JP2008275249A - Refrigerating cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve COP while preventing global warming in a refrigerating cycle. <P>SOLUTION: This refrigerating cycle is constituted by successively connecting a compressor 20, a gas cooler 30, a variable pressure reducing unit 90 and an evaporator 100 by a refrigerating pipe, and operated when the high pressure of a sealed CO<SB>2</SB>refrigerant exceeds critical pressure. This refrigerating cycle has an inside heat exchanger for exchanging heat between a high pressure CO<SB>2</SB>refrigerant coming out of the gas cooler 30 and a low pressure CO<SB>2</SB>refrigerant sucked in the compressor 20 by the coming-out of the evaporator 100, and a bypass circuit 94 for merging a part of the CO<SB>2</SB>refrigerant coming out of the gas cooler 30 into a low pressure side inlet of the inside heat exchanger 60. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a refrigeration cycle, and is particularly suitable for a refrigeration cycle for air conditioning applications in which the high pressure of a CO ₂ refrigerant (carbon dioxide refrigerant) operates above a critical pressure. The CO ₂ refrigerant includes a CO ₂ single refrigerant and a CO ₂ mixed refrigerant.

In recent years, from the viewpoint of protecting the ozone layer, attention has been focused on a refrigeration cycle using a CO ₂ refrigerant, which is a natural refrigerant that has an ozone depletion coefficient of zero and a global warming coefficient that is much smaller than that of chlorofluorocarbons. However, if a CO ₂ refrigerant is used in an air conditioning application with the same refrigeration cycle configuration as that of a chlorofluorocarbon refrigerant, the COP (coefficient of performance) is lowered, so that it has not spread. In a refrigeration cycle using a CO ₂ refrigerant, the high pressure part can be a transcritical cycle in which the critical pressure exceeds the critical pressure. Therefore, when used in a refrigeration cycle for hot water supply, the efficiency is high and it is being widely used in that field. Therefore, it is desired to improve the COP of the refrigeration cycle using the CO ₂ refrigerant, which has the advantage that the environmental load is small, to expand it as an air conditioning application, and to further improve the efficiency in a hot water supply application.

As a conventional refrigeration cycle using a CO ₂ refrigerant, there are refrigeration cycles shown in FIGS. 5 and 7 using an internal heat exchanger. The solid line in FIGS. 5 and 7 is the flow of refrigerant during cooling, and the broken line is the flow of refrigerant during heating. Incidentally, JP 2000-346466 A (Patent Document 1) is cited as a thing related to the refrigeration cycle of FIG. 5, and JP 6-515570 A (Patent Document 2) as a thing related to the refrigeration cycle of FIG. ).

  The refrigeration cycle in FIG. 5 will be described. During cooling, the refrigerant discharged from the compressor 10 is cooled by the heat source side heat exchanger 30 serving as a gas cooler through the four-way valve 20, and is cooled by the internal heat exchanger 62 through the heat source side variable pressure reducing device 40 that is fully opened. The pressure is reduced to low pressure and low temperature by the use side variable pressure reducing device 90 through the blocking valve 70a, and while the air is cooled by the use side heat exchanger 100 serving as an evaporator, it is heated and passes through the connecting pipe 80b and the blocking valve 70b. Heated by the internal heat exchanger 62 and sucked into the compressor 10. During heating, the flow of the refrigerant is reversed, and the variable pressure reducer 90 is fully opened and the variable pressure reducer 40 reduces the pressure.

  The effect of this refrigeration cycle during cooling will be described with reference to the ph diagram (Mollier vapor pressure diagram) in FIG. In FIG. 6, the alphabet is the same as the position of the alphabet shown in FIG. 6 is a ph diagram of a cycle when the internal heat exchanger 62 is not used, and a solid line is a ph diagram of a cycle when the internal heat exchanger 62 is used. As is clear from FIG. 6, by exchanging heat between CD and FA, the specific enthalpy difference EF on the evaporator side is extended, and the performance is improved. Note that when chlorofluorocarbon refrigerant is used in the refrigeration cycle shown in FIG. 5, the specific enthalpy difference on the evaporator side increases, but at the same time, the inclination of the isentropic line of the compressor section increases, resulting in increased compressor power and COP. The improvement effect cannot be obtained.

  The refrigeration cycle in FIG. 7 will be described. This refrigeration cycle is obtained by adding an accumulator 200 for adjusting the refrigerant amount to the refrigeration cycle shown in FIG. The accumulator 200 is installed between the four-way valve 20 and the low pressure side of the internal heat exchanger 60. In the case of the refrigeration cycle shown in FIG. 7, since the refrigerant at the outlet of the accumulator 200 is automatically controlled to a high degree of prestige, the low pressure side of the internal heat exchanger 60 is used for superheating the refrigerant.

  On the other hand, as a refrigeration cycle using a chlorofluorocarbon refrigerant, there is a refrigeration cycle shown in FIG. 8 using an internal heat exchanger. The solid line in FIG. 8 is the refrigerant flow during cooling, and the broken line is the refrigerant flow during heating.

  In the refrigeration cycle shown in FIG. 8, during cooling, a part of the refrigerant flowing out of the condenser 30 is taken out as a bypass, decompressed by the variable decompression device 95 and flows to the bypass heat exchanger 64, and the bypass heat exchanger 64. Then, heat is exchanged with the remaining refrigerant flowing out of the condenser 30, the remaining refrigerant is cooled, and it is overheated and then sucked into the compressor. As a result, the cold flow of the bypass refrigerant can be recovered by the bypass heat exchanger, and the flow rate of the refrigerant flowing through the connection pipe and the evaporator can be reduced. Therefore, the performance can be improved because the refrigerant pressure loss is reduced.

JP 2000-346466 A Japanese translation of PCT publication No. 6-515570

  However, in the refrigeration cycle shown in FIGS. 5 and 7, since all the refrigerant flows through the connection pipe and the evaporator, the refrigerant pressure loss is increased, resulting in performance degradation. In addition, since the refrigerant overheated by the internal heat exchanger 62 is sucked into the compressor 10, there is a possibility that the reliability of the compressor may be lowered when the temperature of the refrigerant rises abnormally. In the refrigeration cycle of Patent Document 1, when the temperature of the refrigerant sucked into the compressor rises, the internal heat exchanger is bypassed so that a part of the refrigerant flows so as to suppress the temperature rise of the refrigerant. However, since the refrigerant flowing through the connection pipe and the evaporator is bypassed, the efficiency is lowered.

Furthermore, the refrigeration cycle shown in FIG. 8 aims at improving the performance of the refrigeration cycle using the chlorofluorocarbon refrigerant, and application to the refrigeration cycle using the CO ₂ refrigerant has not been considered.

  The objective of this invention is obtaining the refrigerating cycle which can aim at COP improvement, aiming at prevention of global warming.

The first aspect of the present invention for achieving the above object is configured by sequentially connecting a compressor, a gas cooler, a variable pressure reducer, and an evaporator with refrigerant piping, and the high pressure of the enclosed CO ₂ refrigerant is critical. A refrigeration cycle having an internal heat exchanger that is operated over pressure and exchanges heat between the high-pressure CO ₂ refrigerant exiting from the gas cooler and the low-pressure CO ₂ refrigerant exiting from the evaporator and sucked into the compressor And a bypass circuit that joins a part of the CO ₂ refrigerant that has come out of the gas cooler to the low-pressure side inlet of the internal heat exchanger is provided.

The second aspect of the present invention, the compressor, the switching valve, the heat source-side heat exchanger is configured variable pressure reducer and the use side heat exchanger are sequentially connected by refrigerant pipes, encapsulated CO ₂ refrigerant The high-pressure pressure is operated above the critical pressure, and the high-pressure CO ₂ refrigerant discharged from the heat source side heat exchanger or the usage side heat exchanger and the usage side heat exchanger or the heat source side heat exchanger are An internal heat exchanger that exchanges heat with the low-pressure CO ₂ refrigerant sucked into the compressor, and the switching valve includes the compressor, the heat source side heat exchanger, the variable pressure reducer, and the use side heat during cooling. Switch so that the CO ₂ refrigerant flows in the order of the exchanger, and operate to switch the CO ₂ refrigerant to flow in the order of the compressor, the use side heat exchanger, the variable pressure reducer, and the heat source side heat exchanger during heating. In the refrigeration cycle The inner part of the CO ₂ refrigerant discharged from the utilization-side heat exchanger during the heating with a portion of the CO ₂ refrigerant discharged from the heat source-side heat exchanger is bypassed to the low pressure side inlet of the internal heat exchanger A bypass circuit for joining the low pressure side inlet of the heat exchanger is provided.

A more preferable specific configuration example in the present invention is as follows.
(1) The high-pressure side flow and the low-pressure side flow of the internal heat exchanger are configured to face each other during the cooling and the heating.
(2) An accumulator for adjusting the refrigerant amount is provided at the low pressure side inlet of the internal heat exchanger, a bypass variable pressure reducer is provided in the bypass circuit, and the bypass variable pressure reducer is controlled so as to adjust the discharge temperature of the compressor. A control device is provided.

  According to the refrigeration cycle of the present invention, COP can be improved while preventing global warming.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to FIGS. The same reference numerals in the drawings of the respective embodiments indicate the same or equivalent. The solid line in FIGS. 1 to 4 is the flow of refrigerant during cooling, and the broken line is the flow of refrigerant during heating.
(First embodiment)
The refrigeration cycle of the first embodiment of the present invention will be described with reference to FIG.

The refrigeration cycle of the present embodiment includes a compressor 10, a four-way valve 20 that is a switching valve, an outdoor heat exchanger 30 that is a heat source side heat exchanger, a heat source side variable pressure reducer 40, a use side variable pressure reducer 90, and a use side heat. The indoor heat exchanger 100 which is an exchanger is sequentially connected by refrigerant piping. This refrigeration cycle is a transcritical cycle in which the high pressure of the enclosed CO ₂ refrigerant is operated above the critical pressure. Global warming can be prevented by using a CO ₂ refrigerant.

  The four-way valve 20 is switched so that the refrigerant flows in the order of the compressor 10, the outdoor heat exchanger 30, the heat source side variable decompressor 40, the use side variable decompressor 90, and the indoor heat exchanger 100 during cooling, and the compressor 10 during heating. Then, the indoor heat exchanger 100, the use side variable pressure reducer 90, the heat source side variable pressure reducer 40, and the outdoor heat exchanger 30 are operated so as to switch the refrigerant to flow in this order.

In this refrigeration cycle, the high-pressure CO ₂ refrigerant exiting from the outdoor heat exchanger 30 or the indoor heat exchanger 100 and the low-pressure CO ₂ exiting from the indoor heat exchanger 100 or the outdoor heat exchanger 30 and sucked into the compressor 10 are used. An internal heat exchanger 60 for exchanging heat with the _two refrigerants is provided.

  Further, a part of the high-pressure refrigerant exiting from the outdoor heat exchanger 30 during cooling is bypassed to the low-pressure side inlet of the internal heat exchanger 60 and a part of the refrigerant exiting from the indoor heat exchanger 100 during heating is internally A bypass circuit 94 that bypasses the low pressure side inlet of the heat exchanger 60 is provided. The bypass circuit 94 is provided with a bypass variable pressure reducer 95.

  First, the operation during cooling will be described. The high-temperature and high-pressure refrigerant from the compressor 10 passes through the four-way valve 20 and releases heat to the outdoor air ventilated by the outdoor fan (heat source side fan) 50 in the outdoor heat exchanger 30 serving as a gas cooler. The refrigerant discharged from the outdoor heat exchanger 30 is guided to the high-pressure side flow path of the internal heat exchanger 60 through the heat-source-side variable pressure reducer 40 in which the amount of pressure reduction is reduced to the limit. After being cooled by the refrigerant flowing through the passage, the pressure is reduced by the use side variable pressure reducer 90 through the blocking valve 70a and the connection pipe 80a. The decompressed refrigerant removes heat from the indoor air ventilated by the blower 110 in the indoor heat exchanger (use side heat exchanger) 100 serving as an evaporator, and again passes through the connection pipe 80b and the blocking valve 70b, and again becomes a four-way valve. 20, guided to the low pressure side flow path of the internal heat exchanger 60, heated by the refrigerant flowing through the high pressure side flow path in this low pressure side flow path, and then sucked into the compressor 10 again.

  Further, a part of the high-pressure refrigerant before entering the internal heat exchanger 60 that has exited from the outdoor heat exchanger 30 serving as a gas cooler is taken out as a bypass, decompressed by the bypass variable decompression device 95, and the low-pressure side flow of the internal heat exchanger 60 It joins the road entrance. Here, the bypass flow rate is controlled by the variable bypass pressure reducer 95 provided in the bypass circuit 94 so as to adjust the compressor discharge temperature.

  During cooling of this refrigeration cycle, the effect of improving the performance by increasing the inherent specific enthalpy difference of the internal heat exchanger 60, and the connection pipe 80a by bypassing part of the high-pressure refrigerant, the indoor heat exchange that becomes the evaporator The pressure loss of the vessel 100 can be reduced at the same time, and the COP can be improved. In addition, since the cold heat of the bypass refrigerant is recovered by the internal heat exchanger 60, there is no loss.

  The above is the operation at the time of cooling. When the four-way valve 20 is switched and the flow of the refrigerant is set to the broken arrow, the operation of heating is performed. In this case, the pressure reduction amount of the variable pressure reducer 90 is reduced to the limit and the pressure is reduced by the variable pressure reducer 40. In this refrigeration cycle, the effect of reducing the pressure loss of the connecting pipe 80a is lost, but the pressure loss of the outdoor heat exchanger 30 serving as an evaporator can be reduced. Therefore, the inherent specific enthalpy difference of the internal heat exchanger 60 is reduced. The effect of increasing the performance and increasing the performance and the reduction of the pressure loss of the outdoor heat exchanger 30 by bypassing a part of the high-pressure refrigerant can be simultaneously achieved, and the COP can be improved. As a result, it can be expanded as an air conditioning application, and the efficiency in a hot water supply application can be further improved. In addition, since the cold heat of the bypass refrigerant at the time of heating is also collected by the internal heat exchanger 60, there is no loss.

As described above, according to the present embodiment, it is possible to ensure the reliability of the compressor and improve the COP while preventing global warming.
(Second Embodiment)
Next, the refrigerating cycle of 2nd Embodiment of this invention is demonstrated using FIG. The second embodiment is different from the first embodiment in the points described below, and the other points are basically the same as those in the first embodiment, and thus redundant description is omitted.

  In the refrigeration cycle of the second embodiment, in the refrigeration cycle of the first embodiment, an accumulator for adjusting the refrigerant amount is provided at the low-pressure side inlet of the internal heat exchanger, a bypass variable decompressor is provided in the bypass circuit, and the compression An additional control device for controlling the bypass variable pressure reducer is provided to adjust the discharge temperature of the machine.

  The accumulator 200 is generally an effective means for adjusting the amount of refrigerant in the cycle. However, when used in combination with the internal heat exchanger 60, the accumulator 200 raises the temperature of the refrigerant sucked by the compressor, and the compressor has a high pressure ratio or the like. Under the condition that the discharge temperature becomes high, there is a risk that the discharge temperature will rise until the reliability is lowered.

However, in the second embodiment, by adjusting the pressure reduction amount of the bypass variable pressure reducer 95 and bypassing more refrigerant, the temperature of the compressor suction refrigerant can be adjusted, and the reliability is improved. be able to. In this case, since the cold heat of the bypass refrigerant is recovered by the internal heat exchanger 60, there is no significant COP reduction.
(Third embodiment)
Next, the refrigeration cycle of 3rd Embodiment of this invention is demonstrated using FIG. The third embodiment is different from the first embodiment in the points described below, and the other points are basically the same as those in the first embodiment, and thus redundant description is omitted.

In the third embodiment, four check valves 120 are added, and the flow of the high-pressure side flow path and the flow of the low-pressure side flow path of the internal heat exchanger 60 are opposed to each other during cooling and heating. It is comprised so that it may become. Specifically, two series of two check valves 120 are provided in parallel to the series circuit of the internal heat exchanger 60 and the variable pressure reducer 40, and the intermediate point of the series circuit of one check valve 120 is provided. One side of the outdoor heat exchanger 30 is connected to the other side, and one side of the indoor heat exchanger 100 is connected to an intermediate point of the series circuit of the other check valve 120. According to the third embodiment, the high pressure side flow path and the low pressure side flow path of the internal heat exchanger 60 are opposed to each other during cooling and heating, so that the heat exchange capability is improved and the variable pressure reducing device 40 is installed. Since it can be configured by one, it can be made inexpensive.
(Fourth embodiment)
Next, the refrigeration cycle of 4th Embodiment of this invention is demonstrated using FIG. The fourth embodiment is different from the first embodiment in the following points, and the other points are basically the same as those in the first embodiment, and thus redundant description is omitted.

  This 4th Embodiment is an example utilized for the heat pump type water heater. Specifically, there is no four-way valve 20, blocking valves 70a and 70b, connection pipes 80a and 80b, and a water / refrigerant heat exchanger 300 that exchanges heat between water and refrigerant is used as a use side heat exchanger. is there. The water / refrigerant heat exchanger 300 includes a water circuit 300a used for hot water supply and a refrigerant circuit 300b used for a gas cooler. Water is supplied to the water circuit 300a by the water pump 310, heated by the water / refrigerant heat exchanger 300, and discharged. In this heat pump type water heater, if the temperature of the feed water is high, the discharge pressure of the compressor 10 will increase. Therefore, by adjusting the bypass variable pressure reducer 95, a large amount of refrigerant flows through the evaporator 30, and the discharge pressure becomes an appropriate discharge pressure. Can be adjusted.

It is a block diagram of the refrigerating cycle of 1st Embodiment of this invention. It is a block diagram of the refrigerating cycle of 2nd Embodiment of this invention. It is a block diagram of the refrigerating cycle of 3rd Embodiment of this invention. It is a block diagram of the refrigerating cycle of 4th Embodiment of this invention. It is a block diagram of the refrigerating cycle of the prior art example 1. FIG. 6 is a ph diagram of the refrigeration cycle in FIG. 5. It is a block diagram of the refrigerating cycle of the prior art example 2. It is a block diagram of the refrigerating cycle of the prior art example 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Compressor, 20 ... Four-way valve, 30 ... Outdoor heat exchanger (heat source side heat exchanger, gas cooler at the time of cooling), 40 ... Heat source side variable decompressor, 50 ... Outdoor fan (heat source side fan), 60 ... Inside Heat exchanger, 70a, 70b ... blocking valve, 80a, 80b ... connection piping, 90 ... use side variable pressure reducer, 94 ... bypass circuit, 95 ... bypass variable pressure reducer, 100 ... indoor heat exchanger (use side heat exchanger) Gas cooler during heating), 110 ... indoor blower (use side blower), 120 ... check valve, 200 ... accumulator, 300 ... use side heat exchanger, 310 ... water pump.

Claims (4)

A compressor, a gas cooler, a variable pressure reducer and an evaporator are sequentially connected by refrigerant piping,
The high pressure of the enclosed CO ₂ refrigerant is operated above the critical pressure,
In the refrigeration cycle comprising an internal heat exchanger for exchanging heat between the high-pressure CO ₂ refrigerant coming out of the gas cooler and the low-pressure CO ₂ refrigerant coming out of the evaporator and sucked into the compressor,
A refrigeration cycle, comprising a bypass circuit that joins a part of the CO ₂ refrigerant that has come out of the gas cooler to the low-pressure side inlet of the internal heat exchanger. A compressor, a switching valve, a heat source side heat exchanger, a variable pressure reducer, and a use side heat exchanger are sequentially connected by a refrigerant pipe,
The high pressure of the enclosed CO ₂ refrigerant is operated above the critical pressure,
CO ₂ pressure refrigerant sucked into the compressor out of the heat source-side heat exchanger or said high-pressure CO ₂ refrigerant discharged from the utilization-side heat exchanger utilization side heat exchanger or the heat source-side heat exchanger An internal heat exchanger that exchanges heat with
The switching valve switches so that CO ₂ refrigerant flows in the order of the compressor, the heat source side heat exchanger, the variable pressure reducer, and the usage side heat exchanger during cooling, and the compressor, the usage side heat during heating. In the refrigeration cycle that operates to switch the CO ₂ refrigerant to flow in the order of the exchanger, the variable pressure reducer, and the heat source side heat exchanger,
A part of the CO ₂ refrigerant exiting from the heat source side heat exchanger during the cooling is bypassed to the low pressure side inlet of the internal heat exchanger and one of the CO ₂ refrigerant exiting from the use side heat exchanger during the heating. A refrigeration cycle, characterized in that a bypass circuit is provided for joining a part to the low-pressure side inlet of the internal heat exchanger.   3. The refrigeration cycle according to claim 2, wherein the flow on the high-pressure side and the flow on the low-pressure side of the internal heat exchanger are opposed to each other during the cooling and the heating.   3. The variable bypass according to claim 1 or 2, wherein an accumulator for adjusting the amount of refrigerant is provided at a low pressure side inlet of the internal heat exchanger, a bypass variable decompressor is provided in the bypass circuit, and a discharge temperature of the compressor is adjusted. A refrigeration cycle comprising a control device for controlling a decompressor.

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