JPS6015084Y2 - Refrigeration equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to a refrigeration system, in particular, a refrigeration system equipped with a water heat exchanger on the user side and an air heat exchanger on the heat source side. It is an object of the present invention to provide a refrigeration system which can defrost the air and prevent discharged gas from being overheated even if the amount of heat to be defrosted becomes small at the end of defrosting.

Generally, in a refrigeration system, when a heat exchanger functioning as an evaporator becomes frosted, a method is used in which hot gas is flowed into the air on the heat source side and defrosted using the latent heat of condensation of the hot gas.

In a heat pump type refrigeration system, this hot gas method switches the four-way switching valve to reverse the refrigeration cycle and sends hot gas to the heat exchanger that acts as an evaporator, and then sends hot gas to the heat exchanger that acts as a condenser to evaporate. It uses a so-called reverse cycle method that acts as a container.

However, in the case of this reverse cycle system, the refrigeration cycle during normal operation is reversed, so the low pressure side suddenly switches to high pressure and the high pressure side to low pressure, and the switch is reversed again after the refrigeration system is finished. As a result, for example, the pressure balance during switching may be disrupted, causing noise or vibration in the piping.
The expansion valve may malfunction due to pressure fluctuations, liquid may back up during switching, or the switching circuit of the four-way switching valve may increase and dust may become trapped, causing malfunction, or condensation may occur. Since the refrigerant is evaporated in the heat exchanger, which acts as a heat exchanger and heats the hot water, there were problems such as a drop in the temperature of the hot water.

However, in order to solve the problems of the conventional reverse cycle system, a hot gas bypass pipe was connected to the discharge pipe of the compressor, and a heat exchanger was created that reduced the pressure of the discharge gas flowing through the discharge pipe and acted as an evaporator. A hot gas bypass method was proposed in which the heat exchanger is defrosted.

However, although this method can solve the problem of the reverse cycle method described above, when the amount of heat to be defrosted is small, for example just before the end of defrost, the degree of superheating of the gas sucked into the compressor becomes very large. There was a problem that the discharge gas temperature rose and overheated.

Therefore, when using this hot gas bypass system, it is conceivable to open the expansion valve used in normal operation and send the liquid refrigerant to the heat exchanger together with the hot gas to control the degree of superheating on the suction side of the compressor.

However, when liquid refrigerant is made to flow in order to prevent overheating of the discharged gas as described above, even if the amount of heat to be defrosted becomes zero, the temperature of the discharged gas does not rise and overheating occurs. The amount of heat available for refrigerant is reduced, the defrost time becomes longer, and if the mixing ratio of the hot gas and the liquid refrigerant that is mixed with the hot gas through the expansion valve is not accurate, it may result in wet operation or overheating. Therefore, precision is required for controlling the mixing ratio, and the control mechanism becomes expensive, resulting in a problem of increasing the cost of the entire device.

In view of the above-mentioned problems, this idea was developed to prevent overheating of discharged gas without mixing liquid refrigerant with hot gas. In a refrigeration system in which a liquid container, an expansion mechanism, and a heat source side air heat exchanger are connected in order, an electromagnetic on-off valve that closes during defrosting is provided between the liquid receiver and the heat source side air heat exchanger, and the liquid receiver A hot gas bypass pipe which bypasses the expansion mechanism and the electromagnetic on-off valve and communicates with the air heat exchanger on the heat source side is connected to the gas region, and an on-off valve that opens during defrosting is installed in the middle of this bypass pipe. The air heat exchanger is characterized by being equipped with a pressure reducing mechanism for reducing the pressure of the hot gas, so that the hot gas in the gas region of the liquid receiver is bypassed during defrosting, thereby defrosting the air heat exchanger. .

That is, in the present invention, when the amount of heat to be defrosted is large and the discharge gas temperature is low, heat is taken from the hot water of the user-side water heat exchanger that acts as a condenser to perform defrost operation with a large amount of heat. When the amount of heat to be defrosted decreases and the high and low pressures increase, heat is given to the hot water in the water heat exchanger to perform defrost operation with a small amount of heat, and defrost should be performed after defrosting is completed. Even if the amount of heat is lost, the discharged gas is cooled to approximately the water temperature of the water heat exchanger, so that the gas taken into the compressor is not excessively overheated, and an abnormal rise in the temperature of the discharged gas is prevented. It is.

Embodiments of the refrigeration system of the present invention will be described in detail below based on the drawings.

In the figure, 1 is a compressor such as a screw compressor, 2 is a water heat exchanger on the user side, 3 is a liquid receiver, 4 is an expansion valve, and 5 is a heat source side air heat exchanger equipped with a fan 6. Each is connected by refrigerant piping.

The water heat exchanger 2 uses a shell-and-tube type heat exchanger, and receives a load 10 such as a heater, a hot water tank, or an air-conditioner through a water pipe 7 and a water return pipe 8 that are equipped with a pump 9. When connected, the water heat exchanger 2 is used as a condenser to supply hot water, and when the water heat exchanger 2 is used as a heat pump type evaporator as shown in FIG. By supplying water, it can be used to perform heating, cooling, or hot water supply.

The one shown in FIG. 1 uses the water heat exchanger 2 as a constant condenser to produce only hot water, but the one shown in FIG. 2 is equipped with a four-way switching valve 11 to operate the refrigeration cycle. The water heat exchanger 2 is reversible, and the water heat exchanger 2 is used as a condenser or an evaporator to enable heating and cooling operation.
In the figure, in addition to the expansion valve 4, an expansion valve 41 that operates during cooling operation is provided, and each of the expansion valves 4, 41 has a check valve 1.
1 and 12 are connected in parallel via side pipes 13 and 14.

Therefore, in the refrigeration system configured as described above, the present invention bypasses the expansion valve 4 to the gas region of the liquid receiver 3,
A hot gas bypass pipe 1 communicating with the air heat exchanger 5
5 is connected, and an on-off valve 16 that opens during defrosting is interposed in the middle of this bypass pipe 15, and the liquid receiver 3 is connected during defrosting.
The hot gas in the gas region is passed through a bypass pipe to defrost the air heat exchanger 5.

In the drawing, a valve mechanism 17 such as a manual valve or a constant pressure expansion valve is installed along with the on-off valve 16 in the middle of the bypass pipe 15 (7). The expansion valve 4
An electromagnetic on-off valve 19 is interposed in the liquid pipe 18 which is interposed therein.

The valve mechanism 17 lowers the pressure P2 of the hot gas in the liquid receiver 3 by a predetermined pressure ΔP, and when a manual valve is used, the predetermined pressure ΔP can be set to a desired value.

Instead of providing this valve mechanism 17, the bypass pipe 15 is
The pipe diameter may be set to have a predetermined pipe resistance, or a capillary may be used.

In the above configuration, the discharge gas refrigerant is sent to the water heat exchanger 2, the discharge gas refrigerant is condensed in the water heat exchanger 2,
When hot water is being produced, the air heat exchanger 5 acts as an evaporator, taking heat from the outside air and evaporating it.

During this operation, if the air heat exchanger 5 is not frosted, the on-off valve 16 is closed, the on-off valve 19 is opened, and a normal operation is performed in which the refrigerant circulates through only the liquid pipe 18. If the air heat exchanger 5 is frosted, the on-off valve 16 is opened and the on-off valve 19 is closed in response to a defrost command, thereby performing a defrost operation.

During this defrosting operation, if the amount of heat to be defrosted is large as at the beginning, the pressure is high as shown in Figure 3.
2. The low pressure P1 is both low, so the discharge gas temperature becomes lower than the hot water temperature (for example, 45°C) of the water heat exchanger 2, which takes away heat from the hot water, and the pressure inside the liquid receiver 3 also decreases. Since the amount of heat decreases, the heat amount of the refrigerant in the liquid receiver 3 is also taken away, and the hot gas entering the air heat exchanger 5 from the bypass pipe 15 performs defrosting at Δi with a large amount of heat.

Further, when the frost in the air heat exchanger 5 is melted by this defrosting and the amount of heat Δi to be defrosted decreases, both the high pressure P2 and the low pressure P1 rise as shown in FIGS. 4 and 5.

In this case, the temperature of the discharged gas also rises, but since heat is taken away by the hot water of the water heat exchanger 2, the high pressure P2 does not rise above the pressure corresponding to the temperature of the hot water.

Furthermore, when the amount of heat to be defrosted becomes zero due to the end of defrosting, the high pressure P2 and the low pressure P1 further increase, but even in this case, as shown in FIG. The refrigerant temperature is not superheated beyond point A, which is isenthalpic expanded by a predetermined pressure ΔP reduced in the bypass pipe 15 from the hot water equivalent temperature in the saturated gas line, and therefore the discharge gas temperature is not superheated. There is no such thing.

As described above, according to the present invention, when the amount of heat to be defrosted is large during defrost operation, the defrost can be performed with a large amount of heat by removing heat from the hot water in the water heat exchanger on the user side and the refrigerant in the liquid receiver. Therefore, the defrosting time can be shortened without having to provide any special means for heating the refrigerant during defrosting, such as a heater, and when the amount of heat to be defrosted decreases, heat is given to the warm water to perform defrosting with the necessary amount of heat. Because of this, the discharged gas will not be overheated even after defrosting is finished.

Moreover, since it does not control overheating by mixing liquid refrigerant into hot gas, in other words, defrost operation is performed by closing the expansion valve without using it, so stable defrost operation cannot be performed, and wet operation may occur due to an error in m+J. There is no possibility of overheating or overheating.

[Brief explanation of the drawing]

FIGS. 1 and 2 are refrigerant piping system diagrams showing an embodiment of the refrigeration system of the present invention, and FIGS. 3 to 6 are molinyl diagrams showing cycles during defrost operation. 2... User side water heat exchanger, 3... Liquid receiver, 4... Expansion valve, 5... Heat source side air heat exchanger, 15 ...Hot gas bypass pipe, 1
6...Open/close valve.

Claims (1)

[Scope of utility model registration request] Compressor 1, user side water heat exchanger 2, liquid receiver 3, expansion mechanism 4
, in a refrigeration system in which heat source side air heat exchangers 5 are connected in sequence, an electromagnetic on-off valve 19 that closes during defrost is provided between the liquid receiver 3 and the heat source side air heat exchanger 5;
A hot gas bypass pipe 15 which bypasses the expansion mechanism 4 and the electromagnetic on-off valve 19 and communicates with the heat source side air heat exchanger 5 is connected to the gas region of the liquid receiver 3. An on-off valve 16 that opens during defrosting and a pressure reducing mechanism 17 that reduces the pressure of the hot gas are interposed in the middle of the process, and during defrosting, the hot gas in the gas area of the liquid receiver 3 is bypassed and the heat exchanger 5 on the heat source side is A refrigeration device characterized by being designed to perform defrosting.