JPH0340297B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a refrigeration cycle device having an injection circuit.

Conventional Structure and its Problems Conventionally, in order to lower the discharge temperature of a refrigeration cycle, a device as shown in FIG. 1 has been proposed. In FIG. 1, 1 is a compressor, 2 is a condenser, 3 is a first throttle device, 4 is a gas-liquid separator, 5 is a second throttle device, and 6 is an evaporator, which are connected in an annular manner as shown in the figure. , first and second flow control valves 7 and 8 are provided in the piping for introducing the gas component from the top of the gas-liquid separator 4 and the piping for introducing the liquid component from the bottom, respectively, and the flow rate control valves 7 and 8 are provided in the piping for introducing the gas component from the top of the gas-liquid separator 4 and the piping for introducing the liquid component from the bottom, respectively. The gas refrigerant or liquid refrigerant is selected or mixed and guided to a position where the pressure is at an intermediate pressure. In such a device, especially when lowering the discharge temperature, the liquid refrigerant is injected into the compressor 1 while the first flow control valve 7 is closed and the second flow control valve 8 is opened. The latent heat of vaporization can be used to lower the discharge temperature. This mode of action will be explained with reference to the refrigerant pressure versus enthalpy diagram shown in FIG. The solid line in Figure 2 is the conventionally used R2
This figure shows the characteristics during liquid injection under heat source temperature conditions using a single refrigerant such as No. 2, R12, etc., and symbols a to j correspond to the conditions in the apparatus shown in FIG. Here, point i is the state before the refrigerant sucked by the compressor 1 is compressed and mixed with the liquid refrigerant from the injection extraction circuit 9, and point j is the state where the temperature has decreased after being mixed with the liquid refrigerant. Therefore, at the outlet of the compressor 1, the discharge temperature becomes _T1 at point a, which is lower than when no liquid injection is performed.

However, in this case, although the discharge temperature can be lowered, the amount of refrigerant flowing through the evaporator 6 is reduced, so not only is the refrigerating capacity reduced, but if the heat source temperature further increases, as shown by the broken line in FIG. , even if the second flow control valve 8 is fully opened,
The state of the compressor 1 outlet is point a′, and the discharge temperature is
rising from T ₁ to T ₂ , deterioration of the thermal stability of refrigerants and oils,
This caused problems such as material corrosion. In addition, in recent years, as the need for high-temperature water supply using refrigeration cycles has increased, it is necessary to increase the condensing temperature, and for such applications, conventional methods have been used to prevent excessive increases in discharge temperature. It was difficult to do.

OBJECT OF THE INVENTION The present invention solves the above-mentioned drawbacks in a conventional refrigeration cycle device having an injection extension circuit, and
It has been particularly devised to lower the discharge temperature, and is intended to achieve this by slightly changing the composition of the refrigerant.

Structure of the Invention The refrigeration cycle device of the present invention has an injection circuit at a position where the pressure is at the intermediate pressure of the compressor, and is constructed by adding a small amount of a refrigerant with a low critical pressure to the refrigerant that is the main component. be. In other words, the discharge temperature changes from moment to moment depending on the temperature conditions of the refrigeration cycle, and is not a physical property unique to the refrigerant.However, as a result of examining the discharge temperature in an ideal cycle under various temperature conditions, a certain law was discovered. . An example of the regularity we found will be explained using Figure 3. Figure 3 shows the discharge temperatures of various fluorocarbon refrigerants in an ideal cycle with a condensing temperature of 55°C, a degree of supercooling of Odeg, an evaporation temperature of 7°C, and a degree of superheating of 11deg, and this shows the critical pressure unique to the refrigerant. It was found that there is a substantially proportional relationship. In other words, the higher the critical pressure of the refrigerant, the higher the discharge temperature under any temperature conditions, and conversely, the lower the critical pressure of the refrigerant, the lower the discharge temperature. Ideal compression under the temperature conditions shown does not result in a superheated gas state at the compressor outlet. In addition, like this,
R21 and R22 generally have a high discharge temperature, and R114 and
Although it has been known that RC318 has a low discharge temperature, this is believed to be the first time that this has been found to be related to the critical pressure unique to the refrigerant. The relationship between the discharge temperature and the physical properties unique to the refrigerant is that the critical pressure is almost inversely proportional to the molecular weight of the refrigerant, so it was found that the discharge temperature tends to be higher as the molecular weight is smaller. The linearity seems to be stronger at critical pressure. It was also discovered that specific heat and the like differ depending on temperature conditions, so they cannot be used as a basis for changing the composition of the refrigerant, and that they have little correlation with the standard boiling point or critical temperature. That is,
In Figure 3, for example, R13B1 and R125 are R22
On the other hand, although R12 and R114 have higher standard boiling points than R22, they both have lower critical pressures than R22, so their discharge temperatures are lower than R22.

Based on the above studies, the discharge temperature can be lowered by adding a small amount of refrigerant with a lower critical pressure than R22 or R12, especially in refrigeration cycle equipment that uses R22 or R12, and especially in refrigeration cycle equipment that uses R22 or R12, the discharge temperature can be lowered. The present invention has been devised and is highly effective in refrigeration cycle equipment.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below. One embodiment described here is the main component of the refrigeration cycle device shown in FIG. 1, which is the same as the conventional example.
It is made by adding a small amount of R152a, which has a lower critical pressure than R22, to R22. At this time, R22 is a low boiling point refrigerant,
R152a is a high boiling point refrigerant, and its operating state in such a configuration, especially during liquid injection, will be explained with reference to FIG. FIG. 4 is a schematic explanatory diagram of a temperature versus composition diagram with the horizontal axis representing the mole fraction of the low boiling point refrigerant R22 when the high pressure, intermediate pressure, and low pressure are each constant; in this combination, the non-azeotropic mixed refrigerant However, at each constant pressure, the upper side shows the saturated gas line, and the lower side shows the saturated liquid line. Also, on the diagram in Figure 4,
The pressure and temperature of each part of the apparatus shown in FIG. 1 are shown. In FIG. 4, gas refrigerant a in a high pressure state at the outlet of a compressor 1 is condensed and liquefied to a supercooled state b in a condenser 2, and is reduced in pressure to an intermediate pressure by a first throttle device 3, and from a state of gas to liquid at a point c. It flows into the separator 4, where it is separated into a gas refrigerant d rich in R22 and a liquid refrigerant e rich in R152a. At the time of liquid injection explained here, the first
Since the flow control valve 7 is closed and the second flow control valve 8 is open, a part of the liquid refrigerant e is injected into the compressor 1 through the injection circuit 9, so that the liquid refrigerant e is injected from the gas-liquid separator 4 into the second throttle device. 5, the refrigerant f, which is richer in R22 than the refrigerant at point c, flows into the refrigerant.
The refrigerant at point f is further reduced in pressure to a low pressure by the second throttle device 5 to a point g, and is evaporated in the evaporator 6 to become a heated gas state h. The gas refrigerant at point h is sucked into compressor 1 and compressed to an intermediate pressure, and is then transferred to point i.
However, in the cylinder (not shown) in the compressor 1, it is mixed with the liquid refrigerant e and the temperature is reduced to the state j, where it is further compressed and the compressor 1
Return to exit state a.

In this configuration, not only is R152a added, which has the effect of lowering the discharge temperature compared to R22, but also the injection
The liquid refrigerant e injected into the device is
Since it is richer in R152a than the composition ratio of R152a, the effect of lowering the discharge temperature is greater. Also
Since R152a is a small amount added to R22, its refrigeration capacity is not much different from R22. Although R152a is a flammable refrigerant, if the mixing ratio is around 30%,
This eliminates the disadvantage of flammability. In cases such as when the heat source temperature rises further, the second
By fully opening the flow rate control valve 8, the compressor 1
This increases the amount of R152a liquid refrigerant that cools the fuel, making it possible to prevent the discharge temperature from rising more than before.

In the above examples, the combination of R22 and R152a, which has a lower critical pressure than R22, is explained, and this combination becomes a non-azeotropic refrigerant mixture.
Since R152a has a higher boiling point than R22, it has a greater effect on lowering the discharge temperature, but this combination is not necessarily required, and a refrigerant with a lower critical pressure than the main component refrigerant. By adding a small amount of , it is effective to reduce the rise in discharge temperature in a refrigeration cycle device having an injection circuit.

In addition, in the explanation of this embodiment, the effect during liquid injection was particularly explained, but it is also effective in slightly lowering the discharge temperature during gas injection. In a refrigeration cycle device having a circuit, if it is desired to further lower the discharge temperature, a small amount of a refrigerant having a lower critical pressure may be added to the main component refrigerant. Furthermore, although the refrigeration cycle device according to the present invention has been described as a single-function device, it may also be applied as an air-conditioning device via a four-way valve (not shown), or a two-stage compressor (not shown). The refrigerant may be injected between the two.

Effects of the Invention As explained above, the refrigeration cycle device according to the present invention connects a compressor, a condenser, a throttle device, a gas-liquid separator, an evaporator, etc. in a ring, and supplies refrigerant from the gas-liquid separator through an injection circuit. This device is configured to be injected into the intermediate pressure position of the compressor, and is characterized by the addition of a small amount of refrigerant with a lower critical pressure to the main refrigerant, which prevents overheating such as a rise in heat source temperature. Even under heavy load conditions, the effect of preventing a rise in discharge temperature is significant. Furthermore, a refrigerant having a lower critical pressure than the main component refrigerant has a higher boiling point than the main component and is particularly effective when forming a non-azeotropic mixed refrigerant.

[Brief explanation of the drawing]

Fig. 1 is a refrigerant circuit diagram showing one embodiment of a refrigeration cycle device for explaining the present invention, Fig. 2 is an explanatory diagram of the mode of operation of a conventional refrigeration cycle device, and Fig. 3 is a requirement of the present invention. FIG. 4 is an explanatory diagram showing the relationship between refrigerant discharge temperature and critical pressure, and FIG. 4 is an explanatory diagram of the mode of operation when the present invention is constructed using the refrigerant circuit of FIG. 1. 1... Compressor, 2... Condenser, 3, 5... Throttle device, 4... Gas-liquid separator, 6... Evaporator, 7...
injection circuit.

Claims (1)

[Claims] 1. A configuration in which a compressor, a condenser, a throttling device, a gas-liquid separator, and an evaporator are connected in a ring, and refrigerant is injected from the gas-liquid separator through an injection circuit to a position where the pressure is at the intermediate pressure of the compressor. A refrigeration cycle device in which a refrigerant with a lower critical pressure is added to the main refrigerant. 2. The refrigeration cycle device according to claim 1, wherein the refrigerant having a lower critical pressure than the main component is a refrigerant having a higher boiling point. 3. The refrigeration cycle device according to claim 1 or 2, wherein the main component refrigerant and the refrigerant having a lower critical pressure constitute a non-azeotropic refrigerant mixture.