THERMOTUNNELING REFRIGERATION SYSTEM
A refrigeration system is provided. The refrigeration system includes at least one thermal blocking thermotunneling device. The thermal blocking thermotunneling device comprises a first and a second surface separated by a nanoscale gap of less than about 20 nm, such that tunneling of electrons causes a unidirectional transfer of heat from the first surface to the second surface. Further, the at least one thermal blocking thermotunneling device has a thermal back path of less than about 70 percent.
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This invention was made with Government support under contract number DE-FC26-04NT42324 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.
BACKGROUNDEmbodiments of the invention relate generally to refrigeration systems, and particularly, to high efficiency solid state refrigeration systems using solid state thermotunneling devices.
Standard refrigeration systems, including refrigerators, work by the action of a heat pump, which is used to pump heat from the interior of a thermally insulated enclosure to the external environment or ambient, thus causing the interior to cool below the ambient temperature. In refrigerators, the main compartment, often referred to as the fresh food compartment or the refrigeration compartment, is maintained at a temperature of a few degrees above the freezing point of water. In contrast, there may be additional freezer compartments, which are maintained at temperatures below the freezing point of water. Typically, a household refrigerator contains both refrigeration and freezer compartments that are separated from each other.
A vapor compression cycle is used in most refrigeration systems to act as the heat pump, and thus to provide cooling. For example, in a refrigerator, an evaporator section in the vapor compression system cools the air which comes in contact with the exterior of evaporator tubes, and this cooled air in turn cools the inside of the freezer and fresh food compartments.
The typical vapor compression cycle refrigerator suffers from several drawbacks. Foremost, the cooling efficiency of such systems is typically low, around 40 percent. Additionally, the vapor compression cycle requires the use of refrigerant fluids, such as Freon, which must be carefully engineered to avoid deleterious ozone effects. Further, continuous moving parts in the compressor gives rise to reliability problems, as well as unwanted operational noises. Also, the use of a single heat pump utilizing a compression cycle means that separately controllable zonal or localized cooling is not practical.
Refrigerators may also use Peltier or thermoelectric elements where the Peltier effect uses electricity directly to pump heat. However, typical Peltier devices and modules available in the market have low cooling efficiencies of around 3 to 8 percent. This limited cooling power and efficiency of such Peltier devices make full-scale household refrigerators using the Peltier effect impractical from an energy usage standpoint. Furthermore the Peltier devices must be kept in constant operation, as a large leakage of heat will occur through the devices when not powered.
BRIEF DESCRIPTIONIn accordance to certain embodiments of this invention, a refrigeration system is provided. The refrigeration system includes at least one thermal blocking thermotunneling device wherein the thermal blocking thermotunneling device includes a first and a second surface separated by a nanoscale gap of less than about 20 nm, such that tunneling of electrons causes a unidirectional transfer of heat from the first surface to the second surface. The thermal blocking thermotunneling device has a thermal back path of less than about 70 percent.
In accordance to certain embodiments of this invention, a refrigeration system is provided, which includes an enclosure; and a first and a second temperature control module and a control system configured to control operation of the first and second temperature control modules. The temperature control modules are disposed in a first and a second region respectively within the enclosure to regulate the temperatures of the first and second regions, and at least one of the first and second temperature control modules comprises at least one thermal blocking thermotunneling device.
In accordance to certain embodiments of this invention, a refrigeration system is provided which includes at least one temperature control module. The temperature control module includes one or more thermal blocking thermotunneling devices wherein the thermal blocking thermotunneling device(s) has a first and a second surface separated by a nanoscale gap of less than about 20 nm, such that tunneling of electrons causes a unidirectional transfer of heat from the first surface to the second surface. At least one surface of the temperature control module may be non-planar.
In accordance to certain embodiments of this invention, a refrigeration system is provided. The refrigeration system includes at least one temperature control module, a structure to receive an object to be cooled, and a thermal interface to facilitate heat transfer between the temperature control module and the object to be cooled. In this embodiment, the temperature control module comprises at least one thermal blocking thermotunneling device, wherein the thermal blocking thermotunneling device comprises a first and a second surface separated by a nanoscale gap of less than about 20 nm, such that tunneling of electrons causes a unidirectional transfer of heat from the first surface to the second surface.
In accordance to certain embodiments of this invention, a refrigeration system is provided. The refrigeration system comprises at least one temperature control module, and at least one heat exchanger selected from the group comprising of fins, plates, and heat pipes in thermal communication with the temperature control module. In this embodiment, the temperature control module includes at least one thermal blocking thermotunneling device, wherein the thermal blocking thermotunneling device comprises a first and a second surface separated by a nanoscale gap of less than about 20 nm, such that tunneling of electrons causes a unidirectional transfer of heat from the first surface to the second surface.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
A thermal blocking thermotunneling device works by tunneling hot electrons from a first electrode or surface to a second electrode or surface across a nanoscale gap and in the process cooling the first surface. A temperature difference is thus created between the two surfaces. This is called the reverse Nottingham Effect.
Referring now to the drawings,
In one embodiment, during operation, upon application of a voltage differential between the first surface 105 and the second surface 106, hot electrons from the first surface tunnel across the nanoscale gap 107 to the second surface, as shown by an arrow 110. In this process, a unidirectional flow of heat 120 is obtained and the first surface 105 is cooled, which in turn cools the inside volume 203 of the refrigeration system. The second surface 106 heats up, and throws heat to the outside of the refrigerator, optionally via a heat exchanger (not shown). As described earlier, some heat may also flow back (130) in the form of heat leakage from the second surface to the first surface. In another embodiment, during operation, depending on the connection from the power supply, hot electrons can flow (110) from second surface to the first surface, thus causing the first surface to heat up, which in turn, heats the inside volume 203 of the refrigeration system or a localized volume or compartment within the enclosure 202.
Thermal backpath is calculated as a ratio between the reverse heat flow 130 (from the hot surface to the cold surface) and the forward heat flow 120 (from cold surface to hot surface)), expressed as a percentage. Having a low thermal backpath allows the thermal blocking thermotunneling device to act as a thermal insulator, even during the “off” cycle of the refrigeration system when the device is not pumping heat. This effectively leads to lower power consumption for the whole refrigeration system.
In one embodiment refrigeration system 200 (
In one embodiment of the invention, the refrigeration system (200, in
Table (a) in
In one embodiment of the invention, the thermal blocking thermotunneling device 101 has a peak cooling power density of at least about 5 Watts per cm2. It should be noted that in certain embodiments, the thermal blocking thermotunneling device 101 may have a peak cooling power density of more than about 30 Watts per cm2. In one embodiment of the invention, the thermal blocking thermotunneling device 101 has a cooling efficiency of at least about 15 percent. In a further embodiment of the invention, the thermal blocking thermotunneling device 101 may have a cooling efficiency of at least about 40 percent.
In one embodiment of the invention, the refrigeration system 701 further includes one or more temperature-sensing device(s) 741 electrically coupled to the control system 705 and configured to detect the temperatures in at least one of first region 721 and second region 731. In one embodiment, the temperature-sensing device 741 may include a thermocouple element. In operation, the temperature-sensing device 741 provides feedback about the existing temperature in a particular region to the control system 705 which in turn can control the operation of temperature control modules 711 and 712 to regulate the temperature of the respective regions.
In one embodiment of the invention, the region 731 may be located in the fresh food compartment 730 and the temperature control module 711 may be thermally coupled with a wall of the fresh food compartment. In a further embodiment, the region 721 may be located in the freezer compartment 720 and the temperature control module 712 may be thermally coupled with to a wall of the freezer compartment.
In one embodiment of the invention, the refrigeration system 701 comprises at least one additional temperature control thermotunneling module 713 positioned so as to provide a zone 732 in the fresh food compartment 730 which is maintained at a different temperature than the remaining volume of the fresh food compartment 730. This additional temperature control thermotunneling module 713 may be controlled by the control system 705, or by a separate control system. Further, the refrigeration system 705 may include an additional temperature-sensing device 741, which may be positioned to measure the temperature of the zone 732. During operation, the temperature-sensing device 741 may provide feedback to the control system 705 on the temperature of zone 732, and the control system 705 may in turn operate the temperature control thermotunneling module 713 to regulate the temperature of zone 732. The localized temperature control in zone 732 may be useful for a variety of applications. For example, in a household refrigerator, zone 732 can be used as a medicine compartment to keep medicines refrigerated at a particular temperature. In another embodiment, this zone 732 can also be a defrosting zone, which can be used for defrosting frozen food.
In one embodiment of the invention, the freezer compartment may include sub compartments 725 that may, for example, be designed to hold ice. In one embodiment, one or more temperature control thermotunneling module(s) 714 can be thermally coupled to a wall of such a sub compartment 725, and be configured to regulate the temperature of the sub compartment 725.
In one embodiment of the invention, as seen in
In one embodiment of the invention shown schematically in
In one embodiment of the invention, the temperature control thermotunneling module 901 is located on a wall of a bottle holding compartment 751 and is thermally coupled to a surface of the bottle holding compartment 751 or integrally forms at least a portion of the bottle holding compartment 751. In one further embodiment of the invention, the non-planar surface 902 of the temperature control thermotunneling module 901 is shaped to conform to a curvature of a surface 903 of the bottle holding compartment 751.
In one embodiment of the invention, the temperature control thermotunneling module 901 is located on a wall of an egg holding compartment 911 and is thermally coupled to a surface of the egg holding compartment 911 or integrally forms at least a portion of the egg holding compartment 911. In one further embodiment of the invention, the non-planar surface 902 of the temperature control module 901 is shaped to conform to a curvature of a surface of the egg holding compartment 911.
In one embodiment of the invention, the temperature control thermotunneling module 901 is located on a wall of a sub compartment 725, which is designed to hold ice and is located in the freezer compartment 720, and is thermally coupled to a surface of the sub compartment 725. In one further embodiment of the invention, the non-planar surface 902 of the temperature control module 901 is shaped to conform to a curvature of a surface of the sub compartment 725. In one particular embodiment, the ice holding sub compartments 725 can be formed into different novelty shapes as figures of animals, birds, flowers, fruits, etc. The above embodiment will serve to form ice of different shapes and sizes, and thus enhance the aesthetics of the ice formed by this refrigeration system.
In another embodiment of the invention, as seen in
As
As illustrated in
The refrigeration system as described in the various embodiments described above provides efficient cooling along with certain other advantages over traditional refrigerators. This refrigeration system can provide accurate localized cooling, with the ability to separately control the temperatures of different regions and compartments of the refrigerator. This can be very useful for maintaining different food and other items at different temperatures as required by the user. For example, one can easily contemplate a separate sub compartment for medicines that need to be refrigerated at a certain temperature as a part of this refrigeration system. The temperatures at which a user would like beverages to be maintained can also be selected without affecting the temperature of the other items in the refrigerator. The refrigeration system described herein also provides for more usable refrigeration space as the temperature control thermotunneling modules are very small in size when compared to the standard vapor compression system. For example, space savings of around 2 cubic feet for a conventional household refrigerator is possible thus providing additional storage space inside the refrigerator. This system being a solid state system with no moving parts in the cooling units also provides for better reliability and noise free operation. Additionally, this refrigeration system can provide for fast cooling of beverage bottles, fast formation of ice, and instant cooling of water that can be accessed through a water dispensing system without opening the refrigerator door.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
Claims
1. A refrigeration system, comprising:
- at least one thermal blocking thermotunneling device wherein the at least one thermal blocking thermotunneling device comprises a first and a second surface separated by a nanoscale gap of less than about 20 nm, such that tunneling of electrons causes a unidirectional transfer of heat from the first surface to the second surface, wherein the at least one thermal blocking thermotunneling device has a thermal back path of less than about 70 percent.
2. The refrigeration system of claim 1, wherein the first and the second surface are separated by a nanoscale gap of about 4 nm to about 20 nm.
3. The refrigeration system of claim 1, wherein the refrigeration system has a cooling power per unit volume of greater than about 10 Watts/ft3.
4. The refrigeration system of claim 1, wherein the refrigeration system has a total cooling power of greater than about 200 Watts.
5. The refrigeration system of claim 1, wherein the thermal blocking thermotunneling device has a thermal back path of less than about 50 percent.
6. The refrigeration system of claim 1, where the thermal blocking thermotunneling device has a thermal back path of less than about 15 percent.
7. The refrigeration system of claim 1, where the thermal blocking thermotunneling device has a peak cooling power density of at least about 5 W/cm2.
8. The refrigeration system of claim 1, where the thermal blocking thermotunneling device has a peak cooling power density of at least about 30 W/cm2.
9. The refrigeration system of claim 1, where the cooling efficiency of the thermal blocking thermotunneling device is at least about 15 percent.
10. The refrigeration system of claim 1, where the cooling efficiency of the thermal blocking thermotunneling device is at least about 40%.
11. A refrigeration system, comprising:
- an enclosure;
- a first and a second temperature control module disposed in a first and a second region respectively within the enclosure to regulate the temperatures of the first and second regions, wherein at least one of the first and second temperature control modules comprises at least one thermal blocking thermotunneling device; and
- a control system configured to control operation of the first and second temperature control modules.
12. The refrigeration system of claim 11, wherein the thermal blocking thermotunneling device comprises:
- a first and a second surface separated by a nanoscale gap of less than about 20 nm, such that tunneling of electrons causes a unidirectional transfer of heat from the first surface to the second surface.
13. The refrigeration system of claim 12, where the device has a cooling power density of at least 30 W/cm2.
14. The refrigeration system of claim 12, further comprising a temperature sensing device electrically coupled to the control system and configured to detect temperature in at least one of the first and second regions.
15. The refrigeration system of claim 12, wherein at least one of the first and second regions is positioned in a fresh food compartment.
16. The refrigeration system of claim 15, wherein at least one of the first and second temperature control modules is thermally coupled to a wall of the fresh food compartment.
17. The refrigeration system of claim 15, wherein one or more additional temperature control modules are positioned so as to provide a zone in the fresh food compartment, which is maintained at a lower temperature than the remaining compartment.
18. The refrigeration system of claim 11, wherein at least one of the first and second regions is positioned in a freezer compartment.
19. The refrigeration system of claim 18, wherein at least one of the first and second temperature control modules is thermally coupled to a wall of the freezer compartment.
20. The refrigeration system of claim 19, wherein at least one of the first and second temperature control modules is thermally coupled to a wall of sub compartments inside the freezer compartment.
21. The refrigeration system of claim 11, wherein one or more of the temperature control modules are thermally coupled to a surface of a bottle holding compartment.
22. The refrigeration system of claim 21, wherein the bottle holding compartment is located along the door of a fresh food compartment of a refrigerator.
23. A refrigeration system, comprising:
- at least one temperature control module, comprising at least one thermal blocking thermotunneling device wherein the at least one thermal blocking thermotunneling device comprises a first and a second surface separated by a nanoscale gap of less than about 20 nm, such that tunneling of electrons causes a unidirectional transfer of heat from the first surface to the second surface;
- wherein at least one surface of the temperature control module has a non-planar profile.
24. The refrigeration system of claim 23, wherein the at least one surface of the module is shaped to conform to a curvature of a surface of a bottle holding compartment.
25. The refrigeration system of claim 23, wherein the at least one surface of the module is shaped to conform to a curvature of a surface of an egg holding compartment.
26. The refrigeration system of claim 23, wherein the at least one surface of the module is shaped to conform to a curvature of a surface of an ice holding compartment.
27. The refrigeration system of claim 23, further comprising a water dispensing system, wherein the at least one surface of the module is shaped to conform to a curvature of a conduit of a water dispensing system.
28. A refrigeration system comprising:
- at least one temperature control module, comprising at least one thermal blocking thermotunneling device, wherein the at least one thermal blocking thermotunneling device comprises a first and a second surface separated by a nanoscale gap of less than about 20 nm, such that tunneling of electrons causes a unidirectional transfer of heat from the first surface to the second surface;
- a structure to receive an object to be cooled; and
- a thermal interface to facilitate conductive heat transfer between the at least one temperature control module and the object to be cooled.
29. The refrigeration system of claim 28 further comprising a solid heat exchanger.
30. The refrigeration system of claim 29 wherein the solid heat exchanger comprises a material selected from the group consisting of metals, alloys, graphite, filled epoxies and polymers.
31. A refrigeration system comprising:
- at least one temperature control module, comprising at least one thermal blocking thermotunneling device, wherein the at least one thermal blocking thermotunneling device comprises a first and a second surface separated by a nanoscale gap of less than about 20 nm, such that tunneling of electrons causes a unidirectional transfer of heat from the first surface to the second surface; and
- at least one heat exchanger selected from the group comprising of fins, plates, and heat pipes in thermal communication with the at least one temperature control module.
32. The refrigeration system of claim 31, wherein the at least one heat exchanger is positioned to transfer heat from an inside compartment of the refrigerator to the at least one temperature control module.
33. The refrigeration system of claim 31, wherein the at least one heat exchanger is positioned to transfer heat to outside of the refrigerator.
Type: Application
Filed: Jul 31, 2007
Publication Date: Feb 5, 2009
Applicant: GENERAL ELECTRIC COMPANY (Schenectady, NY)
Inventors: Stanton Earl Weaver, JR. (Northville, NY), Mehmet Arik (Niskayuna, NY), James William Bray (Niskayuna, NY), Ahmed Elasser (Latham, NY), Robert John Wojnarowski (Ballston Lake, NY), Mark Wayne Wilson (Simpsonville, KY), Jason Knud Klindtworth (Schenectady, NY), Surajit Atha (Bangalore)
Application Number: 11/830,890
International Classification: F25B 21/02 (20060101);