JPS5828905B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration system, and particularly to a refrigeration system having a pressure reducing device comprising a fixed throttle suitable for use in automobile air conditioning.

Conventionally, in this type of refrigeration system, one has been proposed in which a capillary tube 1, which also serves as piping from a condenser 2 to an evaporator 3, is used as a pressure reducing device, as shown in FIG.

To explain its operation, once the required refrigerant flow rate is determined to a certain extent by the heat load of the refrigeration cycle, the state (supercooling degree or dryness) of the refrigerant at the inlet of capillary tube 1 is adjusted to allow that flow rate to flow. Determined from flow characteristics.

In other words, if the refrigerant flow rate (weight flow rate) is insufficient for the heat load, the refrigerant at the outlet of the evaporator 3 will become superheated, so the liquid refrigerant in the accumulator 4 will vaporize and
As a result, the degree of supercooling SC of the refrigerant at the outlet of the condenser 2 becomes A in FIG.
The refrigerant flow rate increases according to the characteristics shown in FIG. 2, and the cycle is balanced.

Conversely, if the heat load decreases, 1. Part of the refrigerant at the outlet of the evaporator 3 becomes liquid refrigerant, the refrigerant is stored in the accumulator 4, the exit-side supercooling area in the condenser 2 becomes smaller, the degree of supercooling SC of the refrigerant at the condenser exit becomes smaller, and further. is C in Figure 3.
The cycle shown in is constructed to have a degree of dryness χ,
As a result, the refrigerant flow rate is reduced and the cycle is balanced.

It is known that for this balance to improve cycle efficiency, it is better for the refrigerant at the condenser outlet to have some degree of subcooling in order to increase the difference in refrigerant enthalpy between the inlet and outlet of the evaporator 3. .

In automobile air conditioning refrigeration systems, where the heat load fluctuates widely, the refrigerant flow rate also fluctuates widely, so even if the degree of subcooling SC in B during normal operation in Figure 3 is 5°C, a high flow rate flows during high load operation, and the degree of supercooling decreases. SC becomes excessive as shown in A in FIG.

Then, the required amount of heat dissipation in the condenser 2 increases, and the high pressure becomes abnormally high, resulting in drawbacks such as release of refrigerant gas from the safety valve and deterioration of performance due to pressure increase.

Therefore, a fixed throttle with small fluctuations in the degree of supercooling and a variable flow rate characteristic has been strongly desired.

The present invention has been proposed to meet the above requirements, and focuses on the fact that among fixed throttles, the orifice has a large flow rate change in the dryness range, and makes it possible to utilize this in the supercooling range as well.

That is, by providing another resistance means on the upstream side of the orifice, it is possible to make the refrigerant dry at the inlet of the downstream orifice, so that due to a slight change in the degree of subcooling of the refrigerant at the condenser outlet, Particularly, in the present invention, which is characterized by providing a refrigeration system that can increase the change in refrigerant flow rate, the ratio l/d between the minimum diameter d and the minimum diameter length l of the orifice is set to 0. 8<l/d
By setting in the range <2.5, the change in refrigerant flow rate due to the change in the degree of supercooling can be further effectively increased.

Embodiments of the present invention shown in the figures will be described below.

In FIG. 4, a condenser 2 is connected downstream of a compressor 5 driven by an automobile engine (not shown) via an electromagnetic clutch 5a.

This condenser 2 is installed around a radiator in the engine room of an automobile, and is cooled by a fan 2a.

The evaporator 3 installed at the bottom of the instrument panel inside the vehicle interior is used to cool the air inside or outside the vehicle blown by a fan 3a, and the cooling air is supplied from an air outlet (not shown). It is designed to blow out into the passenger compartment.

A pressure reducing device 6 is provided between the condenser 2 and the evaporator 3, and this pressure reducing device 6 is composed of an orifice 7 and a capillary tube 8 provided upstream thereof.

An accumulator 4 provided at the outlet of the evaporator 3 stores liquid refrigerant and causes the compressor 5 to suck the gas refrigerant.

The operation of the device of the present invention in the above configuration will be explained.

The high temperature and high pressure gas refrigerant discharged from the compressor 5 is sent to the condenser 2.
The liquid is cooled and liquefied, and then passes through the capillary tube 8 and orifice 7 of the pressure reducing device 6 to be depressurized and expand adiabatically.

Thereby, the refrigerant becomes a mist and flows into the evaporator 3, where it evaporates and becomes a gas.

This gas refrigerant passes through the accumulator 4 and is sucked into the compressor 5 again, and the above cycle is repeated.

Next, the action of the pressure reducing device 6 will be explained in more detail using the Mollier diagram shown in FIG. 5. PH is the outlet pressure at the outlet position of the condenser 2, that is, the inlet pressure of the capillary tube 8. do.

PL is the outlet pressure at the outlet position of the orifice 7, and PC is the intermediate pressure at the intermediate position between the capillary tube 8 and the orifice 7.

For example, when the degree of subcooling of the refrigerant at the outlet of the condenser 2 is 12°C, if a capillary tube 8 with a flow rate characteristic such that the pressure loss is 3.5 kg/cm2 is used, the PC case 15-3
．． 5 = 11.5 kg/crrL2.

Now, if the degree of supercooling SC of the inlet refrigerant of the capillary tube 8 is 12°C in the Mollier diagram of FIG.
Then, the degree of dryness is χ20, and the degree of supercooling of the inlet refrigerant is S.
As C becomes smaller, the degree of dryness χ at PC increases, and when the degree of supercooling SC becomes 0, the degree of dryness χ becomes χ0 (for example, 0.0
5).

In this way, the degree of dryness of the refrigerant at the inlet of the orifice 7 changes from 0 to 0.05, so the refrigerant flow rate changes at the orifice 7.
It changes greatly depending on the characteristics (customized flow rate in the dryness region shown in Figure 2).

That is, by using the capillary tube 8 and the orifice 7 together as the pressure reducing device 6, the refrigerant flow rate can be varied over a wide range due to a slight change in the degree of subcooling of the refrigerant at the condenser outlet.

As understood from the above explanation, the flow rate characteristics of the refrigerant are greatly influenced by the flow rate characteristics of the orifice 7 alone.
The inventor of the present invention therefore conducted a detailed study on the relationship between the shape of the orifice 7 and the flow rate characteristics of the refrigerant.

Figures 6a, b, and c show three examples of the shape of the orifice 7. Figure 6a is a thin-blade orifice that is generally said to have an ideal orifice shape, and has a length of the minimum diameter d. The value of L is almost zero.

On the other hand, in the orifice 7 shown in FIG. 6C, the portion having the minimum diameter d has a predetermined length l.

The present invention provides a ratio l/d between the minimum diameter d and the minimum diameter length l.
When the rate of change in the refrigerant flow rate was investigated by varying the refrigerant flow rate, the results shown in FIG. 7 were obtained.

In this Figure 7, the horizontal axis shows the ratio l/d, and the vertical axis shows the refrigerant flow rate Gχ=0 when the dryness χ of the refrigerant at the condenser outlet is 0, and the refrigerant when the dryness χ==Q, Q5. The flow rate ratio Gχ=0.05/Gχ=0 with the flow rate Gχ=0.05,
The smaller the flow rate ratio Gχ20.05/Gχ=0, the greater the rate of change in the refrigerant flow rate.

As can be seen from the experimental results shown in Figure 7 above, #/d==1
．． 5, the flow rate ratio Gχ = 0.05/GχO becomes the minimum value (approximately 0.4), and within the range Z of l/d = 0.8 to 2.5, the flow rate ratio Gχ20.05/Gχ- It is possible to keep 〇 to a small value that approximates the minimum value.

Therefore, in the present invention, the ratio l/d of the minimum diameter d and the minimum diameter length l of the orifice 7 is set in the range 2 above, that is, 0.8 to 2.
．． 5 to maximize the rate of change in the refrigerant flow rate.

In Fig. 8, the horizontal axis shows the degree of subcooling SC and dryness χ of the refrigerant at the outlet of the condenser, and the vertical axis shows the refrigerant flow rate (kg/h). The case is shown using an orifice set in the range of 0.8 to 2.5.
Line C shows the case where an orifice with l/d=0.5 and line C show the case where an orifice with l/d=0.5 is used.

From the comparison of lines A22B and C, it can be seen that the change in the refrigerant flow rate due to the change in dryness χ is the largest in the case of the present invention.

Next, FIG. 9 shows a preferred specific embodiment of the orifice 7, in which the diameter of the outlet portion 8a of the capillary tube 8 is expanded by tube expansion, and an O-ring 34 flange 1 is formed by bulging in the middle. 8b is integrally formed to bulge, and an orifice 7 is formed on the inner periphery of the O-ring joint part 8b.
is retained and fixed.

The capillary tube 8 is made of, for example, a copper tube, and after expanding the outlet portion 8a and loosely fitting the nut 11 around its outer periphery, the outlet side portion 8c is further expanded from the position of the O-ring flange 34 flap 1 portion 8b. Thereafter, the orifice 7 is inserted and the exit side portion 8c is drawn to form the O-ring flange 34 flange 1 portion 8b, and at the same time, the orifice 7 is fixed to the inner periphery thereof.

The orifice 7 is formed by making a small hole in the center of a metal disk such as brass.

An aluminum half union 9 is joined to the evaporator 30 inlet pipe 3a (for example, made of aluminum) by brazing,
Attach an O to the O ring fin 34 f1 part 8b of the capillary tube 8.
After fitting the ring 10, the outlet side portion 8c is inserted into the inner periphery of the half union 9, and the O ring 10 is positioned within the recess 9a at the tip of the half union 9.

Then, tighten the nut 11 made of brass or aluminum to the threaded part 9b of the half union 9, and tighten the capillary tube 8.
The outlet portion 8a of the...- is tightly coupled to the union 9, and the O-ring 10 is compressively deformed to reliably maintain the seal of the coupled portion.

The orifice 7 can also be integrally formed on the inner periphery of the half union 9 by cutting, as shown by the two-dot chain line T in FIG.

Further, in the above embodiment, the capillary tube 8 was used as the resistance means provided upstream of the orifice 7, but the same effect can be obtained by using a constant differential pressure valve 12 as the resistance means as shown in FIG. .

This constant differential pressure valve 12b consists of a spring 12a and a valve 12b, and the differential pressure before and after the valve 12b is a constant value, for example, 2 to 3.5.
It is preferable to set the spring 12a so that the valve opens when the pressure exceeds kg/c1rL2.

11 and 12 show another embodiment of the present invention, in which a capillary tube 8 and an orifice 13 are provided in series on the upstream side of the orifice 7 as resistance means. It is.

In FIG. 12, an orifice 13 is provided upstream of the orifice 7 as a resistance means.

As described above, various types of resistance means can be used on the upstream side of the orifice 7, and in any case, by imparting dryness to the refrigerant at the inlet of the orifice 7, the flow rate of the refrigerant can be varied over a wide range.

As described above, in the present invention, as a pressure reducing device, the resistance means 8 and 13 are further provided on the upstream side of the orifice 7 to make the refrigerant dry at the orifice inlet. This has the excellent effect of increasing the change in the refrigerant flow rate with little variation in the degree of cooling, that is, maintaining an appropriate degree of cooling even in cases where load fluctuations are large, such as in automobile air conditioning refrigeration systems.

In particular, in the present invention, by setting the ratio l/d between the minimum diameter d and the minimum diameter length l of the orifice 7 in the range of 0.8 to 2.5, the change in the refrigerant flow rate due to the orifice 7 is maximized. As a result, the above effects can be exhibited even more effectively.

[Brief explanation of drawings]

Fig. 1 is a cycle diagram of a conventional refrigeration system, Fig. 2 is a custom flow rate diagram of a fixed throttle to explain the conventional refrigeration system and the device of the present invention, and Fig. 3 is a Mollier diagram for explaining the operation of the conventional refrigeration system. FIG. 4 is a cycle diagram of an embodiment of the refrigeration apparatus according to the present invention, FIG. 5 is a Mollier diagram for explaining the operation of the apparatus according to the present invention, and FIG. 6a. b, c are cross-sectional views showing examples of orifice shapes, FIGS. 7 and 8 are graphs showing experimental performance examples of the present invention, and FIG. 9 is a cross-sectional view of one embodiment of the decompression device part according to the present invention. FIG. 10, FIG. 11, and FIG. 12 are cycle diagrams showing other embodiments of the pressure reducing device section. 2... Condenser, 3... Evaporator, 4... Accumulator, 5... Compressor, 6... Pressure reducing device, 7...
Orifice, 8.13...A capillary tube or orifice that serves as a resistance means.

Claims (1)

[Claims] 1 As a pressure reducing device provided between the condenser and the evaporator, an orifice is provided on the downstream side, and a resistance means that provides resistance is provided on the upstream side, and the ratio of the minimum diameter d of the orifice to the minimum diameter length l A/d, 0.8 < l/
A refrigeration device characterized in that d is set in a range of 2.5.