JP2006153454A - Supercritical refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supercritical refrigerating device having improved durability while preventing the output degradation of a compressor in the state that an outside air temperature is low. <P>SOLUTION: The supercritical refrigerating device comprises a branch part X via which refrigerant flowing out of a high pressure side heat exchanger 12 for cooling compressed refrigerant branches, a first depressurizer 13 for depressurizing one branching refrigerant, an evaporator 14 for evaporating the refrigerant depressurized by the first depressurizer, the compressor 11 for compressing the refrigerant flowing out of the evaporator into supercritical pressure and discharging it to the high pressure side heat exchanger, a bypass circuit 16 for guiding the other branching refrigerant to an intermediate pressure part 11d of the compressor, an opening/closing valve 17 for opening/closing the bypass circuit, a second depressurizer 18 for depressurizing the refrigerant flowing in the bypass circuit, an outside air temperature detector 32 for detecting an outside air temperature, and a control means 3 for controlling the opening/closing operation of the opening/closing valve so that the opening/closing valve is opened for carrying the other refrigerant into the bypass circuit and guiding it to the intermediate pressure part of the compressor when the temperature detected by the outside air temperature detector is a preset temperature or lower. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a supercritical refrigeration apparatus, and more particularly to a supercritical refrigeration apparatus using outside air as a heat source fluid of an evaporator.

In a supercritical refrigerating apparatus using outside air as a heat source fluid of an evaporator and using a two-stage compressor as a compression apparatus, generally, when the outside air temperature decreases, the evaporation pressure, that is, the low pressure side pressure decreases. Further, the discharge side pressure of the low stage compressor, that is, the intermediate pressure is reduced with the reduction of the low pressure side pressure. On the other hand, the discharge pressure of the high-stage compressor, that is, the high-pressure side pressure is high because the discharge-side gas of the high-stage compressor is used as a heat source for heating the use-side heat exchange medium such as water or air. When it is necessary to keep the temperature of the discharge side gas of the stage side compressor high, that is, when the high pressure side pressure needs to be kept high (for example, when the high pressure pressure is not lowered). is there. In this case, in the refrigeration apparatus using the two-stage compressor, the pressure difference between the high-pressure side pressure and the intermediate pressure increases as the outside air temperature decreases.
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  However, when the pressure difference between the high-pressure side pressure and the intermediate pressure increases as the outside air temperature decreases in this way, the high-low pressure difference of the high-stage compressor increases, and the compression efficiency deteriorates. That is, in a cold region, in a low temperature state where the outside air temperature is 0 ° C. or lower, not only is it difficult to maintain the output of the compression device, but also the force acting on each member increases and the durability decreases. I was worried that it would occur. For example, when the high / low pressure difference becomes large, for example, the vane valve or the discharge valve in the high stage compressor may be damaged.

  The present invention has been made paying attention to such problems existing in the prior art. The object is to provide a supercritical refrigeration apparatus capable of preventing a reduction in the output of the compression apparatus during operation when the outside air temperature is low and improving the durability.

  In the first aspect of the present invention, the high-pressure side heat exchanger (12) for cooling the refrigerant compressed so that the pressure becomes supercritical, and the refrigerant flowing out from the high-pressure side heat exchanger (12) are branched. A branching section (X) to be discharged, a first pressure reducing device (13) for depressurizing one refrigerant branched by the branching section (X), and evaporating the refrigerant depressurized by the first pressure reducing apparatus (13) The evaporator (14) to be discharged, the compressor (11) for compressing the refrigerant flowing out of the evaporator (14) so that the pressure becomes supercritical, and discharging the compressed refrigerant to the high-pressure side heat exchanger (12), A bypass circuit (16) for guiding the other refrigerant branched at the branch section (X) to the intermediate pressure section (11d) of the compressor (11), and an on-off valve (17) for opening and closing the bypass circuit (16) ), And a second reduction for reducing the pressure of the refrigerant flowing through the bypass passage (16). A device (18), an outside temperature detector (32) for detecting the outside temperature, and when the temperature detected by the outside temperature detector (32) is below a predetermined temperature, the on-off valve (17) is opened. Control means (3) for controlling the opening and closing of the on-off valve (17) so that the other refrigerant branched at the branch (X) flows into the bypass circuit (16) and is led to the intermediate pressure part (11d) of the compressor 11. It is characterized by comprising.

  According to a second aspect of the present invention, in the supercritical refrigeration apparatus according to the first aspect, when the temperature detected by the outside air temperature detector (32) is 0 ° C. or less, the control means (3) The on-off valve (17) is opened and the other refrigerant branched at the branch portion (X) flows into the bypass circuit (16) and is guided to the intermediate pressure portion (11d) of the compressor 11. To do.

  According to a third aspect of the present invention, in the supercritical refrigeration apparatus according to the first aspect, the refrigerant is carbon dioxide.

  Since the present invention is configured as described above, when the outside air temperature is lowered, the high pressure side pressure can be maintained high, and the temperature of the discharge gas of the compressor can be maintained high. It is possible to prevent a decrease in output of the compression device at the time, and it is possible to increase the durability of the compression device, so that a supercritical refrigeration device suitable for use in a cold region can be obtained.

  The pressure becomes supercritical for the purpose of providing a supercritical refrigeration system capable of preventing a decrease in output of the compressor during operation at a low outside temperature and enhancing durability. A high-pressure side heat exchanger that cools the compressed refrigerant, a branch part that branches the refrigerant that has flowed out of the high-pressure side heat exchanger, and a first pressure reduction that decompresses one of the refrigerants branched at the branch part An apparatus for evaporating the refrigerant depressurized by the first depressurizing apparatus, and a compression for compressing the refrigerant flowing out from the evaporator so that the pressure becomes supercritical and discharging it to the high-pressure side heat exchanger A bypass circuit for guiding the other refrigerant branched at the branching portion to the intermediate pressure portion of the compression device, an on-off valve for opening and closing the bypass circuit, and a second pressure reducing the refrigerant flowing through the bypass circuit Pressure reducing device An outside air temperature detector for detecting the outside air temperature, and when the temperature detected by the outside air temperature detector is equal to or lower than a predetermined temperature, the on-off valve is opened and the other refrigerant branched at the branch portion is used as a bypass circuit. This is realized by comprising a control means for controlling the opening and closing of the on-off valve so as to guide it to the intermediate pressure portion of the flow compressor 11.

  Hereinafter, an embodiment in which the present invention is embodied in a heat pump type hot water supply apparatus will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of a hot water supply apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of pressure control according to the embodiment of the present invention.

  As shown in FIG. 1, the heat pump hot water supply apparatus A includes a supercritical refrigeration cycle apparatus 1, a hot water supply unit 2, and a control device 3. In this embodiment, the control device 3 is installed in the supercritical refrigeration cycle apparatus 1. The supercritical refrigeration cycle apparatus 1 and the hot water supply unit 2 are connected by connecting water pipes 5 and 6.

  The supercritical refrigeration cycle apparatus 1 includes an inverter-driven two-stage compressor (compressor) 11, a high-pressure side heat exchanger 12, an electric expansion valve (first decompressor) 13, an evaporator 14, and an accumulator 15. The refrigerant circuit is connected sequentially. Further, the flow of the refrigerant in the refrigerant circuit is as indicated by solid line arrows in FIG.

  The inverter-driven two-stage compressor 11 includes a low-stage compressor (low-stage compression section) 11a, a high-stage compressor (high-stage compression section) 11b, and a high-stage side in a common sealed housing 11H. A common electric motor 11c that drives the compressor 11a and the low-stage compressor 11b is built in, and the discharge side of the low-stage compressor 11a and the suction side of the high-stage compressor 11b communicate with each other as an intermediate pressure. It is connected by a pipe (intermediate pressure part) 11d. Further, the space in the sealed housing 11H is filled with the intermediate pressure gas, that is, the discharge gas of the low-stage compressor 11a.

  Further, during the supercritical refrigeration cycle operation, the inverter-driven two-stage compressor 11 is controlled in operating frequency by the control device 3 described later, and the rotational speed is variably controlled. A discharge gas temperature detector 31 for detecting the temperature of the discharge gas discharged from the high-stage compressor 11b is provided in the discharge pipe of the high-stage compressor 11b.

  The high-pressure side heat exchanger 12 includes a refrigerant heat exchange tube 12 a for introducing the high-pressure refrigerant discharged from the high-stage compressor 11 b and hot water supplied from a hot water storage tank 21 disposed in the hot water supply unit 2. The water heat exchange tube 12b for introducing water is formed in a heat exchange relationship. Therefore, the high-temperature and high-pressure refrigerant gas discharged from the high stage compressor 11b is cooled by the hot water supplied from the hot water storage tank 21, and this hot water is heated by the heat of the discharge gas of the high stage compressor 11b. The

  The electric expansion valve 13 depressurizes the high-pressure gas refrigerant cooled by the high-pressure side heat exchanger 12, is driven by a pulse motor, and controls the opening degree by the control device 3 described later during supercritical refrigeration cycle operation. Has been.

  The evaporator 14 heat-exchanges the low-pressure gas-liquid mixed refrigerant decompressed by the electric expansion valve 13 with the outside air as a heat source medium, and vaporizes the refrigerant. The evaporator 14 is provided with an outside air temperature detector 32 for detecting the outside air temperature, and an outside air temperature detection signal detected by the outside air temperature detector 32 is transmitted to the control device 3.

  In the refrigerant circuit configured as described above and having the above-described components, one end side is branched at the branching portion X in the middle of the outlet side piping of the high-pressure side heat exchanger 12, and the other end side is joined at the joining portion Y. , A bypass circuit 16 connected to a connecting pipe 11d that connects the low-stage compressor 11a and the high-stage compressor 11b is provided, and an electromagnetic open / close valve (open / close valve) is provided in the middle of the bypass circuit 16. 17 and a capillary tube (second decompression device) 18 are provided.

  The refrigerant circuit is filled with carbon dioxide (CO2) as an alternative refrigerant. Typical natural refrigerants for refrigeration and air conditioning include hydrocarbons (HC: propane, isobutane, etc.), ammonia, air, and CO2. However, as a refrigerant characteristic, while hydrocarbon and ammonia have good energy efficiency, there are problems such as flammability and toxicity, and air has problems such as inferior energy efficiency outside the ultra-low temperature range. In contrast, carbon dioxide is safe without flammability and toxicity.

  Next, the hot water supply unit 2 includes a hot water storage tank 21, a hot water circulation pump 22, a hot water supply pipe 23, and a water supply pipe 24. The upper and lower portions of the hot water storage tank 21 are connected to the water heat exchange tube 12b by a hot water circulation circuit P including communication water pipes 5 and 6.

  The hot water circulation circuit P feeds the low temperature water at the bottom of the hot water storage tank 21 to the water heat exchange tube 12b, and guides the high temperature water heated by the water heat exchange tube 12b to the top of the hot water storage tank 21. Is formed. A hot water circulation pump 22 is attached in the hot water circulation circuit P. In the hot water storage tank 21, hot water having a high temperature is stored in the upper part and water having a low temperature is stored in the lower part due to a difference in specific gravity. Further, the hot water temperature in the upper part of the hot water storage tank 21, that is, the raising temperature is measured by a raising temperature detector 33 provided in the upper part of the hot water storage tank 21.

  The hot water supply pipe 23 is for supplying hot water to a hot water faucet, a bathtub, or the like, and is connected to the upper part of the hot water storage tank 21 so that hot water at a high temperature in the hot water storage tank 21 can be supplied. The hot water supply circuit is provided with an on-off valve 25 for hot water supply. The water supply pipe 24 is capable of constantly supplying tap water into the hot water storage tank 21, and is connected to the bottom of the hot water storage tank 21 via a check valve 26 and a pressure reducing valve 27.

  The control device 3 controls the operating frequency of the inverter-driven two-stage compressor and the opening of the electric expansion valve 13 according to a predetermined procedure during steady operation. When the outside air temperature decreases, the control device 3 is as follows. Take control. That is, when the outside air temperature detected by the outside air temperature detector 32 is a predetermined temperature, for example, 0 ° C. or less, the opening degree of the electric expansion valve 13 is controlled so as to suppress the decrease in the high-pressure side pressure against the decrease in the outside air temperature. At the same time, the rotation speed (operation frequency) of the inverter-driven two-stage compressor 11 is controlled so as to make the compression function force substantially constant.

  Further, the control device 3 opens the electromagnetic on-off valve 17 when the outside air temperature decreases to the predetermined temperature (0 ° C.). When the electromagnetic on-off valve 17 is opened, the high-pressure gas refrigerant is bypassed to the intermediate pressure communication pipe (intermediate pressure portion) 11d as indicated by the broken line arrow in FIG.

  By controlling as described above, as shown in FIG. 2, the high-pressure side pressure is controlled so as to maintain a substantially constant pressure against a decrease in the outside air temperature. Further, the intermediate pressure decreases as shown by the broken line in FIG. 2 when there is no bypass circuit 16 as in the prior art, whereas in this embodiment, the pressure drop decreases as shown by the solid line in FIG. It is suppressed. Therefore, an increase in the high / low pressure difference of the high stage compressor 11b is suppressed. Further, since the high-pressure side refrigerant gas bypassed at this time is cooled by the high-pressure side heat exchanger 12, the degree of superheat of the refrigerant gas sucked into the high stage compressor 11b is reduced.

  As for the intermediate pressure, the pressure difference between the present invention and the conventional one is increased with respect to the decrease in the outside air temperature, but this is due to the action of the capillary tube 18. Further, in FIG. 2, the pressure diagram is shown only up to the outside air temperature of −10 ° C., but this is due to the fact that the allowable operating range of the hot water supply device is determined to be −10 ° C. by chance.

  According to the embodiment configured as described above, when the outside air temperature is lowered, in the high-stage compressor 11b, the high-low pressure difference is reduced, thereby eliminating the possibility of breakage of the discharge valve and the vane valve. The durability of the compression device is improved. Further, since the compression ratio of the high stage compressor 11b is reduced and the degree of superheat of the intake gas is reduced, the operation efficiency is improved. As a result, the output of the compressor is prevented from being lowered even in winter operations such as in cold regions where the outside air temperature is 0 ° C. or lower.

  Moreover, since the high pressure side pressure is kept high when the outside air temperature is lowered, the discharge side gas temperature of the high stage compressor 11b is kept high. In particular, as shown in FIG. 2, when the high-pressure side pressure is kept constant, the hot water supply hot water can be kept at a predetermined value, in this case, at a substantially constant value.

  In this embodiment, since carbon dioxide is used as the refrigerant, there is no problem of flammability and toxicity with respect to the refrigerant gas, and the handling becomes easy.

  The inverter-driven two-stage compressor (compressor) 11 includes a low-stage compressor 11a, a high-stage compressor 11b, and a driving unit in a sealed housing 11H into which discharge gas from the low-stage compressor 11a is introduced. Since the electric motor 11c is built in, the inside of the housing 11H of the compression device becomes an intermediate pressure. Accordingly, the pressure difference between the inside and outside of the cylinder and the inside and outside of the compressor housing is halved, and the force acting on each part is reduced. As a result, the durability performance of the inverter-driven two-stage compressor (compressor) 11 can be further improved in combination with the effect of preventing the increase in the high / low pressure difference by the bypass circuit 16.

  The present invention can be modified and embodied as follows.

  (1) In the above embodiment, the bypass circuit 16 is opened at 0 ° C., but this temperature can be appropriately changed depending on the design of the refrigeration apparatus.

  (2) In addition, the connection order of the electromagnetic open / close valve (open / close valve) 17 and the capillary tube (second decompression device) 18 in the bypass circuit 16 may be reversed. In other words, the bypassed refrigerant gas can pass through the capillary tube 18 and then pass through the electromagnetic on-off valve 17.

  (3) In the above embodiment, the inverter uses the inverter-driven two-stage compressor 11, but another type of variable capacity two-stage compressor may be used.

  (4) In the above embodiment, the supercritical refrigeration apparatus according to the present invention is embodied in a heat pump hot water supply apparatus. The supercritical refrigeration apparatus is heated by another heating apparatus, for example, indoor air. It can also be embodied in a heating machine.

It is a circuit diagram of the hot-water supply apparatus which concerns on embodiment of this invention. It is explanatory drawing of the pressure control which concerns on embodiment of this invention.

Explanation of symbols

1 Supercritical refrigeration cycle device 2 Hot water supply unit 3 Control device (control means)
11 Inverter-driven two-stage compressor (compressor)
11H Sealed housing 11a Low stage compressor (Low stage compressor)
11b High stage compressor (High stage compressor)
11c Electric motor 11d Connecting pipe (intermediate pressure part)
12 High-pressure side heat exchanger 13 Electric expansion valve (first decompression device)
14 Evaporator 15 Accumulator 16 Bypass Circuit 17 Electromagnetic On / Off Valve (On / Off Valve)
18 Capillary tube (second decompression device)
X junction Y junction

Claims (3)

  A high pressure side heat exchanger (12) that cools the refrigerant compressed so that the pressure becomes supercritical, a branch portion (X) that branches the refrigerant that has flowed out of the high pressure side heat exchanger (12), and this branch A first pressure reducing device (13) for depressurizing one of the refrigerants branched in the section (X), an evaporator (14) for evaporating the refrigerant depressurized by the first pressure reducing device (13), and the evaporation A compressor (11) that compresses the refrigerant flowing out from the vessel (14) so that the pressure becomes supercritical and discharges the refrigerant to the high-pressure side heat exchanger (12), and the other branched by the branch portion (X) A bypass circuit (16) for guiding the refrigerant to the intermediate pressure part (11d) of the compressor (11), an on-off valve (17) for opening and closing the bypass circuit (16), and the bypass path (16) A second decompression device (18) for decompressing the flowing refrigerant; When the temperature detected by the outside air temperature detector (32) to be discharged and the temperature detected by the outside air temperature detector (32) is equal to or lower than a predetermined temperature, the on-off valve (17) is opened to branch at the branch portion (X). And a control means (3) for controlling the opening and closing of the on-off valve (17) so that the other refrigerant flows into the bypass circuit (16) and is led to the intermediate pressure portion (11d) of the compression device 11. Supercritical refrigeration equipment.   When the temperature detected by the outside air temperature detector (32) is 0 ° C. or lower, the control means (3) opens the on-off valve (17) and branches the other refrigerant at the branch portion (X). The supercritical refrigeration apparatus according to claim 1, wherein the refrigerant is introduced into the bypass circuit (16) and led to the intermediate pressure part (11 d) of the compression device 11.   The supercritical refrigeration apparatus according to claim 1, wherein the refrigerant is carbon dioxide.

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