JPH07218003A - Control system for refrigerator - Google Patents

Abstract

PURPOSE:To increase a continuous capacity control range, to supply chilled water of always stable temperature even if a temperature range of the water is large and to reduce a burden since starting and stopping frequency of a compressor is low by incorporating a reheating circuit in addition to a capacity control only with the compressor. CONSTITUTION:A load 10 is connected to an evaporator 4 via a chilled water tube 12, and chilled water is circulated by a chilled water pump 11. When heat generated from the load 10 is reduced and a water temperature drop is detected by a temperature sensor 7, a controller 6 so transmits as to reduce an operating frequency to a compressor 1. When the compressor is operated at a minimum frequency and the chilled water temperature is further lowered, the controller 6 does not turn ON, OFF the compressor 1, but opens a solenoid valve 9 to supply high temperature refrigerant to the evaporator 4, thereby suppressing cooling capacity, and hence the water temperature drop is prevented, thereby maintaining a set temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus having a refrigerating cycle comprising a compressor whose capacity is variably controlled, a condenser, an electronic expansion valve and an evaporator.

[0002]

2. Description of the Related Art As a conventional technique, in Japanese Patent Laid-Open No. 2-4165, a capacity control of a refrigerating capacity of a refrigerating device is performed by an inverter in order to absorb the heat load of a heating element and cool the chilled water returned to the refrigerating device. A method is described which enables the cold water to be constantly supplied at a stable temperature.

[0003]

In the conventional refrigeration system,
The output frequency of the inverter is controlled based on the return cold water temperature of the cold water returning from the load or the cold water temperature supplied to the load, and the operating frequency of the compressor is controlled according to the value to control the refrigerating capacity of the refrigeration cycle, This is a method of cooling the cold water circulating between the load and the set temperature, but the lower limit of continuous capacity control of the refrigerating capacity by the inverter can be controlled only up to a certain frequency due to the performance of the compressor. The machine is turned on and off. That is, continuous control is performed in the range from the maximum frequency to a certain frequency, but below that, intermittent control is performed.If this intermittent control is performed frequently, the water temperature fluctuates greatly, and hunting occurs, resulting in further compression. Frequent operation / shutdown of the compressor causes reduction in the life of the compressor. As a means to avoid this, there is a method of installing a heat storage tank in the cold water circulation circuit to secure the amount of water held and alleviate fluctuations in the cold water temperature, but if the cold water temperature is considerably higher than the set temperature, the cold water temperature drop time will be long. There is a problem that the temperature does not converge to the set temperature forever.

An object of the present invention is to provide a highly accurate chilled water temperature control without expanding the capacity control of the refrigeration system and for controlling the capacity of the refrigeration system to control the on / off of the compressor in response to fluctuations in cold water temperature. The refrigerating device to be operated, and control to improve the reliability of the compressor.

[0005]

In order to achieve the above-mentioned object, a refrigerating apparatus according to the present invention has a structure described in the claims.

[0006]

According to the present invention, when the heat generation of the load is reduced and the cold water temperature is lowered, the operating frequency of the compressor is lowered in accordance with the cold water temperature. And, even if the compressor is operating at the lowest frequency, if the chilled water temperature drops further, open the solenoid valve in the reheat circuit and let the high-temperature refrigerant flow into the evaporator to reduce the refrigeration capacity. Prevent water temperature drop. When the heat generation of the load increases and the cold water temperature starts to rise, the solenoid valve in the reheat circuit is closed, and the cooling operation is performed by the capacity control based on the original operation frequency.

[0007]

Embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a system diagram (indicated by a chain line) of the refrigerating apparatus of the present embodiment. As shown in FIG. 1, a compressor 1, a condenser 2, an electronic expansion valve 3, which are variably controlled by an operating frequency.
A refrigeration cycle including an evaporator 4 and a refrigerant pipe 5 connecting them, a controller 6 for controlling the operating frequency, a temperature sensor 7 for detecting the cold water temperature, a reheat circuit 8, and a solenoid valve 9. The cold water cooled by the evaporator 4 is sent to the load 10 by the pump 11 and the cold water pipe 12.

FIG. 2 shows an example of the refrigerating capacity characteristic of the present invention. The horizontal axis of the graph shows the operating frequency of the compressor 1, and the vertical axis shows the refrigerating capacity.

Now, in order to cool the load 10, a pump 11,
It is assumed that the cold water is cooled in the refrigerating device using the cold water pipe 12.
When the amount of heat generated by the load 10 decreases, the temperature of the cold water circulating in the cold water pipe 12 decreases, and the temperature sensor 7 detects the information and transmits it to the controller 6. Based on the information obtained from the temperature sensor 7, the controller 6 transmits so as to reduce the operating frequency of the compressor 1, and reduces the refrigerating capacity so that the chilled water temperature maintains the set value. This control is repeated, and even when the operating frequency of the compressor 1 becomes the minimum, the chilled water temperature is still lowered and when the temperature sensor 7 detects it (point A in FIG. 2), the controller 6 causes the solenoid valve 9 to operate. Control to the open state. Since the electromagnetic valve 9 is opened, the reheat circuit 8 becomes effective, and a part of the high-temperature refrigerant discharged from the compressor 1 flows through the reheat circuit 8 and the evaporator. The refrigerating capacity is suppressed by the high-temperature refrigerant flowing to the evaporator 4 (point B in FIG. 2), and as a result, the decrease in cold water temperature is suppressed and the set temperature can be maintained.
In addition, since the compressor 1 is not stopped during this time, the water temperature fluctuation unlike the on-off control does not occur. Further, by controlling the operating frequency of the compressor 1 (between B and C in FIG. 2) when the reheat circuit 8 is effective as shown in FIG. 2, it is possible to perform highly accurate water temperature control even when the capacity is low. Next, when the calorific value of the load 10 increases and the cold water temperature rises and the temperature sensor 7 detects it, the controller 6 transmits to increase the operating frequency of the compressor 1, and at point C in FIG. If the water temperature rises further, the controller 6 closes the solenoid valve 9 and the reheat circuit 8
Is set to the invalid state (point D in FIG. 2), and the control thereafter is performed by the compressor 1
The refrigeration cycle is controlled by the operating frequency of.

[0010]

According to the present invention, when the refrigerating capacity is further reduced even though the compressor is operating at the lowest frequency, a high-temperature refrigerant is sent to the evaporator without stopping the compressor to improve the refrigerating capacity. Since the water temperature fluctuation is suppressed, the fluctuation of the water temperature can be reduced, and the frequent operation / stop of the compressor is avoided, so that the life can be extended.

[Brief description of drawings]

FIG. 1 is a system diagram of a refrigerating apparatus according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of the refrigerating capacity of the refrigerating apparatus according to the embodiment of the present invention.

[Explanation of symbols]

1. A compressor whose capacity is variably controlled according to the operating frequency,
2 ... condenser, 3 ... electronic expansion valve, 4 ... evaporator, 5 ... refrigerant pipe, 6 ... controller, 7 ... temperature sensor, 8 ... reheat circuit,
9 ... Solenoid valve, 10 ... Load, 11 ... Chilled water pump, 12 ... Chilled water piping.

Claims (1)

[Claims] 1. A refrigeration cycle in which a compressor, a condenser, an electronic expansion valve, and an evaporator whose capacity is variably controlled by an operating frequency are sequentially connected by a refrigerant pipe, and the operating frequency is determined to determine the operating frequency. In a refrigerating apparatus comprising control means for controlling the refrigerating capacity of a refrigerating cycle, and always controlling the cold water cooled by the evaporator at a preset temperature, the electronic device is provided via the discharge side of the compressor and the evaporator. When a reheat circuit having an electromagnetic valve connecting to the inlet of the expansion valve is provided and the temperature of the cold water cooled by the evaporator is lowered and the operating frequency of the compressor is minimized, the cold water temperature is lowered. , Opening the solenoid valve of the reheat circuit, reducing the refrigerating capacity in the evaporator by flowing a high-temperature refrigerant into the evaporator, and controlling the cold water temperature to converge to a set value. Control system of the device.