JPH1137616A - Controlling method for refrigerant circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a temperature in a cabinet of a freezer or of a refrigerator not to increase unnecessarily at the time of defrosting operation by further improving a hot gas defrost system in which defrost is performed by permitting a warm refrigerant gas to pass into an evaporator through a circuit bypassing an expansion valve for a predetermined period of time. SOLUTION: A temperature of a refrigerant gas on the suction side of a compressor 11 is detected by a temperature sensor 15 and, in the case where this detected temperature is lower than a defrosting start temperature, an opening degree of an expansion valve 9 is adjusted to a defrost opening degree. This defrost opening degree is set to such an opening degree that a suction pressure of the compressor 11 becomes two to four times higher than that of the compressor 11 at the time of its ordinary operation. When the temperature of the refrigerant gas becomes higher than a defrosting finish temperature in a state that the opening degree of the expansion valve 9 is adjusted to the defrost opening degree, this opening degree is returned to the opening degree at the time of ordinary operation. In the case where the temperature of the refrigerant gas maintains a lower temperature than the defrosting start temperature in a state that the opening degree of the expansion valve 9 is adjusted to the defrost opening degree and a predetermined period of time elapses, the opening degree of the expansion valve 9 is set to a semi-defrost opening degree. This semi-defrost opening degree means that it is smaller than the defrost opening degree and larger than the opening degree of the expansion valve 9 at the time of ordinary operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for defrosting refrigeration or refrigeration equipment and a method for reducing energy consumption when the cooling load becomes extremely small.

[0002]

2. Description of the Related Art A schematic configuration of a refrigeration or refrigeration apparatus has a configuration in which a compressor, a condenser, an expansion valve, an evaporator, and the like are sequentially connected to a refrigerant circuit downstream of a refrigerant flow.

[0003] When the surface temperature of the evaporator becomes 0 ° C or lower, moisture contained in the air contacting this surface condenses and adheres, and frost is formed. When the thickness of the frost increases, the function of the evaporator as a heat exchanger decreases, and the ability of the freezing or refrigeration equipment decreases.

[0004] There are various methods for removing such frost. For example, a method in which a heater is attached near an evaporator and the heater is temporarily energized when defrosting is performed (referred to as a heater method, for example, Japanese Patent Laid-Open Publication No.
No. 9). There is also a method of passing warm refrigerant gas through an evaporator for a predetermined time by a bypass circuit that bypasses an expansion valve (called a hot gas defrost method, for example, JP-A-63-58082).

[0005]

However, the above-mentioned heater system consumes large power and is uneconomical. Also, the hot gas defrost method using a bypass circuit, which is economically superior, also sets a predetermined time required for defrost in advance, and during that time, a warm refrigerant gas is continuously passed. Therefore, the internal temperature of the freezing or refrigeration equipment is unnecessarily increased, and a large amount of power is often consumed in the subsequent cooling operation.

There is also a need to save energy consumption during a time period such as at night when a door of a freezer or a refrigerator having a refrigerant circuit is hardly opened and closed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is intended to improve the conventional hot gas defrosting method and unnecessarily raise the temperature in the refrigerator or refrigeration equipment. Aims to provide no defrosting method.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, an invention according to claim 1 is directed to a refrigeration or refrigeration apparatus constructed by sequentially connecting a compressor, a condenser, an expansion valve, an evaporator, and the like. In the method for controlling a refrigerant circuit in which defrosting of the refrigerant circuit is performed by a warm refrigerant gas, a step of detecting a temperature of the refrigerant gas on a suction side of the compressor by a temperature sensor, and a case where the detected temperature is lower than a defrost start temperature. Opening the expansion valve to a defrost opening such that the suction pressure of the compressor becomes 2 to 4 times the pressure at the time of the normal operation opening; and opening the expansion valve to the defrost opening. A step of returning the expansion valve opening to the original normal operation opening when the temperature detected in the state becomes higher than the defrost end temperature.

The invention according to a second aspect of the present invention is further configured such that, when the detected temperature is maintained at a temperature lower than the defrost start temperature and a predetermined time has elapsed while the opening of the expansion valve is opened, the defrost opening is reduced. 2. The method according to claim 1, further comprising a step of setting a quasi-defrost opening smaller than the normal operation opening.

[0010] Further, the invention of claim 3 controls a refrigerant circuit which enables an energy-saving operation of a refrigerant circuit in a refrigeration or refrigeration equipment constituted by sequentially connecting a compressor, a condenser, an expansion valve, an evaporator and the like. A method of detecting the temperature of the refrigerant gas on the suction side of the compressor with a temperature sensor; monitoring that the detected temperature is within a predetermined narrow temperature range for a predetermined time; When the temperature reaches a predetermined narrow temperature range for a predetermined period of time, the opening degree of the expansion valve is slightly increased from that in the normal operation to reduce the flow path resistance of the refrigerant circuit. And returning the opening of the expansion valve to the original normal operation opening when the change in temperature detected in the state where the opening is reduced to reduce the road resistance is out of the narrow temperature range. How to control the refrigerant circuit It is.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIG.
3 to FIG.

In a refrigerant circuit 1 of a refrigerator according to this embodiment shown in FIG. 1, a compressor 3, a condenser 5, a dryer 7, an electronic expansion valve 9, an evaporator 11, and a liquid reservoir 13 are provided. It has a configuration connected in this order in the downstream direction.

The refrigerant circuit 1 between the evaporator 11 and the liquid reservoir 13 is provided with a temperature sensor 15 for detecting the temperature of the refrigerant flowing through the refrigerant circuit 1, that is, the refrigerant gas on the suction side of the compressor 3. . Further, a control device 17 that controls the valve opening of the electronic expansion valve 9 based on the detected temperature is provided.

As shown in FIG. 2, the opening degree D of the electronic expansion valve 9 is controlled in accordance with the temperature T of the refrigerant gas detected by the temperature sensor 15. That is, the detected temperature T
Is controlled by comparing with a defrost start temperature T1 (for example, −17 ° C.) and a defrost end temperature T2 (for example, 30 ° C.). Here, T2> T1. The valve opening D as a control result includes a normal operation opening D1, a defrost opening D2, and a quasi-defrost opening D3. Here, D2>D3> D1. The defrost opening D2 is set in advance in the design stage so that the suction pressure at the defrost opening D2 becomes 2 to 4 times (for example, 600 kPa) the suction pressure of the compressor 3 at the normal operation opening D1. Keep it.

When defrosting is performed with the valve opening D of the electronic expansion valve 9 set to the defrost opening D2, the condenser 5
By temporarily stopping the operation of the blower fan (not shown), the condensation capacity of the condenser 5 is temporarily reduced.

In FIG. 2, when the thickness of the frost increases, the function of the evaporator 11 as a heat exchanger decreases, the amount of heat exchange between the refrigerant gas and the surroundings decreases, and the temperature T decreases. When the temperature falls below not only the defrost end temperature T2 but also the defrost start temperature T1 (time t0), the valve opening D of the electronic expansion valve 9 changes from the normal operation opening D1 to the defrost opening D2, and starts defrosting.

That is, the refrigerant has a small pressure change in the electronic expansion valve 9, and a warm (for example, 40 ° C.) refrigerant gas which does not cause much vaporization cooling is sent to the evaporator 11. When this state continues, the frost is removed, the function of the evaporator 11 as a heat exchanger returns, and the refrigerant gas starts to exchange heat with the surroundings. Further, when the frost is removed, the temperature T of the refrigerant gas rises, and eventually exceeds the defrost end temperature T2 (time A-t1).
The valve opening D of the electronic expansion valve 9 returns from the defrost opening D2 to the normal operation opening D1 (FIG. 2A).

In the state of the defrosting operation in which the valve opening D of the electronic expansion valve 9 is opened to the defrosting opening D2, it takes time for the frost itself to be melted due to, for example, an abnormally large thickness of the frost. In some cases, the temperature T of the refrigerant gas does not easily increase.

In this case, a problem such as overheating occurs if the heavy load state of the compressor 3 is continued for a long time.
When the defrost operation has passed a predetermined time, for example, 15 minutes (time t1), the defrost opening D2 is stopped, and the valve opening D is reduced to the quasi-defrost opening D3. The quasi-defrost opening D3 is an opening smaller than the defrost opening D2 and larger than the normal operation opening D1, continues the soft defrost operation, and waits until the temperature T of the refrigerant gas exceeds the defrost end temperature T2. It is for. Then, the temperature T rises and exceeds the defrost end temperature T2 (time B
-T1), the valve opening D of the electronic expansion valve 9 returns from the quasi-defrost opening D3 to the normal operation opening D1 (FIG. 2B).

Even when the quasi-defrosting operation performed by closing the valve opening D of the electronic expansion valve 9 to the quasi-defrosting opening D3 for a predetermined period of time, for example, 15 minutes (time t2), the temperature in the refrigerator rises. Since inconveniences such as excessive running occur, the quasi-defrost opening D3 is stopped and the normal operation opening D1 is returned (FIG. 2C).

Further, during normal operation in which the valve opening D of the electronic expansion valve 9 is the normal operation opening D1, the temperature T of the refrigerant gas becomes a predetermined narrow temperature, for example, 1 ° C. or less (time A-t2).
When a predetermined long time, for example, two hours has elapsed (time At-t3), the valve opening D is slightly opened and the energy saving opening D
4, the load on the compressor 3 is reduced by reducing the flow path resistance of the refrigerant, and the energy consumption is reduced (FIG. 2A).
Although not shown, when the energy saving operation is performed and the temperature T of the refrigerant gas changes by 1 ° C. or more in a short time, the valve opening D of the electronic expansion valve 9 becomes the normal operation opening D1. Return.

FIG. 3 shows a flowchart for executing the control as shown in FIG. That is, when the control is started (S1), the temperature T of the refrigerant gas detected by the temperature sensor 15 is monitored (S2), and when this temperature T falls below not only the defrost end temperature T2 but also the defrost start temperature T1. The valve opening D of the electronic expansion valve 9 is opened from the normal operation opening D1 to the defrost opening D2, and defrosting is started (S3).

By this defrost, the temperature T of the refrigerant gas is
Rises and exceeds the defrost end temperature T2 (S4).
Then, the valve opening D of the electronic expansion valve 9 is returned from the defrost opening D2 to the normal operation opening D1 (S5).

In a defrosting operation in which the valve opening D of the electronic expansion valve 9 is opened to the defrost opening D2, the temperature T of the refrigerant gas is maintained at a temperature lower than the defrost end temperature T2 (S4). After a lapse of time, for example, 15 minutes (S7), the defrost opening D2 is stopped and the valve opening D is reduced to the quasi-defrost opening D3 (S8).

Then, in the quasi-defrost operation in which the valve opening D of the electronic expansion valve 9 is reduced to the quasi-defrost opening D3, the process waits until the temperature T of the refrigerant gas exceeds the defrost end temperature T2 (S9). The degree D3 is stopped and the operation returns to the normal operation opening degree D1 (S5).

Also, when the quasi-defrost operation in which the valve opening D of the electronic expansion valve 9 is reduced to the quasi-defrost opening D3 for a predetermined time, for example, 15 minutes (S10), the quasi-defrost opening D3 is stopped. To reduce the valve opening D to the normal operation opening D1 (S5).

As described above, according to this embodiment, the temperature T of the refrigerant gas on the suction side of the compressor 3 is detected, and whether or not this temperature T is lower than the defrost start temperature T1, and the defrost end temperature The necessity of defrosting is detected based on whether it is higher than T2, and the electronic expansion valve 9 is only required for a necessary time.
Is set to the defrost opening degree D2 and the hot gas of the refrigerant is supplied to the evaporator 1
1 so that there is no waste in the defrosting operation. That is, it is possible to prevent the temperature in the refrigerator or the refrigerator from being unnecessarily increased.

Also, it is separately monitored whether or not the fluctuation of the temperature T of the refrigerant gas is within a predetermined narrow range, for example, 1 ° C. or less, for a predetermined long time, for example, more than 2 hours. Considering that it is a time zone such as at night when there is almost no opening and closing of the door of a freezer or a refrigerator provided with a valve opening D, the energy consumption is suppressed by setting the valve opening D to the energy saving opening D4.

[0029]

As described above, claim 1 or claim 2
According to the invention, the necessity of defrosting is detected based on the temperature of the refrigerant gas on the suction side of the compressor, and the expansion valve is defrosted only during the necessary period to provide the hot gas of the refrigerant to the evaporator. As a result, the temperature in the refrigerator or the refrigerator is not unnecessarily increased.

According to the second aspect of the present invention, when a long time is required for defrosting, the valve opening of the expansion valve becomes a quasi-defrost opening, so that a large load state of the compressor does not continue for a long time. Inconvenience such as overheating is avoided.

According to the third aspect of the present invention, energy saving operation can be performed at night or the like when the door of the freezer or the refrigerator is hardly opened and closed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an entire circuit of a refrigeration apparatus that implements a method of controlling a refrigerant circuit according to an embodiment of the present invention.

FIG. 2 is a diagram showing a change in a detected temperature and a change in a valve opening of an expansion valve in FIG. 1;

FIG. 3 is a control flowchart showing the control of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refrigerant circuit 3 Compressor 5 Condenser 7 Dryer 9 Expansion valve 11 Evaporator 13 Reservoir 15 Temperature sensor 17 Controller T1 Defrost start temperature T2 Defrost end temperature D1 Normal operation opening D2 Defrost opening D3 Semi-defrost opening

Claims (3)

[Claims] 1. A method for controlling a refrigerant circuit for performing defrosting of a refrigerant circuit in a refrigeration or refrigeration apparatus configured by sequentially connecting a compressor, a condenser, an expansion valve, an evaporator, and the like, using a warm refrigerant gas, A step of detecting the temperature of the refrigerant gas on the suction side of the compressor by a temperature sensor; and, when the detected temperature is lower than a defrost start temperature, the opening degree of the expansion valve and the suction pressure of the compressor during normal operation. Opening the defrost opening so that it becomes 2 to 4 times the pressure at the time of the temperature, and expanding when the temperature detected with the expansion valve opened to the defrost opening becomes higher than the defrost end temperature. Returning the valve opening to the original normal operation opening. 2. When the detected temperature is maintained at a temperature lower than the defrost start temperature for a predetermined time in a state where the opening of the expansion valve is opened, the detected opening temperature is smaller than the defrost opening and lower than the normal operation opening. 2. The method for controlling a refrigerant circuit according to claim 1, further comprising a step of increasing the quasi-defrost opening. 3. A method for controlling a refrigerant circuit in a refrigeration or refrigeration apparatus, which is configured by sequentially connecting a compressor, a condenser, an expansion valve, an evaporator, and the like, to enable an energy-saving operation of the refrigerant circuit. A process of detecting the temperature of the refrigerant gas on the suction side of the machine with a temperature sensor, a process of monitoring that the detected temperature is within a predetermined narrow temperature range for a predetermined time, and a process of monitoring the detected temperature. A process of reducing the flow path resistance of the refrigerant circuit by slightly increasing the degree of opening of the expansion valve as compared with the normal operation when the temperature of the refrigerant enters a narrow temperature range for a predetermined time, and opening the expansion valve to reduce the flow path resistance. A step of returning the expansion valve opening to the original normal operation opening when a change in the temperature detected in the temperature range deviates from the narrow temperature range. .