JP2001235237A - Refrigerating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerating system capable of reducing running cost with a small compressor power without necessity of raising a condensing pressure and reducing an apparatus cost by satisfying when a part of a refrigerant route is designed for a high pressure resistance. SOLUTION: A refrigerant liquid pump 12 is provided between a condenser 4 of a refrigerant forward tube 2 and an expansion valve 6. The other end of a bypass tube 13 connected at one end between the condenser 4 and the pump 12 on the way of the forward tube is connected between the pump 12 and the valve 6 on the way of the forward tube, and an opening/closing valve 14 is provided on the way of the tube 13. In the case of a cooling operation, the valve 14 is opened, and the pump 12 is stopped. However, in the case of a high temperature operation for holding a high temperature in a chamber to be air conditioned, the valve 14 is closed and the pump 12 is driven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system suitable for air conditioning of a room to be conditioned such as a test room in an environmental test apparatus.

[0002]

2. Description of the Related Art In an environmental test apparatus for performing various tests by changing the temperature in an environmental test chamber, a configuration in which the test chamber is cooled or heated to a required temperature by a refrigeration system and an appropriate heater. It has become.

For example, when performing a test in which the test chamber is heated to a high temperature of about 45 ° C. and the test chamber is maintained at a high humidity, the cooling operation by the refrigeration system is stopped, but the inside of the evaporator of the refrigeration system is stopped. If low-temperature refrigerant remains in the evaporator, the moisture in the test chamber will condense on the surface of the evaporator, and the air in the test chamber will be dehumidified, making it impossible to maintain high humidity.
A high-temperature operation is performed to raise the refrigerant evaporation temperature in the evaporator to a temperature close to the test room temperature, for example, about 42 ° C.

In a conventional refrigeration system, the condensing pressure of the refrigerant is increased in order to raise the refrigerant evaporation temperature. However, in order to increase the condensing pressure, the power of the compressor must be increased, which increases the running cost. There's a problem.

Further, the design pressure of the entire refrigeration system must be sufficient to cope with the condensing pressure. In order to increase the condensing pressure, it is necessary to stop heat exchange with the cooling water in the condenser. Since a cooling water bypass mechanism for stopping the supply of the cooling water to the condenser during operation must be provided, there is a problem that the cost of the apparatus is significantly increased.

Further, in recent years, alternative refrigerants having a high condensing pressure have been adopted as refrigerants used in refrigeration systems. For example, the condensing pressure of R22 conventionally used is 1.44 MPa at 40.degree. 1.86MP at 50 ° C
a, but R507A, one of the alternative refrigerants
Is 1.88 MPa at 40 ° C. and 2.3 at 50 ° C.
8 MPa, and the compressor power and the design pressure must be increased, which further increases running cost and equipment cost.

[0007]

[Object] The object of the present invention is to eliminate the need to increase the condensing pressure, to reduce the compressor power and to reduce running costs, and to design a part of the refrigerant path with a high pressure resistance design. It is therefore an object of the present invention to provide a refrigeration system capable of reducing the apparatus cost.

[0008]

In order to achieve the above object, a refrigeration system according to the present invention is provided with a condenser and an expansion valve in a refrigerant outgoing pipe extending from a discharge port of a compressor to an inlet of an evaporator in a room to be air-conditioned. In a refrigeration system having an evaporation pressure regulating valve in the refrigerant return pipe from the outlet of the evaporator to the suction port of the compressor, a refrigerant liquid pump is provided between the condenser and the expansion valve of the refrigerant outward pipe. The other end of the bypass pipe having one end connected between the condenser and the refrigerant liquid pump in the middle of the refrigerant outgoing pipe is connected between the refrigerant liquid pump and the expansion valve in the middle of the refrigerant outgoing pipe. An on-off valve is provided in the middle of the bypass pipe, and in the cooling operation, the on-off valve is opened and the refrigerant liquid pump is stopped, but in the high-temperature operation for keeping the room to be air-conditioned at high temperature, The on-off valve is closed and the refrigerant liquid pump runs. Is the certain as configuration.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a refrigeration system according to the present invention will be described below in detail with reference to specific examples shown in the accompanying drawings. The other end of the refrigerant outward pipe 2 whose one end is connected to the discharge port of the compressor 1 is
An evaporator 9 in an air conditioner 8 provided in a test room 7 which is a room to be air-conditioned via an oil separator 3, a condenser 4, a liquid receiver 5, and an expansion valve 6.
It is connected to the. The other end of the refrigerant return pipe 10, one end of which is connected to the evaporator 9, is connected to the suction port of the compressor 1 via an evaporation pressure adjusting valve 11.

In the refrigeration system according to the present invention, a refrigerant liquid pump 12 is provided between the receiver 5 and the expansion valve 6 in the refrigerant outgoing pipe 2, and the refrigerant liquid pump 12 has the same structure as the inlet side of the pump 12. The inlet and outlet of the bypass pipe 13 are connected to the refrigerant outlet pipe 2 on the outlet side, respectively, and an on-off valve 14 is provided in the middle of the bypass pipe 13.

The refrigerant liquid pump 12 is stopped while the refrigeration system is performing the cooling operation. At this time, the on-off valve 14 of the bypass pipe 13 is opened, and the refrigerant from the receiver 5 is supplied to the bypass pipe 13. Is bypassed to the expansion valve 6, but the refrigerant liquid pump 12
Is driven and the on-off valve 14 of the bypass pipe 13 is
Is closed, and the refrigerant from the liquid receiver 5 is supplied to the refrigerant liquid pump 12.
And is sent to the expansion valve 6.

The condenser 4 and the liquid receiver 5 are provided at a position higher than the refrigerant liquid pump 12 to prevent cavitation, or a supercooler is provided between the liquid receiver 5 and the refrigerant liquid pump 12. In addition, the code | symbol 15 in a figure is a blower, 16
Reference numerals a and 16b denote gas return pipes, and reference numeral 17 denotes a check valve.

Next, the operation of the refrigeration system according to the present invention configured as described above will be described. During the cooling operation, the on-off valve 14 of the bypass pipe 13 is opened, and the refrigerant from the compressor 1 flows from the oil separator 3, the condenser 4, and the receiver 5 to the bypass pipe 13 by the refrigerant forward pipe 2, and the expansion valve 6 through evaporator 9
And heat exchange with the room air flowing through the air conditioner 8 by the blower 15. The refrigerant from the evaporator 9 passes through the refrigerant outgoing pipe 10 via the evaporating pressure regulating valve 11 to the compressor 1.
Returned to

During high-temperature operation, the air in the test chamber is heated by a heater or the like (not shown), and in the refrigeration system, the on-off valve 14 of the bypass pipe 13 is closed and the refrigerant liquid pump 12 is driven.

The expansion valve 6 is driven by driving the refrigerant liquid pump 12.
The refrigerant pressure on the inlet side of the evaporator 9 increases, and the evaporating pressure of the refrigerant in the evaporator 9 also increases, and the evaporation temperature of the refrigerant in the evaporator is kept close to the temperature in the test chamber. The refrigerant from the evaporator 9 is decompressed by the evaporating pressure regulating valve 11 and
Returned to

Next, using R22 as a refrigerant,
The operation of the refrigeration system according to the present invention will be described in more detail based on a specific example when performing a high-temperature operation in which the inside temperature is maintained at, for example, 45 ° C. When the inside of the test chamber 7 is kept at 45 ° C., it is necessary to raise the evaporation temperature of the refrigerant in the evaporator to about 42 ° C. in order to prevent the dehumidifying action on the surface of the evaporator 9. Must be increased to a pressure at which the refrigerant condensing temperature becomes about 50 ° C.

FIG. 2 is a Mollier diagram of the refrigerant in the refrigeration system at the time of the high-temperature operation described above, wherein a is the inlet of the compressor 1, b is the same outlet, c is the inlet of the refrigerant liquid pump 12, d is the inlet of the expansion valve 6, e is the evaporator 9 inlet, f is the evaporating pressure regulating valve 11
The state of each refrigerant at the inlet is shown. In the drawing, a pressure difference ΔP ₁ between a and ab is a pressure increase by the compressor 1, and a pressure difference ΔP ₂ between cd and a pressure increase by the refrigerant liquid pump 12.
At a pressure of 40 ° C. for the condensation temperature (1.44 for R22).
It is sufficient to increase the pressure up to MPa).

FIG. 3 shows a Mollier diagram of a conventional refrigerant shown for comparison with the refrigeration system of the present invention, wherein a ′ is shown.
Is the compressor inlet, b 'is the same outlet, d' is the expansion valve 6 inlet,
e 'indicates the state of each refrigerant at the inlet of the evaporator 9 and f' indicates the state of each refrigerant at the inlet of the evaporation pressure regulating valve 11. In the drawing, the pressure difference ΔP between a ′ and b ′ is all pressure rise by the compressor, and therefore, it is necessary to raise the pressure to a pressure of 50 ° C. (1.86 MPa for R22) in the compressor.

As apparent from FIGS. 2 and 3, the power of the compressor in the refrigeration system according to the present invention can be made significantly smaller than that of the conventional refrigeration system. It is understood that the refrigerant path to the inlet does not need to have a high withstand pressure.

Next, the required power in the refrigeration system according to the present invention will be described based on specific numerical values shown in Table 1 below. The numerical values in the following Table 1 are extracted from a performance table of a certain refrigerator currently in practical use. The refrigerant used is R22, and the suction gas temperature is 5 ° C.

[0021]

[Table 1]

First, the circulating amount of the refrigerant is 112.77 for each enthalpy when R22 condenses at 40 ° C. and evaporates at 42 ° C.
Since kcal / kg and 152.19 kcal / kg, the refrigerant circulation amount = 337.6 × 3320 / (152.19−112.77) = 28433 (kg / h) = 0.419 (m ³ / min) Become. Therefore, the power of the refrigerant liquid pump is as follows: the specific weight of R22 at 40 ° C. liquid is 1132 kg / m ³ ,
Assuming that the efficiency of the refrigerant liquid pump is 0.5, pump power = 0.419 × 42 × 1132 / (6122 × 0.5) = 6.5 (BKw).

The cooling capacity at 40 ° C. is 379.5 (JRT) from Table 1. However, since the actual condensation temperature at the expansion valve inlet is 50 ° C., the cooling capacity is the cooling capacity at 50 ° C. 6 (JRT), and assuming that the shaft power is simply proportional to the cooling capacity, the shaft power (compressor power) = 296.3 x 337.6 / 379.5 = 263.6 (BKw ), And the total power = 263.6 + 6.5 = 270.1 (BKw).

In the conventional refrigeration system, since the pressure is raised to 50 ° C. by the compressor, the power of the compressor is 365.8 (BKw) from Table 1. Therefore, the total power of 270.1 (BKw) by the refrigeration system of the present invention can achieve a power reduction of about 26% as compared with the conventional one.

[0025]

In the refrigeration system according to the present invention, the refrigerant liquefied in the condenser by pressurization in the compressor is further pressurized by the refrigerant liquid pump and sent to the expansion valve during high temperature operation in which the room to be air-conditioned is kept at a high temperature. In addition, there is no need to increase the condensation pressure of the refrigerant in the condenser so much.

Therefore, it is not necessary to increase the power of the compressor, so that the running cost can be reduced, and only the refrigerant path from the refrigerant liquid pump to the expansion valve can be designed to withstand high pressure. For the other refrigerant paths, normal design pressure is sufficient, and there is no need to switch the cooling water path to the condenser to increase the condensation pressure. it can.

Even when an alternative refrigerant having a higher condensing pressure than conventional refrigerants is employed, the entire refrigeration system does not need to have a high pressure resistance and the power of the compressor is large. No need to break
There is also an advantage that an alternative refrigerant can be adopted without increasing the equipment cost and the running cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a refrigeration system according to the present invention.

FIG. 2 is a Mollier diagram of a refrigerant during a high-temperature operation of the refrigeration system according to the present invention.

FIG. 3 is a Mollier diagram of a refrigerant during a high-temperature operation of a conventional refrigeration system.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 compressor 2 refrigerant outgoing pipe 3 oil separator 4 condenser 5 liquid receiver 6 expansion valve 7 test chamber 8 air conditioner 9 evaporator 10 refrigerant return pipe 11 evaporation pressure regulating valve 12 refrigerant liquid pump 13 bypass pipe 14 on-off valve 15 Blower 16a, 16b Gas return pipe 17 Check valve

Claims (1)

[Claims] 1. A condenser and an expansion valve are provided in a refrigerant outgoing pipe extending from a discharge port of a compressor to an inlet of an evaporator in a room to be air-conditioned.
In a refrigeration system having an evaporation pressure regulating valve in a refrigerant return pipe from the outlet of the evaporator to the suction port of the compressor, a refrigerant liquid pump is provided between a condenser and an expansion valve of the refrigerant outward pipe, The other end of the bypass pipe having one end connected between the condenser and the refrigerant liquid pump in the middle of the refrigerant outgoing pipe is connected between the refrigerant liquid pump and the expansion valve in the middle of the refrigerant outgoing pipe. An on-off valve is provided in the middle of the bypass pipe, and in the cooling operation, the on-off valve is opened and the refrigerant liquid pump is stopped, but in the high-temperature operation for keeping the room to be air-conditioned at a high temperature, the on-off valve is provided. The refrigeration system has a configuration in which the refrigerant liquid pump is driven while the pump is closed.