Actuator device utilizing radiative cooling

Patent metadata

Field	Value
Publication number	US-11022066-B2
Application number	US-202016818279-A
Country	US
Kind code	B2
Filing date	Mar 13, 2020
Priority date	Mar 15, 2019
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

An actuator device includes a housing that defines an enclosed volume region, the housing comprising a movable surface such that at least a portion of the housing is expandable between an expanded state to a contracted state, and the enclosed volume region having a characteristic dimension that is defined as a cube root of an average of a volume of the enclosed volume region in the expanded state and in the contracted state, a working fluid within the enclosed volumetric region, the working fluid comprising a substantially transparent compressible fluid and electromagnetic (EM) radiation-absorbing solid elements distributed within the compressible fluid, wherein the solid elements have an absorptivity in a particular range of EM radiation wavelengths, a heating system for directing thermal energy into the working fluid at predetermined times, and wherein the housing includes an EM radiation transmitting portion having a sufficient area and a sufficient transparency such that more than 25% of the thermal energy directed into the working fluid by the heating means is radiative emitted through the EM radiation transmitting portion as black body EM radiation emitted by the solid elements of the working fluid.

First claim

What is claimed is:

1. An actuator device comprising:
a housing that defines an enclosed volume region, the housing comprising a movable surface such that at least a portion of the housing is expandable between an expanded state to a contracted state, and the enclosed volume region having a characteristic dimension that is defined as a cube root of an average of a volume of the enclosed volume region in the expanded state and in the contracted state;
a working fluid within the enclosed volumetric region, the working fluid comprising a substantially transparent compressible fluid and electromagnetic (EM) radiation-absorbing solid elements distributed within the compressible fluid, wherein the solid elements have an absorptivity in a particular range of EM radiation wavelengths, and wherein the solid elements have a thickness substantially less than the inverse of the absorptivity and occupy a fraction of the enclosed volume that is of the order of the inverse of the product of the absorptivity and the characteristic dimension of the enclosed volume region;
a heating system for directing thermal energy into the working fluid at predetermined times; and
wherein the housing includes an EM radiation transmitting portion having a sufficient area and a sufficient transparency such that more than 25% of the thermal energy directed into the working fluid by the heating means is radiative emitted through the EM radiation transmitting portion as black body EM radiation emitted by the solid elements of the working fluid.

2. The actuator device according to claim 1 , wherein the movable surface comprises a plunger moveable within the housing, wherein the plunger and the housing define the enclosed volume region.

3. The actuator device according to claim 2 , wherein the plunger is substantially transparent to the EM radiation emitted from the absorptive material such that the plunger forms at least a portion of the EM radiation transmitting portion.

4. The actuator device according to claim 2 , further comprising a seal disposed between the plunger and the rest of the housing to inhibit the working fluid from leaking out of the enclosed volume region.

5. The actuator device according to claim 4 , wherein the seal comprises a bellows formed of a deformable material.

6. The actuator device according to claim 1 , wherein the solid elements comprise a substantially one-dimensional (1D) material.

7. The actuator device according to claim 6 , wherein the substantially 1D material is at least one of tungsten nanotubes and carbon nanotubes.

8. The actuator device according to claim 1 , wherein the solid elements comprise a substantially two-dimensional (2D) material.

9. The actuator device according to claim 8 , wherein the substantially 2D material comprises graphene sheets.

10. The actuator device according to claim 9 , wherein the graphene sheets comprise at least one of ordered graphene sheets and disordered graphene sheets.

11. The actuator device according to claim 9 , wherein the graphene sheets are separated by spacers.

12. The actuator device according to claim 11 , wherein the spacers comprise a substantially one-dimensional (1D) material.

13. The actuator device according to claim 12 , wherein the 1D material comprises nanotubes or nanotube bundles.

14. The actuator device according to claim 1 further comprising a control unit connected to the heating system to control the heating of the working fluid provided by the heating system.

15. The actuator device according to claim 14 , wherein the heating system is configured to provide EM radiation to the working fluid to radiatively heat the working fluid during the expansion stage, and the control unit is configured to control the EM radiation provided by the heating system.

16. The actuator device according to claim 15 , wherein the heating system includes at least one of an incandescent lamp, a light emitting diode, a gas discharge lamp, and a laser as a source of EM radiation.

17. The actuator device according to claim 14 , wherein the control unit is configured to control the heating provided by the heating system to heat the working fluid periodically at a predetermined period.

18. The actuator device according to claim 14 , wherein the control unit is configured to control the heating provided by the heating system to heat the working fluid non-cyclically to produce expansion of the working fluid by a controlled amount during the expansion stage.

19. The actuator device according to claim 14 , wherein the solid elements are electrically conductive such that the working fluid is electrically conductive, and the heating system is configured to provide an electronic current through the working fluid to resistively heat the working fluid during the expansion stage.

20. The actuator device according to claim 15 , wherein the solid elements comprise graphene sponge.

21. The actuator device according to claim 1 , wherein, during operation, the working fluid is heated to a first temperature, averaged over the enclosed volume region, to move the housing from the contracted state to the expanded state, and is cooled to a second temperature that is less than the first temperature, averaged over the enclosed volume region, to move the housing from the expanded state to the contracted state; and
wherein the absorptivity is greater than 10 6 m −1 and the particular range of EM radiation wavelengths is a range from one-half of a peak emission wavelength of a black body radiator at a temperature that is an average of the first and second temperatures to twice the peak emission wavelength.

22. The actuator device according to claim 1 , wherein an average physical separation between solid elements in the working fluid is such that the thermal equilibration time between the solid elements and the compressible fluid is substantially less than the time required for black body radiation emitted from the solid elements to reduce the absolute temperature of the working fluid by 25%.

Assignees

• Univ British Columbia

Inventors

• Nojeh Alireza
• Whitehead Lorne A

Classifications

• F02G2256/00

  Coolers · CPC title

• F02G1/04 Primary

  of closed-cycle type · CPC title