JPH10111029A - Vapor compression refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat exchange efficiency in a condenser and shorten the whole length of a refrigerant flow passage pipe in a vapor compression freezer where a vapor refrigerant is recirculated in the condenser by providing a bypass pipe parallely to the refrigerant flow passage pipe of the condenser and further providing circulation means for recirculating the vapor refrigerant to the bypass pipe. SOLUTION: A high temperature vapor refrigerant supplied from a compressor 1 is supplied to a refrigerant inflow part of a condenser 2. Thereupon, a bypass pipe 5 and a circulation pump 7 are connected between an upstream side part 6a and a downstream side part 6b of a freezing flow passage pipe 6 of the condenser 2 whereby the vapor refrigerant from the bypass pipe 5 is mixed to a gas/liquid two phase state refrigerant in the condenser 2 at the upstream side part 6a, and a recirculation vapor refrigerant amount is adiusted with the circulation pump 7 such that the dryness before and behind the mixing part is increased by about 15 %. Further, in the downstream side part 6b, the vapor refrigerant is condensed by heat exchange with the surroundings and hence the dryness is lowered to 60%, and most of the vapor refrigerant in the gas/liquid two phase state refrigerant is recirculated to the upstream side part 6a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor compression refrigeration system used for cooling and heating operations, hot water supply and freezing.

[0002]

2. Description of the Related Art Conventionally, a vapor compression refrigeration system used for indoor air conditioning mainly comprises four component devices. Hereinafter, the refrigeration cycle will be described with reference to FIG. As shown in the figure, a compressor 1 and a condenser 2
, A decompressor 3 and an evaporator 4 constitute a refrigeration cycle, and the respective component devices are connected via metal piping. Then, a refrigerant such as R22 (chlorodifluoromethane) circulates through the refrigeration cycle, and the refrigerant changes into a gas state or a liquid state, thereby absorbing or releasing heat.

The compressor 1 converts the low-pressure gaseous refrigerant sent from the evaporator 4 into a high-temperature and high-pressure gaseous refrigerant by compressing the gaseous refrigerant, and connects the condensate connected to the compressor 1 via a metal pipe. A gaseous refrigerant compressed to a high temperature and a high pressure is sent to the vessel 2.

The condenser 2 cools the high-temperature and high-pressure gaseous refrigerant sent from the compressor 1 with air or water, thereby removing heat from the high-temperature and high-pressure gaseous refrigerant and converting the gaseous refrigerant. Liquefy.

[0005] The pressure reducer 3 is connected to the condenser 2 via a metal pipe, and a high-pressure liquid refrigerant is sent from the condenser 2. The decompressor 3 converts the high-temperature and high-pressure liquid refrigerant into a low-temperature gas-liquid two-phase refrigerant that is easily evaporated by decompression.

[0006] The evaporator 4 is connected to the decompressor 3 via a metal pipe, from which a low-temperature gas-liquid two-phase refrigerant is sent. The gas-liquid two-phase refrigerant sent into the evaporator 4 evaporates by removing heat from the surroundings while passing through the evaporator 4, and the low-pressure gaseous refrigerant is sent back into the compressor 1. It is.

By repeating the above refrigeration cycle, heat is radiated by the condenser 2 and heat is absorbed by the evaporator 4 to generate refrigeration. Next, with reference to FIG. 6, a change in the state of the refrigerant by each element device in the refrigeration cycle will be described. FIG. 6 shows a Mollier diagram of the refrigeration cycle, in which the vertical axis represents pressure and the horizontal axis represents enthalpy. In the drawing, x is a curve indicating the boundary between the gas phase state, the liquid phase state, and the gas-liquid two-phase state of the refrigerant, the curve part on the right side from the vertex y indicates the saturated vapor line, and the curve on the left side from the vertex y. The part shows the saturated liquid line.

In the region on the right side of the saturated vapor line, the refrigerant is superheated vapor, and in the region on the left side of the saturated vapor line, the refrigerant is wet vapor in a gas-liquid two-phase state (liquid refrigerant and vapor refrigerant). I have. Further, the refrigerant is in a liquid state in a region on the left side of the saturated liquid line, and is in a wet vapor in a region on the right side of the saturated liquid line. Therefore, between a and b in the figure, the refrigerant is compressed by the compressor 1 to become high-temperature and high-pressure superheated steam. Further, between bc in the figure, the refrigerant is condensed in the condenser 2 to change from a superheated vapor state to a liquid state. Then, between cd in the figure, the refrigerant is decompressed by the decompressor 3 to be in a gas-liquid two-phase state. The refrigerant in the gas-liquid two-phase state is between the e-
Evaporates by removing heat from the surroundings and becomes superheated steam. Then, the refrigerant that has become the superheated steam is again compressed by the compressor 1.
Will be sent inside.

Next, the heat exchange operation in the condenser 2 will be described. FIG. 7 is a schematic sectional view showing a state change of the refrigerant inside the condenser 2. As can be seen from FIG. 7, the gaseous refrigerant of the superheated vapor sent from the compressor 1 is condensed by radiating heat to the surroundings while passing through the inside of the condenser 2, and becomes only the liquid refrigerant at the outlet of the condenser 2. . It has been experimentally confirmed that the heat exchange efficiency inside the condenser 2 at this time differs depending on the state of the refrigerant inside the condenser 2. Specifically, as shown in FIG. 8, on the refrigerant inflow side of the condenser 2 in which the ratio of the liquid refrigerant in the refrigerant is small, the heat transfer coefficient at that point is large, and the ratio of the liquid refrigerant is large. The heat transfer coefficient has a tendency to decrease as the ratio of the vapor refrigerant inside decreases. In general, the ratio of the vapor refrigerant in the refrigerant, that is, the ratio of the vapor refrigerant to the refrigerant in the gas-liquid two-phase state in which the liquid refrigerant and the vapor refrigerant coexist is called dryness.

[0010]

For this reason, in the conventional condenser 2, as shown in FIG. 8, the heat transfer coefficient decreases as the distance from the refrigerant inflow side increases, and particularly, the refrigerant whose dryness becomes 30% or less is used. Heat exchange is performed in a state where the heat transfer coefficient is considerably low in the refrigerant flow path pipe portion on the discharge side. As a result, the total length of the refrigerant flow path pipe of the condenser 2 has to be increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made in view of the above circumstances. The present invention has a vapor compression type in which the heat exchange efficiency in a condenser is increased and the total length of a refrigerant flow pipe of the condenser is shorter than that of a conventional apparatus. An object is to provide a refrigeration apparatus.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a vapor compression refrigeration system in which a vapor refrigerant is recirculated in a condenser. Specifically, the refrigerant is arranged in parallel with a refrigerant flow pipe of the condenser. A bypass pipe is provided, and circulation means for recirculating the vapor refrigerant is provided in the bypass pipe.

By using this configuration, by setting the ratio of the vapor refrigerant to the refrigerant in the gas-liquid two-phase state in the condenser to be higher, heat exchange is performed with the surroundings in a state of high dryness. Will be.

Further, it is possible to use a mixed refrigerant in which difluoromethane and pentafluoroethane are mixed at approximately 50% by weight, respectively. By using this configuration, the pressure loss due to the recirculation of the vapor refrigerant in the condenser can be reduced, and the work of the compressor 1 due to the recirculation does not increase.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vapor compression refrigeration system according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram of a refrigerant circuit of a vapor compression refrigeration apparatus showing one embodiment of the present invention. The same components as those in the above-described conventional example (FIG. 5) are denoted by the same reference numerals.

In the drawing, reference numeral 5 denotes a refrigerant flow pipe 6 of the condenser 2.
The bypass pipe 7 is provided in the middle of the bypass pipe 5 and serves as a circulating means for recirculating the vapor refrigerant in the condenser 2 from the downstream side of the refrigerant flow pipe 6 to the upstream side. It is a circulation pump.

Specifically, one end of the bypass pipe 7 is connected to the upstream portion 6a of the refrigerant flow pipe 6 where the dryness is about 60% so that the region of high dryness in the condenser 2 is widened. The other end is connected to the downstream portion 6b of the condenser 2 on the refrigerant outflow side. Then, the refrigerant flow pipe 6 is moved by the circulation pump 7.
The amount of the vapor refrigerant supplied by the circulation pump 7 is adjusted so that the dryness in the upstream portion 6a of the circulating fluid is about 75%.

Next, with regard to the heat exchange operation in the condenser 2 in the vapor compression refrigeration system having the above-mentioned configuration, refer to a schematic sectional view (FIG. 2) showing the state change of the refrigerant inside the condenser 2 of the present embodiment. I will explain. Note that the basic operation principle of the refrigeration cycle of the present invention is the same as that of the above-described conventional example, and thus detailed description is omitted.

As shown in FIG. 2, the high-temperature vapor refrigerant supplied from the compressor 1 is supplied to a refrigerant inlet 6c of the condenser 2. The bypass pipe 5 and the circulation pump 7 are connected between the upstream part 6 a and the downstream part 6 b in the middle of the refrigerant flow pipe 6 of the condenser 2. Thereby, the condenser 2
In the upstream portion 6a, the refrigerant in the gas-liquid two-phase state in the condenser 2 is mixed with the vapor refrigerant from the bypass pipe 5, and before and after this, the circulating pump 7 increases the dryness by about 15%. Is adjusted. As a result, in the present embodiment, the dryness increases from about 60% to about 75% around the upstream portion 6a.

In the downstream portion 6b of the condenser 2 to which the other end of the bypass pipe 5 is connected, the vapor refrigerant is condensed by heat exchange with the surroundings, and the dryness is reduced to 60%. Most of the vapor refrigerant in the refrigerant in the phase state is
a. For this reason, the dryness sharply decreases in the area after the downstream portion 6b, and immediately after that, the portion becomes the refrigerant discharge portion of the condenser 2.

Next, FIG. 3 shows the relationship between the degree of dryness in the condenser and the heat transfer coefficient. Here, the vertical axis of FIG.
The horizontal axis represents (1-dryness) in%. As shown in the figure, when the dryness is about 30%, the heat transfer coefficient decreases at a considerable rate as the dryness decreases,
When the dryness is 30% or less, the heat transfer coefficient does not change so rapidly, but tends to decrease gradually.

Therefore, in the conventional apparatus shown in FIG.
As is clear from FIG. 2, the average heat transfer coefficient per unit length in the condenser 2 was suppressed to be low. On the other hand, according to the above-described configuration of the present application, as described above, the dryness is set to 60% or more in most of the area of the refrigerant flow pipe of the condenser 2 and the condenser is recirculated by the vapor refrigerant. The heat transfer coefficient at each position of the condenser 2 increases as shown by the solid line in FIG. 4 due to the increase of the heat transfer coefficient due to the increase in the flow velocity inside the 2, and the average heat transfer coefficient per unit length is smaller than that of the conventional device. And rise considerably.

In the present embodiment, a case is described in which the dryness is 60% or more in most of the area in the condenser 2. However, the recirculation is performed by recirculating the vapor refrigerant. Since the dryness in the area increases and the average heat transfer coefficient per unit length increases compared to the conventional device,
It is not always necessary to configure within this range.

As a refrigerant, difluoromethane (R3
2) and pentafluoroethane (R125) in a ratio of 50: 5
When a mixed refrigerant (R410A) mixed at a weight ratio of 0 is used, the R410A refrigerant is replaced with another refrigerant, for example, R22.
Pressure loss due to recirculation of the vapor refrigerant is smaller than that of R407C which is a mixed refrigerant of R32, R125 and 1,1,1,2-tetrafluoroethane (R134a).
The work load of the compressor 1 due to recirculation does not increase.

As described above, according to the present invention, by exchanging heat in a state of high dryness in the condenser, it is possible to perform heat exchange with an improved heat transfer coefficient as compared with the prior art.
The description of the above embodiments is for describing the present invention, and limits the invention described in the claims.
Or should not be construed as reducing the range. In addition, the configuration of each part of the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.

For example, in the description of the above embodiment, the upstream part 6a and the downstream part 6b of the condenser are connected to the bypass pipe 5
Although the case where the refrigerant is connected and recirculated is described above, a configuration in which the refrigerant is recirculated to a plurality of locations in the refrigerant flow path may be used.

[0028]

As described above, according to the present invention, by setting the ratio of the vapor refrigerant to the refrigerant in the gas-liquid two-phase state in the condenser to be high, it is possible to maintain a high dryness with the surroundings. Heat is exchanged, and the heat transfer coefficient in the evaporator can be remarkably improved as compared with the conventional apparatus.

As a result, the total length of the refrigerant flow pipe of the condenser can be reduced as compared with the conventional apparatus, and the size of the refrigeration apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a refrigerant circuit of a vapor compression refrigeration apparatus of the present invention.

FIG. 2 is a schematic cross-sectional view showing a state change of a refrigerant inside a condenser of the present invention.

FIG. 3 is a diagram illustrating a relationship between dryness and heat transfer coefficient in a condenser.

FIG. 4 is a diagram showing a change in heat transfer coefficient inside the condenser of the present invention.

FIG. 5 is a schematic configuration diagram of a refrigerant circuit of a conventional vapor compression refrigeration apparatus.

FIG. 6 is a Mollier chart of a refrigeration cycle in the vapor compression refrigeration apparatus.

FIG. 7 is a schematic sectional view showing a state change of a refrigerant inside the condenser.

FIG. 8 is a diagram showing a change in heat transfer coefficient inside a conventional condenser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3 Pressure reducer (expansion valve) 4 Evaporator 5 Bypass pipe 6 Refrigerant flow path pipe 7 Circulation pump (Circulation means)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takayuki Maskawa 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Yukio Miyamura 2-chome Keihanhondori, Moriguchi-shi, Osaka No.5 Sanyo Electric Co., Ltd. (72) Inventor Kenji Nasako 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A vapor compression refrigeration system comprising a compressor, a condenser, a decompressor, and an evaporator to constitute a refrigeration cycle, wherein a vapor refrigerant is recirculated in the condenser. Vapor compression refrigeration equipment. 2. The vapor compression system according to claim 1, wherein a bypass pipe is provided in parallel with the refrigerant flow pipe of the condenser, and the bypass pipe is provided with a circulating means for recirculating the vapor refrigerant. Type refrigeration equipment. 3. The vapor compression refrigeration system according to claim 1, wherein a mixed refrigerant in which difluoromethane and pentafluoroethane are mixed at approximately 50% by weight, respectively.