EP4321831A1

EP4321831A1 - A heat exchanger and a method of transferring thermal energy

Info

Publication number: EP4321831A1
Application number: EP22189975.0A
Authority: EP
Inventors: Emilia MOTOASCA
Original assignee: Vito NV
Current assignee: Vito NV
Priority date: 2022-08-11
Filing date: 2022-08-11
Publication date: 2024-02-14

Abstract

The invention relates to a heat exchanger and a method of transferring heat. The heat exchanger comprises a heat transfer interface including a member configured to contact a heat source, wherein the heat transfer interface includes a plurality of deformable heat conducting structures distributed on the surface of the member to be exposed to a flow of heat exchange medium, wherein the structures emerge from said surface and are configured to deform as a function of a local temperature change of the member through thermal contact with the heat source, wherein the structures are adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction.

Description

FIELD OF THE INVENTION

The invention relates to a heat exchanger comprising a heat transfer interface including a member configured to contact a heat source. Additionally, the invention relates to a method of transferring heat using a heat exchanger. The invention also relates to an energy system comprising at least one heat exchanger. Furthermore, the invention relates to a method of manufacturing a heat exchanger. Also, the invention relates to a heat transfer interface of a heat exchanger, and a method of manufacturing said heat transfer interface.

BACKGROUND TO THE INVENTION

Heat exchangers often employ thermal energy interfaces (also known as heat transfer interfaces) to separate the heat transfer media (fluids) on the primary and the secondary sides of the heat exchangers. Typically, metallic interfaces are employed which have an invariant shape. It is common that the interface is made of homogeneous and isotropic materials with constant thermal properties. The heat transfer between the primary and the secondary side is enhanced typically by fins in contact with the heat source.
The heat transfer between the primary and the secondary side of the heat exchanger is strongly influenced by the shape of the fins.. The fins can be applied on the surface or created through deformations of the interface. The heat transfer performance of these heat exchangers is influenced by the shape of the fins. The shape can also have a large impact on the flow characteristics and thus on the heat transfer.
Heat exchangers comprising smart materials, such as smart memory alloys (SMA), for enhancing heat transfer are known in the art. SMA are materials able to change their shape depending on the applied temperature. The changes in the shape of the fins or of the interface in heat exchanger surfaces can lead to an increased heat exchange, thus an increased efficiency of the heat exchanger , as here is need to be able to further improve the heat transfer in heat exchangers.
Publication "Design and test of shape memory alloy fins for self-adaptive liquid cooling device" (Regany et al. 2022) describes a set of adaptive SMA fins that can change shape depending of the temperature of the heat transfer medium. The space of the fins changes progressively and heat transfer is enhanced only through the variable shape of the fins.
Publication "Smart microchannel heat exchanger based on the adaptive deformation effect of shape memory alloys" (Chu et al. 2021) describes the development of a SMA vortex generator that through its adaptive shape may improve heat removal from local hotspots, which is considered as a special case of non-uniform heat flux .
Publication US10557671B2 describes a self-regulating heat exchanger with SMA where the heat exchange is increased through the variable shape of the interface (fins) due to temperature of the heat transfer medium.

SUMMARY OF THE INVENTION

It is an object of the invention to provide for a method and a system that obviates at least one of the above mentioned drawbacks.
Additionally or alternatively, it is an object of the invention to improve the thermal energy transfer in heat exchangers.
Additionally or alternatively, it is an object of the invention to obtain more uniform thermal energy transfer in heat exchangers.
Additionally or alternatively, it is an object of the invention to improve the energy efficiency of heat exchangers.
Thereto, the invention provides for a heat exchanger comprising a heat transfer interface including a member configured to contact a heat source, wherein the heat transfer interface includes a plurality of deformable heat conducting structures distributed on the surface of the member to be exposed to a flow of heat exchange medium, wherein the structures emerge from said surface and are configured to deform as a function of a local temperature change of the member through thermal contact with the heat source, wherein the structures are adapted to deform differently as a function of said local temperature change depending on their position on the member wall in the flow direction of the heat exchange medium.
As the structures deflect/deform differently as a function of said local temperature change depending on its position on the member in the flow direction, the local heat transfer at the structures can be adapted such that an improved heat transfer and/or a more uniform heat transfer can be obtained. The structures on the member arranged at different discrete locations seen in the flow direction may selectively have different deformations/deflections as a function of local temperature change, such as to compensate for non-uniform heat transfer under predetermined operating conditions of the heat exchanger. Hence, the structures arranged at the different discrete locations seen in the flow direction may have non-uniform deformations/deflections. The variable deformation characteristics may change gradually along the position in the flow direction. In some examples, some structures are arranged next to each other at a same location seen in the flow direction, wherein these structures may have substantially the same deformation/deflection as a function of local temperature change. With other words, structures arranged next to each other (e.g. in a same row of a two-dimensional array arrangement of structures, wherein the columns extend in the flow direction) may have substantially the same configuration such as to have a substantially equal deformation/deflection.
The structures may be adapted to deform differently as a function of said local temperature change based on temperatures expected at their locations at the surface of the member during use. For example, during use, the heat exchanger may be configured to provide a warm fluid in a first temperature range, and a cold fluid in a second temperature range. For predefined flow regimes and the first and second temperature ranges, the structures may be adapted to deform differently such as to improve the heat transfer and/or to provide a more uniform heat transfer over the surface of the member.
It will be appreciated that thermal contact of the member with the heat source can be a direct thermal contact or an indirect thermal contact. In some examples, the thermal contact is a conductive thermal contact.
Optionally, the heat exchanger is configured to operate with a substantially uniform heat flux input at the surface of the member.
It will be appreciated that a uniform heat flux may be understood as a working regime in which the surface of member is free of localized temperature hotspots.
A distinction can be made between several heat flux distributions over the surface of the member, namely a uniform high heat flux, a uniform medium heat flux, and a non-uniform heat flux (cf. temperature hotspots).
For a heat exchanger configured to operate with a uniform (high) heat flux, the heat transfer can be effectively improved whilst obtaining a more uniform heat transfer in the heat exchanger.
As the structures are configured to deform differently as a function of said local temperature change depending on its position on the member the flow direction, the heat transfer may be non-uniform when the heat exchanger operates with a uniform high heat flux . However, there will be temperature differences between the heat exchange medium and the heat source (e.g. between cold fluid and warm fluid) at different locations on the surface of the member. These temperature differences can depend on the flow direction. For example, if heat is transferred from a warm fluid to a cold fluid with substantially uniform high heat flux, then the cold fluid located more upstream will be colder than the cold fluid more downstream. This will also impact the temperatures of the structures, such that they will have different temperatures depending on their position on the member in the flow direction. Advantageously, the heat transfer can be improved, or even optimized, by effectively configuring the structures such that they deform differently as a function of said local temperature change depending on their position on the member the flow direction. How differently the extent to which the structures are to deform depends on the operating regimes of the heat exchanger. The structures can be adapted or preconfigured to take those parameters into account. In some examples, the way the structures deform and thus their configuration is determined by performing simulations or experiments, for example computational fluid dynamics simulations and/or multi-physics computational analysis.
The structures are adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction, such that a substantially similar or equal deformation is obtained for the structures for a predefined uniform medium heat flux. Advantageously, for the uniform/medium heat flux, the heat transfer can be improved or even maximized.
If all the structures would have the same deformation as a function of local temperature changes, then the structures would deform differently in a medium heat flux. For example, if the heat exchanger is used for transferring thermal energy from a heat source (warm fluid) to a cold fluid flowing in a flow direction then structures located more upstream with respect to the flow direction of the cold fluid would have a deformation different than that of the structures located more downstream with respect to the flow direction. In contrast, according to the heat exchanger of the invention, wherein the structures are adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction, the structures may deform in a similar way (e.g. same deflection).
In some examples, in a uniform high heat flux, the structures are adapted to substantially have different deformations depending on their location on the surface the flow direction.
In some examples, in a uniform medium heat flux, the structures at different locations on the surface are adapted to substantially have the same deformations in the flow direction.
Optionally, the structures are configured to project upwardly from said surface of the member. In some examples, the structures have one or more free ends or tips. In some examples, the one or more free ends or tips deflect in function of the temperature.
Optionally, the structures form fins having end portions configured to deflect away from said surface of the member as a function of said local temperature change of the member, wherein the fins have different end portion deflections in response to predefined temperatures depending on its position on the member in the flow direction.
Optionally, the structures are configured to have variable shapes in function of temperature, wherein the structures are adapted to reshape/deform differently depending on their position on the member the flow direction.
Optionally, structures located more upstream in the flow direction have a higher end portion deflection in response to predefined temperatures compared to structures located more downstream in the flow direction.
Optionally, consecutive fins arranged on the member in the flow direction have gradually decreasing end portion deflections in response to predefined temperatures.
Optionally, the structures are configured such as to have substantially same end portion deflections when the surface of the member has a non-uniform temperature distribution as a result of one or more predefined flow and temperature operating regimes.
Optionally, structures have different properties depending on their location on the member the flow direction, resulting in different deformations as a function of local temperature changes.
Optionally, the structures have substantially same dimensions whilst having different material and/or actuation properties depending on its position on the member in the flow direction.
Optionally, the structures are made of functionally graded materials . The structures may be functionally graded so as to deflect differently as a function of said local temperature change depending on their position on the member in the flow direction.
Functionally graded materials can be understood as materials with variable properties along one or more directions. The structures or vortex generators made of functionally graded smart memory alloys may significantly improve both the heat exchange along the whole length of the heat exchangers as well as reduce the thermal stresses in the heat exchangers.
Optionally, a grid of structures are arranged on the surface of the member to be exposed to the flow of heat exchange medium, wherein the subsets of structures arranged next to each other on a same position in the flow direction have the same configuration such as to deform similarly as a function of the local temperature change.
Optionally, the heat exchanger includes a first side with a first thermal energy transfer medium at a first temperature, and a second side with a second thermal energy exchange medium at a second temperature, wherein the first and second temperatures are different. In some examples, the structures extend in the second side.
The heat transfer interface can be arranged between the first side and the second side of the heat exchanger, wherein the heat transfer interface includes a solid member from which the plurality of structures extend to the second side, and wherein the second medium is caused to flow along the heat transfer interface in a flow direction. The structures are configured to deform in response to temperature changes. Furthermore, the structures are configured such that they deform differently as a function of temperature depending on its position on the member along the flow direction.
In some alternative examples, the first side is free of thermal energy exchange medium. For example, thermal energy may be exchanged directly through a solid material (cf. thermal conduction).
Optionally, the structures are adjustable in function of temperature between a first state, in which they are located closer to the surface of the member, and a second state, in which they protrude more, are positioned farther away (more remote - remotely?) from the surface of the member, and at least one intermediate state between the first state and the second state. The structures may be configured to have a plurality of intermediate states between the first state and the second state. In some examples, the structures can gradually deform between the first state and the second state. This can for example be achieved by means of a memory shape alloy. According to the disclosure, the structures can have varying adjustment characteristics depending on its position in the flow direction (e.g. of the second thermal energy exchange medium).
In some examples, the heat exchanger has a higher temperature region and a lower temperature region, wherein the heat transfer interface is provided between the higher temperature region and the lower temperature region, wherein at the interface the plurality of adaptive structures are arranged, wherein the structures at different locations along the flow direction have different deformation characteristics in function of the temperature.
Optionally, the heat source is provided by a flow of working fluid.
In some examples, the flow of working fluid at the heat source side is reversed with respect to the flow direction of the heat exchange medium to which the structures are exposed.
Optionally, the structures are plates dimensioned and adapted to facilitate turbulent flow in the heat exchange medium.
The different deflections/deformations of the structures can result in different flow regimes and different vortex formations. More vortices may improve the heat transfer in some examples. For examples, in some cases a more turbulent flow may be obtained which can improve mixing and thus heat transfer.
Optionally, the structures include one or more actuators.
In some examples, the structures are connected or coupled to an actuator. Alternatively, the structures may form the actuators, for example the structures may be made of shape memory alloys. Other materials that adequately change their shape in function of temperature may also be used.
In some examples, the actuators are micro-actuators.
Optionally, the one or more actuators are passive actuators.
The passive actuators may provide actuator without requiring an external energy source such as a battery, or electrical actuation. The passive actuators may be configured to deform in function of the temperature. The passive actuators may be not actively controlled. However, actively controlled actuators may also be used. Such actively controlled actuators may be controlled using a controller. For this purpose, in some examples, one or more sensory data may be collected, for instance using temperature sensors. The actuation of the active controllers may be based on the monitored temperature(s).
Optionally, the structures include temperature dependent actuators, such as shape memory alloys.
With memory shape alloys different deformations can be obtained in an accurate and predictable manner. Furthermore, a cost-effective design of fin-like structures can be obtained. The properties of the memory shape alloys may change depending on their location on the member the flow direction.
Various other actuators may be used. In some examples, piezoelectric actuators are used.
It will be appreciated that the structures may have various arrangements. Different shapes and dimensions can be employed. For examples, the structures may be plate-like structures. In some examples, the structures form fins. However, it is also envisaged that feather like structures are employed. In some examples, the structures have one or more apertures through which a heat exchange medium can flow. Although various examples are given with the thermal energy exchange medium being a fluid, various other types of thermal exchanged mediums can be used. The thermal energy exchange medium can be a heat transfer medium. In some cases, a liquid is used. However, it is also possible that the medium is substantially in a gas phase, a vapor phase, etc. It is also possible that the medium is in a gas phase with solid or liquid particles suspended therein.
In some examples, the heat flux is substantially constant or within a predetermined relatively small range.
In some examples, the heat flux is variable and is allowed to change within a predetermined relatively large range.
According to an aspect, the invention provides for a method of transferring heat using a heat exchanger, the heat exchanger having a heat transfer interface including a member configured to contact a heat source, wherein the heat transfer interface is provided with a plurality of deformable heat conducting structures distributed on the surface of the member exposed to a flow of heat exchange medium, wherein the deformable heat conducting structures emerge from said surface and are configured to deform as a function of a local temperature change of the member through thermal contact with the heat source, wherein the deformable heat conducting structures are adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction.
It will be appreciated that the structures may be arranged to change shape and/or deform in function of its temperature. In some examples, the structures are adapted/configured to deform in predetermined temperature ranges. For examples, the desired/targeted deformations may occur in the predetermined temperature range at which the heat exchanger is expected to operate under normal conditions. For instance, at lower temperatures, no deformation may occur. Similarly, the deformations may occur until a certain maximum threshold temperature is reached.
According to an aspect, the invention provides an energy system comprising at least one heat exchanger according to the disclosure.
According to an aspect, the invention provides for a method of manufacturing a heat exchanger, the method comprising: arranging a heat transfer interface including a member configured to contact a heat source; and providing the heat transfer interface with a plurality of deformable heat conducting structures, wherein the structures are distributed on the surface of the member to be exposed to a flow of heat exchange medium, and wherein the structures are constructed to emerge from said surface; and wherein the structures are configured to deform as a function of a local temperature change of the member through thermal contact with the heat source, and wherein the structures are adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction.
In some examples, the structures have different properties, such as for example material properties and/or geometrical properties, such as to deform differently as a function of said local temperature change depending on its position on the member in the flow direction. In this way, the heat transfer can be effectively promoted in a simple way.
The structures can be configured to deflect away or towards the surface as a result of temperature differences. In this way, the heat transfer through the structures can be influenced based on the temperature. The structures may be preconfigured such as to obtain adequate orientations (cf. deflections) in predetermined temperature ranges.
According to an aspect, the invention provides for a heat transfer interface for use in a heat exchanger, wherein the heat transfer interface includes a plurality of deformable heat conducting structures, wherein the structures are distributed on the surface of the member to be exposed to a flow of heat exchange medium, and wherein the structures are constructed to emerge from said surface; and wherein the structures are configured to deform as a function of a local temperature change of the member through thermal contact with the heat source, and wherein the structures are adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction.
Advantageously, the heat transfer in the heat exchanger can be improved. Moreover, a more uniform heat transfer can be obtained in an effective way.
According to an aspect, the invention provides for a method of manufacturing a heat transfer interface of a heat exchanger.
It will be appreciated that the thermal energy exchange medium may be a thermal energy transfer medium, such as a heat transfer medium.
It will be appreciated that any of the aspects, features and options described in view of the heat exchanger apply equally to the method and the described system. It will also be clear that any one or more of the above aspects, features and options can be combined.

BRIEF DESCRIPTION OF THE DRAWING

The invention will further be elucidated on the basis of exemplary embodiments which are represented in a drawing. The exemplary embodiments are given by way of non-limitative illustration. It is noted that the figures are only schematic representations of embodiments of the invention that are given by way of non-limiting example.
In the drawing:

Fig. 1a, 1b show respectively a top view and a cross sectional side view of a schematic diagram of an embodiment of an exemplary heat transfer interface of a heat exchanger;
Fig. 2a, 2b show cross sectional side views of a schematic diagram of an embodiment of an exemplary heat transfer interface of a heat exchanger;
Fig. 3a, 3b show cross sectional side views of a schematic diagram of an embodiment of an exemplary heat transfer interface of a heat exchanger;
Fig. 4 shows a cross sectional side view of a schematic diagram of an embodiment of an exemplary heat transfer interface of a heat exchanger;
Fig. 5 shows a cross sectional side view of a schematic diagram of an embodiment of an exemplary heat transfer interface of a heat exchanger;
Fig. 6 shows a cross sectional side view of a schematic diagram of an embodiment of an exemplary interface system;
Fig. 7 shows a cross sectional side view of a schematic diagram of an embodiment of an exemplary heat transfer interface of a heat exchanger;
Fig. 8 shows a cross sectional side view of a schematic diagram of an embodiment of an exemplary heat transfer interface of a heat exchanger; and
Fig. 9a, 9b show perspective views of a schematic diagram of an embodiment of an exemplary heat transfer interface of a heat exchanger.

DETAILED DESCRIPTION

Fig. 1a, 1b show respectively a top view and a cross sectional side view of a schematic diagram of an embodiment of an exemplary heat transfer interface 1 of a heat exchanger. The heat transfer interface 1 comprises a member 3 configured to contact a heat source. The heat transfer interface 1 includes a plurality of deformable heat conducting structures 5 distributed on the surface 7 of the member 3 to be exposed to a flow of heat exchange medium 9. In this example, the flow of heat exchange medium 9 is hot or warm fluid, however, it can be the other way around with the flow of heat exchange medium 9 being a cold fluid (and the heat source being warmer). The structures 5 emerge from said surface 7 and are configured to deform as a function of a local temperature change of the member 3 through thermal contact with the heat source. In this example, the heat source is provided by cold fluid. However, the heat source can also be a heat source (e.g. warm fluid), in which case the heat exchange medium is a cold fluid. The structures 5 are adapted to deform differently as a function of said local temperature change depending on its position on the member 3 in the flow direction A of the heat exchange medium 9. An improved heat transfer can be obtained in an advantageous way. Moreover, a more uniform heat transfer may be obtained.
Fig. 2a, 2b show exemplary heat transfer interfaces 1. The structures 5 are fins which can deform or re-orientate in function of the temperature. In this example, it is illustrated that the structures can deform differently for different heat sources due to different temperatures at the surface 7 of the member 3. The structures 5 are adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction A. In this example, the variation in deformation characteristics is in a dimension not visible in the cross sectional view.
In fig. 2a, warm fluid flows from left to right, and the heat exchanger is configured to transfer heat to a cold fluid flowing from right to left. If all the structures would have the same deformation characteristics in function of temperature, a higher heat transfer would be obtained by the structures at the right side, because the structures at the right side have a lower temperature than the structures on the left side since the cold liquid is colder when encountering the structures at the right side, and thus results in a higher temperature difference and thus heat transfer. However, this can be effectively compensated according to the disclosure by suitably adapting the structures to deform differently as a function of said local temperature change depending on its position on the member in the flow direction.
Fig. 3a, 3b show exemplary heat transfer interfaces 1 with structures 5 that are adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction A. In this example, the variation in deformation characteristics is in a dimension clearly visible in the cross sectional view.
In some examples, a functionally graded material is used for the structures 5 or actuator. The material may have variable properties along the flow direction A (as illustrated by its greyscale darkness in the figure). In this way, the structures can be adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction, in an advantageous way, leading in increased thermal energy transfer in the heat exchanger. In some examples, the structures are made of functionally graded materials, wherein the grading is performed depending on its position on the member in the flow direction A. In some examples, the grading is linearly changed depending on its position on the member in the flow direction.
The combination of smart memory alloys and functionally graded materials may provide for a significantly better design of the interface. This combination can lead to significantly improved. heat transfer along the whole length of the heat exchangers and in the same time improve the thermal stresses that may be induced in the heat exchanger.
Fig. 4 shows an exemplary heat transfer interface 1 with a uniform high heat flux resulting in different deformations of the structures depending on its position on the member in the flow direction. The heat source is a flow of hot fluid in reverse direction with respect to the flow of cold heat exchange medium 9. In this way, the change in temperature of the heat exchange medium 9 resulting from the uniform high heat flux can be compensated for, such that an improved heat transfer can be obtained by the heat transfer interface 1.
Fig. 5 shows an exemplary heat transfer interface 1 similar to the example shown in fig. 4, however, in this case the flow of hot fluid and cold fluid are substantially parallel to each other along the interface.
Fig. 6 shows an exemplary heat transfer interface 1. In this example, the structures 5 are tapered structures. Various other shapes or deformation characteristics are envisaged.
Fig. 7 shows an exemplary heat transfer interface system 1' comprising a first heat transfer interface 1a and a second heat transfer interface 1b. The two heat transfer interfaces 1a, 1b share a heat source, namely a flow of hot fluid. Alternatively, the heat source may be something else than a flowing fluid, for example a hot solid heat source.
In this example, both first and second heat interfaces 1a, 1b have structures selectively adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction.
It will be appreciated that an inverse situation is also possible, with the heat source being cold and the flow of exchange medium along the structures being a hot fluid.
Fig. 8 shows an exemplary heat transfer interface 1. In this example, the structures 5 are configured to become wider in function of the temperature. Various other deformation characteristics are possible.
Fig. 9a, 9b show perspective views of a schematic diagram of an embodiment of an exemplary heat transfer interface of a heat exchanger. In fig. 9a, a uniform medium heat flux is provided, wherein the temperature at the surface of the member is influenced by the flow of heat exchange medium. In fig. 9b, a uniform high heat flux is provided, wherein the temperature at the surface of the member is not substantially influenced by the flow of heat exchange medium 9.
Advantageously, the heat transfer is improved by effectively configuring the structures such that they deform differently as a function of said local temperature change depending on their position on the member the flow direction. For this purpose, the structures are preconfigured based on predefined working regimes of the heat exchanger so as to compensate for the temperature change of the heat exchange medium 9 which would detrimentally affect the heat transfer.
For a uniform high heat flux as shown in fig. 9b, the high heat flux can keep the temperature of the surface of the member substantially constant. In contrast, for a uniform medium heat flux, the temperature of the surface of the member tends to change depending on the location on the surface the flow direction. As a result, a substantial temperature difference on the surface of the member can be obtained the flow direction. The structures are adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction, such that a substantially similar or equal deformation is obtained for the structures for a predefined uniform medium heat flux. Advantageously, for the uniform/medium heat flux, the heat transfer can be improved or even maximized.
In various examples, the warm fluid and the cold fluid have an opposite flow direction. However, it will be appreciated that, alternatively, the heat exchanger may be configured to have warm fluid and cold fluid in a substantially same flow direction. Other configurations are also possible, for instance, with the flow of warm fluid and the cold fluid being at a different angle with respect to each other. In some alternative examples, a solid is employed instead of fluids. The solid can be employed at the warmer side and/or at the colder side.
Herein, the invention is described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications, variations, alternatives and changes may be made therein, without departing from the essence of the invention. For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, alternative embodiments having combinations of all or some of the features described in these separate embodiments are also envisaged and understood to fall within the framework of the invention as outlined by the claims. The specifications, figures and examples are, accordingly, to be regarded in an illustrative sense rather than in a restrictive sense. The invention is intended to embrace all alternatives, modifications and variations which fall within the scope of the appended claims. Further, many of the elements that are described are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, in any suitable combination and location.
In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word 'comprising' does not exclude the presence of other features or steps than those listed in a claim. Furthermore, the words 'a' and 'an' shall not be construed as limited to 'only one', but instead are used to mean 'at least one', and do not exclude a plurality. The term "and/or" includes any and all combinations of one or more of the associated listed items. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to an advantage.

Claims

A heat exchanger comprising a heat transfer interface including a member configured to contact a heat source, wherein the heat transfer interface includes a plurality of deformable heat conducting structures distributed on the surface of the member to be exposed to a flow of heat exchange medium, wherein the structures emerge from said surface and are configured to deform as a function of a local temperature change of the member through thermal contact with the heat source, wherein the structures are adapted to deform differently as a function of said local temperature change depending on their position on the member in the flow direction of the heat exchange medium.
The heat exchanger according to claim 1, wherein the heat exchanger is configured to operate with a substantially uniform heat flux input at the surface of the member.
The heat exchanger according to claim 1 or 2, wherein the heat conducting structures form fins having end portions configured to deflect away from said surface of the member as a function of said local temperature change of the member, wherein the fins have different end portion deflections in response to predefined temperatures depending on their position on the member in the flow direction.
The heat exchanger according to claim 3, wherein structures located more upstream in the flow direction have a higher end portion deflection in response to predefined temperatures compared to structures located more downstream in the flow direction of the heat exchange medium.
The heat exchanger according to claim 3 or 4, wherein consecutive fins arranged on the member in the flow direction of the heat exchange medium have gradually decreasing end portion deflections in response to predefined temperatures.
The heat exchanger according to any one of the preceding claims 3-5, wherein the structures are configured such as to have substantially same end portion deflections when the surface of the member has a non-uniform temperature distribution as a result of one or more predefined flow and temperature operating regimes.
The heat exchanger according to any one of the preceding claims, wherein the structures have substantially same dimensions whilst having different material and/or actuation properties depending on their position on the member in the flow direction of the heat exchange medium.
The heat exchanger according to any one of the preceding claims, wherein a grid of structures are arranged on the surface of the member to be exposed to the flow of heat exchange medium, wherein the subsets of structures arranged next to each other on a same position in the flow direction have the same configuration such as to deform similarly as a function of the local temperature change.
The heat exchanger according to any one of the preceding claims, wherein the heat source is provided by a flow of working fluid.
The heat exchanger according to any one of the preceding claims, wherein the structures are plates dimensioned and adapted to facilitate turbulent flow generation in the flow of heat exchange medium.
The heat exchanger according to any one of the preceding claims, wherein the structures include one or more actuators.
The heat exchanger according to any one of the preceding claims, wherein the one or more actuators are passive actuators.
The heat exchanger according to any one of the preceding claims, wherein the structures include temperature dependent actuators, such as shape memory alloys.
A method of transferring heat using a heat exchanger, the heat exchanger having a heat transfer interface including a member configured to contact a heat source, wherein the heat transfer interface is provided with a plurality of deformable heat conducting structures distributed on the surface of the member exposed to a flow of heat exchange medium, wherein the deformable heat conducting structures emerge from said surface and are configured to deform as a function of a local temperature change of the member through thermal contact with the heat source, wherein the deformable heat conducting structures are adapted to deform differently as a function of said local temperature change depending on its position on the member in the flow direction.
An energy system comprising at least one heat exchanger according to any one of the preceding claims 1-13.