JPH07122523B2 - Refrigeration equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a refrigerating apparatus, more specifically, a screw compressor, a condenser, a decompressor, and an evaporator connected via a refrigerant pipe, and a discharge side of the compressor. The present invention relates to a refrigerating device in which a branch liquid pipe connected to a compression process portion of a screw rotor is branched from a refrigerant pipe between a condenser connected to the compressor and a pressure reducing device.

(Prior Art) Conventionally, as this type of refrigerating device, a device in which a liquid refrigerant is injected into a compression process part of a screw rotor by a bypass pipe having a temperature-sensitive expansion valve is disclosed, for example, in Japanese Examined Patent Publication No. 63-25255.
It is already known as shown in the publication.

In the refrigerating apparatus as described above, as shown in FIG. 5, a screw compressor (A), a condenser (B), a decompressor (C) and an evaporator (D) are connected via a refrigerant pipe (E). Then, the bypass pipe (G) having the temperature type automatic expansion valve (F) interposed therein is branched from the outlet side of the evaporator (D) and connected to the compression process portion of the screw rotor (H). The liquid refrigerant is injected from (G) into the compression process portion of the screw rotor (H) under the control of the temperature type automatic expansion valve (F) to keep the superheat degree of the discharge gas constant and the discharge gas temperature abnormal. I try to suppress the rise.

Incidentally, (K) is an external pressure equalizing pipe, and (L) is a temperature sensing cylinder of the temperature type automatic expansion valve (F).

(Problems to be solved by the invention) By the way, in the refrigerating apparatus as described above, since the expensive thermal automatic expansion valve (F) is provided in the bypass pipe (G), the cost is high and the discharge is high. Since the degree of superheat of the gas temperature is constant, when the condensation temperature of the condenser (B) becomes higher, the temperature of the discharge gas becomes higher than a predetermined temperature, and the temperature is sensitive to a sudden change in the discharge pressure and the like. There is a problem that the response of the expansion valve is delayed and the temperature of the discharged gas becomes higher than a predetermined temperature.

The present invention has been made in view of the above problems, and an object thereof is to easily discharge gas without using an expensive temperature-sensitive expansion valve, with a simple configuration, at low cost, and without reducing compression efficiency. It is an object of the present invention to provide a refrigeration system capable of reliably preventing the temperature from rising above a certain temperature.

(Means for Solving the Problem) In order to achieve the above object, the present invention provides a screw compressor (1), a condenser (2), a decompression device (3) and an evaporator (4) in a refrigerant pipe (5). ) And a refrigerant pipe (5) between the condenser (2) and the pressure reducing device (3), which are connected to the discharge side of the compressor (1), to the compression process part of the screw rotor (6). A branching liquid pipe (7) connected to the first refrigeration apparatus, wherein the branch liquid pipe (7) is connected to a compression end side of a compression process part of the screw rotor (6), The screw rotor (6) comprises a second branch pipe (7b) connected to the suction side from the connection position of the first branch pipe (7a) in the compression process portion, and the discharge side temperature of the compressor (1) is Discharge side temperature detecting means for detecting is provided to the front of the second branch pipe (7b). Discharge side temperature by detection of the discharge side temperature detection means is to that interposed solenoid valve (10) that opens when it becomes higher than a predetermined temperature.

(Operation) Since the first branch pipe (7a) is connected to the compression end side of the compression process part of the screw rotor (6), a standard pressure ratio operation (suction pressure) that does not require much cooling liquid refrigerant and has a low discharge pressure During operation with a small ratio between the discharge pressure and the discharge pressure), since the differential pressure between the discharge pressure and the pressure on the compression end side of the compression process portion of the screw rotor (6) is small, the liquid refrigerant is always discharged from the first branch pipe (7a). Even if it is supplied, the supply of the liquid refrigerant is small and it is possible to prevent the discharge gas temperature from rising without lowering the compression efficiency.

Also, a high pressure ratio operation that requires a large amount of cooling liquid refrigerant and has a high discharge pressure (operation with a large ratio of suction pressure and discharge pressure)
At time, the differential pressure between the discharge pressure and the pressure on the compression end side of the compression process portion increases, so the differential pressure increases as the discharge pressure increases, and the liquid refrigerant supply amount from the first branch pipe (7a) increases. The discharge pressure automatically increases in response to the increase in the discharge pressure, and the discharge gas temperature can be prevented from rising above a certain temperature.

Moreover, when the discharge side temperature becomes higher than the predetermined temperature due to the insufficient supply amount of the liquid refrigerant despite the supply of the liquid refrigerant from the first branch pipe (7a), for example, based on the discharge pressure or the suction pressure. The electromagnetic valve (10) is opened by the detection of the discharge side temperature detecting means for detecting the discharge side temperature of the compressor (1), and the differential pressure is applied from the compression end side of the compression process section connecting the first branch pipe (7a). Liquid refrigerant is supplied to the large low pressure side from the second branch pipe (7b) to the compression process part of the screw rotor (6),
The shortage of the refrigerant flow rate from the branch pipe (7a) can be compensated for, and the discharge gas temperature can be reliably prevented from rising above a certain temperature.

(Embodiment) The refrigerating apparatus shown in FIG. 1 comprises a condenser (2) for liquefying a high-pressure gas refrigerant and a decompressor for depressurizing the liquid refrigerant in order from the discharge side to the suction side of the screw compressor (1). 3) and an evaporator (4) for evaporating the liquid refrigerant are connected in series via a refrigerant pipe (5), and a high-pressure gas refrigerant is supplied to the condenser (2) by the operation of the compressor (1). And liquefy, and then the liquid refrigerant whose pressure is reduced by the pressure reducing device (3) is supplied to the evaporator (4) to absorb the heat in the evaporator (4) to become a low-pressure gas refrigerant. It circulates to the suction side of the compressor (1).

Further, a branch liquid pipe (7) is branched from a refrigerant pipe (5) between the condenser (2) and the pressure reducing device (3), and the branch pipe (7) is compressed in the compression process part of the screw rotor (6). Connected to.

Thus, in the refrigerating apparatus thus configured, the first branch pipe (7a) connecting the branch liquid pipe (7) to the compression end side of the compression process portion of the screw rotor (6).
And a second branch pipe (7b) connected to the suction side from the connection position of the first branch pipe (7a) in the compression process portion of the screw rotor (6), and the compressor (1)
Discharge side temperature detection means for detecting the discharge side temperature of
The second branch pipe (7b) is provided with a solenoid valve (10) which opens when the discharge side temperature becomes higher than a predetermined temperature as detected by the discharge side temperature detecting means.

The discharge side temperature detecting means includes a high pressure switch (8) that operates when the discharge pressure provided on the discharge side of the screw compressor (1) is equal to or higher than a predetermined pressure, and a suction pressure provided on the suction side of the compressor (1). A low pressure switch (9) that operates when the pressure is lower than a predetermined pressure is used to open the solenoid valve (10) by operating the high pressure switch (8) or the low pressure switch (9).

Specifically, the first branch pipe (7a) is connected to the branch liquid pipe (7), and the capillary (11) is interposed in the first branch pipe (7a) to compress the screw rotor (6). It is connected to the compression end side of the process part.

Further, a second branch pipe (7b) is connected to the branch liquid pipe (7), and a capillary (12) and a solenoid valve (10) are interposed in the second branch pipe (7b) to connect the screw rotor (7). The connection is made from the connection position of the first branch pipe (7a) in the compression process part of 6) to the suction side.

Moreover, generally, the temperature of the discharge gas discharged from the compressor (1) becomes higher as the discharge pressure becomes higher when the suction pressure (LP) is the same, and when the discharge pressure (HP) is the same, The lower the suction pressure (LP), the higher it becomes. Therefore, the discharge pressure (HP) and suction pressure (LP) are hatched in Fig. 2 so as not to exceed 100 ° C, which is said to be the upper limit of the discharge gas temperature. In order to open the solenoid valve (10) when in the indicated region, the discharge side of the screw compressor (1) has a high pressure switch (8) which operates when the discharge pressure is equal to or higher than a predetermined pressure. ) Is provided, and a low pressure switch (9) that operates when the suction pressure is equal to or lower than a predetermined pressure is provided on the suction side.

For example, when Freon R-22 is used as the refrigerant, the high pressure switch (8) is used when the discharge pressure (HP) is 20 kg / cm ² or more.
Is set so that the suction pressure (LP) is 1.
The low pressure switch (9) is set to operate when the pressure is 0 kg / cm ² or less. Therefore, the discharge pressure (HP) is 20
In kg / cm ² or more, and, the suction pressure (LP) is 1.0 kg / cm ² even when below the solenoid valve (10) is in the opening operation, the discharge pressure (HP) is 20 kg / cm ² or less And suction pressure (LP)
Is 1.0 kg / cm ² or more, the solenoid valve (10) is closed.

In this way, the refrigerant is always supplied from the first branch pipe (7a), and the second refrigerant is supplied only when the electromagnetic valve (10) is opened.
Refrigerant is supplied from the branch pipe (7b) to the low pressure side in the compression process section, and the first branch pipe (7a) serves as the main system for supplying the refrigerant and the second branch pipe (7b) serves as the sub system. .

That is, the capillary (1) interposed in the first branch pipe (7a)
Due to 1), a high pressure ratio operation in which the discharge pressure becomes high, for example, an air-cooled condensation in which the condensation pressure (temperature) becomes higher than that in the case where the condenser (2) is an air-cooled condenser, that is, a water-cooled condenser. When the compressor is used, the amount of liquid refrigerant flowing through the first branch pipe (7a) is set to be an appropriate refrigerant flow rate, and during the high pressure ratio operation, the compression process portion of the screw rotor (6) The liquid refrigerant at an appropriate flow rate is supplied by the pressure difference between the pressure on the compression end side and the discharge pressure, and the supply of this liquid refrigerant suppresses the rise in the discharge gas temperature.

The second branch pipe (7b) is connected to the compression end side of the compression process portion of the screw rotor (6).
It is connected to the low pressure side from the connection part of the branch pipe (7a), and the pressure difference between the pressure and discharge pressure at the connection part of this second branch pipe (7b) is compared with the pressure difference between the pressure on the compression end side and the discharge pressure. Since it is large and the liquid refrigerant easily flows, the capillary (12) is provided in the second branch pipe (7b) and
The electromagnetic valve (10) is interposed so that a large amount of liquid refrigerant is not supplied to the compression process part of the rotor (1) when the electromagnetic valve (10) is opened.
By 2), the flow rate of the refrigerant flowing through the second branch pipe (7b) is adjusted.

When the refrigeration system configured as described above is operated at the standard pressure ratio, the discharge pressure (P) is not so high as shown in FIG. 3, and therefore the discharge gas temperature does not rise so much, and the rotor (6) Since it does not require a large amount of refrigerant for cooling,
A small amount of refrigerant needs to be supplied from the first branch pipe (7a), and the differential pressure between the pressure (P ₂ ) and the discharge pressure (P) on the compression end side of the compression process portion of the screw rotor (6) is small. 1
Even if the liquid refrigerant is constantly supplied from the branch pipe (7a), the supply amount of the liquid refrigerant is small and it is possible to prevent the discharge gas temperature from rising without lowering the compression efficiency.

Then, as shown in FIG. 4, when the high pressure ratio operation in which the ratio of the suction pressure (Ps) to the discharge pressure (P) is larger than the standard pressure ratio operation is performed, the pressure (P ₂ )
Since the differential pressure between the discharge pressure (P) and the discharge pressure (P) becomes larger than the differential pressure during the standard pressure ratio operation, the flow rate of the refrigerant flowing through the first branch pipe (7a) via the capillary (11) increases according to the differential pressure. With a simple configuration, it is possible to reliably prevent the discharge gas temperature from rising above the set temperature. Therefore, for example, even when an air heat exchanger having a higher condensation temperature than the water heat exchanger is used as the condenser (2) in place of the water heat exchanger, it is possible to prevent the discharge gas temperature from rising.

In addition, if the rise in discharge gas temperature cannot be suppressed even if the refrigerant flow rate in the first branch pipe (7a) increases in accordance with the differential pressure, the discharge pressure (HP) is 20 kg / cm ² or more or suction pressure. (LP)
Is 1.0 kg / cm ² or less, the solenoid valve (10) opens, and the screw rotor (6) passes through the second branch pipe (7b).
The liquid refrigerant can be supplied to the compression process part of the above, and the pressure (P ₁ ) in the compression process part to which the second branch pipe (7b) is connected is the first.
The pressure is lower than the pressure (P ₂ ) on the compression end side where the branch pipe (7a) is connected, and the differential pressure with the discharge pressure (P) is large by that much, so it is possible to reliably compensate for the deficient refrigerant amount, and the discharge gas temperature It is possible to reliably prevent the temperature from rising above the set temperature.

Therefore, it is possible to avoid contact due to the difference in thermal expansion between the screw rotor (6) of the screw compressor (1) and the casing, and prevent damage to the screw compressor (1).

On the discharge side of the compressor (1), a high temperature detection switch (1
3) is installed in parallel with the high-pressure switch (8) to deal with the case where the discharge gas temperature rises faster and faster than the discharge pressure rise. The valve (10) is opened.

Also, (14) is a high pressure stop switch that stops the compressor (1) when the discharge pressure becomes 26.5 kg / cm ² , and (15) when the suction pressure becomes 0.2 kg / cm ² or less. It is a low pressure stop switch for stopping the compressor (1).

(Effects of the Invention) As described above, according to the present invention, the branch liquid pipe (7)
Is connected to the compression end side of the compression process part of the screw rotor (6), and the first branch pipe (7a) of the compression process part of the screw rotor (6).
The second branch pipe (7b) connected to the suction side from the connection position of a) is provided with a discharge side temperature detecting means for detecting the discharge side temperature of the compressor (1). 7b) is equipped with a solenoid valve (10) that opens when the discharge side temperature becomes higher than a predetermined temperature by the detection of the discharge side temperature detecting means. During the pressure ratio operation (operation in which the ratio of the suction pressure and the discharge pressure is small), the difference in pressure between the discharge pressure and the compression end side of the compression process portion of the screw rotor (6) is small, so the first branch pipe (7a Even if the liquid refrigerant is constantly supplied from (1), the supply amount of the liquid refrigerant is small and it is possible to prevent the discharge gas temperature from rising without lowering the compression efficiency.

Also, a high pressure ratio operation that requires a large amount of cooling liquid refrigerant and has a high discharge pressure (operation with a large ratio of suction pressure and discharge pressure)
At time, the differential pressure between the discharge output and the pressure on the compression end side of the compression process portion increases, so the differential pressure increases as the discharge pressure increases, and the liquid refrigerant supply amount from the first branch pipe (7a) increases. Will automatically increase in response to the increase in the discharge pressure, and it is possible to prevent the discharge gas temperature from rising above a certain temperature.

Moreover, when the discharge side temperature becomes higher than the predetermined temperature due to the insufficient supply amount of the liquid refrigerant despite the supply of the liquid refrigerant from the first branch pipe (7a), for example, based on the discharge pressure or the suction pressure. The electromagnetic valve (10) is opened by the detection of the discharge side temperature detecting means for detecting the discharge side temperature of the compressor (1), and the differential pressure is applied from the compression end side of the compression process section connecting the first branch pipe (7a). Liquid refrigerant is supplied to the large low pressure side from the second branch pipe (7b) to the compression process part of the screw rotor (6),
The shortage of the refrigerant flow rate from the branch pipe (7a) can be compensated for, and the discharge gas temperature can be reliably prevented from rising above a certain temperature.

Therefore, the discharge gas is controlled without controlling the supply amount of the liquid refrigerant and without using an expensive temperature-sensitive expansion valve for making the superheat degree of the discharge gas constant, and without lowering the compression efficiency. Thus, it is possible to provide a refrigeration system capable of reliably preventing the temperature from rising above a certain temperature.

[Brief description of drawings]

FIG. 1 is a piping diagram of a refrigerating apparatus according to the present invention, FIG. 2 is a graph showing an opening / closing area of a solenoid valve, and FIGS. 3 and 4 are diagrams showing a compression process portion between a first branch pipe and a second branch pipe. FIG. 3 is a graph showing the relationship between connection position and pressure, FIG. 3 is a graph of pressure in standard pressure ratio operation, FIG. 4 is a graph of pressure in high pressure ratio operation, and FIG. 5 is an explanatory view showing a conventional example. is there. (1) …… Screw compressor (2) …… Condenser (3) …… Decompressor (4) …… Evaporator (5) …… Refrigerant piping (6) …… Screw rotor (7) …… Branching liquid Pipe (7a) …… First branch pipe (7b) …… Second branch pipe (8) …… High pressure switch (9) …… Low pressure switch (10) …… Solenoid valve

Claims (1)

[Claims] 1. A screw compressor (1), a condenser (2),
The pressure reducing device (3) and the evaporator (4) are connected via a refrigerant pipe (5), and between the condenser (2) and the pressure reducing device (3) connected to the discharge side of the compressor (1). Refrigerant piping (5)
A branching liquid pipe (7) connected to the compression process part of the screw rotor (6), wherein the branch liquid pipe (7) is compressed in the compression process part of the screw rotor (6). The first branch pipe (7
a) and a second branch pipe (7b) connected to the suction side from the connection position of the first branch pipe (7a) in the compression process portion of the screw rotor (6), and the compressor (1) Discharge side temperature detecting means for detecting the discharge side temperature is provided, and a solenoid valve (10) that opens when the discharge side temperature becomes higher than a predetermined temperature by the detection of the discharge side temperature detecting means in the second branch pipe (7b). A refrigerating device characterized by being inserted.