic spring result in mechanical displacement (e.g., curvature) of the bi-metallic spring due to the differences in coefficients of thermal expansion and causing theheat load 106 to be moved the axially away from theheat source 100 and thereby increasing the thermal resistance to heat flow from theheat source 100 to the head load. -
FIGS. 5A-5B illustrate a further embodiment of the variable-thermal-resistance mounting system 130 configured in a manner similar to the embodiment ofFIGS. 4A-4B and wherein thebellows 192 may provide for direct control of the thermal resistance. In the embodiment shown inFIGS. 5A-5B , thebellows 192 may be directly coupled to thecylinder 136 end and theheat load 106 orthermal device 102. In addition, thebellows 192 may be thermally isolated from a thermally low-conductive shaft 190 that may be slidable within ashaft guide 198 mounted within thecylinder 136. In an embodiment, theshaft guide 198 may be formed of material having a relatively low thermal conductivity to minimize heat flow from thecylinder 136 into therod 140. Heat from theheat source 100 may flow along thecylinder 136 walls and into the bellows fluid 194. The heating of the bellows fluid 194 may cause axial displacement of therod 140 from a retracted position (FIG. 5A ) to any one of a variety of different extended positions 154 (FIG. 5B ) as described above. In any embodiment, the bellows fluid 194 may have a composition that becomes less thermally conductive with an increase in the temperature of the bellows fluid 194. In this manner, the system may provide a non-linear change in thermal resistance in response to increases in temperature at theheat source 100. -
FIGS. 6A-6B illustrate an embodiment of the variable-thermal-resistance mounting system 130 configured similar to the embodiment ofFIGS. 5A-5B and wherein thecylinder 136 and therod 140 have a vernier-type structure 212. In this regard, thecylinder 136 and/or therod 140 may each include one or more axially-spaced, segmentedthermal contacts 210. The segmentedthermal contacts 210 may provide a further means for tailoring the rate of change of the thermal resistance of the system with changes in the temperature of theheat source 100. For example, thecylinder 136 and therod 140 inFIGS. 6A-6B are shown as each having two sets of segmentedthermal contacts 210 positioned along thecylinder 136 between thecylinder 136 and therod 140. Thethermal contacts 210 may have defined thermal resistances. Thethermal contacts 210 inFIGS. 6A-6B are of unequal length which may result in a non-linear change in heat resistance with changes inextension length 156 of therod 140 relative to thecylinder 136. Advantageously, the vernier-type structure 212 disclosed herein may provide a means for significantly changing the thermal resistance of the mounting system with minimal displacements (e.g., several millimeters) of therod 140. -
FIGS. 7A-7B illustrate an embodiment of the variable-thermal-resistance mounting system 130 with the vernier-type structure 212 of therod 140 andcylinder 136 having alinear configuration 216. In this regard, therod 140 and thecylinder 136 may each include axially-spacedthermal contacts 210 that may be substantially equal in length. The segmentedthermal contacts 210 of therod 140 may be sized to provide a sliding fit with the segmentedthermal contacts 210 of thecylinder 136. Thethermal contacts 210 in any embodiment disclosed herein may preferably have a relatively high surface hardness to minimize wear of thethermal contacts 210 during sliding movement. In an embodiment, thethermal contacts 210 may be formed of nickel-plated copper, aluminum, steel, or other material. Thethermal contacts 210 may optionally be provided with an oxidized or anodized surface. The substantially equal lengths of the axially-spacedthermal contacts 210 may result in a linear decrease in thecontact surface area 144 between thethermal contacts 210 when therod 140 is axially displaced relative to thecylinder 136. In this manner, the substantially equal lengths of the axially-spacedthermal contacts 210 may result in a linear change in thermal resistance upon axial displacement of therod 140. -
FIGS. 7C-7D illustrate an embodiment of the variable-thermal-resistance mounting system 130 with the vernier-type structure 212 having anon-linear configuration 214. In this regard, the axially-spacedthermal contacts 210 for each one of therod 140 and thecylinder 136 may be of unequal lengths. The unequal lengths of the axially-spacedthermal contacts 210 may result in a non-linear decrease incontact surface area 144 between thethermal contacts 210 when therod 140 is axially displaced relative to thecylinder 136. In this manner, the unequal lengths of thethermal contacts 210 may provide a non-linear change in thermal resistance between theheat source 100 and theheat load 106. - In
FIGS. 7A-7D , the vernier-type structure 212 arrangement for therod 140 and thecylinder 136 may advantageously provides a means for adjusting the thermal resistance of the system independent of axial displacement of therod 140 relative to thecylinder 136. In this regard, the total contact surface area between thethermal contacts 210 at any given axial position of therod 140 relative to thecylinder 136 may be determined by the quantity ofthermal contacts 210, the geometry at the interface between thethermal contacts 210, the thermal contact length, the thermal contact width, and the thickness of thethermal contacts 210. In addition, the relative thermal resistance at a given axial displacement of therod 140 may be determined by a combination of the thermal contact sizes, shapes, and configurations, the material of thethermal contacts 210, and other parameters which may collectively provide a wide range of capability for adjusting the thermal resistance of thesystem 130. -
FIG. 8 illustrates an embodiment of a variable-thermal-resistance mounting system 130 that may include achimney 230 arrangement for convective cooling of a heat load, 106, anelectronics enclosure 112, athermoelectric generator 110, or anythermal device 102 that may be included with aheat load 106 or which may be thermally coupled to theheat load 106 or located adjacent to theheat load 106. InFIG. 8 , thechimney 230 may be applied to any of the above-describedmounting system 130 embodiments. Theheat shield 158 may be configured to form a shaft orchimney 230 having an open bottom end 232 and an opentop end 234. The heating of the thermal device 102 (e.g., the thermoelectric generator 110) may cause cool air 236 to be drawn into the bottom end of thechimney 230. The cool air 236 may pass over theelectronics enclosure 112 and/or thethermoelectric generator 110 for convective cooling thereof. The air may exit out of the top end of thechimney 230. -
FIGS. 9A-9B illustrates an embodiment of an actively-controlled variable-thermal-resistance mounting system 130 and which may include amotor 160 for controlling the extension or axial displacement of therod 140 relative to thecylinder 136. In an embodiment, themotor 160 may comprise a direct current (DC) motor 160 although any type of motor may be used. Themotor 160 may be powered by athermoelectric generator 110 although themotor 160 may be powered by other means such as a battery. Themotor 160 may be coupled to a drive mechanism such as ascrew drive mechanism 162. Themotor 160 may receive a signal from the thermal device 102 (e.g., heat load 106) such as when theheat load 106 reaches a predetermined temperature. For example, a signal may be provided to themotor 160 when theheat load 106 reaches an upper limit temperature or when the warm-side temperature 114 or range is exceeded causing activation of themotor 160 to axially extend therod 140 further out of thecylinder 136 from a retracted position (FIG. 9A ) toward an extended position 154 (FIG. 9B ). In this manner, themotor 160 may move theheat load 106 away from theheat source 100 and thereby decrease heat flow into theheat load 106. In some embodiments, when theheat load 106 reaches a low temperature limit such as when the warm-side temperature 114 falls below a predetermined value or range, a signal may activate themotor 160 to retract therod 140 into thecylinder 136 to move theheat load 106 toward theheat source 100. In this manner, themotor 160 may actively control the displacement of therod 140 relative to thecylinder 136 to adjust the thermal resistance therebetween and thereby control heat flow from theheat source 100 to theheat load 106. -
FIGS. 10-11 illustrate embodiments of a variable-thermal-resistance mounting system 130 having athermal divider 250 positioned between the thermal device 102 (e.g., heat load 106) and theheat source 100. InFIG. 11 , thethermal device 102 may be configured as athermoelectric generator 110 which may have aseparate electronics enclosure 112 or which may integrate the electronics components within thethermoelectric generator 110. Thethermal divider 250 may be included in applications where theheat source 100 operates at a relatively high upper temperature. The embodiment may further include aheat shield 158 as described above and located between theheat load 106 and thethermal divider 250 to further minimize radiative heating of thethermal device 102. Advantageously, thethermal divider 250 may includeradiator fins 252 for rejecting heat to the ambient environment. In this manner, the thermal device 102 (e.g., thermoelectric generator 110) may be protected from relatively high heat flow. The ratio of heat flow through the radiator to heat flow through theheat load 106 may be adjustable by adjusting the displacement of therod 140. - In some embodiments disclosed herein, the arrangement of the
rod 140 andcylinder 136 may be configured such that therod 140 is connected to theheat source 100 and thecylinder 136 is connected to the thermal device 102 (e.g.,heat load 106,thermoelectric generator 110, etc.). For example, in contrast to the embodiment ofFIGS. 1A-1B , therod 140 may be fixedly coupled on one end to theheat source 100, and thecylinder 136 may be fixedly coupled on an opposite end to thethermal device 102. Thecylinder 136 may be displaced relative to therod 140 by any one of the above-described embodiments including by manual means, passive means (e.g., with a fluid-filled cylinder or fluid-filled bellow), or active means (e.g., with a motor). - Although each of the embodiments is described as having a
single rod 140 sliding within asingle cylinder 136, the mounting system may be provided with two ormore rods 140 arranged in parallel and sliding within two ormore cylinders 136. In any one of the above described embodiments, a temperature-indicating device such as a strip may be provided on an exterior of thecylinder 136 or thethermal device 102 to provide an indication of the temperature of the system. For example, a liquid crystal strip may be mounted on an exterior of thethermal platform 104 of theheat load 106 or on an exterior of athermoelectric generator 110. The strip may change color corresponding to changes in temperature and may provide a visual indication to an observer as to whether thethermal platform 104 is in the desired temperature range. - Referring to
FIG. 12 , shown is a flow chart illustrating one or more operations that may be included in amethod 300 of regulating heat flow between aheat source 100 and aheat load 106 such as athermoelectric generator 110. Step 302 of themethod 300 may include coupling arod 140 to aheat source 100 or aheat load 106, and coupling acylinder 136 to the remainingheat source 100 or theheat load 106. For example, as illustrated inFIGS. 1A-6 and 8-11, theheat source 100 may be coupled to an end of thecylinder 136 and theheat load 106 may be coupled to an end of therod 140. However, the variable-thermal-resistance mounting system 130 may be configured with theheat source 100 may be coupled to an end of therod 140 and theheat load 106 coupled to an end of thecylinder 136. In some embodiments, theheat source 100 may be coupled to therod 140 or thecylinder 136 using amechanical mount 132 formed of material providing a desired level of thermal resistance between theheat source 100 and thecylinder 136 orrod 140. Theheat load 106 may be coupled to therod 140 or thecylinder 136 using athermal platform 104 comprised of one or more materials or layers of material each having predetermined thermal conductivity value as discussed above, and/or a selected geometry (e.g., cross-sectional geometries and/or thicknesses) selected in consideration of a desired operating temperature range of theheat load 106 or the electronics. - Step 304 of the
method 300 may include axially moving therod 140 relative to thecylinder 136 between acollapsed position 152 and anextended position 154 as shown inFIGS. 1A-1B . For example, theheat load 106 may be manually pulled away from theheat source 100 which may result in therod 140 being extended at least partially out of thecylinder 136. Therod 140 may be axially moved to any position between thecollapsed position 152 and theextended position 154. Extending therod 140 at least partially out of thecylinder 136 may result in changing (e.g., decreasing) thecontact surface area 144 between therod 140 andcylinder 136. - Step 306 of the
method 300 may include changing a heat flow between theheat source 100 and theheat load 106 in response to moving therod 140 between thecollapsed position 152 and theextended position 154. For example, when therod 140 is extended out of thecylinder 136, the change (e.g., decrease) incontact surface area 144 may result in altering (e.g., decreasing) heat flow between theheat source 100 and theheat load 106 as a means to at least initially set or adjust the warm-side temperature 114 of theheat load 106. In some embodiments, themethod 300 may optionally include mounting a heat shield 158 (FIGS. 1A-1B ) and/or a thermal divider 250 (FIG. 10 ) between theheat load 106 and theheat source 100 as shown inFIGS. 1A , 1B, and 2, for reducing radiative heat transfer to theheat load 106. - Step 308 of the
method 300 may include adjusting the warm-side temperature 114 of theheat load 106 in response to changing the heat flow. In some examples, the warm-side temperature 114 may be initially adjusted to a substantially optimal value which, in the present disclosure, may be described as within a relatively small range of the optimal value. In some embodiments, the warm-side temperature 114 may be initially adjusted by manually pulling therod 140 out of thecylinder 136 to a position that initially results in substantially achieving the optimal warm-side temperature 140 or relatively small range based on a given temperature of theheat source 100. If the heat source temperature changes, then further adjustment of the position of therod 140 may be required to accordingly adjust the warm-side temperature 114. In an embodiment, the method may include clamping or fixing the position of therod 140 relative to thecylinder 136 after the warm-side temperature 114 has been adjusted. For example, therod 140 may be clamped to thecylinder 136 such as by using amechanical clamp 146, an embodiment of which is shown inFIG. 1C described above. - In some embodiments, the variable-thermal-
resistance mounting system 130 may be operated in a passive manner without manually or actively displacing (e.g., manually or actively pulling) therod 140 axially outwardly from thecylinder 136 or manually or actively (e.g., with a motor—FIGS. 9A-9B ) pushing therod 140 inwardly back into thecylinder 136. For example, certain passive embodiments of the variable-thermal-resistance mounting system 130 may include acylinder 136 containing acylinder fluid 172 such as a gas, a liquid, or a 2-phase fluid as shown inFIGS. 3A-3B and described above. In such embodiments, themethod 300 may further include heating thecylinder fluid 172 with heat from theheat source 100, and expanding thecylinder fluid 172 when heated causing an increase incylinder fluid pressure 176 within thecylinder 136. The increase incylinder fluid pressure 176 may cause therod 140 to at least partially extend out of thecylinder 136, resulting in an increase in thermal resistance between therod 140 andcylinder 136. The increase in thermal resistance may result in a reduction in heat flow between theheat source 100 and theheat load 106. - The
method 300 of varying the thermal resistance between aheat load 106 and aheat source 100 may also be implemented in a passive manner using a variable-thermal-resistance mounting system 130 having abellows 192 containing a bellows fluid 194. Thebellows 192 may be mounted between theheat load 106 and thecylinder 136 as shown inFIGS. 3A-7D . In such an embodiment, themethod 300 may include heating the bellows fluid 194 with the heat flow from theheat source 100, expanding the bellows fluid 194 when heated causing thebellows 192 to increase in length, and extending therod 140 out of thecylinder 136 due to the increasing length of thebellows 192. Themethod 300 may further include increasing the thermal resistance between therod 140 and thecylinder 136 due to the extension of therod 140, and reducing the heat flow between theheat source 100 and theheat load 106 as a result of the increase in the thermal resistance. - In some embodiments, the
bellows 192 may be thermally isolated from therod 140 in a manner such that the heat flow from theheat source 100 may be conducted along thecylinder 136 and directly into the bellows fluid 194 as shown inFIGS. 4A-6B and described above. In other embodiments, thecylinder 136 and therod 140 may each include at least two axially-spaced segmentedthermal contacts 210 forming a vernier-type structure 212. Thethermal contacts 210 of therod 140 may be slidably engaged to thethermal contacts 210 of thecylinder 136. The vernier-type structure 212 may have alinear configuration 216 with substantially equal lengththermal contacts 210 for each of therod 140 andcylinder 136 as shown inFIGS. 7A-7B . For alinear configuration 216, themethod 300 of varying the thermal resistance between theheat source 100 andheat load 106 may include axially moving therod 140, and linearly changing the thermal resistance of thecylinder 136 androd 140 in response to axially moving therod 140. For anon-linear configuration 216 214 of the vernier-type structure 212 wherein each one of therod 140 andcylinder 136 has unequal lengththermal contacts 210 as shown inFIGS. 7C-7D , axially moving therod 140 relative to thecylinder 136 may result in linearly changing the thermal resistance of thecylinder 136 androd 140. - In some embodiments, the variable-thermal-
resistance mounting system 130 may be actively operated to vary the thermal resistance between theheat source 100 andheat load 106. For example, in the embodiment shown inFIGS. 9A-9B having amotor 160 operatively coupled to therod 140, themethod 300 may include actively displacing or axially moving therod 140 relative to thecylinder 136. For example, themethod 300 may include using a motor 160 (e.g., a D.C. motor) coupled to therod 140 with ascrew drive mechanism 162 to actively axially displace therod 140 relative to thecylinder 136. In some embodiments, the method may include powering themotor 160 using thethermoelectric generator 110 which may be theheat load 106 for which the temperature is being regulated using the variable-thermal-resistance mounting system 130. In other embodiments, themotor 160 may be powered using one or more batteries or another power source. - In some embodiments, the
method 300 may include mounting theheat load 106 within achimney 230 as shown inFIG. 8 . Thechimney 230 may be formed using one ormore heat shields 158. In addition to axially displacing therod 140 to control the heat flow from theheat source 100 into theheat load 106, thechimney 230 may further facilitate controlling the temperature of theheat load 106. For example, themethod 300 may include drawing cool air 236 into the open bottom end 232 of thechimney 230, passing the cool air 236 over a heat load such as athermoelectric generator 110 and/orelectronics enclosure 112 to convectively cool thethermoelectric generator 110 and/orelectronics enclosure 112, and discharging the air out of a top end of thechimney 230. - Additional modifications and improvements of the present disclosure may be apparent to those of ordinary skill in the art. Thus, the particular combination of parts described and illustrated herein is intended to represent only certain embodiments of the present disclosure and is not intended to serve as limitations of alternative embodiments or devices within the spirit and scope of the disclosure.
Claims (21)
1. A variable-thermal-resistance mounting system, comprising:
a cylinder coupled to one of a heat source and a heat load, the heat load having an optimal warm-side temperature;
a rod movably engaged to the cylinder and being coupled to a remaining one of the heat source and heat load; and
the rod being axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in heat flow between the heat source and the heat load such that the warm-side temperature of the heat load is initially set at a substantially optimal value.
2. The system of claim 1 , wherein:
the rod extending out of the cylinder by an extension length when the rod is in an extended position;
the cylinder has a cylinder inner surface;
the rod having a rod outer surface in contact with the cylinder inner surface along a contact surface area; and
the contact surface area increasing and decreasing in correspondence with a respective increase and decrease in the extension length.
3. The system of claim 1 , wherein:
the heat load comprises a thermoelectric generator.
4. The system of claim 1 , further comprising:
a mechanical clamp configured to axially lock an axial position of the rod relative to the cylinder.
5. The system of claim 1 , further comprising:
a mechanical mount coupling the heat source to the rod or the cylinder and being formed of material providing a desired level of thermal resistance between the heat source and the cylinder or rod.
6. The system of claim 1 , further comprising:
a thermal platform coupling the heat load to the rod or the cylinder; and
the thermal platform being formed of one or more thermal materials having a predetermined thermal conductivity and geometry selected to provide a desired operating temperature range of the heat load.
7. The system of claim 1 , wherein:
the cylinder contains a cylinder fluid that expands when heated causing an increase in pressure within the cylinder; and
the increasing cylinder pressure extending the rod out of the cylinder causing an increase in a thermal resistance between the rod and cylinder and a reduction in the heat flow between the heat source and the heat load.
8. The system of claim 1 , further comprising:
a bellows located between the heat load and the cylinder, the bellows containing a bellows fluid that expands when heated causing the bellows to increase in length; and
the increase in bellows length causing extension of the rod and a reduction in heat flow between the heat source and the heat load.
9. The system of claim 8 , wherein:
the bellows fluid contracts upon cooling causing the bellows to decrease in length; and
the decrease in bellows length resulting in retraction of the rod and an increase in heat flow between the heat source and the heat load.
10. The system of claim 1 , wherein:
the cylinder and the rod each include at least two segmented contacts in axially slidable engagement with one another; and
the segmented contacts being sized and configured such that axial movement of the rod causes a change in thermal resistance of the cylinder and rod.
11. The system of claim 10 , wherein:
the cylinder and rod each have at least two segmented contacts axially spaced from one another and of substantially equal length such that axial movement of the rod causes a linear change in thermal resistance of the cylinder and rod.
12. The system of claim 10 , wherein:
the cylinder and rod each have at least two segmented contacts axially spaced from one another and of unequal length such that axial movement of the rod causes a non-linear change in thermal resistance of the cylinder and rod.
13. The system of claim 1 , wherein:
a motor coupled to the rod and actively controlling axial displacement of the rod relative to the cylinder for adjusting a thermal resistance between the rod and the cylinder.
14. A variable-thermal-resistance mounting system, comprising:
a cylinder coupled to a heat source;
a rod movably engaged to the cylinder and being coupled to a thermoelectric generator having an optimal warm-side temperature; and
the rod being axially slidable relative to the cylinder between a collapsed position and an extended position in a manner causing a change in thermal resistance between the heat source and the thermoelectric generator such that the warm-side temperature of the thermoelectric generator is initially set at a substantially optimal value.
15. A method of regulating heat flow between a heat source and a heat load, comprising the steps of:
coupling a rod to one of a heat source and a heat load, and coupling a cylinder to a remaining one of the heat source and the heat load;
axially moving the rod relative to the cylinder between a collapsed position and an extended position;
changing a heat flow between the heat source and the heat load in response to moving the rod between the collapsed position and the extended position; and
adjusting a warm-side temperature of the heat load in response to changing the heat flow.
16. The method of claim 15 , wherein the cylinder has a cylinder inner surface, the rod has a rod outer surface slidably engaged to the cylinder inner surface along a contact surface area, the method further comprising:
extending the rod out of the cylinder;
changing the contact surface area in correspondence with extending the rod; and
altering the heat flow between the heat source and heat load in response to changing the contact surface area.
17. The method of claim 15 , wherein the cylinder contains a cylinder fluid, the method further comprising:
heating the cylinder fluid with heat from the heat source;
expanding the cylinder fluid when heated causing an increase in pressure within the cylinder;
extending the rod out of the cylinder in response to the increasing cylinder pressure;
increasing a thermal resistance between the rod and cylinder in response to pushing the rod; and
reducing the heat flow between the heat source and the heat load in response to increasing the thermal resistance.
18. The method of claim 15 , wherein a bellows is mounted between the heat load and the cylinder, the bellows containing a bellows fluid, the method further comprising:
heating the bellows fluid with heat from the heat source;
expanding the bellows fluid when heated causing the bellows to increase in length;
extending the rod at least partially out of the cylinder in response to increasing a bellows length;
increasing a thermal resistance between the rod and cylinder in response to extending the rod; and
reducing the heat flow between the heat source and the heat load in response to increasing the thermal resistance.
19. The method of claim 18 , further comprising:
allowing the bellows fluid to cool;
contracting the bellows fluid upon cooling resulting in the bellows decreasing in length;
retracting the rod at least partially into the cylinder in response to decreasing the bellows length;
decreasing a thermal resistance in response to retracting the rod; and
increasing the heat flow between the heat source and the heat load in response to decreasing the thermal resistance.
20. The method of claim 15 , wherein the cylinder and the rod each include at least two axially-spaced segmented contacts of substantially equal length and in axially slidable engagement with one another, the method further comprising;
axially moving the rod relative to the cylinder; and
linearly changing a thermal resistance of the cylinder and rod in response to axially moving the rod.
21. The method of claim 15 , wherein the cylinder and the rod each include at least two axially-spaced segmented contacts of unequal length and in axially slidable engagement with one another, the method further comprising;
axially moving the rod relative to the cylinder; and
non-linearly changing a thermal resistance of the cylinder and rod in response to axially moving the rod.
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US14/084,587 US20140137570A1 (en) | 2012-11-19 | 2013-11-19 | Variable thermal resistance mounting system |
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US201261728233P | 2012-11-19 | 2012-11-19 | |
US14/084,587 US20140137570A1 (en) | 2012-11-19 | 2013-11-19 | Variable thermal resistance mounting system |
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