JPH1047794A - Freezer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent operation of a freezer from being interrupted under high fresh air temperature by providing means for changing over the flow of a liquid refrigerant to a gas/liquid heat exchanger and a bypass circuit on an inlet side of the liquid refrigerant of the gas/liquid heat exchanger, and controlling the changeover means such that discharge gas temperature from a compressor falls within a predetermined range. SOLUTION: Once discharge gas temperature from a compressor 3 exceeds an allowed value, a controller 17 that has received an output from a discharge gas temperature sensor 13 changes over an outlet of a three-way valve 14 from a gas/liquid heat exchanger 8 side to a bypass pipe 15 side. Thereupon, a fluid refrigerant from a condenser 4 bypasses the gas/liquid heat exchanger 8 and is fed to an expansion valve 9 after passage through the bypass pipe 15 where it undergoes heat insulation expansion. In the cource of its flowing through art evaporator 10 it heat exchanges and is evaporated with circulation air in a refrigerator into a gas refrigerant which in turn enters the gas/liquid heat exchanger 8. Since the liquid refrigerant is unlikely to flow through the gas/liquid heat exchanger 8, the gas refrigerant is prevented from heat exchanging with the liquid refrigerant, and hence it is returned to the compressor 3 without increasing the degree of overheating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system used for land transportation and the like.

[0002]

2. Description of the Related Art A refrigeration unit for land transportation (hereinafter, abbreviated as a refrigeration unit) is mainly installed on a truck, and performs a cooling operation, a heating operation, and the like, so that a temperature inside a freezer mounted on the truck is adjusted to an arbitrary temperature. To maintain. One example of a conventional refrigeration system is shown in FIGS. 3 is an overall equipment diagram of a general refrigeration unit for land transportation, FIG. 4 is a system diagram showing an overall configuration of a conventional refrigeration system, and FIG. 5 is a refrigeration cycle diagram on a refrigerant Mollier diagram.

[0003] In FIG.
The condensing unit 1 is installed on the outer lower part of the refrigerator 0 and the evaporator unit 2 is installed in the freezer 100. These are connected by a high-pressure refrigerant pipe 30 and a low-pressure refrigerant pipe 40.

In FIG. 4, when the compressor 3 of the condensing unit 1 is driven by the power of an engine or the like (not shown), the high-pressure and high-temperature gas refrigerant compressed by the compressor 3 is sent to a condenser 4, where , And is cooled by the outside air 50 introduced by the condenser fan 5 and condensed and liquefied. The liquid refrigerant passes through a receiver 6 and a dryer 7 and is sent to a gas-liquid heat exchanger 8 disposed in the evaporator unit 2 by a high-pressure refrigerant pipe 30 connecting the condensing unit 1 and the evaporator unit 2, where the liquid The refrigerant exchanges heat with the low-pressure, low-temperature gas refrigerant sent from the evaporator 10, and the liquid refrigerant is further supercooled. The supercooled liquid refrigerant that has exited the gas-liquid heat exchanger 8 is adiabatically expanded by the expansion valve 9, enters the evaporator 10, and flows through a pipe in the evaporator 10, and is sent by the evaporator 11 to the freezer 1.
The air exchanges heat with the circulating air in the cooling water 100, and is cooled by the evaporator fan 11 to be blown into the freezer 100 as cooling air 60. The refrigerant that has exchanged heat with the circulating air in the freezer 100 in the evaporator 10 evaporates and is sent to the gas-liquid heat exchanger 8, where it is heated by exchanging heat with the liquid refrigerant as described above, and the degree of superheat increases. The superheated gas refrigerant is sent to the accumulator 12 via the low-pressure refrigerant pipe 40 connecting the evaporator unit 2 and the condensing unit 1, and returns to the compressor 3 therefrom.

FIG. 5 shows a refrigeration cycle of the refrigeration apparatus on a refrigerant Mollier chart. The cycle of ABCD shown by the solid line in this figure is A'-B'-C'- shown by the dotted line when the gas-liquid heat exchanger 8 is not provided.
The cycle of D 'is a case where the gas-liquid heat exchanger 8 is provided. In FIG. 5, C and C ′ are refrigerant states at the inlet of the expansion valve 9, and the degree of supercooling of the liquid refrigerant is increased by the gas-liquid heat exchanger 8 (shown in the range of C to C ′). This indicates that the evaporator 10 can obtain an increase in the refrigerating capacity corresponding to the increase in the enthalpy indicated by the range from D to D '. On the other hand, A and A 'indicate the state of the refrigerant at the inlet of the compressor 3, and the gas refrigerant at the inlet of the compressor 3 is heated by the gas-liquid heat exchanger 8, and the suction gas of the compressor 3 shown in the range of A to A' As a result, the temperature of the discharge gas of the compressor 3 is increased by the amount shown in the range of B to B ′.

[0006]

In the conventional refrigeration system, a gas-liquid heat exchanger 8 is provided between the condenser 4 and the expansion valve 9 at a position close to the inlet of the expansion valve 9 to enhance the refrigeration capacity. ing. Compressor 3 coming out of evaporator 10
In the gas-liquid heat exchanger 8, the suction gas refrigerant exchanges heat with the high-pressure and high-temperature liquid refrigerant, absorbs heat, and is compressed by the compressor in a state where the degree of superheat is increased. As a result, the temperature of the compressor discharge gas increases with an increase in the degree of superheat of the intake gas, and when the refrigeration system is operated in an atmosphere of a high outside air temperature, the discharge gas temperature of the compressor becomes the allowable upper limit of the refrigeration system. And the frequency of stoppage of the refrigeration system becomes high.

The present invention solves the above-mentioned drawbacks of the prior art, so that the discharge gas temperature of the compressor falls within a predetermined range.
An object of the present invention is to prevent the operation of the refrigeration system from being stopped by the protection device during operation in a high ambient temperature atmosphere, and to increase the allowable operating limit of the refrigeration system.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and comprises a refrigeration cycle formed by a compressor, a condenser, an adiabatic expansion means, and an evaporator. A refrigeration apparatus provided with a gas-liquid heat exchanger for exchanging heat between the liquid refrigerant on the inlet side of the adiabatic expansion means and the gas refrigerant on the outlet side of the evaporator, relates to a refrigeration apparatus having the following characteristics. (1) On the liquid refrigerant inlet side of the gas-liquid heat exchanger, there is provided switching means for switching and controlling the flow of the liquid refrigerant between the gas-liquid heat exchanger and a bypass circuit connected in parallel to the gas-liquid heat exchanger. In addition, a controller is provided for controlling the switching means so that the temperature of the gas discharged from the compressor falls within a predetermined range. (2) In the refrigerating apparatus according to the above (1), the switching means is a three-way valve. (3) In the refrigerating apparatus according to the above mode (1) or (2), the controller includes a temperature sensor for detecting a temperature of the gas discharged from the compressor, and the switching unit switches according to a value detected by the temperature sensor. Control. (4) In the refrigeration apparatus according to the above mode (1) or (2), the controller includes a superheat degree sensor for the suction gas refrigerant of the compressor, and controls the switching unit in accordance with a detection value of the superheat degree sensor. I do.

[0009]

FIG. 1 is a refrigerant piping system diagram showing an entire configuration of a refrigeration apparatus according to a first embodiment of the present invention. In the figure, reference numeral 14 denotes a three-way valve disposed at a position near an inlet of the gas-liquid heat exchanger 8 in a pipe extending from the outlet of the condenser 4 to the gas-liquid heat exchanger 8 via the high-pressure refrigerant pipe 30.
The first outlet is connected to a liquid refrigerant inlet of the gas-liquid heat exchanger 8, the second outlet is connected to a bypass pipe 15, which bypasses the gas-liquid heat exchanger 8, and has an expansion valve. 9 is connected. Reference numeral 16 denotes a check valve provided on the liquid refrigerant outlet side of the gas-liquid heat exchanger 8. Reference numeral 13 denotes a discharge gas temperature sensor attached to an outlet pipe of the compressor 3. 17
Is a temperature calculating means 18 and a three-way valve outlet switching determining means 19
Is a controller composed of The output of the discharge gas temperature sensor 13 is input to the temperature calculating means 18, and the output of the temperature calculating means 18 instructs the output from the three-way valve outlet switching determination means 19. The outlet of the three-way valve 14 is set on the side corresponding to the command. The configuration of other parts is the same as that of the related art.

When the discharge gas temperature of the compressor 3 exceeds a preset allowable value, the controller 17 receiving the output of the discharge gas temperature sensor 13 issues an output command to the three-way valve 14, and the outlet of the three-way valve 14 The gas-liquid heat exchanger 8 is switched to the bypass pipe 15. As a result, capacitor 4
From the air-liquid heat exchanger 8, is sent to the expansion valve 9 via the bypass pipe 15, adiabatically expanded, and flows through the evaporator 10. The gas is exchanged, evaporated and vaporized, and enters the gas-liquid heat exchanger 8 as a gas refrigerant. Since no liquid refrigerant flows through the gas-liquid heat exchanger 8, this gas refrigerant does not exchange heat with the liquid refrigerant, and therefore returns to the compressor 3 without increasing the degree of superheat.

In this embodiment, when the discharge gas temperature detected by the discharge gas temperature sensor 13 exceeds the allowable value, the controller 17 controls the three-way valve 14 disposed on the liquid refrigerant inlet side of the gas-liquid heat exchanger 8. And the liquid refrigerant is switched to the circuit 15 that bypasses the gas-liquid heat exchanger 8, thereby suppressing an increase in the degree of superheat of the suction gas of the compressor 3 and lowering the discharge gas temperature. It is possible to prevent the operation from being stopped, thereby increasing the allowable operation limit of the refrigeration apparatus (for example, the upper limit of the outside air temperature).

FIG. 2 is a refrigerant piping system diagram showing the entire configuration of a refrigeration apparatus according to a second embodiment of the present invention. In the figure, reference numeral 20 denotes a suction gas refrigerant superheat degree sensor mounted on an outlet pipe on the gas refrigerant side of the gas-liquid heat exchanger 8, and 21 denotes a gas refrigerant superheat degree calculation means 22 and a three-way valve switching valve opening degree determination means 23. The controller to be configured. The output of the suction gas refrigerant superheat degree sensor 20 is output from the gas refrigerant superheat degree
When the calculated output is input to the three-way valve switching valve opening determining means 23, the outlet switching valve opening corresponding to the input value is calculated and set, and an output command is issued to the three-way valve 14. On the basis of this command value, the outlet switching valve of the three-way valve 14 is driven by the outlet switching valve driving means mounted on the three-way valve 14.
The outlet opening on the gas-liquid heat exchanger 8 side and the outlet opening on the bypass pipe 15 side are simultaneously and continuously set and controlled. In this embodiment, a suction gas refrigerant superheat degree sensor 20 and a controller 21 are provided instead of the discharge gas temperature sensor 13 and the controller 17 in the first embodiment. Is the same.

Now, when the degree of superheat of the suction gas refrigerant increases,
The outlet switching opening of the three-way valve 14 is calculated by the three-way valve switching valve opening determining means 23 in accordance with the output of the suction gas refrigerant superheat degree sensor 20, and an output command is issued to the three-way valve 14 to output the gas-liquid heat exchanger 8 side. The first outlet opening of the three-way valve 14 connected to the bypass pipe 15 is reduced, and the second outlet opening of the three-way valve 14 connected to the bypass pipe 15 side is set and controlled to increase. As a result, the flow rate of the liquid refrigerant passing through the gas-liquid heat exchanger 8 decreases and the flow rate of the liquid refrigerant bypassing the gas refrigerant increases, so that the amount of heat exchange of the gas refrigerant in the gas-liquid heat exchanger 8 decreases, An increase in the degree of superheat of the gas refrigerant is suppressed, and the gas refrigerant returns to the compressor 3.

In the present embodiment, under conditions where the outside air temperature is high, the controller 21 controls the three-way valve outlet switching valve by the output of the suction gas refrigerant superheat degree sensor 20,
Since the flow rate of the liquid refrigerant to the gas-liquid heat exchanger 8 and the flow rate bypassing the same are continuously controlled, the heat exchange amount of the gas refrigerant in the gas-liquid heat exchanger 8 is controlled, and the discharge gas temperature of the compressor 3 is controlled. , It is possible to raise the allowable operating limit of the refrigerating apparatus while maintaining the effect of increasing the refrigerating capacity by the gas-liquid heat exchanger 8.

[0015]

According to the refrigerating apparatus of the present invention, the flow of the liquid refrigerant is supplied to the liquid refrigerant inlet side of the gas-liquid heat exchanger by a gas-liquid heat exchanger and a bypass circuit connected in parallel to the gas-liquid heat exchanger. In addition to providing switching means for switching control, a controller for controlling the switching means so that the temperature of the discharge gas from the compressor falls within a predetermined range is provided, and the switching means is a three-way valve, and the controller is A temperature sensor for detecting the temperature of the gas discharged from the compressor is provided, and the switching means is controlled in accordance with a value detected by the temperature sensor, or the controller sets a superheat degree sensor for the suction gas refrigerant of the compressor. Since the switching means is controlled in accordance with the detection value of the superheat degree sensor, the operation by the protection device of the refrigerating apparatus which occurs at the time of operation under a high outside air temperature atmosphere is provided. Preventing stop can raise the operation allowable limits of the refrigeration system.

[Brief description of the drawings]

FIG. 1 is a refrigerant piping system diagram showing an entire configuration of a refrigeration apparatus according to a first embodiment of the present invention.

FIG. 2 is a refrigerant piping system diagram showing an entire configuration of a refrigeration apparatus according to a second embodiment of the present invention.

FIG. 3 is an equipment diagram of a general refrigeration apparatus in a vehicle.

FIG. 4 is a system diagram showing an overall configuration of a conventional refrigeration apparatus.

FIG. 5 is a refrigeration cycle diagram on a refrigerant Mollier chart of the refrigeration apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Condensing unit 2 Evaporator unit 3 Compressor 4 Condenser 5 Condenser fan 8 Gas-liquid heat exchanger 9 Expansion valve 10 Evaporator 11 Evaporator fan 13 Discharge gas temperature sensor 14 Three-way valve 15 Bypass pipe 16 Check valve 17 Controller 18 Temperature calculation means 19 Three-way valve outlet switching determination means 20 Intake gas refrigerant superheat degree sensor 21 Controller 22 Gas refrigerant superheat degree calculation means 23 Three-way valve switching valve opening degree determination means 30 High pressure refrigerant pipe 40 Low pressure refrigerant pipe 50 Outside air 60 Cooling air 100 Freezer

Claims (4)

[Claims] A refrigeration cycle is formed by a compressor, a condenser, adiabatic expansion means, and an evaporator, and a liquid refrigerant on an inlet side of the adiabatic expansion means and a gas on an outlet side of the evaporator are provided in a liquid line pipe of the refrigeration cycle. In a refrigerating apparatus provided with a gas-liquid heat exchanger that exchanges heat with a refrigerant, a flow of a liquid refrigerant is arranged in parallel with the gas-liquid heat exchanger and the gas-liquid heat exchanger on the liquid refrigerant inlet side of the gas-liquid heat exchanger. A refrigerating apparatus, further comprising switching means for switching control with a bypass circuit connected to the compressor, and a controller for controlling the switching means so that the temperature of gas discharged from the compressor falls within a predetermined range. 2. The refrigeration apparatus according to claim 1, wherein said switching means is a three-way valve. 3. The controller according to claim 1, wherein the controller includes a temperature sensor for detecting a temperature of a gas discharged from the compressor, and controls the switching means in accordance with a value detected by the temperature sensor. 3. The refrigeration apparatus according to 2. 4. The controller according to claim 1, wherein the controller has a superheat degree sensor for the suction gas refrigerant of the compressor, and controls the switching means according to a detection value of the superheat degree sensor. A refrigeration apparatus according to claim 1.