JP2514936B2 - Refrigeration cycle - Google Patents

Description

The present invention relates to a refrigerating cycle, and more particularly to a refrigerating cycle in which a refrigerant is compressed in two stages.

(Prior Art) A two-stage compression refrigeration cycle in which two compressors are provided in series to compress a refrigerant in two stages is adopted for the purpose of improving compression efficiency.

5 and 6 show a conventional two-stage compression refrigeration cycle. In FIGS. 5 and 6, reference numeral 1 is a low-stage compressor, 2 is a high-stage compressor, and 3 is a condenser. 4 is an evaporator, 5 is an intercooler, 6 and 7 are pressure reducing devices (6 is a high-stage side, 7
Is the lower stage). In the refrigeration cycle of FIG. 5, the refrigerant discharged from the compressor 1 and the refrigerant discharged from the decompression device 6 via the condenser 3 are mixed in the intercooler 5 so that one flows to the evaporator 4 side and the other flows. It flows to the suction side of the compressor 2. Also, the sixth
In the refrigeration cycle shown in the figure, the refrigerant discharged from the compressor 1 and the refrigerant leaving the decompression device 6 via the condenser 3 are mixed in the intercooler 5 and flow to the suction side of the compressor 2, while being discharged from the condenser 3. It flows to the evaporator 4 side through a pipe penetrating the inside of the intercooler 5. The Mollier diagrams of the refrigeration cycle of Fig. 5- (a) and Fig. 6- (a) are shown in Fig. 5- (b) and Fig. 6- (b), respectively, and Fig. 5- (b). A to F in Fig. 5- (a) correspond to each part A to F in Fig. 5- (a), and
A to F in FIG. 6B correspond to respective parts A to F in FIG. 6-A.

FIG. 7 shows a conventional one-stage compression gas injection cycle, in which the refrigerant discharged from the compressor 1 is introduced into the condenser 3 for heat exchange, and then the compressor 1 is passed through the gas-liquid separator 5. It is configured to inject into the cylinder. The Mollier diagram of the refrigeration cycle in Fig. 7- (a) is
It is shown in Fig. 7- (b), and A to F in Fig. 7- (b) are shown in Fig. 7-.
(A) Corresponds to each part AF of the figure.

Further, FIG. 8 shows a conventional example of a heat storage cycle in which a heat storage device is provided in a two-stage compression refrigeration cycle. In FIG. 8, reference numeral 8 denotes a heat storage device, and the compressor 2 is provided in the heat storage device 8.
A heat storage heat exchanger 10a that stores heat in the heat storage material 9 by the discharged gas that comes out and a heat radiation heat exchanger 10b that is branched from the pipe that exits the condenser 3 are provided. The exchanged refrigerant is configured to be returned to the suction side of the compressor 2.

Further, FIG. 9 is a view showing a refrigerating cycle of a conventional hot water supply heat pump, in which reference numeral 11 is a four-way valve, 12
Is an indoor heat exchanger, 13 is an outdoor heat exchanger, and 14 is a hot water supply heat exchanger. One compressor 1 is a one-stage cycle. 9th-
Fig. 9 (b) shows the Mollier diagram of the refrigeration cycle in Fig. 9- (a), and A to D in Fig. 9- (b) correspond to the parts A to D in Fig. 9- (a). ing.

(Problems to be Solved by the Invention) However, the refrigeration cycles shown in FIGS. 5 to 9 have the following problems.

That is, in the two-stage compression refrigeration cycle of FIG. 5, when the intermediate liquid cooler 5 cools the intermediate liquid refrigerant to a saturated state as is clear from the Mollier diagram, there is a problem in oil recovery. However, there is a possibility that the temperature gradually shifts to the lower stage side, and there is a problem that the effect is very small, though the refrigeration cycle has improved efficiency and capacity.
On the other hand, in the two-stage compression refrigeration cycle of FIG. 6, as is clear from the Mollier diagram, the intermediate liquid refrigerant cannot be cooled to the saturated state by the intercooler 5, and the enthalpy on the evaporator side is lost (see -(B) shows the difference between F'and F), and there is a similar problem in terms of efficiency improvement and capacity improvement.

Further, in the gas injection cycle of FIG. 7, the enthalpy on the evaporator side becomes large as shown in the Mollier diagram, but the enthalpy on the high-stage side does not become saturated (see FIG. 7- (b). B '), that is, the discharge temperature becomes high, and there is a problem from the viewpoint of efficiency improvement and capacity improvement.

On the other hand, in the two-stage compression refrigeration cycle provided with the heat accumulator of FIG. 8, there is a problem that the heat exchanger for heat storage and the heat exchanger for heat radiation are required, and the structure is complicated and the cost is high.
There is also a problem in efficiency that a heat transfer leak occurs between both heat exchangers.

Further, in the refrigeration cycle of the hot water supply heat pump shown in FIG. 9, there is a problem that the condensation temperature of the heating rises unnecessarily and the efficiency deteriorates because the hot water supply and the heating have the same condensation temperature as shown in the Mollier diagram. In addition, the pressure must be raised to the condensing temperature required for hot water supply during cooling hot water supply as well, resulting in poor efficiency.

The present invention has been made in view of the above circumstances, and an object thereof is to solve the problems of the above-described conventional refrigeration cycles and to improve the compression efficiency and the capacity with a simple configuration. It is to provide a refrigeration cycle that can.

[Structure of Invention]

(Means for Solving the Problems) The refrigeration cycle of the present invention includes a low-stage compressor that compresses a refrigerant in two stages and a high-stage compressor that decompresses the refrigerant in two stages. In a two-stage compression refrigeration cycle provided with a pressure reducing device and a low pressure reducing device, one end is connected between the low pressure compressor and the high pressure compressor, and the other end is the high pressure reducing device. It is characterized in that the flow direction of the refrigerant in the intermediate pressure portion connected to the low-pressure reducing device is reversible.

(Operation) In the refrigeration cycle of the present invention, an intermediate pressure portion is provided between the low-stage side compressor and the high-stage side compressor and between the high-stage side pressure reducing device and the low-stage side pressure reducing device, and the refrigerant in this intermediate pressure portion is provided. The flow of
By reversing the direction of flow from the compressor to the pressure reducing device side and the opposite direction, it is possible to improve compression efficiency and capacity with a simple configuration.

(Embodiment) An embodiment of the refrigeration cycle according to the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a refrigeration cycle of the present invention. Reference numeral 1 is a low-stage compressor, 2 is a high-stage compressor, 3 is a condenser,
4 is an evaporator, and 6 and 7 are pressure reducing devices (6 is a high-stage side, 7 is a low-stage side). Although a heat exchanger is provided in the intermediate pressure portion between the compressors 1 and 2, here, the case where the heat storage device 8 is used as the heat exchanger is shown.

The heat storage unit 8 is composed of a heat storage material 9 filled inside the heat storage unit 8 and constitutes the intermediate heat exchanger.
Has one end connected to the pipe between the compressors 1 and 2 and the other end connected to the pipe between the pressure reducing devices 6 and 7.

Next, the operation of the refrigeration cycle configured as described above will be described.

Figure 1- (a) shows the heat storage cycle, that is, the case where the intermediate heat exchanger is used as a condenser. At this time, the relationship between the intermediate pressure Pil (liquid side output) and Pig (gas side pressure) is Pil <Pig. To control. This control is performed by increasing the gas-side intermediate pressure Pig by controlling the compressor 1 to a large capacity and the compressor 2 to a small capacity, while squeezing the decompression device 6 higher and the decompression device 7 lower. This is done by lowering the liquid side intermediate pressure Pil.

Then, the relation of Pil <Pig is established by the above control, the flow direction as the condenser is set as shown by the arrow I, and the refrigerant exchanges heat in the intermediate heat exchanger and is stored in the heat storage material 9. . The Mollier diagram at this time is No. 1-
As shown in the figure (b), in this case, the temperature Ti of the refrigerant flowing into the intermediate heat exchanger is set higher than the temperature of the heat storage material 9. Also, there are various ways to change the discharge capacity of the compressor,
For example, when the compressor is independent, it is convenient to change the rotation speed by an inverter, and for a 2-cylinder compressor having two compression mechanisms on one shaft, one or both of which has a bypass valve to control the capacity. do.

On the other hand, in FIG. 2, the flow of the refrigerant is opposite to that described above, that is, the intermediate pressure Pil> Pig is controlled.
This control is carried out by controlling the compressor 1 to a small capacity and the compressor 2 to a large capacity so that the gas side intermediate pressure Pi
While decreasing g, the pressure reducing device 6 is squeezed to a low level and the pressure reducing device 7 is squeezed to a high level to increase the liquid-side intermediate pressure Pil. And by the above control
The relationship of Pil> Pig is established, and the flow direction of the evaporator is set as shown by arrow II, and the refrigerant absorbs heat from the heat storage material and evaporates in the intermediate heat exchanger to improve the heating capacity. The Mollier diagram at this time is shown in Fig. 1- (b).

As described above, in the embodiment shown in FIG. 1 and FIG. 2, the intermediate pressure of the two-stage compression refrigeration cycle is controlled, the flow direction of the refrigerant in the intermediate heat exchanger is reversible, and the flow direction is reduced from the compressor. By storing heat when the device is used and radiating heat when the device is used in the opposite direction, high capacity and high efficiency of the refrigeration cycle can be achieved. Further, since only one heat exchanger is required, the capacity can be increased in the same space and the cost can be reduced. Moreover, heat transfer between heat exchangers is eliminated, and heat loss is reduced.

Next, another embodiment of the refrigeration cycle of the present invention will be described with reference to FIGS.

FIG. 3 shows a refrigeration cycle of another embodiment,
The same components as those of the embodiment shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 3, reference numeral 11 is a four-way valve, 12 is an indoor heat exchanger, 13 is an outdoor heat exchanger, 14 is a hot water heat exchanger, and 15
Is a pressure reducing device, and 16 and 17 are check valves. In this embodiment, the indoor and outdoor heat exchangers 12 and 13 are provided at the intermediate pressure portion, and the hot water supply heat exchanger 14 is provided at the high pressure side. Then, during heating and hot water supply, the intermediate pressure is Pil <Pig and is controlled to be higher than the room temperature in the same manner as in Fig. 1, and the Mollier diagram at this time is shown in Fig. 4- (a). Be done. Further, during cooling hot water supply, the intermediate pressure is controlled to be Pil> Pig and lower than the outdoor temperature, and the Mollier diagram at this time is shown in Fig. 4- (b). As described above, in the present embodiment, the condensing temperature can be set for each of the heating and the hot water during heating and hot water supply, so that the efficiency is improved without performing unnecessary compression. Further, during cooling and hot water supply, heat can be absorbed not only from the inside of the room but also from the outside, so that high-performance and high-efficiency operation can be performed as compared with the refrigeration cycle of the conventional hot-water supply heat pump.

As another embodiment, if the intermediate heat exchanger in FIG. 1 is a refrigerant heater, it can be applied to a refrigerant heating heat pump. Furthermore, it can be applied to a multi-air conditioner that uses an intermediate heat exchanger as an indoor unit.

〔The invention's effect〕

As described above, according to the present invention, the low-stage compressor and the high-stage compressor that compress the refrigerant in two stages, and the high-stage pressure reducing device and the low stage that decompress the refrigerant in two stages. In a two-stage compression refrigeration cycle including a side pressure reducing device, one end is connected between the low pressure side compressor and the high pressure side compressor, and the other end is connected to the high pressure side pressure reducing device and the low pressure side pressure reducing device. Since the flow direction of the refrigerant in the intermediate pressure part connected between and is reversible, only one heat exchanger is required, the capacity can be increased in the same space, the cost is low, and the heat Since heat transfer between the exchangers is eliminated and heat loss is reduced, it is possible to improve compression efficiency and capacity with a simple configuration.

Further, by providing a heat accumulator in the intermediate pressure section, heat is stored in the heat accumulator when the refrigerant flows from the compressor to the pressure reducing device, and heat is radiated from the heat accumulator when flowing in the opposite direction, and heat is accumulated and stored by the reversible flow of the refrigerant. Can dissipate heat.

Furthermore, by providing an indoor / outdoor heat exchanger in the intermediate pressure part and a hot water supply heat exchanger on the high pressure side, which is the discharge side of the high-stage side compressor, if applied to a hot water supply heat pump, the compression efficiency during heating and hot water supply is improved. In addition, it is possible to improve and improve the compression efficiency and capacity at the time of cooling hot water supply, and when applied to the refrigerant heating heat pump, it is possible to heat the refrigerant while absorbing heat outside the room, and the capacity and effect are improved.

Further, if the refrigeration cycle of the present invention is applied to a hot water supply heat pump, it is possible to improve compression efficiency during heating and hot water supply, and compression efficiency and capacity during cooling and hot water supply.

Furthermore, when the refrigeration cycle of the present invention is applied to a refrigerant heating heat pump, refrigerant heating is possible while absorbing heat outside the room, and the capacity and efficiency are improved.

[Brief description of drawings]

1 and 2 are a refrigeration cycle diagram and a Mollier diagram showing an embodiment of the refrigeration cycle according to the present invention, FIG. 3 is a refrigeration cycle diagram showing another embodiment of the present invention, and FIG. 4 is a FIG. 5 and 9 are the refrigerating cycle diagram and the Mollier diagram of the conventional refrigerating cycle. 1 ... Low-stage compressor, 2 ... High-stage compressor, 3 ... Condenser, 4 ... Evaporator, 6 ... High-stage pressure reducing device, 7 ... Low-stage pressure reducing device, 8 ... … Heat storage unit, 9 …… Heat storage material, 12 …… Indoor heat exchanger, 13 …… Outdoor heat exchanger, 14 …… Hot water heat exchanger.

Claims (5)

(57) [Claims] 1. A low-stage compressor and a high-stage compressor for compressing a refrigerant in two stages, and a high-stage decompressor and a low-stage decompressor for decompressing the refrigerant in two stages. In a two-stage compression refrigeration cycle, one end is connected between the low-stage side compressor and the high-stage side compressor and the other end is connected between the high-stage side pressure reducing device and the low-stage side reducing device. A refrigerating cycle characterized in that the flow direction of the refrigerant in the pressure section is reversible. 2. A means for reversing the flow direction of the refrigerant in the intermediate pressure section, wherein the throttle ratio of the low-stage pressure reducing device and the high-stage pressure reducing device is changed.
Refrigeration cycle according to item. 3. The discharge capacity ratio of the low-stage side compressor and the high-stage side compressor is changed as means for reversing the flow direction of the refrigerant in the intermediate pressure portion. 1
Refrigeration cycle according to item. 4. A heat accumulator is provided in the intermediate pressure section, and heat is accumulated in the heat accumulator when the refrigerant flows from the compressor to the pressure reducing device,
The refrigeration cycle according to claim 1, wherein heat is radiated from the regenerator when flowing in the reverse direction. 5. An indoor / outdoor heat exchanger is provided in the intermediate pressure section,
The refrigeration cycle according to claim 1, further comprising a heat exchanger for hot water supply provided on a high pressure side which is a discharge side of the high-pressure stage compressor.