Electrocaloric effect heat transfer device dimensional stress control
View Patent ↗Technologies are generally described herein for electrocaloric effect heat transfer devices and methods effective to facilitate thermal energy transfer while mitigating mechanical stresses caused by expansion or contraction of electrocaloric effect material layers during thermal energy transfer operations. Some example heat transfer devices may include heat transfer stacks with at least two electrocaloric effect materials. Expanding electrocaloric effect material and contracting electrocaloric effect material are utilized to cancel the aggregate longitudinal dimensional change during application of an electric field. Some example heat transfer devices may utilize segmented electrocaloric effect material layers with stress relief gaps separating segments to mitigate delamination stress caused by lateral expansion or contraction of the electrocaloric effect material.
1. A method to transfer thermal energy from a heat source to a heat dump, the method comprising:
applying at least one electric field across a first electrocaloric effect material layer and across a second electrocaloric effect material layer of a heat transfer device in thermal contact with the heat source and the heat dump; and
in response to the applied at least one electric field, transferring thermal energy between the first electrocaloric effect material layer and the second electrocaloric effect material layer in a direction from the heat source toward the heat dump while restricting thermal energy transfer in a direction from the heat dump toward the heat source and at least partially canceling a dimensional change of the first electrocaloric effect material layer due to expansion by a dimensional change of the second electrocaloric effect material layer due to contraction so as to maintain an approximate total length of the heat transfer device.
2. The method of claim 1 , wherein the approximate total length of the heat transfer device corresponds to a fixed distance between the heat source and the heat dump.
3. The method of claim 1 , wherein applying the at least one electric field across the first electrocaloric effect material layer and across the second electrocaloric effect material layer comprises:
applying an electric field across a plurality of first electrocaloric effect material layers effective to provide an aggregate longitudinal expansion distance that includes as a contribution the dimensional change of the first electrocaloric effect material layer due to expansion; and
applying the electric field across a plurality of second electrocaloric effect material layers to provide an aggregate longitudinal contraction distance that is substantially equivalent to the aggregate longitudinal expansion distance, wherein the aggregate longitudinal contraction distance includes as a contribution the dimensional change of the second electrocaloric effect material layer due to contraction.
4. The method of claim 3 , wherein applying the electric field across the plurality of first electrocaloric effect material layers and across the plurality of second electrocaloric effect material layers comprises:
applying a first voltage across the plurality of first electrocaloric effect material layers effective to provide the aggregate longitudinal expansion distance; and
applying a second voltage across the plurality of second electrocaloric effect material layers effective to provide the aggregate longitudinal contraction distance,
wherein the first voltage and the second voltage are determined such that the aggregate longitudinal contraction distance is approximately equivalent to the aggregate longitudinal expansion distance.
5. The method of claim 4 , wherein the first voltage is different than the second voltage.
6. The method of claim 3 , wherein the electric field comprises one of: an oscillating voltage, a pulsed signal, a pulsed direct current (DC) voltage, an alternating current (AC) voltage, a ramped signal, a sawtooth signal, or a triangular signal.
7. The method of claim 1 , wherein applying the at least one electric field across the first electrocaloric effect material layer and across the second electrocaloric effect material layer comprises simultaneously applying the at least one electric field across the first electrocaloric effect material layer and across the second electrocaloric effect material layer.
8. A method to transfer thermal energy from a heat source to a heat dump through a heat transfer device, the method comprising:
expanding a first electrocaloric effect material layer and contracting a second electrocaloric effect material layer of the heat transfer device, wherein the heat transfer device is in thermal contact with the heat source and the heat dump; and
transferring thermal energy between the first electrocaloric effect material layer and the second electrocaloric effect material layer in a direction from the heat source toward the heat dump while restricting thermal energy transfer in a direction from the heat dump toward the heat source and at least partially canceling expansion of the first electrocaloric effect material layer by contraction of the second electrocaloric effect material layer so as to maintain an approximate total length of the heat transfer device.
9. The method of claim 8 , wherein the approximate total length of the heat transfer device corresponds to a fixed distance between the heat source and the heat dump.
10. The method of claim 8 , wherein:
expanding the first electrocaloric effect material layer comprises applying a first electric field across the first electrocaloric effect material layer; and
contracting the second electrocaloric effect material layer comprises applying a second electric field across the second electrocaloric effect material layer.
11. The method of claim 10 , wherein applying the first electric field across the first electrocaloric effect material layer comprises applying the first electric field across a plurality of first electrocaloric effect material layers effective to provide an aggregate longitudinal expansion distance that includes as a contribution an expansion distance of the first electrocaloric effect material layer.
12. The method of claim 11 , wherein applying the second electric field across the second electrocaloric effect material layer comprises applying the second electric field across a plurality of second electrocaloric effect material layers to provide an aggregate longitudinal contraction distance that includes as a contribution a contraction distance of the second electrocaloric effect material layer.
13. The method of claim 10 , wherein applying the first electric field across the first electrocaloric effect material layer comprises applying a first voltage across a plurality of first electrocaloric effect material layers effective to provide an aggregate longitudinal expansion distance that includes as a contribution an expansion distance of the first electrocaloric effect material layer.
14. The method of claim 13 , wherein:
applying the second electric field across the second electrocaloric effect material layer comprises applying a second voltage across a plurality of second electrocaloric effect material layers effective to provide an aggregate longitudinal contraction distance that includes as a contribution a contraction distance of the second electrocaloric effect material layer; and
the first voltage and the second voltage are determined such that the aggregate longitudinal contraction distance is approximately equivalent to the aggregate longitudinal expansion distance.
15. The method of claim 14 , wherein applying a first value of the first voltage is not equal to applying a second value of the second voltage.
16. The method of claim 10 , wherein applying the first electric field or the second electric field comprises applying one of: an oscillating voltage, a pulsed signal, a pulsed direct current (DC) voltage, an alternating current (AC) voltage, a ramped signal, a sawtooth signal, or a triangular signal.
17. A method to transfer heat through a heat transfer device between a heat source and a heat dump, the method comprising:
applying a first electric field to a first electrocaloric effect material configured to expand and to change temperature of the first electrocaloric effect material in response to application of the first electric field;
applying a second electric field to a second electrocaloric effect material configured to contract and to change temperature of the second electrocaloric effect material in response to application of the second electric field, wherein a thermal rectifier material of the heat transfer device is in thermal contact with the first electrocaloric effect material and the second electrocaloric effect material;
transferring thermal energy, facilitated by the thermal rectifier material, between the first electrocaloric effect material and the second electrocaloric effect material in a direction from the heat source toward the heat dump while maintaining an approximate total length of the heat transfer device; and
limiting transfer of the thermal energy, facilitated by the thermal rectifier material, between the second electrocaloric effect material and the first electrocaloric effect material.
18. The method of claim 17 , wherein maintaining the approximate total length of the heat transfer device comprises maintaining a first longitudinal distance associated with an expansion of the first electrocaloric effect material in response to application of the first electric field to be approximately equivalent to a second longitudinal distance associated with a contraction of the second electrocaloric effect material in response to application of the second electric field.
19. The method of claim 17 , further comprising:
providing a plurality of layers of the first electrocaloric effect material;
providing a plurality of layers of the second electrocaloric effect material; and
providing a plurality of thermal rectifier material layers disposed between adjacent layers of the first and second electrocaloric effect materials.
20. The method of claim 19 , wherein maintaining the approximate total length of the heat transfer device comprises:
expanding each of the plurality of layers of the first electrocaloric effect material a first longitudinal distance along a longitudinal axis of the heat transfer device in response to application of the first electric field; and
contracting each of the plurality of layers of the second electrocaloric effect material a second longitudinal distance along the longitudinal axis of the heat transfer device in response to application of the second electric field.
21. The method of claim 17 , wherein applying the first and second electric fields comprise:
controlling application of the first and second electric fields from a power source to the first and second electrocaloric effect materials during operation of the heat source to:
control expansion of each of a plurality of layers of the first electrocaloric effect material a first longitudinal distance along a longitudinal axis of the heat transfer device in response to application of the first electric field, and
control contraction of each of a plurality of layers of the second electrocaloric effect material a second longitudinal distance along the longitudinal axis of the heat transfer device in response to the application of the second electric field,
wherein an aggregate contraction of the plurality of layers of the second electrocaloric effect material is approximately equivalent to an aggregate expansion of the plurality of layers of the first electrocaloric effect material.
22. A heat transfer system, comprising:
a heat source;
a heat dump;
a heat transfer device in thermal contact with the heat source and the heat dump, the heat transfer device comprising:
a first electrocaloric effect material layer;
a second electrocaloric effect material layer in thermal contact with the first electrocaloric effect material; and
a plurality of electrodes positioned to apply at least one electric field across the first and second electrocaloric effect material layers to transfer thermal energy between the first and second electrocaloric effect material layers in a direction from the heat source toward the heat dump while thermal energy transfer in a direction from the heat dump toward the heat source is restricted, wherein a dimensional change of the first electrocaloric effect material layer due to expansion is at least partially cancelled by a dimensional change of the second electrocaloric effect material layer due to contraction so as to maintain an approximate total length of the heat transfer device.
23. The heat transfer system of claim 22 , wherein the heat dump is separated from the heat source by a fixed distance and the approximate total length of the heat transfer device corresponds to the fixed distance.
24. The heat transfer system of claim 22 , wherein:
the heat source comprises an electronic component or a computer component; and
the heat dump comprises an electronics case or a computer case.
25. The heat transfer system of claim 22 , wherein the at least one electric field comprises a first electric field and a second electric field, and wherein the plurality of electrodes comprises:
a plurality of first electrodes positioned to apply the first electric field across the first electrocaloric effect material; and
a plurality of second electrodes positioned to apply the second electric field across the second electrocaloric effect material; the heat transfer system further comprising:
a power source electrically coupled to the plurality of first electrodes and the plurality of second electrodes and configured to provide a first electrode control signal to the plurality of first electrodes that is effective to cause the plurality of first electrodes to apply the first electric field and to provide a second electrode control signal to the plurality of second electrodes that is effective to cause the plurality of second electrodes to apply the second electric field; and
a controller communicatively coupled to the power source and configured to control application of the first and second electrode control signals by the power source.