JPH0120705B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration system in which the refrigerating capacity is improved by improving the condenser so that a suitably supercooled liquid refrigerant can be obtained at the inlet of the expansion valve of the refrigeration system.

As a method to improve the refrigeration capacity of refrigeration equipment,
One conventionally known method is to increase the enthalpy difference before and after evaporation of the refrigerant in the evaporator by giving the refrigerant a degree of supercooling at the inlet of the expansion valve of the refrigeration system. However, conventionally, in order to carry out this method, another condenser was provided downstream of the liquid receiver to cool the liquid refrigerant coming out of the liquid receiver again to obtain supercooled refrigerant. However, this implementation method has the drawback that it requires a large number of condensers and is therefore expensive, and is also difficult to install in a cooling system for an automobile.

The present invention overcomes the drawbacks of the prior art mentioned above and
It is an object of the present invention to provide a condenser that can obtain supercooled refrigerant at the inlet of an expansion valve by using only one condenser.

The invention began with the recent appearance of condensers in automobile cooling systems that divide a refrigerant passage into two and allow refrigerant to flow in parallel. That is,
In order to reduce the power required for cooling or to improve cooling capacity, condensers have become larger and the pressure loss on the refrigerant side has also increased accordingly. In order to reduce this pressure loss, it was considered to divide the refrigerant passage into two and run them in parallel. As will be described later, the present invention relates to a condenser having two such parallel refrigerant passage pipes. This is 2
Having multiple parallel refrigerant passage pipes not only helps to obtain the supercooled refrigerant of the present invention, but also helps to reduce the above-mentioned pressure loss on the refrigerant side, which overcomes the drawbacks of the present invention. means that it is not familiar at all.

The main point of the present invention is to provide two parallel refrigerant passage pipes in a condenser of a refrigeration system, and to make the lengths of the passage pipes different from each other by an appropriate degree. The objective is to obtain appropriately supercooled liquid refrigerant in a liquid container. In a conventional combination of a condenser and a liquid receiver using one refrigerant passage pipe, refrigerant in both gas and liquid phases exists in the liquid receiver as a saturated gas and a saturated liquid. Therefore, the liquid refrigerant sent from the liquid receiver to the expansion valve is almost never in a supercooled state, and the degree of supercooling is usually less than 2° to 3°C. If a liquid refrigerant with a degree of supercooling of several tens of degrees is injected into the receiver in this state, heat exchange will naturally begin between the refrigerant in both gas and liquid phases within the receiver. Since heat exchange occurs only at the gas-liquid interface, it takes time to reach thermal equilibrium, and under normal usage conditions,
The supercooled liquid refrigerant is sent as is from the liquid receiver to the evaporator. As a method of obtaining the supercooled liquid medium to be injected into the liquid receiver described above, one additional refrigerant passage pipe is added to the condenser, and its length is made longer than the other passage pipes. This is the main point of the claimed invention.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, refrigerant vaporized in an evaporator 5 is sent to a compressor 1, compressed, and further sent to a condenser 2 through a pipe 6. The gas phase refrigerant sent is cooled and liquefied by the condenser 2, and then flows into the pipe 9.
The liquid-phase refrigerant in the liquid receiver 3 passes through the expansion valve 4 and expands, becoming a low-temperature, low-pressure refrigerant and being sent to the evaporator 5. The gas phase refrigerant that has undergone the refrigeration action in the evaporator is sent to the compressor 1 again and this circulation process is repeated. Of this process, the condenser 2 will be explained in detail below.

In Fig. 2, the pipe 6 coming from the compressor branches at a branching part 7, and a small condenser part 2a is made up of a refrigerant passage pipe with a shorter total length, and a small condenser part 2a is made up of a refrigerant passage pipe with a longer total length. Divided into a large condenser section 2b,
The liquids join together again at the branch part 8 and are sent to the liquid receiver 3 through the pipe 9. The above two condenser parts 2a, 2
The refrigerant passage pipes b meander and reciprocate within the condenser, and in this embodiment, the small condenser section has five straight sections and the large condenser section has seven straight sections that run in parallel.
The refrigerant passage pipe is made of aluminum material and has a flat cross-sectional shape. In addition, a large number of corrugated fins also made of aluminum are interposed between the parallel refrigerant passage pipes and welded to the refrigerant passage pipes. A pipe 10 is connected to the liquid receiver 3 so that only the liquid phase refrigerant in the liquid receiver 3 is sent to the expansion valve 4.

The transition state of the gas-liquid phase of the refrigerant will be explained with reference to FIG. The area filled with dots is the gas phase, and the area filled with broken lines is the liquid phase. First, looking at the small condenser section 2a, only liquid phase refrigerant is sent from the liquid receiver 3 to the evaporator 5, so it is impossible for vapor phase refrigerant to continuously flow into the liquid receiver. be. Therefore, the small condenser 2a
At the outlet of the refrigerant, the refrigerant is almost completely condensed. Next, regarding the large condenser section 2b, it is the same as the case of the small condenser 2a that at least the refrigerant must have almost completely condensed at its outlet. However, both condensers 2a,
When considering the flow rate of refrigerant that can pass through each of the large condensers 2b, it can be seen that the position at which condensation is completed in the large condenser 2b is further limited. In other words, the proportion of the refrigerant flow rate flowing through each condenser depends on the ratio of the magnitude of refrigerant pressure loss in each condenser, and the refrigerant pressure loss decreases as it condenses mainly in the gas phase region, and decreases in the liquid phase region. Its value becomes almost negligible. If we assume that condensation is completed at the outlet of the large condenser 2b as well as the small condenser 2a, the pipe length in the large condenser 2b is longer, the gas phase region is also longer, and the refrigerant pressure loss will be large. Therefore, the amount of refrigerant flowing through the large condenser 2b is smaller than the amount of refrigerant flowing through the small condenser 2a. On the other hand, the point at which condensation is completed is related to the flow rate of the gas phase refrigerant and the cross-sectional length of the heat transfer surface. Therefore, if the flow rate through the large condenser 2b is smaller than the flow rate through the small condenser 2a, the length of the gas phase region until condensation is completed becomes shorter, which contradicts the above assumption. It will be appreciated that the flow of refrigerant is thus balanced with the flow rates through both condensers being equal and the lengths of the gas phase regions in both condensers being equal. FIG. 3 shows this state. In the figure, (y-
Since heat is dissipated also in the part x), supercooled refrigerant is obtained at the outlet.

The effects of the present invention have been confirmed through experiments, and the results are quantitatively shown in FIG. In the experiment, the total length of the refrigerant passage pipes in both condensers (x
+y) is kept constant, that is, the heat dissipation area of the condenser section is kept constant, and only the ratio y/x is changed,
The ratio of the corresponding refrigeration capacities is shown based on the case where x=y. As can be seen from the figure, the refrigeration capacity ratio reaches its maximum at approximately y/x = 1.5,
If it exceeds about 1.7, it is lower than the standard price. This is because if y/x is too large, the total length of the refrigerant passage pipe of the small condenser will be shortened, and compared to the case where x = y, a sufficient heat transfer area will not be obtained and the condensation pressure will increase. This seems to be due to this.

As described above, the present invention includes a condenser having two parallel refrigerant passage pipes having different total lengths,
By locating the liquid receiver near the downstream side, in addition to reducing the refrigerant pressure loss to approximately 1/8, it is also possible to provide the liquid refrigerant supplied to the evaporator with an appropriate degree of subcooling, which increases the refrigeration capacity. It has the excellent effect of improving

[Brief explanation of drawings]

Fig. 1 is a system diagram of a refrigeration system showing one embodiment of the present invention, Fig. 2 is a partial sectional view showing the condenser and liquid receiver portions of Fig. 1, and Fig. 3 is a gas-liquid refrigerant of Fig. 2. FIG. 4, which is a schematic diagram showing the state, is a characteristic diagram showing the refrigerating capacity improvement rate that changes depending on the ratio of the lengths of the two refrigerant passage pipes. In the figure, 1...compressor, 2...condenser, 3
...Liquid receiver, 4...Expansion valve, 5...Evaporator, 2a
... Small condenser section, 2b... Large condenser section, x... Total length of the refrigerant passage pipe of the small condenser section, y... Total length of the refrigerant passage pipe of the large condenser section.

Claims (1)

[Scope of Claims] 1. Two refrigerant passage pipes that are functionally parallel and have substantially similar cross-sectional shapes, and each of the passage pipes has a shape that repeatedly reciprocates within the condenser. 2.
In a refrigeration system having two refrigerant passage pipes and a liquid receiver provided downstream of the passage pipe, the number of times that one of the two refrigerant passage pipes reciprocates within the condenser is greater than the number of times that the other refrigerant passage pipe reciprocates within the condenser. The total length of the refrigerant passage pipe which is larger than the number of times that one refrigerant passage pipe reciprocates and has a larger total length among the two refrigerant passage pipes is 1.7% compared to the total length of the other refrigerant passage pipes. 1. A refrigeration system comprising: a condenser having a capacity equal to or less than 2 times the size of the condenser; and a liquid receiver disposed near the downstream of the condenser.