JPS6311581B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration system equipped with two coolers.
Another object is to reduce the number of times of defrosting by making the refrigerant evaporation temperature on the air inlet side of the second cooler higher than that on the air outlet side.

Figure 1 shows a commonly used flat refrigerating case 1, the main body of which is composed of a heat insulating wall 3 with an opening 2 for storing and taking out products on the top surface, with an appropriate distance from the inner wall of the heat insulating wall. metal partition plate 4
a cold air passage 8 in which plate-fin type first and second coolers 5 and 6 and an axial flow blower 7 are installed; a storage chamber 9; It forms both blowout and suction ports 10 and 11 that open in different directions, and also has a machine room 12 at the bottom of the main body.
A refrigerant compressor 13, a plate fin condenser 14, an axial blower 15, etc., which together with the two coolers constitute a refrigeration system, are installed in the first and second coolers.
The cold air that has been heat-exchanged by the coolers 5 and 6 is forced to circulate through the blower 7 as shown by the arrow, thereby opening the opening 2.
A low-temperature air curtain CA is formed in the storage room 9.
It is for cooling.

The refrigeration system includes a compressor 13- as shown in FIG.
Condenser 14 - Receiver 16 - Pressure sensitive device 17 such as a thermostatic expansion valve equipped with a temperature sensitive section 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 machine 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.
and 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,
The second cooler 6 is arranged on the leeward side of the blower 7, which is composed of a plurality of metal U-shaped tubes 5D that interconnect adjacent ones of these conduits, and the second cooler 6 is arranged to keep 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 6D 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 _6C1 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 6 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 backing into the container 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 resulted in a situation where the air between the fins 6A of the cooler 6 became clogged with 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℃, temperature 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.

24 is 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 are high pressure liquid branch pipes each having an inlet end connected to the flow divider;
17A and 17B are pressure reducing devices such as temperature-type expansion valves equipped with temperature-sensing parts 17A and 17B, respectively, whose inlet ends are connected to this high-pressure liquid branch pipe, 21A is an outlet end of the pressure reducing device 17A, whose inlet end is connected to the outlet end of the pressure reducing device 17A; The outlet end is connected to the second cooler 6
The low-pressure liquid pipe 21B is connected to the most downstream conduit 6C ₆ on the air outlet side of the second cooler 6, and its inlet end is connected to the outlet end of the pressure reducing device 17B, and the outlet end is connected to the most downstream conduit 6C ₃ on the air inlet side of the second cooler 6. The low pressure liquid pipe 25A is the second
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 collector 27 such as a T-shaped pipe that collects 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 this cooler. This is an evaporation pressure regulating valve that maintains the refrigerant evaporation temperature higher than the air outlet side of the refrigerant.

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 conventional refrigeration systems 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 1 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 6. 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. As a result, it is possible to lengthen the time until each fin 6A is blocked by frost without reducing the heat exchange of the second cooler 6, and it is also possible to
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.

Therefore, according to the present invention, the cold air flow is passed from the first cooler 5 with coarse fin pitch to the second cooler 6 with fine fin pitch, and one of the reduced pressure liquid refrigerant is passed from the air outlet side of the second cooler 6 to the second cooler 6 with fine fin pitch. The air flows through the air outlet side of the first cooler 5 and the other air flows from the air inlet side of the second cooler 6 to the air inlet side of the first cooler 5, and the evaporation pressure regulating valve 27 cools both the first and second coolers. Vessels 5, 6
Since the refrigerant evaporation temperature on the air inlet side of the cooler is maintained higher than that on the air outlet side, the refrigerant can be superheated on the air inlet side of both coolers 5 and 6, and its evaporation temperature can be brought close to that of the cold air flow. It is possible to lengthen the time until the second cooler 6 is blocked by frost without reducing heat exchange, and it is possible to equalize the distribution of air to both coolers 5 and 6, thereby increasing the defrosting cycle and reducing the number of defrosts. You can do less.

Although the present invention has been described with reference to an embodiment in which both the coolers 5 and 6 are separated, it should be noted that the same effect can be achieved by using both coolers in which the left and right tube plates are shared.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a commonly used refrigeration case, FIG. 2 is a refrigerant circuit diagram of a conventional refrigeration system, FIG. 3 is a refrigerant circuit diagram showing an embodiment of the refrigeration system of the present invention, and FIG. FIG. 2 is a characteristic diagram showing cold air flow and refrigerant evaporation temperature in the present invention and a conventional refrigeration apparatus. 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, 27
...Evaporation pressure adjustment valve.

Claims (1)

[Claims] 1. Cool air flows from the first cooler with coarse fin pitch to the second cooler with fine fin pitch, each having a plate fin shape, and one side of the reduced pressure liquid refrigerant is passed from the air outlet side of the second cooler to the second cooler with coarse fin pitch. one from the air outlet side of the second cooler, and the other from the air inlet side of the second cooler.
Configure the pipe to flow to the air inlet side of the cooler,
A refrigeration system comprising an evaporation pressure regulating valve that maintains the refrigerant evaporation temperature on the air inlet side of the second cooler to be higher than the refrigerant evaporation temperature on the air outlet side of the air condenser of the second cooler.