GB2586503A

GB2586503A - Thermal regulation system

Info

Publication number: GB2586503A
Application number: GB1912090.6A
Authority: GB
Inventors: Pathirannahalage Premasiri Gunarathne Godallawaththa
Original assignee: Starimedical Ltd
Current assignee: Starimedical Ltd
Priority date: 2019-08-22
Filing date: 2019-08-22
Publication date: 2021-02-24
Anticipated expiration: 2039-08-22
Also published as: GB2586503B; GB201912090D0

Abstract

A heat exchanger 1 comprising a main body 8, a flow channel comprising a plurality of channel portions 20, an inlet 4, an outlet 6, a spacer 10 and a cover 12. Each channel portion of a plurality of channel portions is in fluid communication with an adjacent channel portion and is separated from an adjacent channel portion by a channel wall 21. The spacer is located between the cover and the main body creating an enclosed space 16 defined between the cover, the spacer and the main body. During use fluid flows from the inlet to the outlet along the flow channel and also flows across the channel wall via the enclosed space. The channel walls may be circular and have one or more openings through the wall to connect the channel portions. A heat pump may be in contact with a second side of the main body opposite the flow channel.

Description

Thermal Regulation System

Field of the Invention

The present disclosure relates to thermal regulation systems, specifically to heat exchanger systems.

Background of the Invention

Thermal regulation systems, with or without integral heat exchangers, are in widespread use in industrial and medical applications. Examples in industrial sector are commonly found in power generation, Heating-ventilation-air-conditioning and refrigeration (HVACR).

In the field of medicine, patient thermoregulation is an essential requirement in critical operations, such as, Cardiopulmonary Bypass (CPB) surgery. Such cardiac surgery is usually carried out under hypothermic conditions (mild hypothermia (32-35°C), moderate hypothermia (28-32°C) and deep hypothermia (< 28°C) depending on case specific requirements). In hypothermic CPB, the patient's body needs to be cooled for surgery in controlled steps. In addition, in cardioplegia, the heart needs to be cooled. The temperature of blood during bypass surgery can be as low as 10°C in some cases and for cardioplegia this could be around 5°C. At the conclusion of the surgery, the body is rewarmed to normothermic conditions, again in controlled steps.

Therefore, such invasive medical procedures require a source for absorption of heat, a source for the generation of heat, and a method for transporting that heat or thermal energy between the source and the patient's body. For this purpose, existing CPB systems rely on the use of industrial vapour compression coolers and electrical heaters. However, in critical applications such as CPB, they pose many difficulties including safety issues.

Thermoregulation systems known in the art generally have three subsystems: A heat generation and absorption subsystem; a heat exchanger subsystem; and, a control subsystem that regulates the heat exchange as required to reach and maintain desired temperature settings, on demand. The heat exchanger mechanism for patient cooling and warming is often in-built within the oxygenator, to which an external source of cool or warm, unsterilized, water is supplied. In the heat exchanger compartment, unsterilized water from the heater/cooler device is separated from the sterile blood by some means: e.g. with stainless steel, aluminium, polyurethane membrane or using a tube-in-tube type geometry. However, they all work based on heat exchange with blood through conduction across an isolating barrier.

During the hypothermia phase, cooling occurs primarily through the heat exchanger by way of conduction. A degree of natural cooling also occurs due to blood being in circulation outside of the body and due to the reduction of body heat generation due to reduced metabolic rate. The patient re-warming phase is also primarily dependent on conductive heat transfer through the heat exchanger supplied with warm water. However, the temperature of warm water cannot exceed 42°C maximum beyond which temperature blood may be damaged.

However, typical conductive heat transfer is slow and inefficient. This is because of the boundary layers formed on either side of the membrane (or the material) separating the blood and water, and due to system's thermal inertia.

Furthermore, the maximum temperature of circulating water must be kept below 42°C, leaving only a few degrees of temperature gradient between water and target temperature of the blood. As a result, the transport of thermal energy across such a small temperature gradient is slow and inefficient.

To mitigate these two factors in existing systems, high water flow rates are used, e.g. 40L/m. However, there is a known risk of bacterial proliferation from the circulating water into the blood, a serious situation, which can be fatal. The present thermoregulation systems are also bulky and heavy as they use industrial heater/coolers to supply warm/cool water to the heat exchanger. Furthermore, there is a considerable energy loss due to waste heat and power required to drive water at high flow rates.

Accordingly, there remains a need for improved heat exchanger systems for use in surgical procedures, for example, to overcome at least one or some of the above problems.

Summary of the Invention

According to a first aspect there is presented a cross-flow heat exchanger comprising a main body, a flow channel, an inlet, an outlet, and a cover, the main body comprises a thermally conductive material and the flow channel extends through the main body and extends between the inlet and the outlet; the flow channel has a depth and is open along the majority of its length on a first side of the main body to the cover and comprises a plurality of channel portions, and each channel portion of the plurality of channel portions is in fluid communication with an adjacent channel portion and is separated from an adjacent channel portion by a channel wall; wherein the cross-flow heat exchanger is configured such that during use fluid flows from the inlet to the outlet along the flow channel, and wherein during use thermal energy is transferred between the main body and fluid flowing through the flow channel.

The cross-flow heat exchanger may comprise a spacer. The spacer may be located between the cover and the main body. An enclosed space may be defined between the cover, the spacer and the main body. During use the fluid may flow from the inlet to the outlet along the flow channel and also flow across the channel wall via the enclosed space.

Accordingly, a cross-flow heat exchanger may comprise a main body, a flow channel, an inlet, an outlet, a spacer and a cover, the main body may comprise a thermally conductive material and the flow channel extends through the main body and extends between the inlet and the outlet; the flow channel has a depth and may be open along the majority of its length on a first side of the main body and comprises a plurality of channel portions, and each channel portion of the plurality of channel portions may be in fluid communication with an adjacent channel portion and may be separated from an adjacent channel portion by a channel wall; the spacer may be located between the cover and the main body and an enclosed space may be defined between the cover, the spacer and the main body; wherein the cross-flow heat exchanger may be configured such that during use fluid flows from the inlet to the outlet along the flow channel and also flows across the channel wall via the enclosed space, and wherein during use thermal energy may be transferred between the main body and fluid flowing through the flow channel.

In embodiments of the present aspect, the direction of fluid flow does not significantly affect the transfer of thermal energy between the fluid flowing through the flow channel and the main body. Accordingly, whilst the term "inlet" and "outlet" are used to describe the ports of the cross-flow heat exchanger of the present aspect, it is to be understood that the specific function of the features described as an "inlet" or "outlet" may be reversed, depending on the direction of flow of fluid through the cross-flow heat exchanger. Accordingly, a given port may receive fluid from an external source and therefore act as an "inlet" during one mode of operation, and in a second mode or second embodiment fluid may flow out of the cross-flow heat exchanger through the same port, that port thereby acting as an "outlet', for example.

During use, thermal energy is transferred between the fluid flowing along the flow channel and the main body. In heat exchangers known in the art, fluid flowing along the flow channel of the heat exchanger typically flows at a flow rate that is sufficiently high to disrupt the boundary layer adjacent to or at the interface between the fluid and the flow channel to thereby improve the efficiency of thermal energy transfer. The cross-flow heat exchanger of the present aspect comprising a spacer provides an enclosed space through which fluid may flow across the channel wall separating two adjacent channel portions. Accordingly, at any given point along the channel portion fluid may be flowing in a direction parallel to the channel wall, and perpendicular to or substantially perpendicular to the channel wall as it flows across the channel wall. The provision of this so-called "cross-flow" induces turbulence within the fluid flowing along the fluid channel and facilitates improved transfer of thermal energy between the fluid and the main body.

As a result, the flow rate of fluid flowing along the flow channel may be significantly lower than that in typical heat exchangers as the induced turbulence in the fluid flow disrupts or substantially disrupts the boundary layer and thereby may be configured for efficient transfer of thermal energy between the fluid and main body.

The flow channel may be open along at least 50% of its length on the first side of the main body. The flow channel may be open along at least 60% of its length on the first side of the main body. The flow channel may be open along at least 70% of its length on the first side of the main body. The flow channel may be open along at least 80% of its length on the first side of the main body. The flow channel may be open along at least 90% of its length on the first side of the main body. The flow channel may be open along substantially the entirety of its length on the first side of the main body.

In some embodiments at least one channel portion of the plurality of channel portions may be curved. In some embodiments at least one channel portion of the plurality of channel portions may be straight or linear. In some embodiments at least one channel portion of the plurality of channel portion may be curved and at least one channel portion of the plurality of channel portions may be straight or linear.

In some embodiments each channel portion within the plurality of channel portions may be curved.

At least one channel portion of the plurality of channel portions may be circular. Alternatively, the plurality of channel portions may form a spiral flow channel.

In embodiments where the flow channel is not a spiral flow channel, the plurality of channel portions may be interconnected by one or more opening within the channel wall. In embodiments where the plurality of channel portions comprises at least three channel portions, the cross-flow heat exchanger may comprise a first opening between a first channel portion and a second channel portion, and a second opening between the second channel portion and a third channel portion, wherein the first opening is offset from the second opening.

Accordingly, during use fluid flows along at least a portion of the first channel portion from the inlet to the opening to the second channel portion, and along at least a portion of the second channel portion from the opening to the first channel portion to the opening to the third channel portion. For example, fluid may flow along at least 20%, 30%, 40%, or 50% of a channel portion from the inlet or opening to the previous channel portion to the opening to the subsequent channel portion.

In some embodiments at least one channel portion within the plurality of channel portions may be circular. At least one channel portion within the plurality of channel portions may be elliptical. At least one channel portion within the plurality of channel portions may be ovoid.

Preferably, each channel portion within the plurality of channel portions is circular. Preferably, each channel portion within the plurality of channel portions are concentric with one another. Accordingly, in preferred embodiments, the plurality of channel portions are concentric circular channel portions. For the avoidance of doubt, each channel portion may define a circle in the main body and the circle defined by each channel portion has a different radius than the other channel portions, and each circle defined by each channel portion of the plurality of channel portions has a common centre. Typically, the inlet is connected to the outermost channel portion and the outlet is connected to the innermost channel portion. The opening connecting the outermost channel portion to the adjacent channel portion may be offset to the inlet. The opening between a given channel portion and a subsequent channel portion may be offset to the opening between the given channel portion and preceding channel portion. For example, the opening between adjacent channel portions may be offset by at least 90°, at least 120° or at least 180°. In some embodiments the opening between adjacent channel portions may be offset by approximately 180°. Accordingly, fluid may be required to flow around half of or approximately half of a channel portion between openings. Furthermore, as the channel portions are circular, fluid may flow in either direction around the circular channel portions from a first opening to a second opening.

In embodiments each channel portion in the plurality of channel portions is circular and the opening in the channel wall between a first and second channel portion is on the side of the cross-flow heat exchanger opposed to the side of the cross-flow heat exchanger on which the opening in the channel wall between the second and a third channel portion such that during use fluid flows into each channel portion of the plurality of channel portions on the side of the channel portion opposed to the opening to the adjacent channel portion such that fluid flows in both directions around substantially half of the circular channel portion to the opening.

The flow channel may comprise at least 2, 3,4, 5,6, 7, 89, 10, 11, 12, 13, 19 or 20 channel portions. The flow channel may comprise at least 6, 7, 8, 14, 15, 16, 17, 18, 9, 10, 11, 12, 13, 14, 15 or 16 channel portions. The flow channel may comprise at least 10, 11, 12, 13, or 14 channel portions.

In some embodiments the outlet may be in or adjacent to the middle of the plurality of channels.

In some embodiments the inlet may be connected to the outermost channel portion within the plurality of channel portions.

At least one channel wall between two adjacent channel portions may comprise a plurality of apertures to allow the flow of fluid through the channel wall.

Typically, the main body comprises a metal. The metal may be selected from the group consisting of aluminium, copper, tin, iron, steel, stainless steel, brass, or an alloy of the same.

The metal may be selected from the group consisting of aluminium, copper or an alloy of the same. The metal may be aluminium or an alloy of aluminium.

The spacer may be from 0.1mm to 2.0mm deep. Accordingly, the depth of the enclosed space defined by the cover, the spacer and the main body may be from 0.1mm to 2.0mm deep. For the avoidance of doubt, the depth of the enclosed space is defined as the distance between the cover and the first side of the main body. The spacer may be from 0.1mm to 0.5mm deep. The spacer may be from 0.1mm to 0.3mm deep. The spacer may be less than 1.5mm deep, less than 1.0mm deep, or less than 0.5mm deep.

Typically, the spacer forms a seal around the enclosed space such that fluid within the enclosed space does not flow through the spacer, between the spacer and the cover, or between the spacer and the main body. The spacer may act as a seal. A sealant may be provided between the spacer and the cover and/or between the spacer and the main body.

The cover may be opaque to visible light. The cover may be transparent to visible light. Accordingly, it may be possible during use for a user to see the fluid flowing through the flow channel. The cover may be transparent to infra-red (IR) radiation. Accordingly, if rapid or additional heating of the fluid flowing through the cross-flow heat exchanger is required, an array of IR light sources may be provided on or adjacent to the cover such that at least a portion of IR radiation emitted by the IR light sources may pass through the cover and be absorbed be the fluid flowing through the flow channel. For example, the array of IR light sources may comprise IR light emitting diodes (LEDs).

In some embodiments, the cover of the cross-flow heat exchanger may be replaced by a second main body. The second main body may comprise a second inlet, a second outlet, and a second flow channel extending between the second inlet and the second outlet. Accordingly, the cross-flow heat exchanger may comprise a first main body, a spacer and a second main body. The spacer may define an enclosed space between the first side of the first main body and the first side of the second main body.

During use, fluid may flow from the inlet to the outlet of the first main body via the flow channel of the first main body and may flow across the channel wall between adjacent channel portions via the enclosed space. Fluid may flow from the second inlet to the second outlet via the flow channel of the second main body and may flow across the channel wall between adjacent channel portions via the enclosed space.

In alternative embodiments, the flow channel of the first main body may be connected to the flow channel of the second main body. Accordingly, the flow channel of the first main body and the flow channel of the second main body may form a single main flow channel. During use fluid may flow from the inlet of the first main body to the out let of the first main body, and fluid may flow from the inlet of the second main body to the outlet of the second main body.

The inlet of the first main body may be aligned with the inlet of the second main body. The inlet of the first main body may be offset from the inlet of the second main body. For example, the inlet of the first main body may be offset from the inlet of the second main body by 900, 120° or 180°. Embodiments where the inlet of the first main body is offset from the inlet of the second main body may induce additional turbulence in the flow of fluid flowing through the single main flow channel.

The cross-flow heat exchanger may comprise a single inlet and a single outlet such that fluid may flow during use from the single inlet to the single outlet via the single main flow channel.

The single inlet may be located on the first main body. The single inlet may be located on the second main body. The single outlet may be located on the first main body. The single outlet may be located on the second main body.

The second side opposed to the first side of the first main body and/or the second main body may be in thermal contact with one or more heat pump. The one or more heat pump may be configured to receive thermal energy from the respective main body. The one or more heat pump may be configured to transmit thermal energy to the respective main body. The one or more heat pump may be configured in a first mode to receive thermal energy from the respective main body and in a second mode to transmit thermal energy to the respective main body.

The second side may be in thermal contact with one to eight heat pumps. The second side may be in thermal contact with one to six heat pumps. The second side may be in thermal contact with one to four heat pumps. The second side may be in thermal contact with four heat pumps, for example.

The one or more heat pump may be a thermoelectric device.

The one or more heat pump may be connected to a heat sink. The heat sink may be an air-cooled heat sink. The heat sink may be a water-cooled heat sink.

In a second aspect there is provided a heat exchanger system comprising a first cross-flow heat exchanger according to the first aspect, at least one heat pump, a first system input and a first system output, wherein the at least one heat pump is in thermal contact with a second side of the main body opposed to the first side such that during use fluid flows from the first system input to the first system output via the flow channel of the first cross-flow heat exchanger such that thermal energy is transferred between the fluid and the at least one heat pump via the material of the first cross-flow heat exchanger.

The system may comprise a second cross-flow heat exchanger according to the first aspect, a second system inlet and a second system outlet, the second side of the main body of the second cross-flow heat exchanger opposed to the first side of the main body may be coupled to the at least one heat pump such that during use thermal energy may be exchanged between the main body of the second cross-flow heat exchanger and the at least one heat pump, wherein during use a first fluid flowing through the first cross-flow heat exchanger may be isolated from a second fluid flowing through the second cross-flow heat exchanger and thermal energy may be transferred between the first fluid and the second fluid.

The first fluid may be a coolant. The first fluid may be water, a fluorocarbon, such as FC75 (C8F160) or any other suitable fluid that does not change to a vapour phase below 50°C. For example, the first fluid may be water.

In some embodiments, the second fluid may be a refrigerant or coolant as defined above for the first fluid. For example, the second fluid may be water.

In some embodiments the second fluid may be a biological fluid. For example, the biological fluid may be blood.

The isolation of the first fluid from the second fluid ensures that there is no possibility of cross contamination between the two fluids. In embodiments where the second fluid is a biological fluid such as blood, it is crucial that the second fluid cannot be contaminated by the first fluid to ensure that second fluid is not contaminated by any foreign species, such as bacteria or viruses.

The at least one heat pump may be a thermoelectric heat pump or thermoelectric module.

The at least one heat pump may be configured to drive the direction of heat transfer across the heat exchanger system.

The heat exchanger system may further comprise a heat storage unit in fluid communication with the first system inlet and the first system outlet such that during use the first fluid may flow from the heat storage unit to the flow channel of the first cross-flow heat exchanger via the first system inlet and from the flow channel of the first cross-flow heat exchanger to the heat storage unit via the first system outlet.

The heat storage unit may comprise a material with a high heat of fusion which, when melting or freezing, is configured to store or release thermal energy respectively. The phase change material is preferably a liquid at biological temperatures and freezes below biological temperatures. For example, the phase change material may be liquid above 5°C, above 10°C or above 15°C. The phase change material may be a solid below 5°C, below 2°C or below 0°C.

Prior to use, the heat storage unit may comprise a solid form of the phase change material in direct contact with the liquid form of the phase change material that is the first fluid and will flow through the first cross-flow heat exchanger. During use, thermal energy transferred to the liquid phase change material in the first cross-flow heat exchanger may be at least partially absorbed by the solid phase change material in the heat storage unit. As the solid phase change material is melted to the liquid form of the phase change material, thermal energy may be stored.

In at least one application of the heat exchanger system of the present aspect is temperature control of blood during surgical procedures. A key feature of many surgical procedures is the controlled lowering and maintaining of the patient's temperature to hyperthermic levels (i.e. below body temperature (i.e. -37°C), such as 28°C for cardiac surgery and 10°C or 5°C for cardiac bypass surgery, for example). Accordingly, in preparation for surgery it is required to reduce the temperature of the blood of a patient to sub-biological temperatures and to maintain them at that temperature through-out the surgical procedure. However, once surgery is completed, it is necessary to elevate the temperature of the blood of the patient back to normal body temperature. Typical heat exchanger systems in the art typically simply dispose of the thermal energy removed from the blood during cooling and require significant input of energy to re-heat the blood after surgery.

In contrast, in embodiments of the present aspect comprising a heat storage unit, the thermal energy stored in the heat storage unit during cooling of the blood of a patient can be used at least in part to re-heat the blood of the patient back to normal body temperature after surgery is completed. Accordingly, the heat exchanger system of the present aspect requires significantly reduced levels of energy to re-heat the blood of a patient after initially cooling that blood, for example.

In some embodiments, the phase change material may be water. Accordingly, the heat storage unit may comprise ice prior to use.

During use in first mode of operation thermal energy may be transferred from a second fluid flowing through the second cross-flow heat exchanger to the first fluid flowing through the first cross-flow heat exchanger via the at least one heat pump. The second fluid is thereby cooled.

The one or more heat pump may draw thermal energy from the main body of the second cross-flow heat exchanger. The main body of the first cross-flow heat exchanger may draw thermal energy from the one or more heat pump and transfer the thermal energy to the first fluid.

During use in a second mode of operation thermal energy may be transferred from the first fluid flowing through the first cross-flow heat exchanger to the second fluid flowing through the second cross-flow heat exchanger via the at least one heat pump. The second fluid is thereby heated.

The one or more heat pump may draw thermal energy from the main body of the first cross-flow heat exchanger. The main body of the second cross-flow heat exchanger may draw thermal energy from the one or more heat pump.

The heat exchanger system may comprise a first pump configured to drive the first fluid through the first cross-flow heat exchanger. The heat exchanger system may comprise a second pump configured to drive the second fluid through the second cross-flow heat exchanger.

In some embodiments the heat exchanger system may comprise a primary heat exchanger module and a secondary heat exchanger module. The primary heat exchanger module may comprise the first cross-flow heat exchanger, the second cross-flow heat exchanger, the first system outlet, the first system inlet, the second system inlet and the second system outlet. The secondary heat exchanger module may comprise a heat exchanger comprising a flow channel, a third inlet and a third outlet, the secondary heat exchanger being configured such that fluid may flow from the third inlet to the third outlet via the flow channel, wherein the third inlet is in fluid communication with the second outlet of the second cross-flow heat exchanger and the third outlet is in fluid communication with the second inlet of the second cross-flow heat exchanger.

The primary heat exchanger module may comprise the heat storage unit. The heat exchanger system may comprise one or more bypass valves that are configured to direct fluid from the heat storage unit to the secondary heat exchanger module and to direct fluid from the secondary heat exchanger module to the heat storage unit. Accordingly, the one or more bypass valves may bypass the first cross-flow heat exchanger and the second cross-flow heat exchanger (the primary heat exchanger module). The heat exchanger system may comprise a switch configured to toggle the one or more bypass valves such that fluid from the heat storage unit can be directed to the first heat exchanger of the primary heat exchanger module or to the secondary heat exchanger module, and fluid from the secondary heat exchanger module can be directed to the second cross-flow heat exchanger or to the heat storage unit.

The secondary heat exchanger module may comprise a third cross-flow heat exchanger according to the first aspect and the inlet of the third cross-flow heat exchanger may be the third inlet of the secondary heat exchanger module and the outlet of the third cross-flow heat exchanger is the third outlet of the secondary heat exchanger.

The secondary heat exchanger module may comprise a fourth cross-flow heat exchanger according to the first aspect, wherein the second side of the main body of the third cross-flow heat exchanger is in thermal contact with the second side of the main body of the fourth cross-flow heat exchanger.

The secondary heat exchanger module may comprise a main body and the main body of the third cross-flow heat exchanger may be a first portion of the main body of the secondary heat exchanger module and the main body of the fourth cross-flow heat exchanger may be a second portion of the main body of the secondary heat exchanger.

The secondary heat exchanger module may comprise at least one heat source arranged adjacent to the cover of the fourth cross-flow heat exchanger such that thermal energy emitted by the at least one heat source passes through the cover and least a portion of the thermal energy emitted by the at least one heat source is transmitted to the fluid flowing through the flow channel of the fourth cross-flow heat exchanger.

The secondary heat exchanger module may comprise a plurality of heat sources. The or each heat source may be one or more IS LEDs.

The secondary heat exchanger module may comprise a fifth inlet, a fifth outlet, a sixth inlet, a sixth outlet, a fifth flow channel, a sixth flow channel, and a source of IS radiation. The fifth flow channel may extend between the fifth inlet and the fifth outlet and may be configured in a helix around the sixth flow channel, the sixth flow channel extending between the sixth inlet and the sixth outlet and configured in a helix around the source of IS radiation. The secondary heat exchanger module may comprise a wall comprising a material that is transparent to at least a portion of the radiation emitted by the source of IS radiation. During use fluid from the primary heat exchanger module may flow through the fifth flow channel and thermal energy may be transferred between the fluid within the fifth flow channel and fluid within the sixth flow channel, wherein additional thermal energy may be transferred to the fluid flowing through the sixth flow channel from the source of IS radiation.

The fifth flow channel may be wrapped helically around the sixth flow channel. The sixth flow channel may be wrapped helically around the source of IS radiation.

Typically, the fifth flow channel and the sixth flow channel share a common wall and during use thermal energy may be transferred between fluid flowing through the fifth flow channel and fluid flowing through the sixth flow channel via the common wall.

The fluid flowing through the fifth flow channel is preferably isolated from the fluid flowing through the sixth flow channel.

Fluid flowing through the sixth flow channel may be a biological fluid. For example, the biological fluid may be blood.

The source of IS radiation may comprise one or more IS LEDs. The source of IS radiation may comprise filament bulb or a halogen bulb that are configured to emit IS radiation.

The secondary heat exchanger module may comprise a plurality of sources of IS radiation. The plurality of sources of IR radiation may comprise a plurality of IR LEDs.

The plurality of sources of IS radiation may be arranged around a central support. The sixth flow channel may be wrapped helically around the central support such that the plurality of sources of IS radiation are spaced regularly along the majority of the extent of the sixth flow channel. Accordingly, during use the intensity of IIR radiation may be substantially equal along the length of the sixth flow channel.

The secondary heat exchanger module may comprise a reflector. The reflector may be adjacent to the source of IR radiation and the sixth flow channel may wrap helically around the source of IS radiation and the reflector.

The reflector may be arranged such that IS radiation emitted by the source of IS radiation may be directed to the fluid flowing through the sixth flow channel.

Accordingly, the intensity of IS radiation directed to the fluid flowing through the sixth flow channel during use may be substantially even. As a result, the level of heating of the fluid flowing through the sixth flow channel during use may be substantially even such that the formation of emboli or the like may be substantially prevented.

According to a third aspect there is provided a cross-flow heat exchanger comprising a main body, a first flow channel, a first inlet, a first outlet, a first spacer and a first cover, a second flow channel, a second inlet, a second outlet, a second spacer, and a second cover, the main body comprises a thermally conductive material and the first flow channel extends through the main body and extends between the first inlet and the first outlet, and the second flow channel extends through the main body and extends between the second inlet and the second outlet; the first flow channel has a depth and is open along the majority of its length on a first side of the main body and comprises a plurality of channel portions, and each channel portion of the plurality of channel portions is in fluid communication with an adjacent channel portion and is separated from an adjacent channel portion by a channel wall; the second flow channel has a depth and is open along the majority of its length on a second side of the main body and comprises a plurality of channel portions, and each channel portion of the plurality of channel portions is in fluid communication with an adjacent channel portion and is separated from an adjacent channel portion by a channel wall; the first spacer is located between the first cover and the main body and a first enclosed space is defined between the first cover, the first spacer and the main body; the second spacer is located between the second cover and the main body and a second enclosed space is defined between the second cover, the second spacer and the main 20 body; wherein the cross-flow heat exchanger is configured such that during use a first fluid flows from the first inlet to the first outlet along the first flow channel and also flows across the channel wall via the first enclosed space, and a second fluid flows from the second inlet to the second outlet along the second flow channel and also flows across the channel wall via the second enclosed space, and wherein during use thermal energy is transferred between the first fluid and the second fluid via the main body.

The first flow channel may form a spiral. The second flow channel may form a spiral.

In some embodiments the at least one channel portion of the second flow channel may at least partially extend into the channel wall between adjacent channel portions of the first flow channel. Accordingly, the channel wall between adjacent channel portions of the first flow channel may have a width that is greater than the width of the at least one channel portion of the second flow channel. The majority of the channel portions of the second flow channel may at least partially extend into the channel wall between adjacent channel portions of the first flow channel. Therefore, it may be that at least the majority of channel portions of the second flow channel may be interleaved with the channel portions of the first flow channel.

Interleaving of channel portions in the cross-flow heat exchanger of the present aspect allows the transfer of thermal energy between the first fluid and the second fluid more efficiently due the reduced volume of material of the main body across which the thermal energy has to be transmitted, whilst retaining complete isolation of the first fluid from the second fluid.

In a fourth aspect there is presented a heat exchanger comprising a first flow channel, a first inlet, a first outlet, a second flow channel, a second inlet, a second outlet, and a central support, the first flow channel arranged helically around the second flow channel, the second flow channel arranged helically around the central support. The first flow channel is connected to the first inlet and the first outlet such that during use a first fluid may flow from the first inlet to the first outlet via the first flow channel. The second flow channel is connected to the second inlet and the second outlet such that during use a second fluid may flow from the second inlet to the second outlet via the second flow channel. The first flow channel and the second flow channel may share a common wall such that during use thermal energy may be transferred from the first fluid to the second fluid via the common wall.

The central support may comprise a source of infra-red (IR) radiation. The second flow channel may comprise a channel wall that faces the central support and is transparent or at least partially transparent to IR radiation such that IR radiation emitted by the source of IR radiation in the central support may be absorbed by the second fluid flowing through the second flow channel to thereby heat the second fluid directly.

The first fluid is preferably isolated from the second fluid.

The sixth fluid may be a biological fluid. For example, the biological fluid may be blood.

The source of IR radiation may comprise one or more IR LEDs. The source of IR radiation may comprise a filament bulb or a halogen bulb that is configured to emit IR radiation.

The central support may comprise a plurality of sources of IR radiation. The plurality of sources of IR radiation may comprise a plurality of IR LEDs.

The plurality of sources of IR radiation may be arranged around the surface of the central support. The second flow channel may be wrapped helically around the central support such that the plurality of sources of IR radiation are spaced regularly along the majority of the extent of the second flow channel. Accordingly, during use the intensity of IR radiation may be substantially equal along the length of the second flow channel.

The central support may comprise a reflector. The reflector may be adjacent to the source of IR radiation. The reflector may be arranged such that IR radiation emitted by the source of IR radiation may be directed to the fluid flowing through the second flow channel.

Accordingly, the intensity of IR radiation directed to the fluid flowing through the second flow channel during use may be substantially even. As a result, the level of heating of the fluid flowing through the second flow channel during use may be substantially even such that the formation of emboli or microbubbles or the like may be substantially prevented.

In a fifth aspect there is provided a heating device comprising a perfusate tube, a heater tube and a cooler tube. The perfusate tube may be arranged within the heater tube. The heater tube may be arranged within the cooler tube. The heater tube may be configured to transmit heat to the perfusate tube such that during use heat may be transferred to a fluid passing through the perfusate tube. The heater tube may comprise one or more sources heat. The one or more heat sources may comprise one or more sources of IR radiation. The one or more sources may comprise an array of IR LEDs.

The cooler tube may comprise a cooler channel, a cooler inlet and a cooler outlet and may be configured such that during use a coolant may flow into the cooler inlet through the cooler channel and out of the cooler outlet. At least a portion of the heat generated by the one or more sources of heat may be transmitted to a coolant flowing through the cooler tube to thereby cool the one or more sources of heat. In embodiments where the one or more sources of heat comprises an array IR LEDs, the coolant may cool the array of IR LEDs thereby increasing the efficiency of the array of IR LEDs.

The heating device may be placed over a tube through which blood is to be transmitted.

Accordingly, the tube through which blood is to be transmitted may become the perfusate tube and during use the heating device may heat blood that is passing through the tube. Therefore, the heating device may be applied to existing equipment used in an extracorporeal blood circulation device in surgery.

In some embodiments the perfusate tube conducts thermal energy such that heat produced by the heater tube is transmitted through the perfusate tube to a perfusate passing through the perfusate tube. In embodiments where the heater tube produces IR radiation, the perfusate tube may be transparent to IR radiation, such that IR radiation produced by the heater tube may be absorbed by a perfusate passing through the perfusate tube.

According to a sixth aspect there is provided a cross-flow heat exchanger comprising a main body, a flow channel, an inlet, an outlet, and a cover, the main body comprises a thermally conductive material and the flow channel extends through the main body and extends between the inlet and the outlet; the flow channel has a depth and is open along the majority of its length on a first side of the main body and comprises a plurality of channel portions, and each channel portion of the plurality of channel portions is in fluid communication with an adjacent channel portion and is separated from an adjacent channel portion by a channel wall; wherein the channel wall between adjacent channel portions comprises a plurality of apertures, wherein the cross-flow heat exchanger is configured such that during use fluid flows from the inlet to the outlet along the flow channel and also flows across the channel wall via the plurality of apertures, and wherein during use thermal energy is transferred between the main body and fluid flowing through the flow channel.

Preferred and optional features of the first aspect excluding the provision of a spacer are preferred and optional features of the sixth aspect.

Brief Description of the Figures

Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the accompanying drawings.

Figure 1: A) A top view of a heat exchanger according to an embodiment, and B) a schematic cross section view of a heat exchanger according to an embodiment; Figure 2: A photograph of a heat exchanger according to an embodiment; Figure 3: A) A photograph showing a perspective view from the front of a heat exchanger according to an embodiment, and B) a photograph showing a perspective view from behind of a heat exchanger according to an embodiment; Figure 4: A) A schematic cross-section view of a heat exchanger according to an embodiment, and B) a schematic perspective view of a heat exchanger according to an embodiment; Figure 5: A schematic cross-section view of a heat exchanger according to an embodiment; Figure 6: A photograph showing a heat exchanger according to an embodiment; Figure 7: A schematic view of a heat exchanger system according to an embodiment; Figure 8: A schematic cross section view of a heat exchanger according to an embodiment; Figure 9: A schematic cross section view of a heat exchanger according to an embodiment; Figure 10: A schematic view of a heat exchanger system according to an embodiment; Figure 11: A schematic cross section view of a heating unit according to an embodiment; Figure 12: A photograph showing components of the heating unit according to an embodiment; Figure 13: A photograph showing a top view of a heat unit according to an embodiment; Figure 14: A schematic of a heat exchanger system according to an embodiment; Figure 15: A schematic top view of a section of a heat exchanger according to an embodiment; Figure 16: A schematic view of a heat exchanger system according to an embodiment; Figure 17: State transition diagram showing the cooling phase according to an embodiment (Primary Exchanger -PE, Cooling Phase Complete -CPC, Mains water Supply -MS, temperature of water in heat storage unit -t4); and Figure 18: State transition diagram showing the rewarming phase according to an embodiment.

Detailed Description

While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as "a", "an" and "the" are not intended to refer to only a singular entity but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

Example 1

With reference to Figure 1 to 3, a heat exchanger 1 comprises a channel 2 (acting as a flow channel), an inlet 4, an outlet 6, a main body 8, a gasket 10 (acting as a spacer) and a cover 12. The cover 12 is fixed to the main body 8 and the gasket 10 by screws 14 such that pressure is exerted on the gasket 10 to thereby form a seal between the cover 12, the gasket and the main body 8. An enclosed space 16 is defined between the gasket 10, the main body 8 and the cover 12.

The channel 2 is made up of circular channel portions such as 20 (acting as channel portions) separated by channel walls (for example 21) interconnected by openings 22. The openings 22 are arranged such that every other opening 24 is aligned with one another and every alternate opening 26 is aligned with one another and offset from every other opening 24 by 180 degrees.

The channel 2 is formed in main body by milling of the main body 8. The main body 8 is made of aluminium.

The inlet 4 is connected to the outermost circular channel portion 28 and the outlet 6 is connected to the innermost circular channel portion 30 such that fluid may flow from the inlet 4 to the outlet 6 via the channel 2.

During use, fluid is pumped into the inlet 4 and flows along the channel 2 to the outlet 6. In addition, fluid fills the channel and flows over the channel walls 21 between adjacent circular channel portions. The flow of fluid along the circular channel portions 20 induces turbulence in the flow due to the unequal rate of flow of the fluid adjacent to the inner wall of a given circular channel portion and the outer wall of that circular channel portion. In addition, the location of the opening between adjacent circular channel portions ensures that fluid flows around the circular channel portion in both directions. When the fluid reaches the opening to the next circular channel portion both flows of fluid from either side of the circular channel portion collide and must then turn through 90 degrees to flow through the opening, thereby further inducing increased turbulence in the fluid, and therefore mixing. Finally, fluid flowing across the channel wall of adjacent circular channel portions is flowing approximately at 90 degrees to the fluid flowing within that channel and therefore induces still further turbulence and therefore mixing in the fluid.

As a result, the heat exchanger 1 provides efficient mixing of the fluid within the channel 2 and therefore efficient transfer of thermal energy between the fluid and the main body 8.

If the fluid flowing through the heat exchanger 1 is to be cooled, the main body 8 may be contacted on the side opposite to the cover with one or more thermoelectric devices 34 and heat sinks 32 that in a cooling mode may remove heat from the main body to maintain the efficiency of transfer of thermal energy or heat from the fluid. In a heating mode the current provided to the thermoelectric devices 34 may be reversed to transmit heat to the main body to thereby heat the fluid flowing through the heat exchanger 1.

The example shown in Figure 3 shows four heat sinks 32 contacted to thermoelectric devices 34 (acting as heat pumps) which are themselves in contact with the main body 8.

Example 2

With reference to Figure 4A and 4B a heat exchanger 40 comprises a first body 42 (acting as a first main body), a second body 44 (acting as a second main body), a spacer 46, four thermoelectric modules 48 with a heat sink 50 (acting as an air-cooled heat sink) attached to each thermoelectric module 48 in thermal contact with the first body 42 and four thermoelectric modules 48 with a heat sink 50 attached to each thermoelectric module 48 in thermal contact with the second body 44. The first body 42 comprises a channel 52 (acting as a flow channel), an inlet 54 and an outlet 56. The second body 44 comprises a channel 58 (acting as a flow channel), an inlet 60 and an outlet 62.

The channel 52 of the first body 42 is made up of circular channel portions (not shown) and the channel 58 of the second body 44 is made up of circular channel portions (not shown). The circular channel portions of the first body 42 are mated with the circular channel portions of the second body 44. Accordingly, the circular channel portions are opposed one another and the channel walls between adjacent circular channel portions are opposed one other.

The spacer 46 contacts the first body 42 and the second body 44 to form an enclosed space 68 between the first body 42, the spacer 46 and the second body 44.

During use, fluid flows into the inlets 54, 60 and out of the outlets 56, 62 of the first body 42 and second body 44 via the channel 52, 58 of the first body 42 and second body 44. Heat is transferred from the fluid flowing through the heat exchanger 40 to the heat sinks 50 via the first body 42 and the second body 44 and the thermoelectric modules 48 attached to each of the first body 42 and second body 44.

Example 3

With reference to Figure 5 and Figure 6, a heat exchanger module 70 comprises a first heat exchanger 72 and a second heat exchanger 74. The first heat exchanger 72 comprises a main body 76, a channel 78 (acting as a flow channel), an inlet 80, an outlet 82, a cover 84 and a spacer 86. The second heat exchanger 74 comprises a main body 88, a channel 90 (acting as a flow channel), an inlet 92, an outlet 94, a cover 96, and a spacer 98.

Thermoelectric modules 100 are in thermal contact with the main bodies 76, 88 such that the first heat exchanger 72 and the second heat exchanger 74 are arranged back to back.

The channel 78 of the first heat exchanger 72 comprises concentric circular channel portions interconnected by openings in the channel wall between adjacent circular channel portions.

The channel 90 of the second heat exchanger 74 comprises concentric circular channel portions interconnected by openings in the channel wall between adjacent circular channel portions.

During use, a first fluid flows through the first heat exchanger and a second fluid flows through the second heat exchanger. Heat is transferred between the first fluid and the second fluid via the main bodies 76, 88 and the thermoelectric modules 100.

Example 4

With reference to Figure 7 a heat exchanger system 110 for use during medical procedures comprises a primary heat exchanger module 112 and a secondary heat exchanger module 114, a heat storage unit 116, a primary heat exchanger pump 118 and a secondary heat exchanger pump 120.

The primary heat exchanger module 112 comprises a heat exchanger module 122 according to Example 3. The heat storage unit 116 comprises a thermally insulated container 124 and a drain 126. The container 124 contains a mixture of ice and water, and the water within the heat storage unit 116 is approximately 0°C prior to use. The primary heat exchanger pump 118 during use pumps water from the heat storage unit 116 to the first heat exchanger of the heat exchanger module 122 and from the first heat exchanger of the heat exchanger module 122 to the heat storage unit 116 in a first water circuit 128.

The secondary heat exchanger module 114 comprises a heat exchanger module 130 according to Example 3. Water is pumped by the secondary heat exchanger pump 120 from the second heat exchanger of the heat exchanger module 122 to the first heat exchanger of the heat exchanger module 130, and from the first heat exchanger of the heat exchanger module 130 to the second heat exchanger of the heat exchanger module 122 in a second water circuit 132. Blood is pumped through the second heat exchanger of the heat exchanger module 130.

During use, in a first mode heat is transferred from blood flowing through second heat exchanger of the heat exchanger module 130 of the secondary heat exchanger module 114 to the heat storage unit 116 via the second water circuit 132 and the first water circuit 128. Ice within the heat storage unit melts, thereby keeping the temperature of the water within the heat storage unit approximately constant, thereby storing the energy from the blood for later use. Once all of the ice has melted the temperature of the water circulating in the first water circuit 128 will begin to rise further storing heat energy. At this point the current supplied to the thermoelectric modules can be increased to supplement the cooling provided by the temperature gradient between the water in the first water circuit 128, the water in the second water circuit, and the blood. The storage of heat energy continues to a point until the process is stopped if the water temperature rises above a set temperature (for example, 50°C). If this temperature is reached, the heat storage unit 116 could be connected to a source of external running water or recharged with additional ice or dry ice.

Once the blood has reached the required temperature (28°C, for example) the temperature of the blood is maintained by adjusting the power provided to the thermoelectric modules of the heat exchanger modules 122, 130.

After the surgical procedure is finished, the mode of operation of the thermoelectric modules of the heat exchanger modules 122, 130 is reversed such that the flow of heat in the heat exchanger system 110 is reversed such that heat is transferred from the heat storage unit 116 to the blood on the secondary heat exchanger module 114. If additional thermal energy is required to heat the blood to body temperature, additional power is provided to the thermoelectric modules of the heat exchanger modules 122, 130.

Example 5

In an alternative example of the system of Example 4, the secondary heat exchanger module 114 comprises a heat exchanger 134 as shown in Figure 8. The heat exchanger 134 comprises a main body 136 having a first side 138 and a second side 140. The first side comprises a channel 142 and the second side 140 comprises a channel 144. A first enclosed space 146 is defined by the first side 138, a first gasket 148 and a first cover 150. A second enclosed space 152 is defined by the second side 140 a second gasket 154 and a second cover 156. An array of IR LEDs 158 are arranged adjacent to the second cover 156.

The channel 142 is connected to the first inlet 160 of the secondary heat exchanger module 114 and the first outlet 162 of the secondary heat exchanger module 114. The channel 144 is connected to the second inlet 164 of the secondary heat exchanger module 114 and the second outlet 166 of the secondary heat exchanger module 114.

During use, in a first mode when the temperature of blood flowing through the channel 144 is to be reduced, heat is transferred from the blood to the heat storage unit 116 via the second water circuit 132 and the first water circuit 128. In a second mode when the temperature of blood flowing through the channel 144 is to be increased, heat is transferred from the heat storage unit 116 to the blood via the first water circuit 128 and the second water circuit 132. If additional heating is required IR radiation is emitted by the array of IR LEDs 158 through the second cover 156 and is absorbed by blood flowing through the channel 144 to thereby directly heat the blood.

The second heat exchanger module 114 is a passive heat exchanger, and therefore does not require any power to operate. Accordingly, in applications where the active action of the primary heat exchanger is sufficient to maintain the temperature gradient across the secondary heat exchanger module 114, the system of the present example may be more energy efficient that the system of Example 4.

Example 6

In a further alternative example, with reference to Figures 9 and 10 the secondary heat exchanger module 170 of Example 4 comprises a first coiled channel 172, a second coiled channel 174, a central support 176, a first inlet 178, a first outlet 180, a second inlet 182, and a second outlet 184. The first inlet 178 and the first outlet 180 are connected to the second water circuit 132 such that during use water flows into the first inlet 178 to the first outlet 180 via the first coiled channel 172.

During use, blood flows into the second inlet 182 and out of the second outlet 184 via the second coiled channel 174.

The first coiled channel 172 is arranged helically around the second coiled channel 174. The second coiled channel 174 is arranged helically around the central support 176. Accordingly, the first coiled channel 172 and the second coiled channel 174 share a common wall 186.

The central support 176 comprises a conical reflector 188, a collimating lens 190, an array of IR LEDs 192, and an outer wall 194 that is substantially transparent to IR radiation. The array of IR LEDs 192 is arranged at the top of central support above the collimating lens 190. The conical reflector 188 is arranged at the bottom of the central support 176 with the broad end of the conical reflector 188 at the bottom of the central support and the narrow end of the conical reflector 188 is arranged towards the top of the central support 176. Accordingly, IR radiation emitted from the array of IR LEDs 192 is collimated by the collimating lens 190 and directed to the second coiled channel 174 through the outer wall 194 by the conical reflector 188.

During use, in a first mode of operation blood flows through the second coiled channel 174 and heat is transferred from the blood to water flowing through the first coiled channel 172 in the second water circuit 132 to water flowing through the first water circuit 128 to the heat storage unit 116 with the thermoelectric modules of the heat exchanger module 122 set to cooling mode. Accordingly, the blood flowing through the second coiled channel is cooled to a target hypothermic temperature, such as 28°C for patient body cooling or close to 5°C for cardioplegia.

In a second mode of operation heat is transferred from the heat storage unit 116 to the blood flowing through the second coiled channel 174 via the first water circuit 128 and the second water circuit 132 with the thermoelectric modules of the heat exchanger module 122 set to heating mode. If additional heating is required to bring the temperature of the blood back to body temperature (-37°C) additional heating can be provided by exposing the coiled channel 174 to IS radiation emitted by the array of IS LEDs 192 to thereby heat the blood directly.

Example 7

With reference to Figures 11-13, a heating tube 202 comprising a perfusate tube 204, an LED tube 206 and a cooler tube 208. The perfusate tube 204 is arranged within the LED tube 206. The LED tube 206 is arranged within the cooler tube 208. An array of IR LEDs 210 is arranged in milled holes 211 helically around the LED tube facing into the interior of the LED tube 206 such that IS radiation emitted by the array of IS LEDs 210 is directed into the perfusate tube 204. The cooler tube 208 comprises a cooler channel 212, a cooler inlet 214 and a cooler outlet 216 and is configured such that during use a coolant flows into the cooler inlet 214 through the cooler channel 212 and out of the cooler outlet 216. At least a portion of the heat generated by the array of IS LEDs 210 is transmitted to coolant flowing through the cooler tube 208 to thereby cool the array of IS LEDs 210 to ensure that the array of IS LEDs 210 run as efficiently as possible.

In this example, the coolant is water.

The heating tube may be applied to any tubing that is carrying a fluid that may require to be heated. For example, the perfusate tube 204 may be a tube being used to carry blood of a patient during surgical procedures from or to a patient to thereby provide heating of that blood.

In an alternative embodiment, the cooler tube 208 comprises a vent (not shown) adjacent to the top of the heating tube 202 to allow expulsion of gas from within the cooler channel 212 that may build up during the cooling process. In this embodiment the cooler inlet 214 and the cooler outlet 216 may be sealed prior to use such that coolant is retained within the cooler channel 212 with an air gap adjacent to top of the cooler tube 208 to allow expansion of the coolant as it is heated. In this way the heating tube 202 may not be required to be connected to flowing coolant, such as water, during use

Example 8

With reference to Figure 14, a further alternative of the system of Example 4 a heat exchanger system 300 comprises bypass valves 302, 303 that are configured to direct water to flow along either the first water circuit 304 and the second water circuit 306 or to flow along a third water circuit 308. The third water circuit 308 allows the flow of water from the heat storage unit 310 to the secondary heat exchanger module 312 directly bypassing the primary heat exchanger module 314. Therefore, the thermoelectric modules 316 of the primary heat exchanger module 314 may only be used when additional cooling or heating is required, thereby reducing the power consumption of the heat exchanger system 300.

Example 9

With reference to Figure 15 A and B, in a further example a heat exchanger 400 comprises a main body 402, a first spiral channel 404, a second spiral channel 406, a first inlet 408, a first outlet 410, a second inlet 412, a second outlet 414, a first cover 416, a second cover 418, a first spacer 420 and a second spacer 422.

The first spiral channel 404 extends from the first inlet 408 to the first outlet 410 on a first side 424 of the main body 402. A first enclosed space 426 is defined between the first cover 416, the first spacer 420 and the first side 424 of the main body. The first inlet 408 is located adjacent to the exterior of the first spiral channel 404 and the first outlet 410 is located adjacent to the centre of the first spiral channel 404, where it terminates.

The second spiral channel 406 extends from the second inlet 412 to the second outlet 414 on a second side 426 of the main body 402 opposed to the first side 424. A second enclosed space 428 is defined between the second cover 418, the second spacer 422 and the second side 426 of the main body 402. The second inlet 412 is located adjacent to the exterior of the second spiral channel 406 and the second outlet 414 is located adjacent to the centre of the second spiral channel 406, where it terminates.

The first spiral channel 404 is interleaved with the second spiral channel 406 such that a portion of the first spiral channel 404 extends into the channel wall of the second spiral channel 406, and vice versa. A section of the interleaving of the first spiral channel 404 and the second spiral channel 406 is shown in Figure 15A and 15B. For the avoidance of doubt, the "cross" symbol represents flow of fluid into the plane of Figure 15B and the "dot" symbol represents flow of fluid out of the plane of Figure 153.

The interleaving of the first spiral channel 404 and the second spiral channel 406 results in a minimum amount of material of the main body 402 being between fluid flowing through the first spiral channel 404 and fluid flowing through the second spiral channel 406 thereby reducing flow resistance and increasing the efficiency of heat transfer between those fluids.

Example 10

In a further alternative example to the system of Example 8, the system further comprises a secondary bypass system 500 comprising a secondary bypass outlet valve 502 that is configured to divert water flowing from the first water circuit 304 and the third water circuit 308 to an outlet 504, and a secondary bypass inlet valve 506 configured to allow water to enter the first water circuit 304 and third water circuit 308 from a mains water supply. A first water pump 508 is configured to pump fluid from the heat storage unit 116 into the first water circuit 304 or the third water circuit 308. A second water pump 510 is configured to pump water around the second water circuit 306.

During use in a cooling mode first water pump 508 and the second water pump 510 pump water around the first water circuit 304 and the second water circuit 306 respectively. The thermoelectric modules 316 of the primary heat exchanger module 312 pumps heat from the water in the second water circuit 306 to the water in the first water circuit 304 and thereby to the heat storage unit 116 and the temperature of the water in the first water circuit 304 rises as heat is transferred to it. The current provided to the thermoelectric modules 316 is increased as the temperature differential across the thermoelectric module 316 is reduced as the water in the first water circuit 304 increases. If the temperature of the water in the first water circuit 304 reaches 50°C (a threshold temperature) the secondary bypass system 500 is engaged such that the secondary bypass outlet valve 502 and the secondary bypass inlet valve 506 open the first water circuit 304 to a mains water supply and the first water pump 508 is switched off. Accordingly, water retained within the heat storage unit 116 is no longer circulated, and cooler water (approximately 15°C) is circulated around the first water circuit 304.

During use in a heating mode the current provided to the thermoelectric modules 316 is reversed such that the direction of heat transfer is reversed. The secondary bypass system 500 is disengaged such that the heated water retained within the heat storage unit 116 is transferred into circulation through the first water circuit 304 and the heat stored in that water is transferred to the water in the second water circuit 306. If the temperature of the water in the first water circuit 304 drops below 2°C the secondary bypass system 500 is engaged to open the first water circuit 304 to the mains water supply.

An example mode of operation of this system is shown in Figure 17 and 18.

While there has been hereinbefore described approved embodiments of the present invention, it will be readily apparent that many and various changes and modifications in form, design, structure and arrangement of parts may be made for other embodiments without departing from the invention and it will be understood that all such changes and modifications are contemplated as embodiments for other heat exchangers and heat exchanger systems as a part of the present invention as defined in the appended claims.

Claims

Claims 1. A cross-flow heat exchanger comprising a main body, a flow channel, an inlet, an outlet, a spacer and a cover, the main body comprises a thermally conductive material and the flow channel extends through the main body and extends between the inlet and the outlet; the flow channel has a depth and is open along the majority of its length on a first side of the main body and comprises a plurality of channel portions, and each channel portion of the plurality of channel portions is in fluid communication with an adjacent channel portion and is separated from an adjacent channel portion by a channel wall; the spacer is located between the cover and the main body and an enclosed space is defined between the cover, the spacer and the main body; wherein the cross-flow heat exchanger is configured such that during use fluid flows from the inlet to the outlet along the flow channel and also flows across the channel wall via the enclosed space, and, wherein during use thermal energy is transferred between the main body and fluid flowing through the flow channel.
2. A cross-flow heat exchanger according to claim 1, wherein at least one channel portion of the plurality of channel portions is curved.
3. A cross-flow heat exchanger according to any of claim 1 or claim 2, wherein at least one channel portion of the plurality of channel portions is circular.
4. A cross-flow heat exchanger according to claim 1 or claim 2, wherein the flow channel forms a spiral channel.
5. A cross-flow heat exchanger according to claim 1 to claim 3, wherein the plurality of channel portions are interconnected by one or more opening within the channel wall. 30
6. A cross-flow heat exchanger according to claim 5, wherein the plurality of channel portions comprises at least an outer circular channel portion and an inner circular channel portion interconnected to the outer circular channel portion by one or more openings within the channel wall between the outer circular channel portion and the inner channel portion, the inlet connected to the outer circular channel portion, wherein the or each opening within the channel wall is offset from the inlet such that during use fluid flows around at least a part of the of outer circular channel portion to the inner circular channel portion through the one or more openings.
7. A cross-flow heat exchanger according to claim 6, wherein each channel portion in the plurality of channel portions is circular and the opening in the channel wall between a first and second channel portion is on the side of the cross-flow heat exchanger opposed to the side of the cross-flow heat exchanger on which the opening in the channel wall between the second and a third channel portion such that during use fluid flows into each channel portion of the plurality of channel portions on the side of the channel portion opposed to the opening to the adjacent channel portion such that fluid flows in both directions around substantially half of the circular channel portion to the opening.
8. A cross-flow heat exchanger according to any preceding claim, wherein the flow channel comprises at least 4, 6, 8 10, 12, 14, 16, 18 or 20 channel portions.
9. A cross-flow heat exchanger according to any preceding claim, wherein the outlet is in or adjacent to the middle of the plurality of channels.
10. A cross-flow heat exchanger according to any preceding claim, wherein the inlet is connected to an outermost channel portion within the plurality of channel portions.
11. A cross-flow heat exchanger according to any preceding claim, wherein at least one channel wall between two adjacent channel portions comprises a plurality of apertures to allow the flow of fluid through the channel wall.
12. A cross-flow heat exchanger according to any preceding claim, wherein the main body comprises a metal selected from the group consisting of aluminium, copper, tin, iron, steel, stainless steel, brass, or an alloy of the same.
13. A cross-flow heat exchanger according to any preceding claim, wherein the spacer extends from the main body from 0.1mm to 2.0mm.
14. A heat exchanger system comprising a first cross-flow heat exchanger according to any one preceding claim, at least one heat pump, a first system input and a first system output, wherein the at least one heat pump is in thermal contact with a second side of the main body opposed to the first side such that during use fluid flows from the first system input to the first system output via the flow channel of the first cross-flow heat exchanger such that thermal energy is transferred between the fluid and the at least one heat pump via the material of the first cross-flow heat exchanger.
15. A heat exchanger system according to claim 14, wherein the system comprises a second cross-flow heat exchanger according to any of claims 1 to 13, a second system inlet and a second system outlet, the second side of the main body of the second cross-flow heat exchanger opposed to the first side of the main body is coupled to the at least one heat pump such that during use thermal energy may be exchanged between the main body of the second cross-flow heat exchanger and the at least one heat pump, wherein during use a first fluid flowing through the first cross-flow heat exchanger is isolated from a second fluid flowing through the second cross-flow heat exchanger and thermal energy may be transferred between the first fluid and the second fluid.
16. A heat exchanger system according to claim 15, wherein the first fluid is a coolant.
17. A heat exchanger system according to claim 15 or claim 16, wherein the at least one heat pump is a thermoelectric module.
18. A heat exchanger system according to claim 15 to claim 17, wherein the at least one heat pump is configured to drive the direction of heat transfer across the heat exchanger system
19. A heat exchanger system according to claim 15 or 18 further comprising a heat storage unit in fluid communication with the first system inlet and the first system outlet such that during use the first fluid may flow from the heat storage unit to the flow channel of the first cross-flow heat exchanger via the first system inlet and from the flow channel of the first cross-flow heat exchanger to the heat storage unit via the first system outlet.
20. A heat exchanger system according to claim 19, wherein the heat storage unit comprises a material with a high heat of fusion which, when melting or freezing, is configured to store or release thermal energy respectively.
21. A heat exchanger system according to any of claims 15 to 20 comprises a primary heat exchanger module and a secondary heat exchanger module, the primary heat exchanger module comprises the first cross-flow heat exchanger, the second cross-flow heat exchanger, the first system outlet, the first system inlet, the second system inlet and the second system outlet, the secondary heat exchanger module comprises a heat exchanger comprising a flow channel, a third inlet and a third outlet, secondary heat exchanger configured such that fluid may flow from the third inlet to the third outlet via the flow channel, wherein the third inlet is in fluid communication with the second outlet of the second cross-flow heat exchanger and the third outlet is in fluid communication with the second inlet of the second cross-flow heat exchanger.
22. A heat exchanger system according to claim 21, wherein the primary heat exchanger module comprises a heat storage unit.
23. A cross-flow heat exchanger comprising a main body, a first flow channel, a first inlet, a first outlet, a first spacer and a first cover, a second flow channel, a second inlet, a second outlet, a second spacer, and a second cover, the main body comprises a thermally conductive material and the first flow channel extends through the main body and extends between the first inlet and the first outlet, and the second flow channel extends through the main body and extends between the second inlet and the second outlet; the first flow channel has a depth and is open along the majority of its length on a first side of the main body and comprises a plurality of channel portions, and each channel portion of the plurality of channel portions is in fluid communication with an adjacent channel portion and is separated from an adjacent channel portion by a channel wall; the second flow channel has a depth and is open along the majority of its length on a second side of the main body and comprises a plurality of channel portions, and each channel portion of the plurality of channel portions is in fluid communication with an adjacent channel portion and is separated from an adjacent channel portion by a channel wall; the first spacer is located between the first cover and the main body and a first enclosed space is defined between the first cover, the first spacer and the main body; the second spacer is located between the second cover and the main body and a second enclosed space is defined between the second cover, the second spacer and the main body; wherein the cross-flow heat exchanger is configured such that during use a first fluid flows from the first inlet to the first outlet along the first flow channel and also flows across the channel wall via the first enclosed space, and a second fluid flows from the second inlet to the second outlet along the second flow channel and also flows across the channel wall via the second enclosed space, and wherein during use thermal energy is transferred between the first fluid and the second fluid via the main body.
24. A cross-flow heat exchanger according to claim 23, wherein the first flow channel and the second flow channel are interleaved.
25. A heat exchanger comprising a first flow channel, a first inlet, a first outlet, a second flow channel, a second inlet, a second outlet, and a central support, the first flow channel arranged helically around the second flow channel, the second flow channel arranged helically around the central support; the first flow channel is connected to the first inlet and the first outlet such that during use a first fluid may flow from the first inlet to the first outlet via the first flow channel; the second flow channel is connected to the second inlet and the second outlet such that during use a second fluid may flow from the second inlet to the second outlet via the second flow channel; wherein the first flow channel and the second flow channel share a common wall such that during use thermal energy may be transferred from the first fluid to the second fluid via 20 the common wall.
26. The heat exchanger according to claim 25, wherein the central support comprises a source of IIR radiation such that during use IIR radiation emitted by the course of IIR radiation is directed to fluid flowing through the second flow channel.
27. A heating device comprising a perfusate tube, a heater tube and a cooler tube, the perfusate tube is arranged within the heater tube, the heater tube is arranged within the cooler tube, wherein the heater tube is configured to transmit heat to the perfusate tube such that during use heat may be transferred to a fluid passing through the perfusate tube.