JPH0337117B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method of operating a forced circulation type low-temperature show case in which a heat exchanger and a blower are arranged in each of the inner and outer layers.

(b) Prior art Japanese Patent Publication No. 42-24797 discloses that a heat exchanger and an air blower are arranged in each of the inner layer and the outer layer, and the circulating air passing through the inner layer and the outer layer is cooled to form two layers in the opening. An open showcasing configuration forming an air curtain is shown. Both heat exchangers are connected in parallel so that only the inner layer heat exchanger is defrosted with hot gas.

(c) Problems to be solved by the invention In the operating system of such an open case, during cooling operation, liquid refrigerant is passed through both the inner and outer layer heat exchangers to evaporate and vaporize, and then pass through the inner and outer layers. In order to cool the circulating air, and during defrosting operation, the hot gas is passed through the inner layer heat exchanger to condense and liquefy, and this heat exchange melts the frost on the inner layer heat exchanger. arise.

During defrosting operation, in which hot gas is passed through the inner layer heat exchanger to condense and liquefy, there is no cold source to cool the circulating air passing through the inner layer, so the temperature of the circulating air and the air in the storage room rises, causing the stored products to rise. This is an unfavorable situation for both.

During defrosting operation, in order to prevent the liquid refrigerant obtained from the inner layer heat exchanger from backing up to the compressor, a defrost storage tank must be provided to evaporate the liquid refrigerant, making effective use of the liquid refrigerant. Unfortunately, the number of components for refrigeration equipment has increased and it has become more expensive.

(d) Means for solving the problems In order to solve the above problems, the present invention provides a method for solving the problems described above.
3 and the outer layer 7 is provided with a window 4C that communicates both the inner and outer tanks, and a damper 4A that can be opened and closed to close this window. The condensed and liquefied refrigerant is evaporated in the outer layer heat exchanger 5, and the damper 4A is opened to guide the circulating air that has passed through the inner layer heat exchanger 11 to the outer layer 7 through the window 4C. After passing through, the liquid refrigerant is blown out through the opening 3 to form an air curtain CA, and before the defrosting operation ends, the residual liquid refrigerant in the inner layer heat exchanger 11 is continuously transferred to the outer layer heat exchanger 5 during the cooling operation. This is a method of operating a low-temperature show case 1 that performs evaporation.

(e) Effect During defrosting operation, high-pressure refrigerant is transferred to the inner layer heat exchanger 11.
The liquid refrigerant is condensed and liquefied by exchanging heat with the frost and circulating air, and then this liquid refrigerant is evaporated by exchanging heat with the circulating air in the outer layer heat exchanger 5, and the inner layer heat is also transferred before the end of the defrosting operation. The residual liquid refrigerant in the exchanger 11 is continuously evaporated and vaporized in the outer layer heat exchanger 5, while the circulating air passing through the inner layer 13 is heated in the inner layer heat exchanger 11 and then flows into the outer layer 7 through the window 4C. The outer layer heat exchanger 5 cools and lowers the temperature, and then forms an air curtain CA at the opening 3 with a temperature lower than that of the outside air. That is, the inner layer heat exchanger 1
During the defrosting operation including refrigerant recovery in step 1, the outer layer heat exchanger 5 has the function of evaporating the liquid refrigerant, and also has the function of cooling the circulating air heated by the inner layer heat exchanger 11 to lower its temperature. to do.

(F) Embodiment 1 shown in Fig. 1 is an open-type low-temperature case whose main body is composed of an insulating wall 2 with an opening 3 for storing and taking out products on the front. A first damper 4A that opens toward the inner layer side (described later), a second damper 4B that opens toward the outer layer side (described later), and a first damper that is closed by these two dampers, respectively, at an appropriate interval.
and an outer layer 7 in which a heat insulating first partition plate 4 having second windows 4C and 4D is disposed, and a plate fin type outer layer heat exchanger 5 and an axial flow type outer layer blower 6 are disposed. , an outer layer air outlet 8 located along the upper edge of the opening, and an outer layer suction port 9 located along the lower edge of the opening and opposite to the outer layer air outlet; A second partition plate 10 made of metal is arranged at an appropriate distance from the inner wall of the first partition plate, and a plate fin type inner layer heat exchanger 11 and an axial flow type inner layer blower 12 are arranged. an inner layer 13, an inner layer air outlet 14 arranged in parallel at the upper edge of the opening and inside the outer layer air outlet 8, and an inner layer air outlet 14 arranged in parallel inside the outer layer suction port 9 at the lower edge of the opening, An inner layer suction port 15 facing the inner layer outlet and a plurality of shelves 16
A storage chamber 17 is formed. Both the first and second dampers are plate-shaped ones made of a heat insulating material, for example, resin, and the first damper 4A is provided upstream in the flow direction of the circulating air when viewed from the second damper 4B. At this time, it is preferable that the tip thereof abuts on the outer wall of the second partition plate 10, and the second damper 4
It is preferable that the tip of B is in contact with or close to the inner wall of the heat insulating wall 2 when opened. The outer layer heat exchanger is located between the first and second dampers 4A and 4B,
It is arranged in the outer layer 5, and the inner layer heat exchanger 1
1 is disposed at a position on the upstream side in the flow direction of the circulating air when viewed from the first damper 4A. Incidentally, both the first and second dampers are opened and closed by an appropriate drive device using a gear motor, cylinder, or the like.

Reference numeral 18 shown in FIG. 2 is a refrigeration system for cooling the low-temperature case, and includes a refrigerant compressor 19, a water-cooled or air-cooled heat exchanger 20 serving as a condenser, a liquid receiver 21, and a temperature sensing section 22A. A pressure reducing valve 22 such as an expansion valve, an inner layer heat exchanger 11, and a gas-liquid separator 23 are connected in an annular manner by a high pressure gas pipe 24, a high pressure liquid pipe 25, a low pressure liquid pipe 26, and a low pressure gas pipe 27. 2
9 is a solenoid valve disposed on the low pressure gas pipe 27; 30 is a flow path switching valve such as a three-way solenoid valve having one inlet port X and two outlet ports Y and Z disposed on the high pressure gas pipe 24; 31 is a solenoid valve A hot gas bypass pipe having one end connected to the outlet port Z of the flow path switching valve and the other end connected to the low pressure gas pipe 27 between the inner layer heat exchanger 11 and the solenoid valve 29; 32 is a high pressure liquid pipe 25; This is a solenoid valve located at Further, the outer layer heat exchanger is arranged in parallel to the inner layer heat exchanger 11,
High pressure liquid pipe 25 and low pressure liquid pipe 27 are connected by high pressure liquid branch pipe 33, low pressure liquid branch pipe 34 and low pressure gas branch pipe 35.
and is connected to. 36 is a solenoid valve arranged in the high pressure liquid branch pipe 33, 37 is a check valve arranged in the low pressure gas branch pipe 35, and 38 is a pressure reducing unit with a temperature sensing part 38A that supplies reduced pressure liquid refrigerant to the outer layer heat exchanger 5. It is a valve.
39 is a defrosting heat exchanger 20, a recovery pipe for recovering refrigerant from the liquid receiver 21, 40 is a solenoid valve installed in the recovery pipe 39, 41 is a controller consisting of a timer device, etc.; Solenoid valve 29, 32, 36, 4
0 to the lines a, b, c,
It is sent from d and e.

Next, the operating system of the low-temperature show case 1 will be explained.

Now, the first damper 4A and the second damper 4B are closed, and the inner layer 13 and the outer layer 7 are closed as shown in FIG.
are independent of each other. At this time, the inlet boat X and the outlet boat Y of the flow path switching valve 30 communicate with each other, and the solenoid valve 2
9 and solenoid valve 32 are open, and solenoid valves 36 and 40 are closed. When the refrigerant compressor 19 is operated in such a state, the refrigerant flows through the compressor 19 - flow path switching valve 30 -
Heat exchanger 20 serving as a condenser - Liquid receiver 21 - Solenoid valve 32 - Pressure reducing valve 22 - Inner layer heat exchanger 11 serving as an evaporator - Solenoid valve 29 - Gas-liquid separator 23 - Compressor 19
The well-known cycle shown by the bold line in FIG. 2 is formed, during which the heat exchanger 20 condenses and liquefies, the pressure reducing valve 22 reduces the pressure, and the inner layer heat exchanger evaporates and vaporizes. In this cooling operation, even if the inner layer blower 12
The circulating air passing through the inner layer heat exchanger 11 exchanges heat with the low pressure liquid refrigerant passing through and becomes cooling air, forming a cold air curtain as shown by the arrow in Fig. 1.
CA is formed to cool the storage chamber 17. on the other hand,
The circulating air passing through the outer layer 7 by the outer layer blower 6 flows along the outside of the cold air curtain CA at the opening 3 as shown by the arrow in FIG. The temperature gradually becomes lower than the surrounding outside air,
It acts as a protective air curtain GA that prevents the cold air curtain CA from coming into contact with the outside air.

As the cooling operation progresses and frost builds up on the inner layer heat exchanger 11, the solenoid valve 36 opens for a predetermined period of time, for example, 30 seconds, and the liquid is diverted to the high-pressure liquid branch pipe 33. This divided liquid refrigerant is depressurized by the pressure reducing valve 38,
It is evaporated in the outer layer heat exchanger 5, which serves as an evaporator, passes through the low pressure gas branch pipe 35, and flows into the low pressure gas pipe 27.
It joins with the low pressure gas refrigerant that has passed through the inner layer heat exchanger 11 and returns to the compressor 19, resulting in a cycle shown by the thick line in FIG. 3. This cycle is performed before the end of the cooling operation, that is, immediately before switching from the cooling operation to the defrosting operation,
Due to this operation, the outer layer heat exchanger 5 becomes low temperature as well as the inner layer heat exchanger 11, and the circulating air passing through the outer layer 7 is heated with the low pressure liquid refrigerant passing through the outer layer heat exchanger 5. The cooling air is exchanged and maintained at approximately the same or slightly higher temperature than the cooling air circulating through the inner layer 13.

During this cooling operation, when the defrosting start signal is output, the solenoid valves 29 and 32 close, and the solenoid valve 4
0 opens, the outlet boat Y of the flow path switching valve 30 switches to Z, and both the first and second dampers 4A, 4B
When the compressor 19 opens, the hot gas from the compressor 19 is transferred from the flow path switching valve 30 to the hot gas bypass pipe 31 - the inner layer heat exchanger 11 - the check valve 28 - the solenoid valve 36 - the pressure reducing valve 38 - the outer layer heat that becomes the evaporator. The refrigerant (mainly liquid refrigerant) stored in the liquid receiver 21 and the heat exchanger 20 flows through the exchanger 5 - gas-liquid separator 23 - compressor 19, and during cooling operation, the refrigerant (mainly liquid refrigerant) flows through the recovery pipe 39 and the solenoid valve 4.
0 and flows to the gas-liquid separator 23, forming a cycle shown by the thick line in FIG. This cycle is a defrosting operation that includes refrigerant recovery, and the hot gas is condensed and liquefied in the inner layer heat exchanger 11, which serves as a condenser, to become a high-pressure liquid refrigerant, and the pressure is reduced by the pressure reducing valve 38 to become a low-pressure liquid refrigerant, which provides heat for the outer layer. It is evaporated in the exchanger 5. As the hot gas is condensed and liquefied, the frost adhering to the inner heat exchanger 11 is gradually melted, and the temperature of the circulating air passing through the inner heat exchanger 11 is gradually increased. The circulating air that has passed through the inner layer heat exchanger is interrupted from flowing in the inner layer 13 by the first damper 4A, flows through the first window 4C to the outer layer 7, and merges with the outer layer circulating air. This combined circulating air is
It is cooled by exchanging heat with the low-pressure liquid refrigerant passing through the outer layer heat exchanger 5. This cooled circulating air is divided by the second damper 4B, and most of it is distributed by the second damper 4B.
It flows from the window 4C to the inner layer 13, and a part of it flows into the second
It passes between the damper 4B and the heat insulating wall 2, flows through the outer layer 5, and is blown out from the inner layer outlet 14 and the outer layer outlet 8 toward the opening 3, and is connected to the air curtains CA, GA in the same way as in the cooling operation. The air circulation path shown in FIG. 4 is followed from the outer layer suction inlet 9 and the outer layer suction inlet 15 to the outer layer 7 and inner layer 13 by the outer layer blower 6 and the inner layer blower 12, respectively.

When the frost on the inner layer heat exchanger 11 melts as the defrosting operation progresses, the solenoid valve 40 is activated for a certain period of time, for example, 30 seconds.
When the outlet boat Z of the flow path switching valve 30 is switched to Y, the residual refrigerant remaining in the inner layer heat exchanger 11 and the outer layer heat exchanger 5 is removed by the check valve 37 and the gas-liquid separator 23. The heat exchanger 2 is passed through the compressor 19.
0, the refrigerant recovery cycle shown by the bold line in FIG. After a predetermined period of time has elapsed from the start of this refrigerant recovery cycle, the condenser 20 and receiver 2
1 reaches a predetermined pressure, that is, when the cooling operation is in standby state, the solenoid valves 29 and 32 open, and the solenoid valve 3
6 closes, both the first and second dampers 4A, 4
B is closed and the cooling operation shown in FIGS. 1 and 2 is resumed.

According to the operating method of the low-temperature case 1,
During cooling operation, both the first and second dampers 4A, 4B
Since the opening 3 is closed, two layers of air curtains CA and GA having different temperatures can be formed in the opening 3 as in the prior art. Also, during defrosting operation, both the first and second dampers 4A and 4B are opened, and the hot gas is condensed and liquefied by exchanging heat with frost and circulating air in the inner layer heat exchanger 11, and then this liquid refrigerant is used for the outer layer. In addition to exchanging heat with the circulating air in the heat exchanger 5 to form a evaporated low-temperature gas refrigerant,
Before the end of the defrosting operation in which refrigerant supply to the inner layer heat exchanger 11 is stopped, that is, during the refrigerant recovery cycle, the residual liquid refrigerant in the inner layer heat exchanger 11 is continuously evaporated and vaporized in the outer layer heat exchanger 5. Not only can liquid backflow to the compressor 19 be prevented, but the heat exchange time in the outer layer heat exchanger 5 can be extended to cool the circulating air until the cooling operation is restarted, and the inner layer heat exchanger 11 can be cooled. It is possible to lower the temperature and improve the heat exchange start-up characteristics when restarting the cooling operation. In addition, after the circulating air in the inner layer 13 is warmed by the inner layer heat exchanger 11, it is passed through the first window 4C to the outer layer 7. After being cooled by the outer layer heat exchanger 5, it is returned to the inner layer 13 through the second window 4D, so that an air curtain CA having a lower temperature than the outside air can be formed in the opening 3, as in the cooling operation. This storage room 17 protects the cold air mass in the storage room 17 from outside air.
The width of the temperature increase can be reduced.

(F) Effects of the Invention As described above, the present invention provides a method for melting frost on the inner heat exchanger with high-pressure refrigerant during defrosting operation of the inner heat exchanger, and melting the liquid refrigerant obtained in the inner heat exchanger. At the same time, the refrigerant supply to the inner layer heat exchanger is stopped. Before the end of the defrosting operation, the residual liquid refrigerant in the inner layer heat exchanger is continuously evaporated in the outer layer heat exchanger. Circulating air that has been evaporated and warmed by the inner layer heat exchanger is led to the outer layer through the window, cooled by the outer layer heat exchanger, and then blown out through the openings to form an air curtain, resulting in the effects listed below. arise.

The circulating air passing through the inner layer heat exchanger, which has become warm, is cooled to a temperature lower than the surrounding air, that is, the outside air, by the outer layer heat exchanger to form an air curtain.The circulating air is then heated by the inner layer heat exchanger. is not directly blown out into the opening, and an air curtain with a lower temperature than the outside air can be formed at the opening. As a result, the range of temperature increase in the storage room during defrosting is reduced, and the temperature of stored products during defrosting is reduced. It can prevent quality deterioration and deterioration.

During defrosting operation, the heated portion of the circulating air passing through the inner layer heat exchanger is cooled by the outer layer heat exchanger, making it possible to reduce the range of temperature increase in the storage room, so that the temperature in the storage room remains at the specified temperature after cooling operation is restarted. The time it takes for the product to cool down (pulldown) is shortened, improving the cooling effect.

In addition to evaporating the refrigerant condensed and liquefied in the inner layer heat exchanger in the outer layer heat exchanger, the residual liquid refrigerant in the inner layer heat exchanger continues to be used in the outer layer heat exchanger during the refrigerant recovery cycle. Since it is evaporated, the cooling time of the circulating air by the outer layer heat exchanger can be extended, and the temperature of the inner layer heat exchanger can be lowered during this time to improve the startup characteristics of the inner layer heat exchanger when cooling operation is restarted. In addition, liquid back-up can be prevented without using a defrosting storage tank.

[Brief explanation of the drawing]

Each of the drawings shows an embodiment of the method of operating a low-temperature show case of the present invention, and FIG. 1 shows a longitudinal cross-sectional view of the low-temperature show case when the damper is closed, and FIG. 4 shows a longitudinal cross-sectional view of the low-temperature show case when the damper is open. , FIG. 2, FIG. 3, FIG. 5, and FIG. 6 are refrigerant circuit diagrams of a refrigeration system for cooling a low-temperature case. 3... Opening, 4A, 4B... First, second damper, 4C, 4D... First, second window, 5... Heat exchanger for outer layer, 6... Blower for outer layer, 7... Outer layer, 1
1... Inner layer heat exchanger, 12... Inner layer blower,
13...Inner layer, CA, GA...Air curtain.

Claims (1)

[Claims] 1. In a low-temperature case where a heat exchanger and a blower are arranged in each of the inner layer and the outer layer, and when the inner layer heat exchanger is in cooling operation, at least two layers of air curtains are formed by circulating air at the openings. The first partition plate that separates the outer layer is provided with a window that communicates both the inner and outer layers, and a damper that can be opened and closed to close this window. During defrosting operation, the refrigerant condensed and liquefied by the inner layer heat exchanger is transferred to the outer layer. At the same time, the damper is opened and the circulating air that has passed through the inner layer heat exchanger is guided to the outer layer through the window, and after passing through the outer layer heat exchanger, it is blown out to the opening and at least One layer of air curtain is formed, and just before the end of the defrosting operation, the refrigerant supply to the inner layer heat exchanger is stopped, and the residual liquid refrigerant in the inner layer heat exchanger is passed through the outer layer heat exchanger to the compressor. How to operate a low-temperature case that is collected in