JP2008514895A - Reverse Peltier defrost system - Google Patents

Abstract

A refrigerator 10 having a freezer compartment 12 and a refrigerator compartment 13 includes a freezer compartment heat pump 14 having a first heat exchanger 15 on one side and a second heat exchanger 16 on the other side. The first heat exchanger 15 is connected to the freezer compartment heat exchanger 17 by a fluid. In the refrigerator compartment 13, there is a refrigerator compartment heat exchanger 19, which is connected to the second heat exchanger 16 of the freezer compartment 12 by fluid. Outside the refrigerating room 13 is a refrigerating room electronic heat pump 20, which has a first heat exchanger 21 on one side and a second heat exchanger 22 on the other side. Have. The first heat exchanger 21 is fluidly connected to the refrigerator compartment heat exchanger 19 and the second heat exchanger 16 in the freezer compartment 12. The second heat exchanger 22 is connected to the high temperature side heat exchanger 23 by a fluid. The dehumidifier 50 includes a plurality of thermoelectric modules 51, and the outside air passes through the low temperature side heat exchanger 52 of the thermoelectric module 51 and then passes through the high temperature side heat exchanger 53. pass. When the polarity of the thermoelectric module is reversed. The previous low temperature side 52 becomes warm and melts the ice formed on the heat exchanger.
[Selection] Figure 1

Description

The present invention relates to the effective removal of ice growing on heat exchangers used in thermoelectric devices or similar electronic heat pump devices for providing cooling means. These heat exchangers include a heat exchanger for a freezer in a household refrigerator and a heat exchanger for appliances that freeze water in the air to produce portable water.

Generally, a refrigerator for home use has a private room divided into a refrigerated room kept at about 5 ° C and a freezer room kept at about -15 ° C to -20 ° C. These chambers are either completely independent or otherwise thermally connected in some way. For this reason, the frosting of the heat exchanger in the freezer compartment may similarly affect the operation of the refrigerator compartment.

When the door is opened, fresh outside air flows into the box, and as a result, ice is formed in the heat exchanger of the freezer compartment. The outside air contains more moisture in the form of water vapor than moisture it has when cooled to the freezer temperature (-15 ° C to -20 ° C). Water vapor present in the outside air introduced by opening the door is condensed into water on a surface that is cooler than the outdoor temperature of the air. The frost-free freezer uses a fan and forces air to recirculate through the heat exchanger (which is the coldest object in the freezer), so most water vapor will exchange this heat. It condenses on the surface of the vessel and then freezes there.

Although there is no fan that allows air to pass through the heat exchanger in a direct cooling system, the heat exchanger is the coldest part of the freezer and is usually made of a material with very good heat conduction. Water vapor tends to move to this heat exchanger where it condenses and freezes.

The amount of ice that grows depends on two factors. This factor is the humidity of the outside air and the frequency and duration of opening the door in one day. In the refrigeration industry, the door opening is typically 25 times per day as a standard. The defrost cycle of a frost-free refrigerator is normally set to be performed every 11 hours or every 12 hours.

This defrost cycle can be done at fixed time intervals, or by sensors that can measure the amount of ice that grows, as in some refrigerators. The defrost cycle is more rationally controlled in the refrigerator with the sensor, and the defrost cycle adds heat to the freezer compartment for effective defrosting, which helps to reduce energy consumption. .

The defrosting in the direct cooling system is not automatic, and the freezing room is manually defrosted.

Ice growth on the heat exchanger depends on the operation of the heat exchanger. A layer of ice between the thermally conductive heat exchanger surface and the room air will create a new thermal resistance for heat transfer, and in order to produce the same heat flux, the temperature in the heat exchanger Need to be further reduced. Under such circumstances, the heat pump will require more electrical input to obtain the same amount of cooling capacity.

In addition, ice growth reduces gaps for air to flow in the frost-free freezer, resulting in increased ventilation resistance. Eventually, the ice will be able to get over the gaps between the fins and completely occlude some areas of the heat exchanger.

The efficiency of the thermoelectric element is easily affected by the temperature difference between the high temperature side and the low temperature side of the thermoelectric module. Therefore, if any new thermal resistance is added that directly increases this temperature difference, the efficiency will drop. The reduction in efficiency results in a decrease in the competitiveness of this technology when compared to conventional vapor compression technology.

The most common method for defrosting a heat exchanger of a home refrigerator is a method using an electric resistance heating wire, that is, an electric heater located immediately below the heat exchanger. Both radiant and convective heat transfer are used to transfer heat to the heat exchanger and melt the ice. When a temperature sensor is normally arranged on the heat exchanger and this temperature sensor reaches a predetermined temperature limit (well above 0 ° C. to ensure complete defrosting), the electric heater Is turned off. In other more complex refrigeration systems, vapor compression is used there, but the compressor is switched to reverse cycle mode to flow hot gas through the evaporator.

The problem with these methods is that they are energy intensive and consequently reduce overall efficiency, or require complex controls and multiple valves.

The fact that the electric heater wire adds a new heat load that the refrigeration system must handle is even more disadvantageous for efficient operation of the thermoelectric refrigerator / freezer.

The thermoelectric module can be easily reversed, that is, it can be reversed simply by reversing the polarity of the voltage applied to the module, and the heat flow can be reversed. It is therefore relatively easy to heat the module, which is usually on the cold side.

A thermoelectric module that uses reverse polarity for defrosting is described in US Patent Application No. US2002 / 0116933. However, the unit described in that application is applied to a relatively small heat exchanger that is used to dehumidify air for cooling electronic components. The configuration described in the application is too small for a home refrigerator. The heat pump voltage polarity reversal process described in the application can be used to heat a freezer heat exchanger in a two-chamber refrigerator and raise the temperature until the ice melts.

If the heat exchanger is directly connected to the thermoelectric module, the heat passes directly through the heat exchanger.

When a liquid is used as a heat exchange medium between the thermoelectric module and the freezer heat exchanger, the liquid must be heated to 0 ° C. or higher and the fluid circuit must be forcedly circulated by a pump.

The heat exchanger mounted directly on the thermoelectric module must be reduced in shape, which reduces its efficiency and makes it unsuitable for application in the freezer compartment of a domestic refrigerator. The liquid heat exchange medium allows larger and hence more efficient freezer heat exchangers to be used.
US Patent Application No. US2002 / 0116933

In the first embodiment of the present invention, the refrigerator includes (1) an electronic heat pump, a heat exchanger, a freezing room having a fluid circuit connecting the heat pump and the heat exchanger, and (2) an electronic heat pump. And a refrigerator having a heat exchanger and a fluid circuit connecting the heat pump and the heat exchanger. The fluid circuit in the freezer compartment is coupled to the fluid circuit in the refrigerator compartment via a freezer compartment heat pump, and the fluid circuit in the refrigerator compartment is coupled to the high temperature side heat exchanger via the refrigerator compartment heat pump. In the defrosting mode of this embodiment, the refrigerating room heat pump operates at a predetermined minimum voltage, and heat is transferred from the refrigerating room to the freezing room via the freezing room heat pump in order to warm the freezer heat exchanger. So that the polarity of the freezer heat pump is reversed.

In the second embodiment of the present invention, the refrigerator is (1) a freezer compartment, an electronic heat pump, a heat exchanger in the freezer compartment, and a fluid circuit connecting the heat pump and the heat exchanger; (2) A refrigeration room, comprising an electronic heat pump, a heat exchanger in the refrigeration room, and a fluid circuit connecting the heat pump and the heat exchanger; (3) A high temperature side heat exchanger, and a high temperature side fluid circuit that connects the high temperature side heat exchanger to the freezer compartment heat pump and the refrigerator compartment heat pump so that the two heat pumps are in series.

In the defrosting mode in the present embodiment of the present invention, the polarity of the freezer compartment heat pump is reversed, and heat is transferred from the high temperature side fluid circuit to the freezer compartment heat exchanger.

Thermoelectric modules are very efficient when used as heaters. The thermoelectric module is a heat pump, and when used as a heater, the COP is greater than 1.0. In other words, the thermal energy supplied to the high temperature side is greater than the consumed electrical energy. This means that for the same level of heating, the thermoelectric module can be achieved with less electrical energy than the heating wire heater.

The advantage of this reverse polarity defrosting compared to the heating wire heater is that the heater wire is away from the heat exchanger, whereas the system proposed here is directly connected to the heat exchanger. It is in that it is. When using heater wires, heat must be transferred by radiant and convective heat transfer. In convective heat transfer, heat is carried by air to the heat exchanger, which recirculates through the room and warms all contents.

The proposed system uses a liquid medium, which is heated by a thermoelectric module and then flows through a heat exchanger and transfers the heat to ice by conduction. No extra heating of the freezer, such as heating the air space or contents, occurs.

Since this liquid flows through the entire heat exchanger by a pump, the heating is extremely uniform, and all parts of the heat exchanger rise to 0 ° C. or more at approximately the same time. This means that it is not necessary to overheat a part of the heat exchanger to ensure that all parts are above the melting point of ice, thus reducing the amount of heat required for defrosting. ing.

A very advantageous aspect of the proposed defrosting system is that the heat introduced into the freezer compartment for defrosting can be drawn from the associated cooled enclosure and then returned generally there, As a result, the net energy consumption is almost zero. In essence, this process follows the law of conservation of energy, and only the irreversible components associated with this heat pump device are lost.

This feature is possible because the refrigerator compartment and the freezer compartment are closely coupled. There is no other way to achieve this simple defrosting.

The object of the third embodiment of the present invention is to extract moisture in the air, freeze the extracted moisture, and use it later as portable water. The present embodiment is (1) a heat exchanger directly mounted on each side of an electronic heat pump such as a thermoelectric module, which is in direct contact with inflow and outflow air, or (2) one of the electronic heat pumps And a heat exchanger in contact with the inflow and outflow air via the fluid circuit and the second radiant heat exchanger.

After being dehumidified for a period of time, ice grows on the final cold side of the heat exchanger. In order to collect this moisture as water, the polarity of the current flowing through the thermoelectric module is reversed. This heat exchanger covered with ice is thereby heated and the ice melts. In addition, the air flow is also reversed so that the air cooled by the frozen heat exchanger can be used to lower the temperature on the hot side of subsequent modules and improve efficiency.

A refrigerator 10 in FIG. 1 includes a box 11 having a freezer compartment 12 and a refrigerator compartment 13. In the freezer compartment 12, there is a freezer electronic heat pump, which in this embodiment is a thermoelectric module having a first heat exchanger 15 on one side and a second heat exchanger 16 on the other side or It is a thermoelectric convector 14. The first heat exchanger 15 is connected to the freezer compartment heat exchanger 17 by a fluid.

In the refrigerator compartment 13, there is a refrigerator compartment heat exchanger 19, which is connected to the second heat exchanger 16 of the freezer compartment 12 by a fluid. Outside the refrigerating room 13, there is a refrigerating room electronic heat pump. In this embodiment, the heat pump has a first heat exchanger 21 on one side and a second heat exchanger 22 on the other side. Module or thermoelectric convector 20. The first heat exchanger 21 is fluidly connected to the refrigerator heat exchanger 19 and the second heat exchanger 16 in the freezer compartment 12. The second heat exchanger 22 is connected to the high temperature side heat exchanger 23 by a fluid.

Thus, in the embodiment shown in FIG. 1, during normal operation, the thermal load of the freezer compartment 12 is transmitted to the refrigerator compartment liquid circuit via the freezer compartment thermoelectric module 14, and then the heat is released to the outside air. A circuit to be transmitted to the high temperature side heat exchanger 23. The freezer temperature is typically -18 ° C, the refrigerator temperature is typically 5 ° C, and the outside temperature is typically 25 ° C.

During the defrosting, the refrigerator compartment thermoelectric module 20 operates at a preset minimum voltage (to prevent heat leakage through the module), and the freezer compartment module 14 is operated with a reverse polarity. As a result, heat is extracted from the refrigerator compartment 13 via the thermoelectric module heat pump 14, thereby heating the freezer compartment liquid (and the freezer compartment heat exchanger ahead of it). The refrigerator compartment circuit is cooled to 5 ° C. or lower by this operation. This means that the energy input to the system is the amount needed only to transfer heat (this amount is less than the amount needed to generate the same amount of heat). Become).

Since the freezer module 14 transfers heat from the high temperature region (5 ° C.) to the low temperature region (−18 ° C.), this heat transfer is accomplished with a very high coefficient of performance (COP) and hence very high efficiency.

When defrosting is complete, the freezer liquid is at or above 0 ° C. (typically between 5 ° C. and 10 ° C.), and the liquid is again cooled to -18 ° C. or slightly below. Furthermore, the body of the heat exchanger 17 must be cooled back to its original operating temperature. At this time, the freezer compartment heat exchanger 14 is returned to its original polarity, and heat is pumped from the freezer compartment liquid to the refrigerator compartment liquid.

The refrigerator compartment liquid is now cooler than the freezer compartment liquid, and the heat is pumped again along a positive temperature gradient, making pumping very efficient. In short, the heat that was pumped into the freezer is now reversed. The heat used to melt the ice is contained in the condensed water, which is drained out of the freezer compartment and can therefore no longer be a heat load.

In the preferred form, this condensed water (being 5 ° C. or below) is routed to the high temperature side heat exchanger coil to help remove heat from the cold room module.

As mentioned above, this process is extremely efficient and achieves the defrost process as quickly as no other process can occur. This helps to counter the effects of defrosting on food in the freezer and improves storage quality. It is particularly suitable for this system to have multiple stages of freezer compartment heat pumps 14 through the refrigerator compartment 13. In order to achieve defrosting, the temperature difference at which heat is transferred (from the refrigerator compartment 13 to the freezer compartment 12 and then back again) is less in a multistage system than in a non-multistage system. Therefore, there are fewer associated irreversible components.

The refrigerator 30 shown in FIG. 2 includes a box 31 having a freezer compartment 32 and a refrigerator compartment 33. In the freezer compartment 32, there is a freezer compartment heat exchanger 34. In contrast to the first embodiment, the freezer compartment thermoelectric module or thermoelectric convector 35 is mounted outside the freezer compartment 32. On one side of the thermoelectric module 35 is a first heat exchanger 36 that is fluidly connected to the freezer compartment heat exchanger 34, and on the other side of the thermoelectric module 35 is a second heat exchanger 37. .

Inside the refrigerator compartment 33 is a refrigerator compartment heat exchanger 38. Outside the refrigerator compartment 33 is a refrigerator compartment thermoelectric module or thermoelectric convector 39. On one side of the thermoelectric module 39 is a first heat exchanger 40 that is fluidly connected to the heat exchanger 38, and on the other side of the thermoelectric module 39 is a second heat of the freezer compartment thermoelectric module 35. There is a second heat exchanger 41 in fluid communication with the exchanger 37 and the high temperature side heat exchanger 42.

The refrigerator shown in FIG. 2 is a variation of the combination of thermoelectric modules, in which the heat in the freezer compartment is pumped directly out of the freezer compartment 32 and into the hot side circuit. Freezer room thermoelectric modules have a larger temperature difference for pumping heat, which affects efficiency. For this configuration, it is often practical to use a multi-stage module.

In this case, the freezer compartment 32 and the refrigerator compartment 33 are not directly connected on the low temperature side. However, connected via the hot side circuits (37, 41 and 42), during defrosting, heat is transferred between them to benefit each other.

In the defrosting, the freezer module 35 is operated in reverse, and heat is transferred from the high temperature side liquid. The hot side liquid is cooled during this process and then passes through the cold room module 39. Since the high temperature side liquid is cooled on the high temperature side and lower than the outside air (by the freezer module 35), the refrigerating room module will operate at a lower temperature difference and up to 5 ° C or less if the same electrical input is present The refrigerator compartment 33 is cooled.

If the temperature of the high temperature side liquid from the cold room module 39 is lower than the outside air, this liquid must not be directed through the high temperature side heat exchanger 42, but in a direction that returns to the freezer room module 35 again. Must be. If it does in this way, the temperature of the liquid which flows in into the high temperature side of the refrigerator compartment module 39 will be maintained at the lowest level, and it will become possible to drive | operate in the state which the efficiency of the refrigerator 31 improved.

When the defrosting is completed, the freezer module 35 is returned to its original polarity, and the refrigerator module 39 can be turned off. The conduction heat through the module cools the hot liquid. The direction of the flow of the high temperature side liquid is reversed so that the direction of passing through the refrigerating room module 39 first before passing through the freezing room module 35 is reversed. In this way, the heat transmitted so as to supercool the refrigerator compartment 33 is returned, and the operation of the freezer compartment module 35 is aided in bringing the freezer compartment 32 back to a desired temperature or lower.

As described above, the condensed water is drained out of the freezer compartment 32 and is turned to the high temperature side heat exchanger coil.

FIG. 3 shows a dehumidifier 50. The dehumidifier 50 includes a set of several thermoelectric modules 51, and outside air passes through the low temperature side heat exchanger 52 of the thermoelectric modules 51. Air is cooled as it passes through a series of heat exchangers 52 from position 1 to position 2. After passing through all the low temperature sides of the heat exchanger 52, the air is recirculated and passes from the position 3 to the position 4 through the high temperature side 53 of the thermoelectric module 51. Since the temperature of the air is cooled, the position 3 is below the outside air, and the operating temperature difference between the heights of the modules 51 is reduced. This feature allows higher efficiencies to be obtained because the efficiency of pumping heat from the thermoelectric module is strongly dependent on the temperature difference.

By the time the air reaches the last module 52 at position 2, it is cooled from the outside air to a low temperature, and the heat exchanger temperature is kept below 0 ° C., so moisture condensed on the surface of the heat exchanger is Freeze immediately. Any bacteria present will break their cell membranes when the water inside forms ice crystals. Therefore, freezing water also improves sterility.

After a certain period of time, the ice grows and if the ice is not removed, it will block the heat exchanger. The thermoelectric module is suitable for the defrosting operation because it is only necessary to change the direction of the current in order to change the cooling side to the heating side.

FIG. 4 shows the direction of heat flow (arrow Qi) when the current is reversed. Until then, 52, which was on the low temperature side, becomes hot and melts all the ice formed. After the ice is thawed, the current is restored to its original polarity and the dehumidification / freezing process is resumed. According to this configuration, while the current is in reverse polarity, no dehumidifying action occurs on the water collection side of the module, so the defrost period is shortened as much as possible.

FIG. 5 shows the situation when both current and air flow are reversed during defrosting. In this case, since the inflowing outside air is in a direction crossing the low temperature side of the entire thermoelectric module, convenient dehumidification occurs during defrosting. Here, the structure which collects water in series from the both sides of the last thermoelectric module is needed. If it does in this way, dehumidification / freezing operation will be able to be performed simultaneously with defrosting, and the whole efficiency can be improved.

It is not necessary for all of the recirculated air to pass through the hot side heat exchanger. The reason is that moisture is removed from the air, the specific heat of the air is lowered, and the temperature of the air rises at a faster rate than the low temperature side. When the air temperature exceeds the outside air temperature, it is clearly desirable to use the outside air for cooling the high temperature side heat exchanger. This can be accommodated by a bypass configuration driven by temperature. An alternative cooling fluid passage on the hot side is shown in FIG.

Various modifications can be made to the details of the design and circuit configuration without departing from the scope of the present invention.

It is a schematic explanatory drawing of the 2 compartment refrigerator which incorporates the defrost system according to 1st embodiment of this invention. It is a schematic explanatory drawing of the 2 compartment refrigerator which incorporates the defrost system according to 2nd embodiment of this invention. It is a schematic explanatory drawing of the dehumidification mode driving | operation of a dehumidifier. It is a schematic explanatory drawing of the defrost mode driving | operation of a dehumidifier. It is a schematic explanatory drawing of the dehumidifier circuit at the time of carrying out reverse operation of air and an electric current at the time of a defrost mode.

Claims (8)

A freezing chamber having a heat pump, a heat exchanger, and a fluid circuit connecting the heat pump and the heat exchanger, a heat pump, a heat exchanger, and a fluid circuit connecting the heat pump and the heat exchanger. A refrigerator equipped with a refrigerator compartment. The fluid circuit of the freezer compartment is connected to the fluid circuit of the refrigerator compartment via the freezer compartment heat pump, and the fluid circuit of the refrigerator compartment is connected to a high temperature side heat exchanger via the refrigerator compartment heat pump. The refrigerator according to claim 1. In the defrosting mode, the refrigerating room heat pump is operated at a preset minimum voltage so that heat is pumped from the refrigerating room to the freezing room through the freezing room heat pump to heat the freezing room heat exchanger. The refrigerator according to claim 1, wherein the polarity of the freezer compartment heat pump is reversed. A freezing room, a heat pump, a heat exchanger in the freezing room, a freezing room having a fluid circuit connecting the heat pump and the heat exchanger, a refrigerating room, the heat pump, and the refrigerating room A refrigerating room having a heat exchanger in the above, a fluid circuit connecting the heat pump and the heat exchanger, a high temperature side heat exchanger and the high temperature side heat exchanger to the freezer room heat pump and the refrigerating room heat pump, A refrigerator comprising a high-temperature fluid circuit that connects the two heat pumps in series. The refrigerator according to claim 4, wherein in the defrost mode, the polarity of the freezer compartment heat pump is reversed, and heat is transferred from the high temperature side fluid circuit to the freezer compartment heat exchanger. A dehumidifier that extracts moisture from the air, freezes the moisture and later collects it as portable water,
A room having an air inlet for air to enter and an air outlet for air to exit, a thermoelectric module in the room, and mounted on both sides of the thermoelectric module A dehumidifier comprising a heat exchanger that is in direct contact with the air flow from the inlet to the outlet. The dehumidifier according to claim 6, wherein the heat exchanger on one side or both sides of the thermoelectric module is in contact with an air inlet and an air outlet through a liquid circuit having a second radiating heat exchanger. The dehumidifier of claim 6, wherein ice growing on the heat exchanger in direct contact with the incoming air is melted by reversing the polarity of the electronic heat pump.