JPH0343568Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to the structure of a refrigeration system in which a hot gas bypass line is provided in a refrigeration circuit in order to expand the operating range.

(Prior Art) A refrigeration system is known in which a hot gas bypass pipe is provided in a refrigeration circuit in order to maintain a bottom suction pressure sufficient to continuously operate a compressor regardless of the magnitude of the load on the evaporator. This is also described in the New Refrigeration and Air Conditioning Handbook, 4th edition, basic edition, Japan Refrigeration Association, published May 30, 1980, page 508509.

Regarding the above-mentioned known technology, one in which a hot gas bypass line 6' having a constant pressure automatic expansion valve 5' is provided as a particularly simple structure is also described.
When this is applied to a refrigeration device such as a spot cooler, as shown in FIG. 3, this is a structure in which control is performed using one constant pressure automatic expansion valve 5'.

(Problems to be Solved by the Invention) When the device shown in Figure 3 is applied to a spot cooler used in an installation environment where the temperature fluctuates rapidly, Figure 2 shows the temperature of the intake air of the evaporator 4. The relationship with the temperature of the blown air using Freon R-22 as a refrigerant
As shown in the example when using the evaporator, when the suction air temperature is in the range of 25℃ to 10℃, the state shown by the dotted line occurs, and the cooling capacity, that is, the air temperature difference before and after the evaporator (△T) = x-y (x is the intake air temperature,
y is the blowing air temperature) (for convenience,
(Latent heat change is ignored), but at point A, 25−16=
9 (℃), but at point ○C', the decrease in performance is quite large, 10-6=4 (℃), and in addition, the decrease in performance is almost linear between point ○A and point ○C'. Therefore, even at the intermediate point ○B' point, 18-11=7 (℃), and the decrease in ability is 77.8% compared to point ○A, and the problem is that the rate of decrease in ability is large. be.

In order to address these problems, the present invention has been developed to provide a device that can eliminate the drawbacks of the conventional method, and takes advantage of the simple structure of the hot gas bypass system using a constant pressure automatic expansion valve. However, by finely controlling the amount of hot gas bypass, the purpose is to suppress the degree of decrease in cooling capacity to a small level.

(Means for Solving the Problems) The present invention will be explained using FIG. 1 corresponding to an embodiment. The discharge gas pipe A of the compressor 1 and the low pressure pipe E are connected by a hot gas bypass pipe 6, and a valve is installed in the middle of the hot gas bypass pipe 6 to start opening when the pressure on the low pressure pipe E side becomes lower than the set pressure. , two or more constant pressure automatic expansion valves 5A, 5B whose opening degree increases as the pressure decreases are connected and arranged in parallel, and each of the constant pressure automatic expansion valves 5
The set pressures of A and 5B are adjusted to each constant pressure automatic expansion valve 5.
It is characterized in that each of A and 5B is different from the other.

(Function) Considering the case where, for example, two constant pressure automatic expansion valves 5A and 5B are connected in parallel, it is common to use two small expansion valves so that the flow rate when fully open is equal to that of only one expansion valve. Therefore, when the second stage expansion valve 5B begins to open while the first stage expansion valve 5A increases its opening degree, the bypass flow rate is reduced compared to the case where only one valve is used. As is clear from the points ○ and ○ in FIG. 2, the temperature difference (ΔT) increases and the cooling capacity increases.

In this way, the temperature of the blown air becomes lower in the shaded area in FIG. 2 than in the case of one blower, and the capacity is increased.

(Example) Next, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 shows a spot cooler according to an embodiment of the present invention, in which the inside of the casing 12 is divided into two chambers, left and right, and one chamber is connected to a first air suction port 13 provided at the upper part of the back plate and a top plate. A condenser 2, a pressure reducer 3 such as a capillary tube (an automatic temperature expansion valve for superheat control may also be used), a condenser fan 8, a filter 10, a two-shaft motor 11 connected to the fan 8;
is stored.

On the other hand, the other rooms have a second air intake port 15 provided at the bottom of the back panel and a cold air outlet 16 provided at the top of the front panel.
A compressor 1, an evaporator 4, and two first and second constant pressure automatic expansion valves 5A, 5 are installed in the room.
A hot gas bypass pipe line 6 having a diameter B, two accumulators 7, and an evaporator fan 9 connected to the two-shaft motor 11 are housed therein.

Then, the compressor 1, the coil of the condenser 2, the pressure reducer 3, the flow divider 17, the coil of the evaporator 4, the accumulators 7 and 7 are connected to the discharge pipe gas pipe A, the high pressure liquid pipe B, the low pressure liquid pipe C, and the suction gas pipe. A well-known refrigeration cycle is formed by connecting with pipes such as D.

Note that E is a low-pressure pipe that collectively refers to the low-pressure liquid pipe C, the evaporator 4, and the suction gas pipe D.

The first and second constant pressure automatic expansion valves (hereinafter referred to as the first and second constant pressure automatic expansion valves)
5A and 5B (abbreviated as second expansion valves) are, for example, those of the same shape and performance that are installed side by side and connected by piping so that they are parallel to each other, and the end of the connected piping that becomes the inflow side is connected to the compressor 1. The hot gas bypass pipe is connected to a discharge gas pipe A connected to the discharge port, and connected to an intake gas pipe D formed by connecting the outflow side end of the pipe to the suction port of the compressor 1. 6 is formed.

The first and second expansion valves 5A and 5B are connected to the evaporator 4.
In order to prevent normal operation from occurring due to frost formation if the pressure drops below a specified level, the valve automatically opens when the outlet side pressure falls below the set pressure.
It operates to increase the valve opening to maintain the pressure at the set pressure, and both expansion valves 5A, 5
B, the set pressure is made different, and the set pressure of the first expansion valve 5A is made higher than that of the second expansion valve 5B.

That is, the set pressure is determined from the viewpoint of preventing frost formation on the evaporator 4. For example, in the case of R-22 refrigerant, the set pressure of the first expansion valve 5A is 5 kg/cm ²
(absolute pressure), and the set pressure of the second expansion valve 5B is
The pressure is set at 4.5Kg/cm ² (absolute pressure).

Note that the second method for setting the set pressure is
It is more preferable to set the pressure of the expansion valve 5B to a predetermined pressure for preventing frost formation.

In the spot cooler having the structure described above, when the compressor 1 and the two-shaft motor 11 are driven to enter cooling operation, the condenser 2 is cooled by the indoor air introduced from the first air suction port 13. On the other hand, the air whose temperature has increased is discharged upward from the exhaust port 14 into the room.

In addition, the indoor air introduced from the second air suction port 15 is cooled by the evaporator 4 and sent out from the cold air outlet 16 as cold air.
There are times when it is necessary to cool down high-temperature objects during the spring, fall, and winter seasons.

During this cooling operation, the indoor air temperature drops,
When the low pressure force decreases to below the set pressure of the first expansion valve 5A, the expansion valve 5A begins to open.

At this valve starting point (point ○ in Figure 2), the air temperature difference △T ₁ is △T ₁ = 25-16 = 9°C, and both the intake and blowout air temperatures further decrease from this state. The opening degree of the first expansion valve 5A increases,
When fully opened, the low pressure starts to drop, so the second
The expansion valve 5B detects that the pressure becomes lower than the set pressure and starts opening at point ○.

At this time, the air temperature difference △T ₂ is △T ₂ = 18−10 =
8°C, and as the temperature of the suction and blowing air further decreases, the opening degree of the second expansion valve 5B increases and becomes fully open at point ○C, and the air temperature difference at this time is △
T ₃ is △T ₃ = 10−5.5 = 4.5°C.

As is clear from the above results, the cooling capacity at point ○B is 88.9% compared to point ○B, and is 14% compared to point ○B' in the conventional expansion valve with one expansion valve 5'.
A capacity increase of about % is achieved.

Note that the shaded area in FIG. 2 is a region where the temperature of the blown air decreases compared to the conventional system, and the capacity increases throughout the operating temperature range.

In addition, if the spot cooler has a relatively large capacity and the diameter of the hot gas bypass line 6 is large, one expansion valve will require a large diameter and become larger, but two expansion valves will be required. By using 5A and 5B, a much smaller size can be used.

Furthermore, it is advantageous in terms of manufacturing cost to use two or more expansion valves with the same diameter and the same opening characteristics, but different expansion valves may be used. For example, in the case of two expansion valves, even if the diameter is the same, the valve lift length from fully closed to fully open is different, and the one with the longer valve lift is used for high set pressure, and the shorter one is used. may be used for low set pressure, or when using two expansion valves with different diameters, the smaller or larger one is used for high set pressure, and the larger or smaller one is used for low set pressure. .

In addition to the suction gas pipe D, the hot gas bypass pipe 6 may be connected to the evaporator 4, the low pressure liquid pipe C, or the flow divider 17.

(Effects of the invention) As detailed above, the present invention includes two or more constant pressure automatic expansion valves 5A and 5B that begin to open when the pressure on the low pressure pipe E side falls below the set pressure, and whose opening degree increases as the pressure decreases. By connecting and arranging them in parallel and making the set pressures of the constant pressure automatic expansion valves 5A and 5B different from each other, the hot gas bypass amount is finely controlled. It is possible to make the difference between the intake air temperature and the outlet air temperature considerably large, thereby increasing the cooling capacity compared to the conventional single expansion valve system, thereby minimizing the decrease in capacity.

[Brief explanation of drawings]

FIG. 1 is a device circuit diagram according to an embodiment of the present invention;
FIG. 2 is a comparison diagram of the cooling capacity according to the example of the present invention and the cooling capacity of a conventional refrigeration system, and FIG. 3 is a device circuit diagram of the conventional refrigeration system. 1...Compressor, 2...Condenser, 3...Compressor,
4... Evaporator, 5A, 5B... Constant pressure automatic expansion valve,
6... Hot gas bypass pipe line, A... Discharge gas pipe, E... Low pressure pipe.

Claims (1)

[Scope of utility model registration request] It is equipped with a compressor 1, a condenser 2, a pressure reducer 3, and an evaporator 4, and the discharge gas pipe A of the compressor 1 and the low pressure pipe E are connected by a hot gas bypass pipe 6, and the hot gas bypass pipe 6. On the way, two or more constant-pressure automatic expansion valves 5A and 5B, which start opening when the pressure on the low-pressure pipe E side becomes lower than the set pressure and whose opening degree increases as the pressure decreases, are connected and arranged in parallel, and each of the above-mentioned constant pressure A refrigeration system characterized in that the set pressures of the automatic expansion valves 5A and 5B are different for each constant pressure automatic expansion valve 5A and 5B.