JPH0481102B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cooling device such as an air curtain type refrigerating case.

(Prior art) A low-boiling point liquefied refrigerant is injected from an expansion valve into a low-pressure evaporation pipe in an evaporator and evaporated, thereby absorbing a large amount of evaporation heat from the circulating cold air, cooling it, and then compressing it. In air curtain-type refrigeration cases, etc., which are equipped with a cooling device that pressurizes the air to high pressure, cools it in a condenser, liquefies it again, and circulates it, a small amount of outside air always gets mixed into the air curtain. , moisture in the air gradually forms frost on the evaporator, reducing its cooling capacity.

Therefore, it is necessary to remove this frost by some means.

Conventionally, for this purpose, an electric heater was installed upwind of the evaporator's air path, and the circulation of the refrigerant was periodically interrupted, and the electric heater was energized to warm the circulating cold air and melt the frost. Frost is removed using so-called electric defrosting, or the high temperature gas refrigerant on the discharge side of the compressor is periodically circulated to the evaporator to melt and remove frost using the latent heat and sensible heat of the refrigerant gas. , so-called hot gas defrosting is generally practiced.

(Problems to be Solved by the Invention) According to the conventional means described above, during defrosting, cooling is interrupted and the temperature inside the case rises rapidly due to the heat supplied by the electric heater or hot gas. , the quality of stored food deteriorates, electricity is required for defrosting, and after defrosting, normal cold storage operation is required to lower the temperature inside the food case, which has once risen, to the specified temperature. Requires more power than time.

In order to solve these problems, special
Publication No. 178176 discloses that two evaporators are provided in the case, and these are used alternately for cooling, and the frosted evaporators are defrosted by the latent heat of vaporization of the high-temperature refrigerant gas discharged from the compressor. At the same time, the refrigerant gas is liquefied, and after defrosting, the refrigerant gas is passed through the condenser as in a normal cooling cycle, and the evaporator used for cooling is always supplied with completely liquefied refrigerant. However, by not interrupting the cooling inside the case even during defrosting, the above-mentioned drawbacks are eliminated, and the water eluted from the evaporator during defrosting is absorbed by the cooling device due to the heat of the refrigerant. This document describes a system that prevents water from freezing when passing through a low-temperature part of the case, and allows this water to be smoothly discharged out of the case.

However, even in this case, problems such as those listed below are recognized.

(a) Since the air path direction of the cold air circulation system is switched by rotating one blower in the forward and reverse directions, the strength of the wind force varies depending on the shape of the fan of the blower, depending on whether the blower is rotated forward or backward. A difference occurs, and the cooling power of the refrigeration case is not constant.

(b) A circulation cold air passage and a bypass path are formed before and after the partition plates installed at the front and rear parts between the outer box and the inner box.
The work of installing the partition plate and the air passage switching shutter is extremely difficult and troublesome. In addition, the partition plate further narrows the circulating cold air passage, and the cold air passing through the narrow circulating cold air passage is pushed back due to strong resistance of the rectifier at the intake/exhaust port, causing turbulence in the circulating cold air passage.

(c) In order to switch the direction of the air path of the cold air circulation device by rotating one blower in forward and reverse directions, a shutter for switching the air path is required at the upper end of the partition plate. If this shutter were not provided, the cold air pushed back by the strong resistance of the rectifier at the intake and outlet ports would flow into the bypass path from the upper end of the partition plate, countering the flow caused by the blower and weakening the wind force of the blower. .

(d) A switching device for the air passage switching shutter that is linked to the switching of the solenoid valve is required, but this switching device is complicated, prone to failure, and expensive.

(Means for Solving the Problems) According to the present invention, the above problems are solved as follows.

After pressurizing the vaporized refrigerant with a compressor,
It is cooled and liquefied in a condenser, and then sent into an evaporation pipe in an evaporator to evaporate it. At this time, the heat of evaporation is taken from the circulating cold air passed through the evaporator by a blower to cool it, and In air curtain type refrigeration cases, etc., in which the vaporized refrigerant is cooled and liquefied again in the condenser and circulated to the evaporator, the evaporator is arranged in parallel with bent evaporation tubes and defrost tubes, and a large number of these are installed. It consists of two sets, front and rear, connected with fins and equipped with temperature sensors at important points, and located at the lower front and rear of the front and rear cold air circulation passages 4a and 4b between the outer box 1 and the inner box 2 of the case. , respectively, are provided with the front evaporator 12a and the front blower 9a, as well as the rear evaporator 12b and the rear blower 9b, and a short partition plate 3a facing obliquely upward at the front end of the upper surface of the front evaporator 12a, In addition, by providing a short partition plate 3b facing diagonally upward at the rear end of the upper surface of the rear evaporator 12b, front and rear cold air circulation passages are provided above the front and rear partition plates 3a, 3b and the evaporators 12a, 12b, respectively. 4a, 4b are formed, and the front and rear bypass passages 5a, 5b are connected to the front evaporator 12a and the rear evaporator 1.
Immediately before the compressor 2b, front and rear blowers 9a and 9b are provided which can send cold air to the corresponding front and rear evaporators 12a and 12b, respectively, and a high pressure gas pipe 21 connected to the discharge port of the compressor 10 is provided.
is connected to the inlet of the condenser 11 via the main solenoid valve 22a, and connected to the outlet of the condenser 11 through a bypass pipe 23 equipped with a sub-electromagnetic valve 22b, so that the outlet of the condenser 11 is connected to the front and back of the condenser 11, respectively. Partial branch pipe 2
4a, 24b, front and rear evaporators 12a, 1
2b, and connect the outlet of the defrosting pipe 18a of the front evaporator 12a to the evaporating pipe 17b of the rear evaporator 12b through the front connecting pipe 25a and the front electromagnetic valve 26a. The outlet of the defrosting pipe 18b of the rear evaporator 12b is connected to the inlet of the evaporation pipe 17a of the front evaporator 12a via the rear connecting pipe 25b and the rear solenoid valve 26b. The outlets of the evaporation pipes 17a and 17b are connected to the suction port of the compressor 10, and when the temperature detected by the temperature sensor 20 is below a predetermined value, the main solenoid valve 22a is closed and the sub solenoid valve 22b is closed. Open up, compressor 10
and the front and rear evaporators 12a, 12b, open the front solenoid valve 26a and close the rear solenoid valve 26b, and furthermore, when the temperature detected by the temperature sensor 20 becomes equal to or higher than a predetermined value. At this time, the main solenoid valve 22a is opened and the sub solenoid valve 22b is closed, so that the condenser 11 is connected between the compressor 10 and the front and rear evaporators 12a, 12b.
interposed, and the front solenoid valve 26a
is closed, and the rear solenoid valve 26b is opened, and by opening and closing the front and rear solenoid valves 26a and 26b,
When one of the front and rear evaporators 12a and 12b is in the cooling cycle, the refrigerant is caused to flow alternately to the front defrost pipe 18a and the rear evaporator pipe 17b, or to the rear defrost pipe 18b and the front evaporator pipe 17a. Own blower 9a or 9b
while operating the other blower 9a or 9.
b, and one evaporator 12a or 12
When the defrosting of b is completed, the blower 9a or 9b is stopped and the other evaporator 12b is stopped.
Or a cooling device such as an air curtain type refrigerating case, characterized in that an electric circuit is configured to operate the blower 9b or 9a of the air blower 12a.

(Example) Hereinafter, the present invention will be specifically described based on the attached drawings.

1 and 2 show an air curtain type refrigerated frozen food display case equipped with the device of the present invention.

In both figures, 1 is an outer box with a heat insulating structure and an opening on the top, 2 is an inner box with an opening on the top and provided inside the outer box 1. Between the outer box 1 and the inner box 2, their lower ends are Communicating front and rear cold air circulation passages 4
a, 4b. The front and back refer to the left and right sides of both figures, respectively.

At the front and rear of the upper end of the inner box 2, there are provided front and rear suction/discharge ports 7a, 7b facing each other, and an air curtain 8 is formed spanning both the suction/discharge ports 7a, 7b.

Evaporators 12a and 12b are provided at the lower portions of the front and rear cold air circulation passages 4a and 4b, respectively.

At the front end of the upper surface of the front evaporator 12a, there is a short partition plate 3a facing diagonally upward, and at the front end of the upper surface of the front evaporator 12a.
At the rear end of the upper surface, there is a short partition plate 3 facing diagonally upward.
b is provided, so that the front and rear partition plates 3a3
b and above the evaporators 12a, 12b, there is a bypass passage 5 connected to the front and rear cold air circulation passages 4a, 4b.
a and 5b are formed.

Immediately after the front evaporator 12a and the rear evaporator 1
Front and rear blowers 9a and 9b, respectively, which can send cold air to the corresponding front and rear evaporators 12a and 12b are provided immediately in front of the evaporators 2b.

10 is a compressor installed at the lower rear part of the outer box 1;
11 is a condenser installed on the rear surface of the outer box 1, 13
a, 13b are the front and rear evaporators 12a, 1, respectively.
2b is the drainage device.

14a and 14b are front and rear drainage devices 1, respectively.
The refrigerant pipes 15a and 15b, which are bent in a meandering manner for heating the refrigerant pipes 3a and 13b, are heat insulating materials that prevent the front and rear drainage devices 13a and 13b from overcooling, respectively, and 16 is a drain pipe.

As shown in FIG. 3, the front evaporator 12a includes a front evaporation pipe 17a bent in a meandering manner and a defrost pipe 18a bent parallel to the front evaporation pipe 17a, which are arranged in a staggered manner. It is formed by having a large number of fins 19 connected to each other.

The rear evaporator 12b also has a similar rear evaporator pipe 17b.
The defrosting tube 18b is formed with a large number of fins.

Front and rear temperature sensors 20a, 20b are provided at key points of both evaporators 12a, 12b, respectively.

In FIG. 1, the front evaporator 12a is defrosting, the rear evaporator 12b is cooling, the cold air circulation blower 9a of the front evaporator 12a is stopped, and the cold air of the rear evaporator 12a is Circulation blower 9b
is being driven.

In FIG. 2, the front evaporator 12a is being cooled, the rear evaporator 12b is being defrosted, the cold air circulation blower 9a of the front evaporator 12a is being operated, and the rear evaporator 12b is being operated. Cool air circulation blower 9
b is stopped.

FIG. 4 and FIG. 5 are piping diagrams of the apparatus of the present invention, and the double lines in each figure indicate the path through which the refrigerant passes.

4 and 5, the high pressure gas pipe 21 connected to the discharge port of the compressor 10 is connected to the main solenoid valve 2.
By a bypass pipe 23 connected to the inlet of the condenser 11 via 2a and equipped with an injection solenoid valve 22b,
It is connected to the outlet of the condenser 11.

The outlet of the condenser 11 is connected to the front and rear drainage devices 13a and 13a by front and rear branch pipes 24a and 24b, respectively.
After passing through refrigerant pipes 14a and 14b of 13b, it is connected to defrosting pipes 18a and 18b of front and rear evaporators 12a and 12b.

The outlet of the defrosting pipe 18a of the front evaporator 12a is connected to the inlet of the evaporation pipe 17b of the rear evaporator 12b by a front communication pipe 25a, via a front electromagnetic valve 26a and a front expansion valve 27a. There is.

The outlet of the defrosting pipe 18b of the rear evaporator 12b is connected to the evaporation pipe 1 of the front evaporator 12a via the rear solenoid valve 26b and the expansion valve 27b via the rear communication pipe 25b.
It is connected to the entrance of 7a.

The outlets of both evaporation tubes 17a and 17b are connected to each other and connected to the suction port of the compressor 10 through a low pressure gas pipe 28.

1 and 4 show the front evaporator 12a being defrosted and the rear evaporator 12b being cooled. The sub solenoid valve 22b and the front solenoid valve 26a are open, the main solenoid valve 22a and the rear solenoid valve 26b are closed, and the refrigerant circulates as shown by the arrows in FIG.

That is, the refrigerant is transferred from the compressor 10 to the front refrigerant pipe 14.
It circulates as follows: a→front defrosting pipe 18a→front electromagnetic valve 26a→front expansion valve 27a→rear evaporation pipe 17b→compressor 10.

The refrigerant gas, which is gradually brought to a high temperature and high pressure by the compressor 10, passes through the front refrigerant pipe 14a and warms the front drainage device 13a, thereby preventing the water eluted from the front evaporator 12a from freezing.

Thereafter, while passing through the front defrosting pipe 18a, this refrigerant gas dissolves and removes the frost on the front evaporator 12a, and is itself cooled and liquefied.

The air then flows into the evaporation pipe 17b of the rear evaporator 12b through the front electromagnetic valve 26a and the expansion valve 27a and is vaporized, taking away a large amount of vaporization from the surroundings and cooling the circulating air passing through the rear evaporator 12b. Thereafter, it returns to the compressor 10 and circulates as described above.

When the rear evaporator 12b is used for cooling, the front blower 9a is stopped and the rear blower 9
The electric circuit is configured so that b is activated.

Therefore, the cold air flows from the rear suction/discharge port 7b toward the front suction/discharge port 7a through the rear cold air circulation passage 4b, forming an air curtain 8.

The circulating air whose temperature has increased due to mixing with outside air passes through the front bypass passage 5a, returns to the rear evaporator 12b, and circulates to cool the inside of the case.

As defrosting of the front evaporator 12a progresses and the temperature rises to, for example, +5°C, the front temperature sensor 20a detects this and, as shown in FIG. 5, opens the main solenoid valve 22a. As it opens, the sub solenoid valve 2
Close 2b.

Then, the refrigerant gas flows to the condenser 11, where it is liquefied with heat dissipation in the same way as in a normal cooling device, and is then sent to the front defrost pipe 18.
a, completes defrosting, and returns to the compressor 10 as described above.

When defrosting is completed, the rear blower 9b stops and the front blower 9a starts operating.

This prevents the rear evaporator 12 from forming frost during operation.
b is defrosted, and the defrosted front evaporator 12a cools the circulating air.

Note that a part of the airflow passing through the bypass paths 5a and 5b is recirculated 38.

Switching between operating and stopping the front and rear blowers 9a and 9b and switching the opening and closing of the front and rear solenoid valves 26a and 26b can be easily and automatically performed in synchronization using a timer or the like.

FIGS. 6 and 7 are piping diagrams showing other examples of the apparatus of the present invention, and the double lines in both figures indicate the path through which the refrigerant passes.

In FIGS. 6 and 7, a high-pressure gas pipe 21 connected to the discharge port of the compressor 10 is connected to the inlet of the condenser 11, and is connected to the inlet of the condenser 11 through a hot gas manifold 29 by a bypass pipe 23. It is connected to front and rear three-way valves 30a and 30b.

The outlet of the condenser 11 is connected to a refrigerant manifold 33 via a main solenoid valve 31 and a refrigerant pipe 32 .

The outlet of the refrigerant manifold 33 is connected to the front and rear solenoid valves 26a, 26b and the front and rear expansion valves 27a, 27 through front and rear branch refrigerant pipes 34a, 34b, respectively.
b to the inlets of evaporation pipes 17a, 17b of the front and rear evaporators 12a, 12b.

Front and rear bypass refrigerant pipes 35a and 35b are connected to the front and rear branch refrigerant pipes 34a and 34b, respectively, which connect the front side of the front and rear electromagnetic valves 26a and 26b and the rear side of the front and rear expansion valves 27a and 27b. Check valves 36a and 36b are provided in the bypass refrigerant pipes 35a and 35b, respectively.

Low pressure gas pipe 28a coming out from the front evaporation pipe 17a
is connected to the low-pressure gas manifold 37 via the rear three-way valve 30b, and the low-pressure gas pipe 28b exiting from the rear evaporator pipe 17b is connected to the low-pressure gas manifold 37 via the front three-way valve 30a.

The outlet of the low pressure gas manifold 37 is connected to the suction port of the compressor 10 by a low pressure gas pipe 28.

FIG. 6 shows a state in which the front evaporator 12a is defrosting and the rear evaporator 12b is cooling, and the main solenoid valve 3
1 is closed, and both three-way valves 30a and 30b are open as shown by dotted lines. Further, the front solenoid valve 26a is closed, and the rear solenoid valve 26b is open.

At this time, the refrigerant flows as shown in the figure: compressor 10 → bypass pipe 23 → hot gas manifold 29 → rear three-way valve 30b → rear low pressure gas pipe 28a → front evaporation pipe 17a → front check valve 36a → front It circulates from the bypass refrigerant pipe 35a to the front branch refrigerant pipe 34a to the refrigerant manifold 33, and along the way, it warms and defrosts the front evaporator 12a and liquefies itself.

The refrigerant that has liquefied and entered the refrigerant manifold 33 passes through the rear electromagnetic valve 26b and the rear expansion valve 27b, and is evaporated in the rear evaporator 12b.The refrigerant is then cooled by absorbing the heat of vaporization from the circulating air passing through it. do.

Next, the refrigerant is supplied from the rear low pressure gas pipe 28b.
The gas enters the low pressure gas manifold 37 via the front three-way valve 30a, and then returns to the compressor 10 via the low pressure gas pipe 28 for circulation.

In this case, a shutter 6a for operating/stopping the cold air circulation path and the blowers 9a, 9b, and switching the air path,
The opening and closing of 6b is the same as in the case of the piping shown in FIGS. 4 and 5.

When the defrosting of the front evaporator 12a progresses and the temperature rises to, for example, +5°C, the front temperature sensor 20a detects this and opens the main solenoid valve 31, and also opens the front three-way valve. 30a is opened as shown by the dotted line, and the rear three-way valve 30b is closed.

Then, the refrigerant gas passes through the condenser 11, liquefies heat as in a normal cooling device, enters the refrigerant manifold 33, and then enters the open rear solenoid valve 26b.
The cooling effect is performed in the rear evaporator 12b.

On the other hand, since the front electromagnetic valve 26a is closed, the front evaporator 12a does not perform a cooling action.

This state is shown in FIG.

After defrosting is completed, the front blower 9a is operated, the rear blower 9b is stopped, and the front solenoid valve 2 is turned on.
6a and the main solenoid valve 31, close the rear solenoid valve 26b, and switch the front and rear three-way valves 30a and 30b, the rear evaporator 12b that has formed frost during operation will be defrosted and removed, as described above. The defrosted front evaporator 12a cools the circulating cold air.

In addition, operation/stop of each blower 9a, 9b, opening/closing switching of solenoid valves 26a, 26b, and three-way valve 3
As described above, switching between 0a and 30b can be controlled using a timer or the like.

(Effects of the Invention) (a) By switching between the two sets of blowers, the wind force of the cold air passing through the circulating cold air passage and the bypass passage can be kept constant.

(b) It is possible to widen the circulation cold air passage, weaken the resistance of the rectifier at the intake and exhaust ports, and also reduce the amount of short circuit air that is generated by passing through the bypass pipe.
Since the air is sent to the evaporator again by the blower and returned to the cold air circulation passage, turbulence does not occur in the cold air circulation passage, and the refrigerating case can be cooled stably.

(c) While one evaporator is defrosting, the other evaporator performs the cooling action, and as there is no interruption in the cooling action during defrosting, unlike in general refrigeration cases, the inside of the case is always kept at a low temperature. The quality of the food inside the case is maintained extremely well.

(d) Since frequent defrosting is possible, the amount of frost formation is small, so even if the pitch of the fins in the evaporator is made small, the circulation of cold air will not be obstructed by frost formation. Therefore, the evaporator can be made compact, and even if there are two evaporators, the occupied volume is not much different from that of conventional devices of the same type.

(e) Simple configuration and low risk of failure.

[Brief explanation of drawings]

FIG. 1 is a center longitudinal sectional right side view of a frozen food display case equipped with the apparatus of the present invention, showing the rear evaporator during cooling. FIG. 2 shows the front evaporator in FIG. 1 during cooling. FIG. 3 is a front view showing an example of an evaporator having a defrosting tube. FIG. 4 is a piping diagram of the cooling device according to the present invention, which uses an evaporator with a defrosting tube, and shows the initial state of defrosting of the front evaporator. FIG. 5 shows the state of the front evaporator at the final stage of defrosting in FIG. 4. FIG. 6 is a piping diagram of the cooling device according to the present invention, which performs hot gas defrosting, and shows the initial state of defrosting the front evaporator. FIG. 7 shows the state of the front evaporator at the final stage of defrosting in FIG. 6. 1... Outer box, 2... Inner box, 3a, 3b... (front and rear) partition plate, 4a, 4b... (front and rear) cold air circulation passage, 5a, 5b... (front and rear) bypass path,
7a, 7b... (front and rear) suction and exhaust ports, 8... air curtain, 9a, 9b... (front and rear) blower, 1
0... Compressor, 11... Condenser, 12a, 12b
... (front and rear) evaporator, 13a, 13b ... (front and rear) drainage device, 14a, 14b ... (front and rear)
Refrigerant pipes, 15a, 15b... (front and rear) insulation material,
16...Drain pipe, 17a, 17b...(front and rear)
Evaporation pipe, 18a, 18b...(front and rear) defrosting pipe,
19...Fin, 20a, 20b...(front and rear)
Temperature sensor, 21... High pressure gas pipe, 22a...
Main solenoid valve, 22b...Sub solenoid valve, 23...Bypass pipe, 24a, 24b...(front and rear) branch pipe, 2
5a, 25b... (front and rear) connecting pipe, 26a, 2
6b... (front and rear) solenoid valve, 27a, 27b...
(Front and rear) Expansion valve, 28, 28a, 28b...Low pressure gas pipe, 29...Hot gas manifold, 3
0a, 30b... (front and rear) three-way valve, 31... main solenoid valve, 32... refrigerant pipe, 33... refrigerant manifold, 34a, 34b... (front and rear) branch refrigerant pipe, 35a, 35b... ( Front and rear) Bypass refrigerant pipe, 36a, 36b... (Front and rear) Check valve, 37
...Hot gas manifold, 38...Reflux, 3
8... Short circuit air.

Claims (1)

[Scope of Claims] 1. After pressurizing the vaporized refrigerant using a compressor, it is cooled and liquefied in a condenser, and then introduced into an evaporation pipe in an evaporator to evaporate. From the circulating cold air that passes through the
In an air curtain type refrigerating case, etc., which captures the heat of evaporation, cools it, cools the vaporized refrigerant again in the condenser, and circulates it to the evaporator, the evaporator is bent. The tubes and the defrost tubes are arranged in parallel, and these are connected with a large number of fins, and there are two sets, front and rear, equipped with temperature sensors at key points, and between the outer box 1 and the inner box 2 of the case. The front evaporator 12a and the front blower 9a, as well as the rear evaporator 12b and the rear blower 9b are provided at the lower front and back of the front and rear cold air circulation passages 4a and 4b, respectively, and at the front end of the upper surface of the front evaporator 12a, By providing a short partition plate 3a facing diagonally upward and a short partition plate 3b facing diagonally upward at the rear end of the upper surface of the rear evaporator 12b, the front and rear partition plates 3a, 3b and the evaporator Front and rear bypass passages 5a and 5b are formed above the front and rear cold air circulation passages 4a and 4b, respectively, on the upper side of the front and rear cold air circulation passages 12a and 12b.
Immediately before the compressor 2b, front and rear blowers 9a and 9b are provided which can send cold air to the corresponding front and rear evaporators 12a and 12b, respectively, and a high pressure gas pipe 21 connected to the discharge port of the compressor 10 is provided.
is connected to the inlet of the condenser 11 via the main solenoid valve 22a, and connected to the outlet of the condenser 11 through a bypass pipe 23 equipped with a sub-electromagnetic valve 22b, so that the outlet of the condenser 11 is connected to the front and back of the condenser 11, respectively. Partial branch pipe 2
4a, 24b, front and rear evaporators 12a, 1
2b, and connect the outlet of the defrosting pipe 18a of the front evaporator 12a to the evaporating pipe 17b of the rear evaporator 12b through the front connecting pipe 25a and the front electromagnetic valve 26a. The outlet of the defrosting pipe 18b of the rear evaporator 12b is connected to the inlet of the evaporation pipe 17a of the front evaporator 12a via the rear connecting pipe 25b and the rear solenoid valve 26b. The outlets of the evaporation pipes 17a and 17b are connected to the suction port of the compressor 10, and when the temperature detected by the temperature sensor 20 is below a predetermined value, the main solenoid valve 22a is closed and the sub solenoid valve 22b is closed. Open up, compressor 10
and the front and rear evaporators 12a, 12b, open the front solenoid valve 26a and close the rear solenoid valve 26b, and furthermore, when the temperature detected by the temperature sensor 20 becomes equal to or higher than a predetermined value. At this time, the main solenoid valve 22a is opened and the sub solenoid valve 22b is closed, so that the condenser 11 is connected between the compressor 10 and the front and rear evaporators 12a, 12b.
interposed, and the front solenoid valve 26a
is closed, and the rear solenoid valve 26b is opened, and by opening and closing the front and rear solenoid valves 26a and 26b,
When one of the front and rear evaporators 12a and 12b is in the cooling cycle, the refrigerant is caused to flow alternately to the front defrost pipe 18a and the rear evaporator pipe 17b, or to the rear defrost pipe 18b and the front evaporator pipe 17a. Own blower 9a or 9b
while operating the other blower 9a or 9.
b, and one evaporator 12a or 12
When the defrosting of b is completed, the blower 9a or 9b is stopped and the other evaporator 12b is stopped.
Or a cooling device such as an air curtain type refrigerating case, characterized in that an electric circuit is configured to operate the blower 9b or 9a of the air blower 12a.