JPH0450510B2 - - 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 temperature of the stored product to rise. This is an extremely undesirable situation. Therefore, when the inner layer blower is stopped, the air volume of the air curtain and the amount of air flowing to the outer layer heat exchanger cannot be secured, so the storage room temperature may rise due to outside air entering, and the outer layer heat exchanger may Because the refrigeration equipment stops (by a normal low-pressure switch) due to the drop in evaporation temperature, it becomes necessary to install a special blower separately.

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. Not only that, but the number of components of the refrigeration equipment has increased, making it more expensive.

(d) Means for solving the problems In order to solve the above problems, the present invention provides
3 and the outer layer 7, a window 4C is provided in a portion located between the inner layer heat exchanger 11 and the outer layer heat exchanger 5, and this window is closed. A damper 4A that can be opened and closed is provided, and during defrosting operation, the refrigerant condensed and liquefied in the inner layer heat exchanger 11 is evaporated and vaporized in the outer layer heat exchanger 5 during cooling operation, and the damper 4A is opened to cool the inner layer. The circulating air that has passed through the heat exchanger 11 is passed through the window 4C to the outer layer 7.
This is a method of operating a low-temperature show case in which the air is introduced into the air, passed through the outer layer heat exchanger 5, and then blown out into the opening 3 to form an air curtain.

(E) Action During defrosting operation, high-pressure refrigerant is transferred to the inner layer heat exchanger 11.
The circulating air is condensed and liquefied by exchanging heat with frost and circulating air at the outer layer heat exchanger 5, and then evaporated by exchanging heat with the circulating air at the outer layer heat exchanger 5, while the circulating air passing through the inner layer 13 is condensed and liquefied. After being heated in the container 11, it flows through the window 4C to the outer layer 7, is cooled in the outer layer heat exchanger 5, and is blown out to the opening 3 in a reduced temperature state.
This opening 3 is formed as an air curtain whose temperature is lower than that of the outside air. That is, during the defrosting operation, 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.

(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 openings 3 for storing and taking out products formed on the entire surface. 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; An inner layer in which a second partition plate 10 made of metal is arranged at an appropriate interval 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. 13, an inner layer air outlet 14 which is arranged in parallel inside the outer layer air inlet 9 at the lower edge of the opening, and an inner layer air outlet 14 which is arranged in parallel inside the outer layer air inlet 9 at the lower edge of the opening; An inner layer suction port 15 facing the inner layer outlet and a storage chamber 17 in which a plurality of shelves 16 are arranged are 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 in 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 in the high pressure gas pipe 24; 31 is a solenoid valve disposed in the low pressure gas pipe 27; 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,
It is connected to the high pressure liquid pipe 25 and the low pressure liquid pipe 27 by a high pressure liquid branch pipe 33, a low pressure liquid branch pipe 34, and a low pressure gas branch pipe 35. 36 is a solenoid valve disposed in the high-pressure liquid branch pipe 33, 37 is a check valve disposed in the low-pressure gas branch pipe 35, and 38 is a pressure reducing unit with a temperature sensing part 38A for supplying the reduced pressure liquid refrigerant to the outer layer heat exchanger 5. It is a valve. 3
Reference numeral 9 denotes a defrosting heat exchanger 20, a recovery pipe for recovering refrigerant from the liquid receiver 21, 40 a solenoid valve installed in the recovery pipe 39, 41 a controller consisting of a timer device, etc.; Solenoid valve 29, 32, 36, 40
open or close signal lines a, b, c, d, for a predetermined period of time.
It is sent from e.

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

The first damper 4A and the second damper 4B are now closed, and as shown in FIG.
are independent of each other. At this time, the inlet port X and outlet port 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 thick line in FIG. 2 is formed, during which the water is condensed and liquefied in the heat exchanger 20, the pressure is reduced in the pressure reducing valve 22, and the water is vaporized in the inner layer heat exchanger. In this cooling operation, even with the inner layer blower 12, the circulating air passing through the inner layer 13 is transferred to the inner layer heat exchanger 11.
It exchanges heat with the low-pressure liquid refrigerant passing through and becomes cooling air, forming a cold air curtain CA as shown by the arrow in FIG. 1 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, as frost builds up on the inner layer heat exchanger 11, the solenoid valve 36 is activated for a predetermined period of time, for example.
It is opened for 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, evaporated in the outer layer heat exchanger 5 which serves as an evaporator, passes through the low pressure gas branch pipe 35, flows to the low pressure gas pipe 27, and is transferred to the inner layer heat exchanger. 11 and returns to the compressor 19, resulting in a cycle shown by the thick line in FIG. This cycle is performed before the end of the cooling operation, that is, immediately before switching from the cooling operation to the defrosting operation, and due to this operation, the outer layer heat exchanger 5 becomes low temperature as well as the inner layer heat exchanger 11, and the outer layer 7 The circulating air passing through the outer layer heat exchanger 5 exchanges heat with the low-pressure liquid refrigerant passing through the outer layer heat exchanger 5, and is maintained at approximately the same or slightly higher temperature than the cooling air circulating through the inner layer 13. Note that during this cooling operation, the operation of the outer layer blower 6 may be stopped.

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 port Y of the flow path switching valve 30 switches to Z, and both the first and second dampers 4A, 4
When B is opened, 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 which becomes the evaporator. The refrigerant (mainly liquid refrigerant) stored in the liquid receiver 21 and the heat exchanger 20 flows through the heat 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. The combined circulating air exchanges heat with the low-pressure liquid refrigerant passing through the outer layer heat exchanger 5 and is cooled. This cooled circulating air
The flow is divided by the damper 4B, and most of it flows from the second window 4D to the inner layer 13, and a part of it passes between the second damper 4B and the heat insulating wall 2, and flows as it is through the outer layer 5, and is sent to the inner layer outlet, respectively. 14 and the outer layer air outlet 8 toward the opening 3, forming air curtains CA and GA in the same way as during cooling operation, and the outer layer air blower 6 and the inner layer air blower 6 from the outer layer suction port 9 and the inner layer suction port 15. The outer layer 7,
The air circulation path shown in FIG. 4 is followed returning to the inner layer 13.

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 port 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 is shown by the thick line in FIG. After a predetermined period of time in this refrigerant recovery cycle, the solenoid valves 29 and 32 open, the solenoid valve 36 closes, and both the first and second dampers 4A and 4B close, resulting in the cooling operation shown in FIGS. 1 and 2. .

According to the operating method of the low-temperature case 1,
During cooling operation, both the first and second dampers 4A, 4B
Since the openings 3 are closed, air curtains CA and GA having different temperatures can be formed in the openings 3. Also, during defrosting operation, both the first and second dampers 4A and 4B
After the hot gas is condensed and liquefied by exchanging heat with frost and circulating air in the inner layer heat exchanger 11, this liquid refrigerant is evaporated and vaporized by exchanging heat with the circulating air in the outer layer heat exchanger 5. In addition, the circulating air in the inner layer 13 is heated by the inner layer heat exchanger 11, flows through the first window 4C to the outer layer 7, and is cooled by the outer layer heat exchanger 5. After the temperature becomes lower than the outside air, the air returns to the inner layer 13 from the second window 4D and is formed as an air curtain CA, so the cold air mass in the storage room 17 is transferred to the outside air using the low temperature air curtain CA, as in the case of cooling operation. It is possible to reduce the range of temperature increase in the storage chamber 17 by protecting the storage chamber 17 from damage.

Furthermore, by opening the first damper 4A toward the inner layer side and opening both second dampers 4B toward the outer layer side, these two dampers can act as directing plates for circulating air, improving the flow characteristics of the circulating air. .

(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. is evaporated by the outer layer heat exchanger during cooling operation, and the circulating air warmed by the inner layer heat exchanger is guided to the outer layer through the window, cooled by the outer layer heat exchanger, and blown out through the opening to cool the storage room. Since a cold air curtain is formed in contact with the air, the effects listed below are produced.

The heated circulating air passing through the inner layer heat exchanger is cooled by the outer layer heat exchanger to a temperature lower than the surrounding air, that is, the outside air, to form an air curtain. 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. Furthermore, there is no need to provide a special blower to ensure the air volume of the air curtain and the flow volume of the outer layer heat exchanger.

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, so the temperature increase width of the storage room can be reduced, so that the storage room remains at the specified level after the recooling operation starts. The time it takes to cool down to the desired temperature (pulldown) is shortened, improving the cooling effect.

Since the refrigerant condensed and liquefied in the inner layer heat exchanger is evaporated in the outer layer heat exchanger, liquid backflow can be prevented without using a defrosting storage tank, and the configuration of the refrigeration system is simplified.

[Brief explanation of drawings]

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. . 2, 3, 5, and 6 are refrigerant circuit diagrams of a refrigeration system for cooling a low-temperature show case. 3... Opening, 4A, 4B... Damper, 5... Heat exchanger for outer layer, 6... Blower for outer layer, 7... Outer layer, 11... Heat exchanger for inner layer, 12... Blower for inner layer, 13 ...Inner layer, CA, GA...Air curtain.

Claims (1)

[Claims] 1. A heat exchanger and a blower are arranged in each of the inner layer and the outer layer, and at least two layers of air curtains are formed by circulating air at the openings during cooling operation of the inner layer heat exchanger. In the low-temperature case, the outer layer heat exchanger is disposed downstream of the inner layer heat exchanger in the air circulation direction, and the first layer partitions the inner layer and the outer layer.
A window that communicates both the inside and outside layers and a damper that can be opened and closed to close this window are provided in the portion of the partition plate located between the inner layer heat exchanger and the outer layer heat exchanger, so that during defrosting operation, the heat exchanger for the inner layer is provided. The refrigerant condensed and liquefied in the exchanger is evaporated and vaporized in the heat exchanger for the outer layer, and the blower for both the inner and outer layers is operated, the damper is opened, and the circulating air that has passed through the heat exchanger for the inner layer is passed through the window and transferred to the outer layer. A method of operating a low-temperature show case, in which air is introduced into the air, passed through an outer layer heat exchanger, and then blown out through an opening to form at least one layer of air curtain. 2. The method of operating a low temperature show case according to claim 1, wherein the damper is opened to the interior side.