US20090031733A1

US20090031733A1 - Thermotunneling refrigeration system

Info

Publication number: US20090031733A1
Application number: US11/830,890
Authority: US
Inventors: Stanton Earl Weaver, Jr.; Mehmet Arik; James William Bray; Ahmed Elasser; Robert John Wojnarowski; Mark Wayne Wilson; Jason Knud Klindtworth; Surajit Atha
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2007-07-31
Filing date: 2007-07-31
Publication date: 2009-02-05

Abstract

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.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH & DEVELOPMENT

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.

BACKGROUND

Embodiments 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 DESCRIPTION

In 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.

DRAWINGS

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:

FIG. 1 is a diagrammatical illustration of a thermal blocking thermotunneling device that forms a part of the refrigeration system in accordance with an embodiment of the present invention.

FIG. 2 is a diagrammatical illustration of a refrigeration system in accordance with an embodiment of the present invention.

FIG. 3 is a diagrammatical illustration of a thermal blocking thermotunneling device that forms a part of the refrigeration system in accordance with an embodiment of the present invention.

FIG. 4 shows a sample of modeling data for a thermal blocking thermotunneling device, one embodiment of which has been shown in FIG. 3.

FIG. 5 is a diagrammatical illustration of a temperature control thermotunneling module that forms a part of the refrigeration system in accordance with an embodiment of the present invention.

FIG. 6 is a diagrammatical illustration of a refrigeration system in accordance with an embodiment of the present invention.

FIG. 7 is a diagrammatical illustration of an exemplary configuration of a refrigeration system in accordance with an embodiment of the present invention.

FIG. 8 is a diagrammatical illustration of sub-compartments designed to hold ice and located in the freezer compartment in accordance with an embodiment of the present invention.

FIG. 9 is a diagrammatical illustration of an exemplary configuration of a refrigeration system in accordance with an embodiment of the present invention.

FIG. 10 is a diagrammatical illustration of bottle holding compartments in accordance with an embodiment of the present invention.

FIG. 11 is a diagrammatical illustration of an exemplary configuration of a refrigeration system with a liquid dispensing system in accordance with an embodiment of the present invention.

FIG. 12 is a diagrammatical illustration of a arrangement of temperature control module along with thermal interface layers and heat exchangers in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

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, FIG. 1 shows a schematic of a thermal blocking thermotunneling device 101, where the surfaces 105 and 106 are separated by a nanoscale gap 107 of less than about 20 nm. The first surface 105 and the second surface 106 are disposed on a first substrate 108 and second substrate 109 respectively, and are connected to a power supply 150. During operation, a voltage difference is applied between the two surfaces resulting in a flow of hot electrons from the first surface 105 to the second surface 106, schematically represented by an arrow 110. This flow of electrons causes a unidirectional heat transfer from the first surface 105 to the second surface 106 (or forward heat flow 120), thus causing the first surface 105 to cool and the second surface 106 to heat up. The temperature difference that develops between the two surfaces might cause a reverse heat flow 130 from the hot surface (the second surface 106, in this case) to the cold surface (the first surface 105, in this case), which may be caused due to conductive leakage, through for example, a support structure, or convective and radiative heat losses. It may be noted that reverse biasing the power supply 150 would, in turn reverse the direction of electron flow 110, forward heat flow 120, and reverse heat flow 130, thus resulting in heating of the first surface 105 and cooling of the second surface 106. In operation, this device can be used in either mode (cooling of first surface 105 or heating of first surface 105), depending on the application of voltage.
FIG. 2 is a schematic of a refrigeration system 200 using a thermal blocking thermotunneling device 101 such as the thermal blocking thermotunneling device illustrated in FIG. 1. The refrigeration system has an enclosure 202 enclosing an inside volume 203 of the refrigeration system 200. The thermal blocking thermotunneling device 101 comprises a first surface 105 and a second surface 106 separated by a nanoscale gap 107. In an embodiment, the nanoscale gap 107 between the first surface 105 and the second surface 106 is less than about 20 nm. In a more specific embodiment, the nanoscale gap 107 between the first surface 105 and the second surface 106 is from about 4 nm to about 20 nm. The thermal blocking thermotunneling device 101 is further connected to a power supply (not shown).
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 (FIG. 2) may include a thermal blocking thermotunneling device 101 having a thermal backpath of less than about 70 percent. In another embodiment, the thermal backpath may be less than about 50 percent. In a further embodiment, the thermal backpath may be less than about 15 percent. FIG. 3 diagrammatically illustrates one embodiment of a thermal blocking thermotunneling device 101 that includes a thermal blocking layer 301 to reduce the thermal backpath. The thermal blocking layer 301 can be used to reduce the conductive heat loss, and thus to reduce the reverse heat flow 130 (FIG. 2), which in turn, would reduce the thermal backpath. As can be seen, a first surface 305 is disposed on a bottom thermally conductive substrate 308. The thermal blocking layer 301 is disposed generally adjacent or in proximity to first surface 305. In this exemplary embodiment, the thermal blocking layer 301 includes one or more of vias 320. Further, the thermal blocking thermotunneling device 101 includes a second surface 306 disposed on the thermal blocking layer 301. The second surface 306 may include a patterned metal layer and the one or more vias 320 may be filled with metal for reducing electrical losses and thermal resistance in the device 101. As shown in FIG. 3, the thermal blocking thermotunneling device 101 may include a plurality of support posts 324 disposed on the second surface 306 to facilitate the bonding of device 101, to substantially prevent the second surface 306 from bowing, as well as to form and maintain a nanoscale gap 307 between the first surface 305 and second surface 306. In the illustrated embodiment, the support posts 324 include oxide posts. Further, thermal blocking thermotunneling device 101 may include a pattered electrical barrier 330 disposed on bottom thermally conductive substrate 308 and a bondable layer 340 disposed on the patterned electrical barrier 330. In certain embodiments, the wafer bondable layer 340 includes a diffusible bonding layer, or a direct bondable metal layer, or a solderable layer, or a eutectic layer.
In one embodiment of the invention, the refrigeration system (200, in FIG. 2) has a cooling power per unit inside volume 203 of greater than about 10 Watts/feet³. In one embodiment of the invention, the refrigeration system has a total cooling power of greater than about 200 Watts where total cooling power is measured as the sum of cooling power output of multiple thermal blocking thermotunneling devices or other forms of heat pumps that may be used in a refrigeration system.
FIG. 4 gives modeling data for thermal blocking thermotunneling devices, an embodiment of which has been shown in FIG. 3. The data was obtained by numerically solving the integral equations that describe tunneling of electrons across the nanoscale gap 307. The thermal backpath was computed by calculating the thermal conductivity of a thermal blocking thermotunneling device using the thermal properties of the constituent materials and the geometry of the thermal blocking thermotunneling device.). As used in FIG. 4, and later in this document, cooling power density is defined as the cooling power (in Watts) per unit area. Peak cooling power density is defined as the maximum cooling power density that can be generated by a thermal blocking thermotunneling device. Cooling efficiency of the thermal blocking thermotunneling device 101 (FIG. 3) is defined as the ratio between the Coefficient of Performance (COP) of the device and the coefficient of Performance of a Carnot cycle (COP_[Carnot]), expressed as a percentage. Further, COP is defined as a ratio of electrical power input and total cooling power of the device, whereas COP_[Carnot] for any heat engine is defined as a ratio of the temperature of the hot side and the temperature difference between the hot side and the cold side, where the temperatures are measured in absolute scale. Work function of a material is the energy, typically measured in electron Volts (eV), needed to remove an electron from the material into the vacuum.
Table (a) in FIG. 4 shows the cooling power density and cooling efficiency exemplary thermal blocking thermotunneling devices under different conditions of hot side and cold side temperatures, work function of the first and second surfaces, voltage differential applied between the first and the second surfaces, and dimensions of the nanoscale gap 107 (FIG. 1) between the first surface 105 and the second surface 106. Table (b) in FIG. 4 shows the thermal backpath of exemplary thermal blocking thermotunneling devices with a fixed cooling power density and nanoscale gap dimension, under different operating conditions of hot and cold side temperatures. It should be understood that the thermal backpath may vary depending on the details of the structure and the operating conditions of the thermal blocking thermotunneling device.
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.
FIG. 5 illustrates a schematic of a temperature control thermotunneling module 501 made of one or more thermal blocking thermotunneling devices 101. In one embodiment, the thermal blocking thermotunneling devices can be connected thermally and electrically in parallel. In another embodiment, a combination of series and parallel thermal and electrical connections can be made between the devices. In one embodiment, the thermal blocking thermotunneling devices 101 are sandwiched between thermally conductive substrates 511 and 512. Additionally, electrical leads 521 and 522 provide the electrical connection for the temperature control thermotunneling module 501 from the power source 530. In operation, when a voltage differential is applied between the electrical leads 521 and 522, a voltage differential develops between the respective first and second surfaces of thermal blocking thermotunneling devices 101 (for example, first surface 105 and second surface 106 as shown in FIG. 1). In one embodiment, the voltage differential between the first and second surfaces may induce tunneling of hot electrons from the first surfaces to the second surfaces in the respective thermal blocking thermotunneling devices 101. As a result, unidirectional flow of heat 120 (FIG. 2) is obtained and the respective first surfaces are cooled, which in turn cools thermally conducting substrate 511. In another embodiment, upon reversal of the power supply from power source 530, the voltage differential between the first and second surfaces of respective thermal blocking thermotunneling devices may induce tunneling of hot electrons from the second surfaces to the first surfaces 106. This leads to the heating of respective first surfaces, which in turn heats thermally conducting substrate 511.
FIG. 6 schematically shows a refrigeration system 601. The refrigeration system includes an enclosure 602, one or more temperature control thermotunneling modules 501, and a control system 605. In one embodiment, the refrigeration system 601 may additionally include one or more temperature control modules (not shown) that do not use any thermal blocking thermotunneling devices. Such temperature control module(s) may include thermoelectric devices, thermoacoustic devices, magnetocaloric devices, vapor compression cycle heat pumps, or any other device that can perform cooling or heating by working as a heat pump. The temperature control thermotunneling module(s) 501 can be operated to cool or heat a thermally conductive substrate such as substrate 511 shown in FIG. 5) as described earlier, and thus cool or heat the inside volume of the refrigeration system 601 (or part thereof). The control system 605 is configured to control the operation of the temperature control modules, including the temperature control thermotunneling module(s), and thus control the cooling/heating of the refrigeration system 601. In one embodiment, the control system 605 may also be configured to receive input from a user, and use the input to control the cooling of the refrigeration system.
FIG. 7 illustrates an exemplary refrigeration system 701 in accordance with one embodiment of the invention. The refrigeration system 701 includes an enclosure 702, temperature control modules (711, 712) and a control system 705. The refrigeration system has at least one freezer compartment 720, and at least one fresh food compartment 730. Although the figures generally illustrate a side-by-side configuration of the freezer and fresh food compartments, the teachings described herein are equally applicable to refrigerator configurations where the freezer compartment is located above or below the fresh food compartment. In one embodiment, the temperature control modules 711 and 712 are disposed in a first region 731 and second region 721 respectively, and the control system is configured to control the operation of the temperature control modules 711 and 712. Regions 721 and 731 are parts of an inside volume of the refrigeration system, which may optionally be separated by different compartments. In certain embodiments, regions 721 and 731 may be localized around modules 712 and 711 respectively, whereas in other embodiments, regions 721 and 731 can span entire compartments within which the regions are located. In operation, the temperature control modules 711 and 712 are controlled by the control system 705 to regulate the temperature of regions 721 and 731. Regulation of temperature includes increasing the temperature, decreasing the temperature, or maintaining the temperature at a constant level. In a specific embodiment, the temperature control modules 711 and 712 can be operated to regulate the temperatures of regions 721 and 731 independent of each other. In one embodiment, at least one of the temperature control modules (711, 712) is a temperature control thermotunneling module (one example of which is shown in FIG. 5) that includes one or more thermal blocking thermotunneling devices.
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. FIG. 8 is a schematic illustrating one embodiment of sub compartments 725 in which the sub compartments are designed to hold ice. As shown, the temperature control thermotunneling module 714 is thermally coupled to at least one wall of the sub compartments 725.
In one embodiment of the invention, as seen in FIG. 7, a bottle holding compartment 751 may be located along a door 750 of the fresh food compartment 730. The bottle holding compartment 751 may be configured to hold different types of containers like plastic or glass bottles, aluminum cans, paper cartons, etc., which are typically used as containers for liquids. In one embodiment, at least one temperature control thermotunneling module 715 is thermally coupled to the bottle holding compartment 751.
In one embodiment of the invention shown schematically in FIG. 9, the refrigeration system 701 comprises at least one temperature control thermotunneling module 901, wherein at least one surface 902 of the temperature control thermotunneling module 901 has a non-planar profile. In one particular embodiment, the surface 902 has a curved profile. The temperature control thermotunneling module 901 comprises at least one thermal blocking thermotunneling device comprising first surface 105 (FIG. 1) and a second surface 106 (FIG. 1) separated by a nanoscale gap 107 (FIG. 1) of less than about 20 nanometers.
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.
FIG. 10 shows a detailed illustration of one embodiment of the bottle holding compartment 751. As can be seen, the temperature control thermotunneling module 901 is coupled to a surface of the bottle holding compartment 751 and its surface is shaped to conform to the curvature of or a surface of the bottle holding compartment 751.
In another embodiment of the invention, as seen in FIG. 10, a thermal interface layer 1020 may be positioned between the temperature control thermotunneling module 901 and the bottle holding compartment 751 to facilitate conductive and/or convective heat transfer between the temperature control thermotunneling module 901 and any object (bottle 1030 in this case) in the bottle holding compartment 751. In a further embodiment of the invention, there may be a solid heat exchanger 1040 between the thermal interface layer 1020 and a wall of the bottle holding compartment 751. The solid heat exchanger can be made of different materials, either singly or in combinations, like metals, alloys, graphite, filled epoxies, polymers, etc. Optionally, a thermal spreader may also be used to further facilitate heat flow between the thermotunneling module 901 and the object (bottle 1030 in this case). Although this figure generally illustrates a thermal interface layer between a curved surface and a bottle holding compartment, the teachings described herein are equally applicable to a thermal interface layer between a planar surface and any structure configured to receive an object to be cooled or heated.
As FIG. 11 illustrates, in one embodiment of the invention, the refrigeration system 701 further comprises a liquid dispensing system 1100 which serves to dispense cold and/or hot liquid directly through a conduit 1101 and a nozzle 1102 without having to open a door 750. Inset (a) shows a schematic of the conduit 1101 according to a particular embodiment of the invention. Inset (b) shows a schematic of a cross-section of the conduit 1101 according to one embodiment of the invention. According to one embodiment, temperature control thermotunneling module 1001 is located on a wall of the conduit 1101 and is thermally coupled to a surface of the conduit 1101. As illustrated, the non-planar surface 1002 of the temperature control thermotunneling module 1001 may be shaped to conform to a curvature of a surface of the conduit 1101. In operation, the temperature control thermotunneling module 1001 can be controlled by a control system such as the control system 705 shown in FIG. 7 to heat or cool the conduit carrying a fluid, and thus, the liquid dispensing system 1100 can dispense instant hot or cold liquid. Further, a user selectable interface (not shown) may be coupled to the control system to allow a user to input a temperature of liquid to be dispensed by the liquid dispensing system 1100. The control system may operate the temperature control thermotunneling module 1001, and thus regulate the temperature of the liquid being dispensed.
As illustrated in FIG. 12, in one embodiment of the invention the refrigeration system includes of at least one temperature control thermotunneling module 1201 and at least one heat exchanger 1205 in thermal communication with the temperature control thermotunneling module 1201. The temperature control thermotunneling module 1201 comprises at least one thermal blocking thermotunneling device 101 (FIG. 1). Thermal interface layer 1206 facilitates heat transfer between the temperature control thermotunneling module 1201 and the heat exchanger 1205. The heat exchanger 1205 can be in the form of fins, plates, heat pipes, or any other conventional forms of heat exchanger. In one particular embodiment, the heat exchanger 1205 can be positioned to transfer heat from an inside volume or a refrigeration system to the temperature control thermotunneling module 1201. In another embodiment, the heat exchanger 1305 can be positioned to transfer heat from the temperature control thermotunneling module 1201 to the outside of the refrigeration system.
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.