JPH0451750B2 - - 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 a 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 and two layers are formed 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 The operation system of such an open show case is such that during cooling operation, liquid refrigerant is passed through both the inner and outer layer heat exchangers to evaporate and vaporize, and the circulating system passes through the inner and outer layers. While cooling the air and stopping the refrigerant supply to the outer layer heat exchanger during defrosting operation,
In order to cause the hot gas to flow through the inner layer heat exchanger and condense and liquefy it, and to melt the frost on the inner layer heat exchanger through this heat exchange, the following problems occur.

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.

Since the frost that adheres during the cooling operation of the outer layer heat exchanger is melted during the defrosting operation, the temperature of the circulating air passing through the outer layer gradually rises to a temperature that is the same as or slightly higher than the temperature of the outside air.

The present invention aims to solve the above problems.

(d) Means for Solving the Problems In order to solve the above problems, the present invention provides a first partition plate that partitions the inner layer and the outer layer with a window that communicates both the inner and outer layers, and a window that can be opened and closed to close this window. Immediately before defrosting operation, the outer layer heat exchanger as well as the inner layer heat exchanger are cooled, and for defrosting operation, the damper is opened and the circulating air that has passed through the inner layer heat exchanger is cooled. This is a method of operating a low-temperature show case in which the heat exchanger is introduced into the outer layer through a window and passed through a heat exchanger for the outer layer during cooling operation.

(E) Effect The cooling operation of the outer layer heat exchanger is performed before the cooling operation of the inner layer heat exchanger ends, that is, immediately before switching from cooling operation to defrosting operation. Similarly, the heat exchanger for the outer layer also becomes low temperature,
The circulating air passing through the outer layer exchanges heat with the low-pressure liquid refrigerant passing through the outer layer heat exchanger, and is maintained at approximately the same or slightly higher temperature than the cooling air circulating in the inner layer. Defrosting operation of the exchanger is started, and the circulating air that has passed through the inner layer heat exchanger passes through the window and is cooled by the outer layer heat exchanger that is in cooling operation.

(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; 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 outlet 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 X and Z disposed in the high pressure gas pipe 24; 31 is a 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
9 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 valves 29, 32, 36,
40 to the lines a, b,
These are sent from c, d, and 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 - liquid receiver 21 - electromagnetic valve 32 - pressure reducing valve 22 - inner layer heat exchanger 11 serving as evaporator - electromagnetic valve 29 - gas-liquid separator 23 - compressor 19 as shown in bold lines in FIG. During this cycle, it is condensed and liquefied in the heat exchanger 20, depressurized in the pressure reducing valve 22, and evaporated in the inner layer heat exchanger. In this cooling operation,
In the inner layer blower 12, the circulating air passing through the inner layer 13 exchanges heat with the low pressure liquid refrigerant passing through the inner layer heat exchanger 11 and becomes cooling air, creating a cold air curtain CA as shown by the arrow in FIG. 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 is circulated through a cold air curtain at the opening 3 as shown by the arrow in FIG.
Flowing along the outside of CA, under the influence of this cold air curtain, the temperature becomes gradually lower than the outside air surrounding the open case 1, and serves as a protective air curtain GA that prevents contact between the cold air curtain CA and the outside air. act.

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 temperature of the outer layer heat exchanger 5 becomes low as well as the inner layer heat exchanger 11, and the circulating air passing through the outer layer 7 exchanges heat with the low pressure liquid refrigerant passing through the outer layer heat exchanger 5. The cooling air is maintained at approximately the same or slightly higher temperature than the cooling air circulating through the inner layer 13. still,
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 heat exchanger 5 -Gas-liquid separator 23-
Flows into the compressor 19, and during cooling operation, on the other hand, the liquid receiver 2
1 and the refrigerant (mainly liquid refrigerant) stored in the heat exchanger 20 passes through the recovery pipe 39 and the electromagnetic valve 40 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, and becomes a high-pressure liquid refrigerant.
The pressure is reduced by the pressure reducing valve 38, and the refrigerant becomes a low-pressure liquid refrigerant, which is evaporated in the outer layer heat exchanger 5. As the hot gas is condensed and liquefied, the frost adhering to the inner layer heat exchanger 11 is gradually melted, and the inner layer heat exchanger 11 is gradually melted.
The temperature of the circulating air passing through increases gradually. 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 is divided by the second damper 4B, and most of it flows through the second window 4C to the inner layer 13, and a part of it passes between the second damper 4B and the heat insulating wall 2 and the outer layer 5. The flow is from the inner layer outlet 14 and the outer layer outlet 8 to the opening 3, respectively.
The air is blown toward the outer layer 7 and the inner layer 13 from the outer layer suction port 9 and the inner layer suction port 15 by the outer layer blower 6 and the inner layer blower 12, forming air curtains CA and GA in the same way as during cooling operation. Follow the air circulation path shown in Figure 4 to return.

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,
Immediately before the end of the cooling operation, when the amount of frost on the inner layer heat exchanger 11 increases as the cooling operation progresses, reduced pressure liquid refrigerant is supplied to the outer layer heat exchanger 5, which acts as an evaporator. Since the air circulating in the outer layer 7 is evaporated by the heat exchanger 5, it is cooled, and therefore even immediately after switching the inner layer heat exchanger 11 from cooling operation to defrosting operation, the air circulating through the opening 3 is cooled. A cold air curtain can be formed in the storage room 1 after switching to defrosting operation.
7 temperature rise can be prevented.

In addition, during defrosting operation, the air whose temperature has increased after passing through the inner layer heat exchanger 11 flows through the window 4C to the outer layer 7 and is cooled by the outer layer heat exchanger 5, so the opening 3 is always filled with indoor air. An air curtain of cold air with a temperature lower than that of the storage room 17 is formed.
can be constantly cooled.

(f) Effects of the invention The present invention described above produces the effects listed below.

Immediately before the end of the cooling operation before the defrosting operation, the reduced pressure liquid refrigerant is supplied to the outer layer heat exchanger and is evaporated in this outer layer heat exchanger, which acts as an evaporator. As a result, even immediately after switching the inner layer heat exchanger from cooling operation to defrosting operation, a cold air curtain can be continuously formed at the opening, and the operation is switched to defrosting operation. It is possible to prevent a sudden temperature rise in the storage room after the storage room is heated.

During defrosting operation, the air whose temperature has risen after passing through the inner layer heat exchanger flows through the window to the outer layer and is cooled by the outer layer heat exchanger, so the openings are always filled with cold air whose temperature is lower than the inside air. Since an air curtain is formed, the storage room can be constantly cooled, and as a result, an increase in the temperature of stored items can be suppressed.

[Brief explanation of the drawing]

The drawings all show an embodiment of the method of operating a low-temperature show case of the present invention, and FIG. 1 is a longitudinal cross-sectional view of the low-temperature show case when the damper is closed, and FIG. 4 is a longitudinal cross-sectional view of the low-temperature show case when the damper is open. shows. 2, 3, 5, and 6 are refrigerant circuit diagrams of a refrigeration system for cooling a low-temperature show case. 3...Opening, 4A...Damper, 4C...Window, 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 when both the blowers are operated and only the heat exchanger for the inner layer acts as an evaporator during cooling operation, at least two In a low-temperature show case formed by forming a layered air curtain, a first partition plate that partitions an inner layer and an outer layer is provided with a window that communicates both the inner and outer layers, and an openable and closable damper that freely opens and closes the window, When the tamper is blocked, the cooling operation of the inner layer heat exchanger and the operation of both the blowers are continued, and immediately before the end of the cooling operation of the inner layer heat exchanger, the outer layer heat exchanger is also operated as an evaporator. When the damper is open, the inner layer heat exchanger is operated for defrosting, the outer layer heat exchanger is operated for cooling, and at least the inner layer blower is operated to cool the inner layer heat exchanger. A method of operating a low-temperature case in which the air that has passed through the window is guided to the outer layer heat exchanger.