How to debug the small cold storage during installation

How to debug the small cold storage during installation

1. Installation technology of expansion valve for small cold storage

　　 1. Check whether the temperature sensor is in good condition before installation;

　　2. The installation position of the expansion valve must be close to the evaporator, and the valve body should be installed vertically, not inclined or upside down;

　　3. When installing, pay attention to keep the liquid in the temperature sensing bag always in the temperature sensing bag, so the temperature sensing bag should be installed lower than the valve body;

　　4. The temperature sensor should be installed as far as possible on the horizontal return pipe of the evaporator outlet, generally it should be more than 1.5M away from the compressor suction port

　　 5. The temperature sensor package cannot be installed on the return pipe with effusion;

　　6. ​​If the evaporator outlet has a gas-liquid exchanger, the temperature sensing package is generally at the evaporator outlet, that is, before the heat exchanger;

　　7. The temperature sensing bag is usually placed on the return air pipe of the evaporator and wrapped tightly against the pipe wall. The contact area should be cleaned;

8. When the diameter of the return air pipe is less than 25MM, the temperature sensing bag can be tied on the top of the return air pipe; when the diameter is greater than 25MM, it can be tied at 45° of the lower side of the return air pipe to prevent oil accumulation at the bottom of the pipe from affecting the temperature sensing bag Temperature effect.

　　 2. Precautions for debugging expansion valve

　　 If the outlet pressure of the expansion valve is too low, the corresponding evaporation pressure and temperature are also too low. However, due to the decrease of the flow entering the evaporator and the decrease of the pressure, the evaporation speed is slowed down, the cooling capacity per unit volume (time) decreases, and the cooling efficiency decreases. On the contrary, if the outlet pressure of the expansion valve is too high, the corresponding evaporation pressure and temperature are also too high. The flow and pressure entering the evaporator are increased,

Due to excessive liquid evaporation, excessive moisture gas (or even liquid) is sucked into the compressor, causing the compressor's wet stroke (liquid hammer), making the compressor unable to work normally, causing a series of bad working conditions and even damaging the compressor. Therefore, expansion The opening degree of the valve should be adjusted according to the current storage temperature, that is, under the pressure corresponding to the storage temperature.

　　 The adjustment of the expansion valve must be carried out carefully and patiently. The pressure adjustment must pass through the evaporator and the storage temperature to produce heat exchange and boiling (evaporate), then enter the compressor suction chamber through the pipeline and reflect it on the pressure gauge. It takes a time process. Every time the expansion valve is adjusted, it generally takes 10 to 15 minutes to stabilize the adjustment pressure of the expansion valve on the suction pressure gauge. The adjustment cannot be performed too hastily. The suction pressure of the compressor is the main parameter for adjusting the pressure of the expansion valve.

　　 It is usually prone to malfunctions such as clogging of the filter and leakage of the temperature sensing agent. The adjustment response is not sensitive, the adjustment is out of control or cannot be adjusted. When frosting occurs at the inlet of the expansion valve (or the valve cover is also frosted), the temperature of the inlet pipe is lower than normal temperature, or even condensation; the suction pressure of the compressor is lower than the corresponding pressure at the storage temperature, and the machine operating temperature And the exhaust temperature is high, the cooling temperature drops slowly or does not drop, mostly because the filter of the expansion valve is blocked, or the fault is blocked by dirty and ice.

　　 Three, expansion valve debugging technology

　　1. The temperature of the evaporator outlet should be measured by a thermometer or the suction pressure should be used to check the superheat;

2. When the expansion valve is adjusted to a low degree of overheating (liquid supply is too large), the adjusting rod should be rotated half a turn or one turn clockwise (that is, increase the spring force and reduce the valve opening) to reduce the refrigerant flow; The number of turns of the thread should not be too many (one turn of the adjusting rod thread, the superheat will change about 1-2°).

　　 3. Expansion valve adjustment experience: Turn the adjusting rod thread to change the valve opening, so that frost or dew can form just outside the evaporator return pipe. For the refrigeration device with the evaporation temperature below 0 degrees, if you touch it with your hands after frosting, you will have a cold feeling of sticking your hands, and the opening degree is appropriate; for the evaporation temperature above 0 degrees, condensation can be seen Situation judgment.

　　4. The correct adjustment of the expansion valve directly affects the cooling effect and energy saving of the cold storage. The cold storage cools slowly, mostly due to improper adjustment of the expansion valve. According to the thermal properties of the refrigerant, the lower the pressure, the lower the corresponding temperature; the higher the pressure, the higher the corresponding temperature. The adjustment of the expansion valve is the most critical. The opening degree of the expansion valve is small, the flow rate of the refrigerant passing through is small, and the pressure is also low; the opening degree of the expansion valve is large, the flow rate of the refrigerant passing through is more, and the pressure is also high.