WO2015100007A1

WO2015100007A1 - High temperature rotary joint apparatus and methods

Info

Publication number: WO2015100007A1
Application number: PCT/US2014/069341
Authority: WO
Inventors: Brian LUPTOWSKI
Original assignee: Abengoa Solar Llc
Priority date: 2013-12-26
Filing date: 2014-12-09
Publication date: 2015-07-02

Abstract

Embodiments include rotary joints, valve stems and bonnets and methods of connecting pipe segments which must be rotated with respect to each other during normal use. The disclosed rotary joint embodiments are useful when a high temperature fluid is contained within the adjacent pipe segments. Selected rotary joint embodiments include arrays of heat pipes in thermal communication with the seal regions of the rotary joint housing elements, which heat pipes provide for the maintenance of the rotary joint seal within a selected high and low temperature range.

Description

HIGH TEMPERATURE ROTARY JOINT APPARATUS AND METHODS

TECHNICAL FIELD

[0001] The embodiments disclosed herein relate to rotary joints or similar devices and methods of controlling the temperature of a seal within a rotary joint. The disclosed embodiments more particularly relate to rotary joints and similar devices suitable for use in high temperature fluid process systems such as concentrated solar power (CSP) electricity generation systems.

BACKGROUND

[0002] Many industrial processes require a system of pipes and associated equipment to maintain and control the flow of a process fluid. Some process piping systems require rotational motion between one pipe or piece of equipment relative to another pipe or piece of equipment. Typically, rotation is required along the axis of the piping while preventing or minimizing leakage of the process fluid flowing through the joint. The design of fluid-tight rotary joints can be particularly complicated if the process fluid must be maintained at a high temperature or maintained within a specific temperature range. Process fluids which are caustic or reactive can also present rotary joint design challenges.

[0003] Various configurations of a high temperature rotary joint are known in the prior art which include supplemental apparatus designed to cool the rotary joint structure. For example, U.S. Patent 3,057,646 (Brumagim) describes a solution for cooling the seal material of a rotary joint with a liquid coolant circulated through various annular passages within flanges extending away from the primary fluid passageway. The Brumagim flanges increase the radial distance between the seal material and process fluid and also facilitate heat transfer with a cooling liquid or gas. Although the Brumagim configuration may be used to maintain the seal material within a selected temperature range, the disclosed apparatus requires a supply of a second coolant liquid to achieve controlled cooling of the seal material. Therefore, a separate fluid circuit with one or more pumps and heat exchangers is required to reject heat collected from the joint. In addition, the selected cooling fluid must have a thermal stability similar to that of the process fluid.

[0004] Other rotary joint designs rely upon air cooling to limit the temperature of the seal material when the rotary joint is used with a high temperature process fluid. For example, U.S. Patent 4,154,446 (Usry) describes a cooled rotary joint for use with a steam system. The Usry joint structure provides both liquid cooling and air cooling via fins. The Usry apparatus is designed to maintain the seal material temperature at a point well below the steam temperature in use. A flange similar to that described in Brumagim is utilized but the Usry flange is significantly extended in an axial direction. The extended flange and accompanying insulation is designed to limit thermal conduction from the steam toward the seal area.

[0005] As noted above, a liquid cooling approach requires a separate fluid circuit with a suitable cooling fluid, pump and heat exchanger to reject the heat collected from the joint. Air cooling is not particularly useful to limit the minimum temperature experienced by the packing material. In addition, air cooling is not well suited for high performance over a large range of internal and external boundary conditions. In air-cooled designs, the rate of heat transfer out of the seal area is dependent on the process fluid and ambient boundary conditions, including air temperature, fluid velocity, and/or precipitation. This results in a very limited ability to control the seal pack temperature with most air-cooled designs.

[0006] For some process fluids of particular use in CSP systems, such as molten nitrite salts, existing seal materials are only compatible with the process fluid at temperatures below the desired process temperature. In addition, the characteristics of a process fluid, such as the freeze point, can set a lower bound on the minimum operating temperature which must be maintained in a joint before process fluid freezing or another undesirable event occurs. Traditional finned joints, which passively reject heat to reduce the seal temperature, cannot maintain the seal pack area within a narrow temperature range over a large range of internal and external boundary conditions.

[0007] The embodiments disclosed herein are directed toward overcoming one or more of the problems discussed above.

SUMMARY OF THE EMBODIMENTS

[0008] One embodiment disclosed herein is a rotary joint for use connecting pipe segments or associated equipment where one segment must be rotated with respect to the other during normal use. The disclosed rotary joint embodiments are particularly useful when a high temperature fluid is contained within the adjacent pipe segments.

[0009] One embodiment of rotary joint includes an inner housing defining the first portion of a fluid passageway. The inner housing also includes an inner bearing surface and an inner seal surface. The rotary joint also includes an outer housing defining a second portion of the fluid passageway. The outer housing includes an outer bearing surface and an outer seal surface. The two housing portions are mated with one or more bearings and a seal. The bearings are in contact with the inner and outer housing bearing surfaces such that the bearings define a rotational axis about which one of the inner housing or the outer housing may be rotated with respect to the other housing portion. The seal is provided in contact with the inner seal surface and the outer seal surface. The seal provides a fluid tight seal between the inner housing and outer housing at all times, but in particular when the inner housing or the outer housing is rotated about the rotational axis. In addition, the rotary joint includes one or more heat pipes in thermal contact with the inner housing near the inner seal surface and one or more heat pipes in thermal contact with the outer housing near the outer seal surface. As used herein, the phrase, "in thermal contact with" is defined as any type of physical connection where heat may be transferred from the housing element or region to the associated heat pipe. The inner and outer heat pipes provide for the maintenance of the seal temperature within a defined temperature range.

[0010] In certain embodiments, the rotary joint includes an annular array of multiple inner heat pipes terminating in the inner housing and arranged concentrically to the inner seal surface. The rotary joint also includes an annular array of multiple outer heat pipes terminating in the outer housing and arranged concentrically to the outer seal surface. In some embodiments the inner and outer heat pipes are implemented with gas-loaded variable conductance heat pipes which includes an evaporator end embedded within the associated housing element and a condenser end extending from the associated housing element into contact with a cold sink medium, typically the ambient air.

[0011] The rotary joint may include thermal insulation around some or all of the inner or outer housing elements. In certain embodiments, the insulation may be implemented with a movable insulation shroud that may be selectively positioned to cover or expose the condenser end of gas-loaded variable conductance heat pipes. Additional temperature control may be provided by one or more fans positioned and configured to move air over the condenser end of at least one heat pipe. The rotary joint may be provided with a temperature sensor in thermal communication with the seal, the inner seal surface or the outer seal surface and a control system to control the fan and move air or another cold sink medium over the condenser end of selected heat pipes in response to the seal temperature as detected by the temperature sensor. [0012] The rotary joint may be implemented in various configurations including but not limited to a fin configuration where each of the inner and outer housings includes an inner conduit wall defining the fluid passageway through the joint and each housing also includes an annular extension extending radially outward from the conduit wall. The radial extensions associated with each conduit wall support an inner housing radial structure and an outer housing radial structure respectively. Thus, the inner and outer annular extensions provide for physical separation between the conduit walls and the inner housing and outer housing radial structures. In one embodiment, the bearing surfaces, seal surfaces and heat pipes are all operatively associated with the inner and outer housing radial structures.

[0013] The rotary joint may be provided with a seal compression element which provides for a selected or adjustable compression to be applied to the seal, thereby assuring a substantially fluid-tight fluid passageway without unduly limiting the ability of the inner and outer housing members to be rotated with respect to each other. In one embodiment, the seal compression element includes a seal compression ring in physical contact with the seal, one or more seal compression bolts and a seal seat bushing. The seal compression bolts provide for the seal compression ring to be drawn against the seal opposite the seal seat bushing, thereby compressing the seal.

[0014] Alternative embodiments include a high-temperature valve stem and bonnet having some or all of the elements described herein with respect to a rotary joint. Other embodiments include methods of providing, implementing or using a high-temperature rotary joint or valve stem and bonnet in fluid process applications optimized for use with high- temperature fluids.

[0015] One particular high-temperature process which may be implemented with the disclosed rotary joints or similar apparatus is a power generation process where heat transfer fluid is heated by concentrated solar flux reflected from a parabolic trough solar reflector. A parabolic trough reflector includes a parabolic reflecting surface which is configured to reflect and concentrate sunlight on a receiver tube or pipe. The parabolic trough is typically rotated through a daily arc related to the motion of the sun from dawn to dusk. Therefore, one or more rotary joints are required to connect each bank of reflectors to other elements of the concentrated solar power generation system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Fig. 1 is a section view of a rotary joint as disclosed herein.

[0017] Fig. 2 is an isometric view of a rotary joint showing insulation. [0018] Fig. 3 is an isometric view of the insulation element of the rotary joint of Fig.

2.

[0019] Fig. 4 is an isometric view of the rotary joint of Fig. 2 with the insulation element removed.

[0020] Fig. 5 is an isometric view of the inner housing, inner seal surface and bearing elements of the rotary joint of Fig. 2.

[0021] Fig. 6 is an isometric view of the outer housing, bearing, seal and seal compression ring elements of the rotary joint of Fig. 2

[0022] Fig. 7 is an isometric view of the outer housing and seal elements of the rotary joint of Fig. 2

[0023] Fig. 8 is an alternative isometric view of the rotary joint of Fig. 2

[0024] Fig. 9 is an alternative isometric view of the rotary joint of Fig. 2

[0025] Fig. 10 is a schematic diagram view of a CSP system featuring a parabolic trough reflector and rotary joint as disclosed.

DETAILED DESCRIPTION

[0026] Unless otherwise indicated, all numbers expressing quantities of ingredients, dimensions, reaction conditions and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about".

[0027] In this application and the claims, the use of the singular includes the plural unless specifically stated otherwise. In addition, use of "or" means "and/or" unless stated otherwise. Moreover, the use of the term "including", as well as other forms, such as "includes" and "included", is not limiting. Also, terms such as "element" or "component" encompass both elements and components comprising one unit and elements and components that comprise more than one unit unless specifically stated otherwise.

[0028] All the features described in this specification (including the claims, description and drawings) and/or all the steps of the described method can be combined in any combination, with the exception of combinations of mutually exclusive features and/or steps.

[0029] Various embodiments are disclosed herein including, but not limited to, high temperature rotary joint embodiments, valve stem embodiments, fluid process system embodiments and methods of providing, implementing or using the described apparatus. Although much of the following description specifically concerns high-temperature rotary joint embodiments, the described structures and methods are applicable to other fluid process and fluid control apparatus such as valve stems. The described rotary joint embodiments are suitable for use in any fluid processing system, but the described embodiments are particularly well-suited for use in a concentrated solar power (CSP) electricity generation system.

[0030] For example, one or more rotary joints are typically associated with each row of parabolic trough reflector elements in a parabolic trough-based CSP system. The trough reflectors served to concentrate reflected sunlight on a receiver containing a heat transfer fluid. The heated heat transfer fluid is caused to flow from the receiver to other elements of the CSP system through a heat transfer fluid circuit. The trough reflectors typically must be pivoted through a daily arc to track the position of the sun and efficiently concentrate solar flux on the receiver. Other system elements are stationary. Therefore, rotary joints suitable for passing high temperature heat transfer fluids are required between banks of parabolic trough reflectors and other CSP system elements.

[0031] In general, a rotary joint is used to connecting adjacent pipe segments or other apparatus where one segment or the other must be rotated in use. The described rotary joint embodiments are operatively positioned between adjacent components and/or piping handling high-temperature materials where the temperature of the seal pack material utilized in the joint must be maintained within a defined and potentially fairly narrow temperature range. With certain seal material and process fluid combinations, seal temperatures equal to the process fluid temperature must be avoided to limit seal breakdown. In addition relatively lower seal temperatures must be avoided to prevent process fluid solidification.

[0032] CSP processes, for example, may be implemented with a heat transfer fluid such as molten nitrate or nitrite salts or molten metals which are liquid at operational temperatures, but which solidify at temperatures well above normal ambient temperatures. In addition, certain heat transfer fluids are highly reactive with otherwise useful seal materials at operational temperatures. Accordingly, the high temperature rotary joints described herein are configured to maintain the joint seals and associated surfaces within a narrow range of operating temperatures which are below the maximum process fluid temperature in normal use but above a temperature at which the process fluid freezes. Traditional finned joints, which passively reject heat to reduce the seal temperature, cannot adequately maintain the seal pack area within a relatively narrow temperature range over a large range of internal and external boundary conditions. [0033] Fig. 1 is a cross section view of one embodiment of rotary joint 100 configured to allow rotation between adjacent system components while maintaining a joint seal within a selected temperature range. The Fig. 1 embodiment is optimized for use in a CSP system utilizing a relatively high temperature heat transfer fluid such as molten nitrate or molten nitrite salt. A dynamic carbon-based seal material, such as Garlock 1200-PBI would provide an appropriate seal, however a carbon-based seal material such as Garlock 1200-PBI will chemically react with the molten nitrate or nitrite salts at the optimum working temperature of a CSP system utilizing this type of heat transfer fluid. Furthermore, mechanical damage can occur to the seal material from crystallization of the heat transfer fluid at temperatures only somewhat below the optimum working temperature. Therefore, the described rotary joint 100 is configured to maintain the temperature of the seal pack area within a specific range to avoid damage to the seal material.

[0034] The rotary joint 100 of Fig. 1 includes an inner housing 102 and an outer housing 104, one of which is typically welded or otherwise attached to an adjacent fixed pipe with the other housing welded to or otherwise attached to adjacent rotating pipe. Either housing may be attached to the rotating pipe or equipment. The inner housing 102 defines an inner seal surface 106 which is operationally positioned to face an outer seal surface 108 on the outer housing 104. The inner and outer seal surfaces 106, 108 are separated by a gap, which in use is filled by a seal 110 or seal pack as described in more detail below.

[0035] The inner housing 102 includes an inner housing conduit wall 112 which defines the first portion of a fluid passageway 114 through the rotary joint 100. The outer housing 104 similarly includes an outer housing conduit wall 116 which defines the second portion of the fluid passageway 114 through the joint. In the embodiment of Fig. 1 , the seal surfaces 106, 108 are located on concentric fins separated from the conduit walls. The concentric fins are referred to herein as inner housing radial structure 118 and outer housing radial structure 120. The inner and outer housing radial structures 118 and 120 are separated from the inner and outer housing conduit walls 112, 116 and from the high temperature process fluid contained therein, to reduce conductive heat transfer to the seal surfaces 106, 108. The inner and outer housing radial structures 118, 120 are separated from the housing conduit walls 112, 116 by an inner housing annular extension 122 and a corresponding outer housing annular extension 124. Thus, as shown in Fig. 1, the inner housing radial structure 118 and the outer housing radial structure 120 mate with each other to concentrically support the bearing and seal elements away from the fluid passageway 114. [0036] In the Fig. 1 embodiment, axial alignment of the inner housing 102 and the outer housing 104 and the respective seal surfaces is in part maintained via multiple bushings 125 distributed through the seal pack and in part by a bearing assembly 126. The bearing assembly 126 is also located between facing surfaces of the inner housing radial structure 118 and the outer housing radial structure 120. Thus, in the Fig. 1 configuration, an outer race 128 of the bearing assembly 126 is attached to the outer housing 104 with a circular array of bearing race bolts 129. The bearing assembly 126 houses multiple ball bearings 130. Other combinations of bearings, bushings or alternative apparatus may be configured to maintain axial alignment between the housing elements while allowing for relative rotation between the housing parts.

[0037] Axial forces resulting from process fluid pressure act to separate the inner housing 102 and outer housing 104. These forces are resisted by the bearing assembly 126. As a result, a proper operational seal compression is not influenced by the process fluid pressure. On the contrary, seal compression may be actively adjusted and maintained by adjusting a seal compression ring 132 with one or more seal compression bolts 134. As shown in Fig. 1, multiple spring washer packs 136 or another type of spring element may be associated with the tensioning bolts 134.

[0038] In use, a circular array of seal compression bolts 134 may be tightened to draw the seal pack compression ring 132 toward the seal 110 thereby compressing the seal against a fixed seat 138. In this manner, a substantially fluid-tight seal between the inner and outer seal surfaces 106, 108 may be maintained without unduly restricting rotation between the inner and outer housings 102, 104. The spring washer stack 136 or other spring element provides for appropriate compression of the seal 110 over time and as the temperature of the rotary joint changes.

[0039] As noted above, in certain processes, including but not limited to the handling of heat transfer fluid in a CSP system, it is important to maintain the seal 110 of a rotary joint 100 below a temperature at which the integrity of the seal material is compromised and above a temperature at which the heat transfer fluid may solidify or crystallize. Thus, the seal 110 must be maintained within a relatively well-defined temperature range.

[0040] Appropriate seal temperature control is provided in the disclosed embodiments with one or more heat pipes thermally associated with the inner and outer housings 102, 104. The heat pipes are used to increase the heat transfer rate from the seal area. Heat pipes provide certain advantages over the circulating cooling fluid or forced air cooling strategies described in the prior art. In particular, in the Fig. 1 embodiment, the rotary joint 100 includes an annular array of inner heat pipes 139 thermally and mechanically associated with the inner housing 102 and an annular array of outer heat pipes 140 thermally and

mechanically associated with the outer housing 104. A heat pipe is a heat-transfer device that leverages the principles of thermal conductivity and phase transition to efficiently provide for the transfer of heat between two interfaces. At the higher temperature interface of a heat pipe, a liquid is vaporized by absorbing heat from a surface. The vapour then travels along the heat pipe to a cold interface or cold sink, for example the ambient atmosphere, where the vapour condenses back into a liquid thereby releasing latent heat. The condensed liquid then returns to the high temperature interface through a mechanism such as capillary action, and the cycle repeats.

[0041] In the Fig. 1 embodiment, the evaporator portion 142 of each heat pipe is embedded in the inner housing 102 or outer housing 104 in the area of the seal surfaces 106, 108. The evaporator portion 142 of the heat pipe is therefore located at the high temperature interface to effectively remove heat from the seal area. At the opposite end of the heat pipe, fins or other radiating elements are attached to a condenser portion 144 of each heat pipe. The condenser portion 144 is located in a cold interface or cold sink such as the ambient air around the rotary joint 100. Accordingly, the condenser portions 144 of the various heat pipes are positioned to transfer heat to the atmosphere as described above.

[0042] Heat pipes offer a significantly increased heat transfer rate across a specific temperature differential in a compact area as a result of the phase changes occurring within the internal heat pipe working fluid. Because phase change occurs at a well-defined temperature or temperature range for a given internal working fluid, heat pipes are able to maintain nearly constant evaporator temperatures over a wide range of heat flux levels.

Several types of heat pipes can be employed in the disclosed embodiments, including, but not limited to, the heat pipe varieties described below.

[0043] A rotary joint 100 may be implemented with a conventional heat pipe which utilizes a phase change working fluid which has a minimum phase change temperature of about 10-20°C above the minimum operating temperature of the process fluid flowing through the joint, but at least about 10-20°C below the maximum operating temperature of the seal material. A conventional heat pipe may therefore provide for controlled heat loss from the seal area and maintain the seal material temperature within the required temperature range even though the seal is exposed to varying internal process fluid temperatures, flow rates or other conditions while the heat pipes are simultaneously exposed to varying ambient air conditions such as temperature, humidity, wind speed, and/or precipitation. [0044] At temperatures below the phase change temperature of the heat pipe working fluid, heat transfer via the heat pipes is limited to simple conduction through the structural materials of the heat pipe. While this does not set an absolute lower temperature limit, the relative non-performance of heat pipes below the phase change temperature dramatically reduces heat rejection from the seal pack area at temperatures below the phase change temperature of the heat pipe working fluid. Due to the limited number of acceptable working fluids for heat pipes and the phase change temperature of those fluids, the employment of conventional heat pipes in the disclosed rotary joint embodiments may be limited for many high temperature applications.

[0045] More advanced heat pipe designs include variable conductance heat pipes

(VCHP) which offer more flexibility in the selection of working fluids while still providing the desired performance characteristics described herein. VCHPs can be gas-loaded, excess liquid, vapour flow modulated VCHPs or other types. The gas-loaded VCHP design is particularly well suited to implementation with rotary joints used to handle the heat transfer fluids of a parabolic trough type CSP system. The gas-loaded VCHP design limits heat flux through the heat pipe by passively varying the condenser area as a function of the temperature in the seal pack evaporator portion. A VCHP heat pipe-based rotary joint works well because a reasonable increase in condenser size does not typically impact the geometry of the evaporator end which is embedded in the inner and outer housings in the seal pack area.

[0046] Regardless of the heat pipe type utilized, heat pipes are advantageously positioned in an annular array having individual heat pipes positioned at angular increments concentrically around (or within ) the inner and outer seal surfaces respectively. A concentric annular heat pipe configuration reduces variations in the circumferential temperature profile of the sealing surfaces. This configuration therefore reduces deformation of the sealing surface which helps to maintain the seal. Nevertheless, the density and cross-sectional shape of the heat pipes embedded in the seal pack area does influence the temperature profile around the circumference of the seal pack area, which can broaden the effective temperature range maintained in the seal pack.

[0047] In cases where a minor broadening of the temperature range maintained in the seal pack adversely affects the performance of the joint and/or impacts the cost of the joint, an alternative vapour chamber design can be used. A vapour chamber could be embedded in the seal pack regions instead of individual heat pipes. A vapour chamber would provide temperature control similar to that provided by the heat pipe configurations discussed above, but would also act as heat spreader and reduce the variation in temperature profile around the circumference of the seal pack area.

[0048] Alternative embodiments of rotary joint may also include heat tracing cables installed on the outer surface of the joint, below any insulation. This heat tracing would primarily be used to preheat the joint for initial filling of the system with process fluid. The heat tracing could also be used to prevent a freeze event in the joint in certain off-design conditions or to recover from an unanticipated freeze event.

[0049] Figs. 2-9 include selected isometric views of the rotary joint 100 embodiment described with respect of Fig. 1. Figs 2 and 3 additionally show thermal insulation 146 in contact with selected portions of the inner and outer housings 102, 104. In the Fig. 2 embodiment, the thermal insulation 146 limits convective heat loss from some or all rotary joint elements other than the condenser portions 144 of the inner and outer arrays of heat pipes 139, 140. In an alternative embodiment, the thermal insulation may include a movable insulation shroud that can be selectively positioned to cover or expose portions of the rotary joint including but not limited to the condenser portions of one or more heat pipes. Thus, insulation may be utilized to enhance the ability of the rotary joint to maintain the seal elements within a designated temperature range

[0050] In most cases, heat pipes as described herein and conventional heat tracing on the outer surface of the joint, below the insulation, should adequately control the seal pack temperature. In the event further control is needed, an alternative embodiment includes an actuated insulated cover for the exposed portion of the heat pipes and condenser fins. When heat rejection must be limited beyond that offered by the heat pipe performance, the insulated shroud can be retracted via an actuator to completely shield the condenser portion of the heat pipes from ambient conditions (including wind and precipitation).

[0051] Alternative embodiments may include electric cooling fans which can increase air flow over the heat pipe fins in the condenser region 144. This can be used to further increase heat transfer from the seal pack area if natural convection does not provide sufficient cooling of the condenser region 144 of the heat pipes. Any provided electric cooling fans may be controlled by control system in response to a seal region temperature detected by a temperature sensor in thermal communication the rotary joint 100 in the region of the inner or outer seal surfaces 106, 108

[0052] Another alternative embodiment includes the use of heat pipes of any variety embedded around the seal pack area of a valve stem bonnet used in high-temperature applications such as a CSP system. Although the relative motion between valve stem and bonnet can be different from motion anticipated with rotary joint embodiments, heat pipes can be used as described herein to maintain the seal material temperatures within a desired range and therefore to avoid or reduce thermal degradation of the seal or heat transfer material solidification.

[0053] As noted above, the described rotary joint and valve stem/bonnet

embodiments are particularly well-suited for use in high-temperature fluid process systems such as a parabolic trough reflector-based CSP system. CSP systems utilize concentrated sunlight to heat a heat transfer fluid which is directly, or indirectly through one or more heat exchange stages, used to drive one or more power generation cycles. The power cycles occur within machinery including but not limited to turbines and compressors or heat engines which in turn drive electric generators.

[0054] For example, Fig. 10 illustrates a highly simplified CSP system which includes parabolic trough reflectors. The CSP system 1000 featuring a receiver 1002 situated at or within the zone of concentrated solar flux of a parabolic trough reflector 1004. Any commercial CSP implementation would include a large number of individual parabolic trough elements connected in many lengthwise rows. As the parabolic trough reflector (or a row of parabolic trough reflectors) 1004 tracks the relative motion of the sun throughout the day, rotation between pipes associated with the receiver and pipes associated with the balance of the CSP system is facilitated by a rotary joint 1006.

[0055] A primary HTF circuit 1008 carries HTF through the rotary joint 1006 and receiver 1002 where the HTF is heated to an operational temperature. Thermal energy from the HTF may be stored at any point in the HTF circuit, for example in thermal energy storage devices 1010 or 1012 to extend the operational timeframe of the system.

[0056] In the simplified diagram of Fig. 10, the heated HTF is conveyed to a heat exchanger 1014 from the receiver 1002 or from TES 1010 where thermal interchange with the HTF causes the heating of pressurized working fluid flowing in a working fluid circuit 1016.

[0057] The thermal energy of the working fluid is utilized to drive a thermal power cycle 1018. In the particular embodiment of Fig. 10, the thermal power cycle 1018 is represented as a highly simplified Brayton cycle featuring a turbine 1020 and compressor 1022 connected by an axle 1024. Expansion of the heated working fluid within the turbine 1020 converts thermal energy of the working fluid to mechanical energy, thereby outputting work (represented by rotational arrow 1026) which can be utilized to drive an electric generator. Heat 1028 is rejected from the system through an air-cooled condenser 1030. Other types of thermal power cycle or heat engines of any level of complexity may also be driven with thermal energy obtained initially from solar flux concentrated with a parabolic trough reflector having rotation relative to the other system elements facilitated by a rotary joint as described herein.

[0058] Various embodiments of the disclosure could also include permutations of the various elements recited in the claims as if each dependent claim was a multiple dependent claim incorporating the limitations of each of the preceding dependent claims as well as the independent claims. Such permutations are expressly within the scope of this disclosure.

[0059] While the embodiments disclosed herein have been particularly shown and described with reference to a number of alternatives, it would be understood by those skilled in the art that changes in the form and details may be made to the various configurations disclosed herein without departing from the spirit and scope of the disclosure. The various embodiments disclosed herein are not intended to act as limitations on the scope of the claims. All references cited herein are incorporated in their entirety by reference.

Claims

CLAIMS What is claimed is:

1. A rotary joint comprising:

an inner housing defining a first portion of a fluid passageway, the inner housing comprising an inner bearing surface and an inner seal surface; an outer housing defining a second portion of the fluid passageway, the outer housing comprising an outer bearing surface and an outer seal surface; one or more bearings in contact with the inner bearing surface and the outer bearing surface, the one or more bearings defining a rotational axis about which one of the inner housing or the outer housing may be rotated with respect to the other of the inner housing or the outer housing;

a seal in contact with the inner seal surface and the outer seal surface, the seal

providing a substantially fluid tight seal between the inner housing and the outer housing when the inner housing or the outer housing is rotated about the rotational axis; and

one or more inner heat pipes in thermal contact with the inner housing near the inner seal surface and one or more outer heat pipes in thermal contact with the outer housing near the outer seal surface, wherein the inner heat pipes and outer heat pipes provide for the maintenance of the seal within a defined temperature range.

2. The rotary joint of claim 1 further comprising:

an annular array of multiple inner heat pipes in thermal contact with the inner

housing, wherein the annular array of multiple inner heat pipes is arrayed concentrically with the inner seal surface; and

an annular array of multiple outer heat pipes in thermal contact with the outer

housing, wherein the annular array of multiple outer heat pipes is arrayed concentrically with the outer seal surface.

3. The rotary joint of claim 1 wherein the one or more inner heat pipes and the one or more outer heat pipes comprise gas-loaded variable conductance heat pipes, with each gas-loaded variable conductance heat pipe comprises an evaporator end embedded within the associated housing and a condenser end extending from the associated housing into contact with the ambient atmosphere.

4. The rotary joint of claim 3 further comprising a thermal insulation medium in thermal contact with at least one of the inner housing and the outer housing.

5. The rotary joint of claim 4 wherein the thermal insulation medium comprises a

movable insulation shroud that may be selectively positioned to cover or expose the condenser end of one or more inner heat pipes or outer heat pipes.

6. The rotary joint of claim 3 further comprising at least one fan providing for the

movement of the air over the condenser end of at least one heat pipe.

7. The rotary joint of claim 6 further comprising:

a temperature sensor in thermal communication with one or more of the inner seal surface, the outer seal surface and the seal; and

a control system to control the at least one fan in response to a seal temperature

sensed by the temperature sensor.

8. The rotary joint of claim 1 further comprising:

an inner housing conduit wall defining the first portion of the fluid passageway; an inner housing annular extension extending radially outward from the inner housing conduit wall;

an inner housing radial structure extending from the inner housing annular extension and separated from the inner housing conduit wall by the inner housing annular extension, wherein the inner bearing surface, the inner seal surface and the inner heat pipes are operatively associated with the inner housing radial structure;

an outer housing conduit wall defining the second portion of the fluid passageway; an outer housing annular extension extending radially outward from the outer housing conduit wall; and

an outer housing radial structure extending from the outer housing annular extension and separated from the outer housing conduit wall by the outer housing annular extension, wherein the outer bearing surface, the outer seal surface and the outer heat pipes are operatively associated with the outer housing radial structure.

9. The rotary joint of claim 1 further comprising a seal compression element providing for a select compression to be applied to the seal.

10. The rotary joint of claim 9 wherein the seal compression element comprises:

a seal compression ring in physical contact with the seal;

one or more seal compression bolts providing for the seal compression ring to be drawn against the seal; and

a seal seat bushing providing a surface opposite the seal compression ring against which the seal may be compressed by the seal compression ring.

11. A concentrated solar power system comprising:

one or more parabolic trough reflectors;

a receiver configured to receive concentrated solar flux reflected from the one or more parabolic trough reflectors and provide for the heating of a heat transfer fluid within the receiver;

a heat transfer circuit in fluid communication with the receiver; and

a rotary joint positioned between the receiver and the heat transfer circuit, providing for the flow of the heat transfer fluid from the receiver to the heat transfer circuit and further providing for the rotation of the receiver with respect to the heat transfer circuit, wherein the rotary joint comprises;

an inner housing defining a first portion of a fluid passageway, the inner housing comprising an inner bearing surface and an inner seal surface;

an outer housing defining a second portion of the fluid passageway, the outer housing comprising an outer bearing surface and an outer seal surface;

one or more bearings in contact with the inner bearing surface and the outer bearing surface, the one or more bearings defining a rotational axis about which one of the inner housing or the outer housing may be rotated with respect to the other of the inner housing or the outer housing; a seal in contact with the inner seal surface and the outer seal surface, the seal providing a substantially fluid tight seal between the inner housing and the outer housing when the inner housing or the outer housing is rotated about the rotational axis; and one or more inner heat pipes in thermal contact with the inner housing near the inner seal surface and one or more outer heat pipes in thermal contact with the outer housing near the outer seal surface, wherein the inner heat pipes and outer heat pipes provide for the maintenance of the seal within a defined temperature range.

A method of controlling the temperature of a rotary joint seal comprising:

providing a rotary joint comprising;

a seal in contact with the inner seal surface and the outer seal surface, the seal providing a substantially fluid tight seal between the inner housing and the outer housing when the inner housing or the outer housing is rotated about the rotational axis; and

one or more inner heat pipes in thermal contact with the inner housing near the inner seal surface and one or more outer heat pipes in thermal contact with the outer housing near the outer seal surface, wherein the inner heat pipes and outer heat pipes provide for the maintenance of the seal within a defined temperature range; and

flowing a high temperature process fluid through the rotary joint.