JPH0439582B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration system in which two coolers with different fin pitches are arranged side by side, and the object thereof is to provide refrigerant to the air inlet side and outlet side of both the first and second coolers. The objective is to separate and flow the ice to reduce frost formation, and furthermore, use an intermittent control device to lengthen the time until the cooler becomes clogged by frost.

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 - Liquid receiver 16 - Pressure reducing device 17 such as a thermostatic expansion valve equipped with a temperature sensing 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 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.
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,
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 first 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 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 connecting 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 the cold air flow temperature in both the first and second coolers 5 and 6 were experimentally confirmed under the ambient conditions of 1 to 6, and the temperature characteristics shown in FIG. 6 were obtained. In FIG. 6, A is the temperature of the cool 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 refrigerant 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.
The refrigerant exits the cooler 6, enters the second cooler 6 at -40°C, is heated 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.

The refrigeration system includes a first refrigerant circuit A and a second refrigerant circuit B. The first refrigerant circuit A is the compressor 13
A-Condenser 1 ventilated and cooled by blower 15A
4A - Liquid receiver 16A - Pressure reducing device 17A equipped with temperature sensing section 17A - Air outlet side of second cooler 6 - First
Air outlet side of cooler 5 - gas-liquid separator 18A, high pressure gas pipe 19A, high pressure liquid pipe 20A, low pressure liquid pipe 21A
The second refrigerant circuit B includes a compressor 13B, a condenser 14B cooled by air blower 15B, a liquid receiver 16B, and a temperature sensing section 17.
A pressure reducing device 17B equipped with B - the air inlet side of the second cooler 6 - the air inlet side of the first cooler 5 - the gas-liquid separator 18B, a high pressure gas pipe 19B, a high pressure liquid pipe 20B,
The low-pressure liquid pipe 21B, the communication conduit 25B, and the low-pressure gas pipe 22A are also connected in a ring to form a refrigerant cycle shown by the arrows.

FIG. 4 shows the electric circuit of the refrigeration system of the present invention, and shows V
is a three-phase AC power supply, and this power supply has both compressors 13
Electric motors CM ₁ and CM ₂ that drive A and 13B are contacts 52C _1a and 52C _2a of an electromagnetic switch for a compressor, which will be described later.
are connected through each. S ₁ ． S ₂ is the operation switch, DT _b is the reverse contact of the defrost timer, which will be described later.
Between this reverse contact and the operating switch _S2 , there are connected a first operating circuit AO of the first refrigerant circuit A, a second operating circuit BO of the second refrigerant circuit B, and a refrigerant circulation circuit of the second refrigerant circuit B. A supply control device DU to be stopped is connected in parallel. The first operating circuit AO includes a compressor electromagnetic switch 52C ₁ , a compressor thermal switch 51C ₁ ,
It forms a series circuit consisting of a compressor protection temperature regulator 49C ₁ and a high/low pressure switch 63PHL ₁ .
The operating circuit BO includes the electromagnetic switch 52C ₂ for the compressor, the reverse contact DUT _b of the supply control device DU, the temperature controller TH for the storage room of the refrigerating case 1, the thermal switch 51C ₂ for the compressor, and the compressor Machine protection temperature regulator 4
_9C2 and a high/low voltage switch _63PHL2 . In addition, the supply control device DU
is a duty timer motor DUTM such as a cycle timer motor that outputs an output when a predetermined time elapses, for example, 20 minutes after the start of driving, and a
It consists of a reverse contact DUT _b that is open for 10 minutes, and is reset after the reverse contact is closed. DT is a defrosting timer, which includes a defrosting timer motor DTM and a reverse contact DT _b that opens at the output of this timer motor.
and a tangent point DT _a that closes the circuit.
52H is an electromagnetic switch for a defrosting electric heater (not shown) disposed on the air inlet side of the first cooler 5;
RL is the defrost indicator lamp, and both are the operation switch S ₁
and the positive contact DT _a of the defrosting timer DT.

According to such a refrigeration system, the compressor 13A of the first refrigerant circuit A normally has a reverse contact point DT _b of the defrosting timer DT.
Operation is stopped only during defrosting operation when the second
Like the compressor 13A of the first refrigerant circuit A, the compressor 13B of the refrigerant circuit B stops operating during defrosting operation, and also has a storage room temperature controller TH that opens periodically.
Or it is stopped by the reverse contact DUT _b of the supply control device DU. Therefore, the supply of the refrigerant being supplied from the air inlet side to the outlet side of the second cooler 6 is periodically stopped by the supply control device DU in addition to the storage room temperature regulator TH. Both compressors 13A, 1
The operating state of 3B is as shown in the time chart shown in FIG.

The results of experiments conducted on the refrigeration system of the present invention under the same conditions as conventional refrigeration systems will now be explained with reference to FIG.
Incidentally, B'5 and B'6 shown in FIG. The evaporation temperature of the refrigerant flowing through the air outlet side of the container 6, that is, the conduits 6C ₆ to 6C ₄ is -40°C, and the evaporation temperature of the refrigerant flowing through the air outlet side, that is, the conduits 6
The evaporation temperature of the refrigerant flowing through _C3 to _6C1 is -35°C, and the evaporation temperature of the refrigerant flowing through the air outlet side of the first cooler 5, that is, the conduits _5C6 to _5C4 , is -35°C, and the evaporation temperature of the refrigerant that flows through the air inlet side, that is, the conduit _5C3. The evaporation temperature of the refrigerant flowing through ~5C ₁ is -30
℃ (evaporation pressure 0.45 to 0.5 Kg/cm ² G), 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 4℃ on the air inlet side of the second cooler 6.
℃, and the load is large (high cold air flow temperature)
The difference between the refrigerant evaporation temperature and the cold air flow temperature on the air inlet sides of both coolers 5 and 6 could be reduced by obtaining superheat of 5° C. with the refrigerant flowing through each air inlet side.
In addition, by intermittently supplying refrigerant to the air inlet side of the second cooler 6 by the supply control device DU, the temperature of the cold air stream becomes slightly higher as shown by the chain line in Fig. 6. Heat was exchanged on the air outlet sides of vessels 5 and 6. As a result, uniform frost formation on both the first and second coolers 5 and 6 can be achieved without substantially reducing heat exchange in the second cooler 6, and approximately 24 hours have passed since the start of cooling operation. Defrosting operation has started.

As described above, according to the present invention, by using the first and second coolers with different fin pitches and the pipe configuration of both coolers, the time until the blockage due to frost formation is lengthened without reducing the heat exchange of the second cooler. In addition, the supply control device can further lengthen the time until both coolers are blocked, making it possible to perform defrosting operation once a day.

[Brief explanation of drawings]

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. 5 is a time chart showing the operating state of the compressor, and FIG. 6 is a characteristic diagram showing a comparison between the refrigerant evaporation temperature and cold air flow temperature in the refrigeration apparatus of the present invention and a conventional refrigeration system. 5...First cooler, 5A...Fin, 5C ₁ ~
5C ₆ ... Conduit, 6 ... Second cooler, 6A ... Fin, 6C ₁ to 6C ₆ ... Conduit, 17A, 17B...
…Reducing pressure device, 25A, 25B…Connecting conduit, DU
...Supply control device.

Claims (1)

[Claims] 1. A flow of cold air is directed from a first cooler with a coarser fin pitch to a second cooler with a finer fin pitch,
One of the depressurized liquid refrigerants is made to flow from the air outlet side of the second cooler to the air outlet side of the first cooler, and the other one is made to flow from the air inlet side of the second cooler to the air inlet side of the first cooler. 1. A refrigeration system comprising a conduit and a supply control device for intermittently stopping refrigerant supply to the air inlet side of a second cooler.