Composition and workflow of small cold storage system

First，Composition of Small Cold Storage System

As shown in the figure, the figure is a refrigeration device composed of a cold storage, mainly including: refrigeration compressor, air cooler, thermal expansion valve, solenoid valve, pressure relay, time relay, temperature relay, pressure difference relay, defrosting terminal, liquid viewing mirror (wet and dry mirror), oil separator and gas-liquid separator.

Second, the refrigeration system principle of cold storage:

The refrigerant flows to the thermal expansion valve TE through the DX drying filter, and the cut-off valve BM is installed in front of the DX drying filter, so that the drying filter can be easily replaced. In front of each thermal expansion valve TE, an electromagnetic valve EVR is installed, which is controlled by a temperature controller (electronic thermostat is widely used now) KP61. The temperature controller switches the solenoid valve according to the temperature at the temperature sensing bulb F. A check valve NRV is installed on the suction pipeline from the evaporator of the low-temperature storage, which can prevent the refrigerant from flowing back to the evaporator of the low-temperature storage when the compressor stops running.

An evaporation pressure regulator KVP is installed on the suction pipeline from the evaporator of the high temperature storage, which can keep the evaporation pressure at 8~10℃ below the required temperature of the refrigerating room. The pressure controller KP15 is a high-low pressure combined controller, which can prevent the compressor suction pressure from being too low or the exhaust pressure from being too high, thus protecting the refrigeration device.

Third, supporting facilities

The refrigerator door is equipped with anti-condensation heating wire (centralized or independent power supply, voltage 24V), which can effectively ensure that the refrigerator door is not frozen and condensed. Generally, there is a pressure balance window in the combined cold storage, which can effectively prevent the warehouse board from bursting due to the increase of pressure in the warehouse. According to the user's requirements, the air curtain machine for the warehouse door is set up, which can reduce the convection of internal and external air when the warehouse door is opened and reduce the loss of cold energy.

Fourth, the refrigeration system function description

(1) The refrigeration system is an automatic control system. When the temperature drops to the set value, the temperature controller and solenoid valve are closed, the liquid supply of the system stops, and the pressure on the low-pressure side of the system decreases. When the pressure drops to the set value, the pressure controller acts, the compressor control power supply and the air cooler control power supply are cut off, and the refrigeration system stops working.

(2) Automatic startup. After the reservoir temperature rises to the set value, the temperature controller acts, the solenoid valve is energized to open the liquid supply, and the pressure on the low-pressure side in the refrigeration system rises. When the pressure rises to the set value, the pressure controller acts, the compressor and the air cooler control the power supply to turn on, and the refrigeration system starts to operate.

(3) Other functions of the pressure controller. In addition to the above functions, the pressure relay can also play a protective role when the pressure on the high and low pressure sides in the system is too high.

(4) Function of differential pressure controller. The oil pressure gauge of the differential pressure relay can reflect the supply state of lubricating oil (frozen oil) of the compressor, and its differential pressure is the difference between the discharge oil pressure of the oil pump and the suction pressure. Under normal conditions, the difference should be greater than 1.5kg/cm2 (pressure gauge value); When the pressure value is less than 1.5kg/cm2, the differential pressure controller will automatically stop within 60s to avoid the compressor running under poor lubrication.

(5) "Electronic protection" function. When the compressor is a semi-closed compressor, the motor coil is located at the low-pressure side. Under normal circumstances, the heat generated by the coil operation is cooled by the low-pressure working medium gas. When the coil heat increases for some reason and cannot be cooled well, the coil heat will increase cumulatively, and the coil will be burned in severe cases. "Electronic protection" can effectively ensure that the motor runs under normal temperature rise.

(6) Function of water flow relay. The water flow relay ensures that the water cooling unit runs in the water state. If the cooling water does not flow in the pipe or the water flow is insufficient, the water flow relay is in the off state and the compressor cannot run.

(7) Crankshaft heating wires are arranged in the compressor crankcase. When the compressor works, the heating pipe stops working; When the compressor stops working, the heating pipe works. Crankshaft heating wire raises the temperature in the crankcase and evaporates the working medium in the mixed liquid into gas, thus ensuring the purity and liquid level of the frozen oil. When the compressor is running, it ensures good lubrication among the moving parts.