JPS6311580B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration system in which at least two coolers are installed in parallel, and the object thereof is to uniformly evaporate the refrigerant at different temperatures on the air inlet and outlet sides of both coolers. The objective is to obtain a good frost formation and to lengthen the defrosting cycle.

1 shown in FIG. 1 is a commonly used flat refrigerating case, the main body of which is composed of a heat insulating wall 3 with an opening 2 formed on the top surface for storing and taking out products.
A cold air passage 8 in which a metal partition plate 4 is disposed at an appropriate distance from the inner wall of the heat insulating wall, and plate fin type first and second coolers 5, 6 and an axial flow type blower 7 are installed. , a storage chamber 9, and both air outlet and suction ports 10 and 11 that open in the longitudinal direction of opposite edges of the opening, and a machine room 12 at the bottom of the main body, together with the two coolers, are formed. Refrigerant compressor 13 and plate fin condenser 14 that constitute the refrigeration system
and an axial flow blower 15 etc. are installed, and the cold air that has been heat exchanged by both the first and second coolers 5 and 6 is forcedly circulated by the blower 7 as shown by the arrow, so that low-temperature air is supplied to the opening 2. The storage room 9 is cooled by forming a curtain CA.

The refrigeration system includes a compressor 13- as shown in FIG.
Condenser 14 - Receiver 16 - Pressure reducing device 17 such as a thermostatic expansion valve equipped with a temperature sensor 17 - Second cooler 6 -
The first cooler 5 - gas-liquid separator 18 is connected to the high pressure gas pipe 1
9. The high-pressure liquid pipe 20, the low-pressure liquid pipe 21, and the low-pressure gas pipe 22 are connected in a ring to form a well-known closed circuit, and the refrigerant is circulated as shown by the arrow for compression.
Forms a cycle of condensation, liquefaction, depressurization, and evaporation. Of the two coolers, the first cooler 5 is composed of a large number of plate-like fins 5A with a coarse pitch and good heat conduction.
, both metal tube plates 5B, 5B disposed on both sides of the fins, and a plurality of metal refrigerant conduits 5C ₁ to 5C ₆ passing orthogonally through each of the fins and both tube plates,
It is constructed of a plurality of metal U-shaped tubes 5D that interconnect adjacent conduits among these conduits, and is arranged on the leeward side of the blower 7, and the second cooler 6 keeps the pitch dense (fine). A large number of plate-shaped fins 6A with good heat conduction, two metal tube plates 6B arranged on both sides of the fins, and a plurality of metal refrigerants passing orthogonally through each of the fins and both tube plates. It is composed of conduits 6C ₁ to 6C ₆ and a plurality of metal U-shaped tubes 6B that interconnect adjacent conduits among these conduits, and is arranged on the leeward side of the first cooler 5, and has an air inlet. The most upstream refrigerant conduit 6C ₁ on the side is connected to the most downstream refrigerant conduit 5 on the air outlet side of the first cooler 5.
It is connected to C ₆ via a communication conduit 23. still,
The open arrows indicate the flow direction of cold air passing through the cooler.

Such a refrigeration system is already known in Japanese Utility Model Publication No. 51-15437, and the evaporation temperature of the refrigerant passing through both the first and second coolers 5 and 6 is the same as that from the air outlet side of the second cooler 6 to the first one. The air flows to the air inlet side of the cooler 5, and the temperature becomes high on this air inlet side, and the temperature of the cold air stream becomes higher than the first temperature.
The temperature gradually decreases from the air inlet side of the cooler 5 to the air outlet side of the second cooler 6, and as a result, the cold air flow is precooled and dehumidified in the first cooler 5, and then heated to a predetermined temperature in the second cooler 6. Due to the lowering action, frost can be dispersed to both coolers 5 and 6 to lengthen the defrosting interval, and the refrigerant on the air inlet side of the first cooler 5 is heated and compressed by the action of the pressure reducing device 17. It is known that this method has the effect of preventing liquid from backing up to the machine 13.

However, in such a refrigeration system, the difference between the refrigerant evaporation temperature of the conduit 6C ₁ of the second cooler 6 and the refrigerant evaporation temperature of the conduit 5C ₁ of the first cooler 5 is large;
A larger amount of moisture contained in the supercooled cold air flow adheres as frost on the air inlet side of each fin 5A of the first cooler 5 than on the air inlet side of each fin 6A of the second cooler 6, but as a result, Fin Pitzchi's dense second
This caused a situation in which the space between each fin 6A of the cooler 6 was first blocked by frost. In order to avoid this situation, it is necessary to change the fin pitch of the second cooler 6 to the first cooler 5.
It would be better if it were brought closer to the fin pitch of the second cooler 6, but at the cost of reducing the amount of frost on the second cooler 6, the heat exchange deteriorated, and a new drawback occurred in that the cold air flow could not be lowered to a predetermined temperature. .

That is, the inventor of the present application has installed a first cooler 5 with a width of 155 cm, a length of 30 cm, a height of 11 cm, and a fin pitch of 16 mm in a refrigerating case 1 with a width of 180 cm, and a first cooler 5 with the same width, length, and height as the first cooler. A second cooler 6 with a fin pitch of 10 mm is installed with a spacing of 5 cm, the refrigerant sealed in the refrigeration system is R-502, the refrigerant evaporation temperature in the conduit of the second cooler 6 is -40°C, and the evaporation pressure is of
Set to 0.3Kg/cm ² G, outside temperature 24℃, humidity 80%
The changes in the refrigerant evaporation temperature and cold air flow temperature in both the first and second coolers 5 and 6 were experimentally confirmed under the ambient conditions of , and the temperature characteristics shown in FIG. 4 were obtained. In FIG. 4, A is the temperature of the cold air passing through both the first and second coolers 5 and 6, B6 is the refrigerant evaporation temperature when it is passing through the second cooler 6, and B5 is the temperature of the coolant passing through the first cooler 5. The refrigerant evaporation temperature, diagonal lines C5 and C6, are the areas where the most frost is formed in both the first and second coolers 5 and 6.

According to this experiment, the cold air flow enters the first cooler 5 at -23°C, is lowered by -12°C and enters the second cooler at -35°C.
Coming out of the cooler 6, the refrigerant enters the second cooler 6 at -40°C, is superheated by 5°C and exits the first cooler 5 at -35°C, so the difference between the refrigerant evaporation temperature and the cold air flow temperature is The temperature is 12°C on the air inlet side of the first cooler 5 and 9°C on the air inlet side of the second cooler 6. The air inlet side of the second cooler 6 became clogged with frost approximately 12 to 14 hours after the start of the cooling operation, resulting in the need for defrosting operations approximately twice a day.

The present invention has been made to further reduce the number of times of defrosting, and an embodiment thereof will be described below with reference to FIG. In FIG. 3, the same reference numerals as in FIGS. 1 and 2 are the same.

Reference numeral 24 denotes a flow divider such as a T-shaped pipe that divides the high-pressure liquid refrigerant from the liquid receiver 16 in two directions; 20A and 20B represent high-pressure liquid branch pipes each having an inlet end connected to the flow divider;
17A and 17B are pressure reducing devices such as thermostatic expansion valves whose inlet ends are respectively connected to the high-pressure liquid branch pipes and equipped with temperature-sensing parts 17A and 17B, respectively; The low pressure liquid pipe 21B has its end connected to the most downstream conduit _6C6 on the air outlet side of the second cooler 6, its inlet end connected to the outlet end of the pressure reducing device 17B, and its outlet end connected to the most downstream conduit 6C6 on the air inlet side of the second cooler 6. Low pressure liquid pipe 25A connected to downstream conduit 6C ₃
The most upstream conduit _6C4 and the first conduit on the air outlet side of the cooler 6
A communication conduit 25B connects the most downstream conduit 5C ₆ on the air outlet side of the cooler 5 and the most downstream conduit 6C ₁ on the air inlet side of the second cooler 6 and the most downstream conduit 5C 6 on the air inlet side of the first cooler 5. A connecting conduit that connects conduit 5C ₃ ,
22A and 22B are low-pressure gas branch pipes whose inlet ends are connected to the most upstream conduit 5C ₄ on the air outlet side and the most upstream conduit 5C ₁ on the air inlet side of the first cooler 5, and 26 are both low-pressure gas branch pipes. A collecting device 27 such as a T-shaped pipe that collects the low-pressure gas from the air and guides it to the low-pressure gas pipe 22 is installed in the low-pressure gas branch pipe 22B, and adjusts the refrigerant evaporation temperature on the air inlet side of the second cooler 6 to the low-pressure gas pipe 22. This is an evaporation pressure regulating valve that maintains the refrigerant evaporation temperature higher than the air outlet side.

According to such a refrigeration system, the refrigerant turned into a low-pressure liquid by the pressure reducing device 17A is transferred from the air outlet side of the second cooler 6 to the air outlet side of the first cooler 5 through the pressure reducing device 1.
The refrigerant that has become a low-pressure liquid by 7B flows from the air inlet side of the second cooler 6 to the air inlet side of the first cooler 5, and evaporates into low-pressure gas branch pipes 22A and 22B.
The cycle of passing through, collecting at the collector 26, and returning to the compressor 13 is repeated. At this time, the evaporation temperature of the refrigerant flowing on the air inlet side of the second cooler 6 is controlled by the evaporation pressure regulating valve 27 so as to obtain superheat higher than the evaporation temperature of the refrigerant flowing on the air outlet side of the second cooler 6. There is.

The results of experiments conducted on the refrigeration system of the present invention under the same conditions as the conventional refrigeration system will be explained with reference to FIG. Note that Lo'5 and Lo'6 shown in FIG.
and the evaporation temperature of the refrigerant passing through both the second coolers 5 and 6.

According to this experiment, the refrigerant evaporation temperature on the air outlet side of the second cooler 6 is -40°C, the refrigerant evaporation temperature on the air inlet side is -35°C, and the refrigerant evaporation temperature on the air outlet side of the first cooler 5 is -35℃, the refrigerant evaporation temperature on the air inlet side is -30℃, and the difference between the refrigerant evaporation temperature and the cold air flow temperature is 7℃ on the air inlet side of the first cooler 5, and the refrigerant evaporation temperature on the air inlet side of the second cooler 5. The temperature reached 4℃, and the evaporation pressure regulating valve 2
7, the refrigerant flowing on the air inlet side of the second cooler 6 is superheated by 5° C., thereby not only reducing the difference between the refrigerant evaporation temperature and the cold air flow temperature on the air inlet side of the second cooler 6. , the difference between the refrigerant evaporation temperature and the cold air flow temperature on the air inlet side of the first cooler 5 is obtained by obtaining superheating of 5° C. (evaporation pressure 0.45 to 0.5 Kg/cm ² G) on the air inlet side of the first cooler 5. can be made smaller, and as a result, it is possible to take a longer time until each fin 6A is blocked by frost without reducing the heat exchange of the second cooler 6.
The frosting on both coolers 5 and 6 was made uniform, and defrosting operation was started approximately 20 hours after the start of cooling operation. Note that the first and second coolers 5 and 6 are provided with tube plates 5B,
6B may be made common.

FIG. 5 shows another embodiment of the present invention, which includes two compressors 13A, 13B and condensers 14A, 14, respectively.
B, liquid receiver 16A, 16B, gas-liquid separator 18A,
18B, the refrigerant flows from the air outlet side of the second cooler 6 to the air outlet side of the first cooler 5, and the refrigerant flows from the air inlet side of the second cooler 6 to the air inlet side of the first cooler 5. are configured to form independent cycles. Both compressors 13A, 1
3B has the same amount of work, or the compressor 13B that supplies refrigerant to the air inlets of both coolers 5 and 6 has a smaller amount of work than the other.

According to such a configuration, even if the evaporation temperatures of the refrigerant flowing through the air inlet side and the outlet side of the second cooler 6 are both set to -40°C, the air out of the cool air flow that exchanges heat with both refrigerants is The temperature on the inlet side is higher than the outlet side, and the refrigerant evaporation temperature on the air inlet side is -35℃, which is higher than the air outlet side.
The refrigerant evaporation temperature on the air inlet side of the cooler 5 is -30 DEG C., which is higher than on the air outlet side, and the temperature characteristics shown in FIG. 4 B'5 and B'6 can be obtained. As a result, the refrigerant can be superheated on the air inlet sides of both coolers 5 and 6, and the difference between the refrigerant evaporation temperature and the cold air flow temperature can be reduced on the air inlet sides of both coolers 5 and 6. 2 without impairing the heat exchange of the cooler 6, the time until each fin 6A is blocked by frost is increased,
In addition, it was possible to make the frosting of both the coolers 5 and 6 uniform, and the defrosting cycle could be lengthened to reduce the number of times of defrosting.

As described above, the present invention provides a first
A cooler and a second cooler with fine fin pitch are installed side by side with a gap between them, and the cool air flow is passed from the first cooler to the second cooler, and the refrigerant is passed from the air outlet side of the second cooler to the first cooler. In a refrigeration system that flows to the air inlet side of a container, there are at least two pressure reducing devices that reduce the pressure of high-pressure liquid refrigerant, and one of the reduced pressure refrigerants is passed from the air outlet side of the second cooler to the air outlet side of the first cooler. , and pipes for flowing the other refrigerant from the air inlet side of the second cooler to the air inlet side of the first cooler, respectively, so the evaporation temperature of the refrigerant flowing in the opposite direction to the flow direction of the cold air flow. Since the slope is made higher from the air outlet side to the air inlet side of both coolers, and superheating of the refrigerant can be obtained on the air inlet side, each cooler can be heated without impairing heat exchange in the second cooler. The time required for the fins to become clogged by frost can be lengthened, and the frost formation on both coolers can be made uniform, so that the number of times of defrosting can be reduced.

[Brief explanation of the drawing]

The first is a longitudinal sectional view of a commonly used refrigeration case, the second is a refrigerant circuit diagram showing a conventional refrigeration system, the third is a refrigerant circuit diagram showing an embodiment of the refrigeration system of the present invention, and the fourth is a Characteristic diagram showing cold air flow and refrigerant evaporation temperature in the present invention and conventional refrigeration equipment,
FIG. 5 is a refrigerant circuit diagram showing another embodiment of the present invention. 5...First cooler, 5A...Fin, 5C ₁ ~
5C ₆ ... Conduit, 6 ... Second cooler, 6A ... Fin, 6C ₁ to 6C ₆ ... Conduit, 17A, 17B...
...Pressure reduction device, 25A, 25B...Communication conduit.

Claims (1)

[Claims] 1 A first cooler with a coarser fin pitch and a second cooler with a finer fin pitch are installed side by side with a gap between them, and the cold air flow is transferred from the first cooler to the second cooler, and the refrigerant is transferred to the air of the second cooler. A refrigeration system in which the air flows from the outlet side to the air inlet side of the first cooler includes at least two pressure reducing devices that reduce the pressure of high-pressure liquid refrigerant, and one of the reduced pressure refrigerants flows from the air outlet side of the second cooler to the first cooling device. A refrigeration system comprising, on the air outlet side of the container, pipes for flowing the other refrigerant from the air inlet side of the second cooler to the air inlet side of the first cooler.