JP2003074997A - Supercritical refrigeration unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supercritical refrigeration unit having a bypass device capable of preventing pressure difference between high pressure and low pressure of a high stage side compressor from increasing and a heat pump water heater using such a supercritical refrigeration unit. SOLUTION: A two-stage compressor 11 having a low stage side compressor 11a and the high side compressor 11b as its components, a high pressure side heat exchanger 12 for cooling gas discharged from the compressor 11b of the compressor 11, an expansion device 13 and an evaporator 14 for effecting heat exchange with outdoor air are connected sequentially so as to form a refrigerant circuit to turn high pressure side pressure into a supercritical state. The refrigerant circuit is provided with a bypass circuit 16 so as to bypass to the discharge side of the low stage side compressor the high pressure refrigerant which has been cooled in the high pressure side heat exchanger when outdoor temperature becomes low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercritical refrigeration system, and more particularly to a supercritical refrigeration system that uses outside air as a heat source fluid for an evaporator and uses a two-stage compressor as a compressor.

[0002]

2. Description of the Related Art In a supercritical refrigeration system using outside air as a heat source fluid for an evaporator and a two-stage compressor as a compressor, generally, when the outside air temperature decreases, the evaporation pressure, that is, the low pressure side pressure decreases. To do. In addition, the discharge-side pressure of the low-stage compressor, that is, the intermediate pressure, decreases as the low-pressure side pressure decreases.
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 gas on the discharge side of the stage compressor high, that is, when it is necessary to keep the pressure on the high pressure high (for example, to prevent the high pressure from decreasing). is there. In this case, in the refrigeration system using the two-stage compressor, the pressure difference between the high-pressure side pressure and the intermediate pressure was large as the outside air temperature decreased.

[0003]

However, when the pressure difference between the high-pressure side pressure and the intermediate pressure increases as the outside air temperature decreases, the pressure difference between the high-stage side compressor and the high-side side pressure increases, resulting in a high compression efficiency. There is a problem in that the durability is deteriorated because the force acting on each member increases with the deterioration. For example, if the high-low pressure difference becomes large, for example, the vane valve and the discharge valve in the high-stage compressor may be damaged.

The present invention has been made by paying attention to the problems existing in such conventional techniques. It is an object of the present invention to provide a supercritical refrigeration system provided with a bypass circuit that prevents an increase in the high-low pressure difference of the high-stage compressor. Another object of the present invention is to provide a heat pump type hot water supply device using such a supercritical refrigeration system.

[0005]

In order to achieve the above object, a supercritical refrigeration system according to the present invention comprises a low-stage compressor and a high-stage compressor as two-stage compression. Machine, high-pressure side heat exchanger that cools the discharge gas from the high-stage side compressor of this two-stage compressor, expansion device, evaporator that exchanges heat with the outside air are sequentially connected so that the high-pressure side pressure becomes supercritical. The refrigerant circuit further includes a refrigerant circuit that bypasses the high-pressure gas refrigerant that has been cooled by the high-pressure side heat exchanger when the outside air temperature decreases to the discharge side of the low-stage compressor. The bypass circuit has a bypass circuit.

According to this structure, since the high-pressure side gas refrigerant of the high-stage compressor is bypassed to the intermediate pressure portion due to the decrease in the outside air temperature, the intermediate pressure rises, and the compression ratio in the high-stage compressor is increased. Get smaller. Further, since the bypassed refrigerant gas has been cooled by the high pressure side heat exchanger, the degree of superheat of the refrigerant gas sucked into the high pressure side compressor is reduced. Therefore, the pressure difference between the high-stage compressor and the low-pressure side becomes small, so that there is no fear of damage to the discharge valve or the vane valve, and the durability of the compressor is improved. Further, since the compression ratio of the high-stage compressor becomes small and the superheat of the intake gas becomes small, the operating efficiency of the compressor improves.

Further, the capacity of the two-stage compressor is controlled so as to suppress the reduction of the compression function force when the outside air temperature decreases, and the expansion valve device has a high stage when the outside air temperature decreases. The opening degree may be controlled so as to suppress the decrease in the discharge pressure of the side compressor. According to this structure, when the outside air temperature decreases, the high pressure side pressure can be maintained high, and the discharge side gas temperature of the high stage side compressor can be maintained high.

The refrigerant circuit may be filled with carbon dioxide as a refrigerant. According to this structure, a supercritical refrigeration cycle in which the temperature of the gas on the discharge side of the high-stage compressor becomes high while using a refrigerant that is inflammable and non-toxic is possible. Further, the action of the bypass circuit can prevent the pressure on the high-pressure side from being lowered, so that the temperature of the discharge-side gas of the high-stage compressor can be kept high.

The two-stage compressor has the low-stage compressor, the high-stage compressor and a driving electric motor built in a hermetically sealed housing into which the discharge gas of the low-stage compressor is introduced. can do. According to this structure, the intermediate pressure acts on the inside of the compressor housing, the pressure difference between the inside and outside of the cylinder of the two-stage compressor 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 two-stage compressor is further improved in combination with the effect of preventing an increase in the high-low pressure difference due to the bypass circuit.

Further, since the heat pump type hot water supply apparatus according to the present invention is an application of the above-mentioned supercritical refrigeration system, when the outside air temperature is lowered, the pressure difference between the high pressure side compressor and the high pressure side is increased. Can be prevented, and high-temperature hot water can be obtained without deteriorating the durability of the device.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments 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 device 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 hot water supply apparatus according to the first embodiment includes a supercritical refrigeration cycle apparatus 1 and a hot water supply unit 2.
And a control device 3. In addition, in this embodiment, the control device 3 is installed in the supercritical refrigeration cycle device 1. Further, the supercritical refrigeration cycle apparatus 1 and the hot water supply unit 2 are connected by the connecting water pipes 5 and 6.

The supercritical refrigeration cycle apparatus 1 includes a refrigerant circuit in which an inverter-driven two-stage compressor 11, a high pressure side heat exchanger 12, an electric expansion valve 13, an evaporator 14 and an accumulator 15 are sequentially connected. Further, the flow of the refrigerant in this refrigerant circuit is as shown by the solid line arrow in FIG. 1 during steady operation.

The inverter-driven two-stage compressor 11 includes a low-stage compressor 11a and a high-stage compressor 11 in a hermetically sealed housing.
b, a common electric motor 11c for driving these compressors 11a and 11b is built in, and the low-stage side compressor 11a
For connecting the discharge side of the high pressure side compressor 11b with the discharge side of the high pressure side compressor 11b
It is connected by 1d. Further, the space inside the closed housing is filled with the intermediate pressure gas, that is, the discharge gas of the low-stage side compressor 11a.

Further, the inverter-driven two-stage compressor 11
In the supercritical refrigeration cycle operation, the operating frequency is controlled by the control device 3 described later, and the rotation speed is 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 is a high stage side compressor 11
a heat exchanger tube 12a for refrigerant for introducing the high-pressure refrigerant discharged from b, and a heat exchanger tube 12b for water for introducing hot water supplied from the hot water storage tank 21 arranged in the hot water supply unit 2, Are 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 the hot water is heated by the heat of the discharge gas of the high-stage compressor 11b. It

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

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 to vaporize the refrigerant. In addition,
An outside air temperature detector 32 for detecting the outside air temperature is attached to the evaporator 14.

The high-pressure side heat exchanger 1 is installed in the refrigerant circuit having the above-mentioned configuration and the above-described components.
The bypass circuit 16 is provided from the outlet side pipe of 2 to the communication pipe 11d connecting the low-stage side compressor 11a and the high-stage side compressor 11b. In the bypass circuit 16, the electromagnetic opening / closing valve 17 and the capillary tube 18 are provided. It is provided.

The inside of the refrigerant circuit is filled with carbon dioxide (CO ₂ ) as an alternative refrigerant. Typical natural refrigerants for refrigeration and air conditioning are hydrocarbons (HC: propane, isobutane, etc.), ammonia,
Examples include air and CO ₂ . However, as the refrigerant characteristics, hydrocarbon and ammonia have high energy efficiency, but on the other hand, they have problems of flammability and toxicity, and air has a problem that energy efficiency is poor except in the ultralow temperature range. On the other hand, carbon dioxide is safe without combustibility and toxicity.

Next, the hot water supply unit 2 includes the hot water storage tank 2
1, hot water circulation pump 22, hot water supply pipe 23, water supply pipe 24
It is configured with. And the upper part and the lower part of the hot water storage tank 21 are different from the heat exchange tube 12b for water.
They are connected by a hot water circulation circuit P including the connecting water pipes 5 and 6.

The hot water circulation circuit P sends water having a low temperature in the lower portion of the hot water storage tank 21 to the water heat exchange tube 12b, and sends water having a high temperature heated by the water heat exchange tube 12b to the upper portion of the hot water storage tank 21. It is formed to guide. 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 portion and water having a low temperature is stored in the lower portion due to the difference in specific gravity. The hot water temperature in the upper part of the hot water storage tank 21, that is, the heating temperature, is measured by the heating 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, etc., and is connected to the upper part of the hot water storage tank 21 so that the hot water of high temperature in the hot water storage tank 21 can be supplied. The hot water supply circuit has an on-off valve 2
5 is attached. 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 degree of the electric expansion valve 13 according to a predetermined procedure during steady operation. Control like this. That is, the outside air temperature detected by the outside air temperature detector 32 is a predetermined temperature, for example, 0.
When the temperature is lower than or equal to ℃, the opening degree of the electric expansion valve 13 is throttle-controlled so as to suppress the decrease in the pressure on the high-pressure side with respect to the decrease in the outside air temperature, and the inverter-driven two-stage is used so that the compression functional force is substantially constant. Rotational speed of compressor 11 (operating frequency)
Is controlled to be larger. In addition, the control device 3
Opens the electromagnetic opening / closing valve 17 when the outside air temperature drops to the predetermined temperature (0 ° C.). Solenoid valve 1
When 7 is opened, the high-pressure gas refrigerant is bypassed to the intermediate-pressure connecting pipe 11d as shown by the broken line arrow in FIG.

By controlling as described above, FIG.
As shown in, the high-pressure side pressure is controlled so as to maintain a substantially constant pressure with respect to the decrease in the outside air temperature. In addition, the intermediate pressure, when there is no bypass circuit 16 as in the conventional case,
While the pressure drops as shown by the broken line in FIG. 2, in the case of this embodiment, the pressure drop is suppressed as shown by the solid line in FIG. Therefore, the increase in the pressure difference between the high-stage compressor 11b and the high-low pressure 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 drawn into the high pressure side compressor 11b becomes small.

Regarding the intermediate pressure, the pressure difference between the present invention and the conventional one increases with the decrease in the outside air temperature, but this is due to the action of the capillary tube 18. is there. 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 operation allowable range of this water heater is accidentally set to −10 ° C.

According to the embodiment configured as described above, when the outside air temperature decreases, in the high-stage compressor 11b, the pressure difference between the high and low sides becomes small, which may damage the discharge valve or the vane valve. Is eliminated and the durability of the compressor is improved. Further, since the compression ratio of the high-pressure stage compressor is small and the superheat of the intake gas is small, the operating efficiency of the compressor is improved.

Further, when the outside air temperature decreases, the high pressure side pressure is kept high, so that the discharge side gas temperature of the high stage side compressor is kept high. In particular, as shown in FIG. 2, when the high-pressure side pressure is kept constant, the hot water for hot water supply is set to a predetermined value,
In this case, it is possible to maintain a substantially constant value. Further, in this embodiment, since carbon dioxide is used as the refrigerant, there is no problem of flammability or toxicity of the refrigerant gas, and the handling is easy.

Further, the inverter-driven two-stage compressor 11
Since the low-stage side compressor 11a, the high-stage side compressor 11b and the drive motor 11c are built in the hermetically sealed housing into which the discharge gas of the low-stage side compressor 11a is introduced, the inside of the compressor housing is at an intermediate pressure. Becomes Therefore, 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 bypass circuit 1
Combined with the effect of preventing the increase in the pressure difference between high and low by 6, the durability performance of the inverter-driven two-stage compressor 11 can be further improved.

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 refrigerator.

(2) In addition, the bypass circuit 16 is provided with an electromagnetic opening / closing valve 17 and a capillary tube 18. Instead of these, an electric valve is used and its opening is gradually increased as the outside air temperature decreases. It is also possible to do so. In this way, when the bypass circuit is opened, the pressure does not suddenly change, and smooth control is possible.

(3) Further, the connection order of the electromagnetic opening / closing valve 17 and the capillary tube 18 in the bypass circuit 16 may be reversed. That is, it is also possible that the refrigerant gas to be bypassed passes through the electromagnetic on-off valve 17 after passing through the capillary tube 18. However, in this case, since the electromagnetic on-off valve 17 opens and closes the flow of the refrigerant gas after being depressurized, there is a drawback that an electromagnetic on-off valve having a large diameter is required to increase the specific volume of the gas to be handled. .

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

(5) Further, in the above embodiment, the supercritical refrigeration system according to the present invention is embodied as a heat pump type hot water supply system. It can also be embodied in a heater that heats air.

[0035]

Since the present invention is constructed as described above, it has the following effects. According to the supercritical refrigeration system of the first aspect of the present invention, a two-stage compressor including a low-stage compressor and a high-stage compressor as constituent elements, and a high-stage compressor of the two-stage compressor. High-pressure side heat exchanger for cooling the discharge gas from the, expansion device, an evaporator for heat exchange with the outside air are sequentially connected, and has a refrigerant circuit formed so that the high-pressure side pressure becomes supercritical. Further has a bypass circuit that bypasses the high pressure gas refrigerant after being cooled by the high pressure side heat exchanger to the discharge side of the low pressure side compressor when the outside air temperature decreases, so that in the high pressure side compressor The pressure difference between high and low is small, there is no risk of damage to the discharge valve or the vane valve, and its durability is improved. Further, in the high-pressure stage compressor, the compression ratio becomes small and the superheat degree of the intake gas becomes small, so that the operating efficiency thereof is improved.

According to a second aspect of the present invention, in the first aspect of the invention, the two-stage compressor is capacity-controlled so as to suppress a reduction in compression functional force when the outside air temperature decreases. Since the expansion valve device is controlled in opening degree so as to suppress the decrease in the discharge pressure of the high-stage compressor when the outside air temperature decreases, the high pressure side pressure is maintained high when the outside air temperature decreases. The temperature of the discharge side gas of the high pressure side compressor can be kept high.

According to the invention of claim 3, in the invention of claim 1 or 2, since the refrigerant circuit is filled with carbon dioxide as a refrigerant, a refrigerant which is not flammable or toxic is used. However, a supercritical refrigeration cycle in which the temperature of the gas on the discharge side of the high-stage compressor becomes high can be achieved. Further, the action of the bypass circuit can prevent the pressure on the high-pressure side from being lowered, so that the temperature of the discharge-side gas of the high-stage compressor can be kept high.

Further, according to the invention of claim 4, in the two-stage compressor, the low-stage compressor and the high-stage compressor are provided in a hermetically sealed housing into which the discharge gas of the low-stage compressor is introduced. Since the machine and the drive motor are built in, the pressure difference between the inside and outside of the cylinder and the inside and outside of the compressor housing of the two-stage compressor is halved, and the force acting on each part is reduced. As a result, the durability performance of the two-stage compressor is further improved in combination with the effect of preventing an increase in the high-low pressure difference due to the bypass circuit.

Further, according to the heat pump type hot water supply apparatus according to the invention described in claim 5, since the supercritical refrigeration system according to any one of claims 1 to 4 is applied, when the outside air temperature is lowered. It is possible to prevent an increase in the pressure difference between the high-pressure stage compressor and the high-pressure compressor, and it is possible to obtain high-temperature hot water without degrading the durability of the device.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a hot water supply device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of pressure control according to the embodiment of the present invention.

[Explanation of symbols]

1 Supercritical refrigeration cycle equipment 2 Hot water supply unit 3 control device 5 Connection water piping 11 Inverter-driven two-stage compressor 11a Low-stage compressor 11b High-stage compressor 11c Drive motor 11d Communication piping 12 High-pressure side heat exchanger 13 Electric expansion valve 14 Evaporator 16 Bypass circuit 17 Solenoid open / close valve 18 capillary tubes 21 Hot water storage tank 32 Outside temperature detector

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F25B 1/00 371 F25B 1/00 371F 395 395Z (72) Inventor Kiyoshi Koyama 1 Otsukimachi, Ashikaga City, Tochigi Prefecture Address Sanyo Denki Air Conditioning Co., Ltd. (72) Inventor Shigeo Desk 1 Otsukimachi, Ashikaga City, Tochigi Prefecture Sanyo Denki Air Conditioning Co., Ltd. (72) Satoshi Hoshino 1 Otsuki Town, Ashikaga City, Tochigi Sanyo Denki Air Conditioning Co., Ltd. (72) Inventor Shichichi 1 Otsuki-cho, Ashikaga City, Tochigi Prefecture Sanyo Electric Air Conditioning Co., Ltd. (72) Inventor Shigumi Ishigaki 1 Otsuki-cho, Ashikaga City, Tochigi Sanyo Electric Air Conditioning Co., Ltd.

Claims (5)

[Claims] 1. A two-stage compressor comprising a low-stage side compressor and a high-stage side compressor as constituent elements, and a high-pressure side heat exchange for cooling discharge gas from the high-stage side compressor of the two-stage compressor. A condenser, an expansion device, and an evaporator that exchanges heat with the outside air are sequentially connected, and have a refrigerant circuit formed so that the high-pressure side pressure becomes supercritical,
The refrigerant circuit further includes a bypass circuit that bypasses the high-pressure gas refrigerant, which has been cooled by the high-pressure side heat exchanger when the outside air temperature decreases, to the discharge side of the low-stage side compressor. 2. The two-stage compressor is capacity-controlled so as to suppress a reduction in compression function force when the outside air temperature is lowered, and the expansion valve device is a high stage compressor when the outside air temperature is lowered. The supercritical refrigeration system according to claim 1, wherein the opening degree is controlled so as to suppress a decrease in discharge pressure of the side compressor. 3. The supercritical refrigeration system according to claim 1, wherein the refrigerant circuit is filled with carbon dioxide as a refrigerant. 4. The two-stage compressor has the low-stage side compressor, the high-stage side compressor and a drive motor built in a hermetically sealed housing into which the discharge gas of the low-stage side compressor is introduced. The supercritical refrigeration apparatus according to any one of claims 1 to 3. 5. A heat pump hot water supply apparatus to which the supercritical refrigeration apparatus according to any one of claims 1 to 4 is applied.