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How To Choose The Thermal Expansion Valve Of Air Compressor
Source: | Author:AUWII | time :2020-12-15 | 151 Browse: | Share:
The selection and matching of thermal expansion valves plays an important role in the performance of the entire air compressor operating system. Proper selection of the thermal expansion valve will maximize the use of the evaporator and always match the evaporator to the thermal load.

The selection and matching of thermal expansion valves plays an important role in the performance of the entire air compressor operating system. Proper selection of the thermal expansion valve will maximize the use of the evaporator and always match the evaporator to the thermal load.

Phenomenon when the thermal expansion valve does not match the system

When a mismatch occurs, the refrigerant flow of the system will be more or less, which will result in a situation in which the cooling capacity of the thermal expansion valve is suddenly reduced.

1. When the opening of the thermal expansion valve is too small, the refrigerant supply is insufficient, and there is not enough refrigerant to evaporate in the evaporator, so that the refrigerant evaporates in a manner of flowing in the evaporator tube. Thereafter, no liquid refrigerant evaporates in the evaporator line, only the steam is overheated. Therefore, a considerable number of evaporators fail to fully utilize their efficiency, resulting in insufficient cooling capacity, slow cooling rate, and reduced cooling effect of the air conditioner, which will have a negative impact on system performance.

2. If the opening of the thermal expansion valve is too large, that is, the amount of liquid supplied to the evaporator by the thermal expansion valve is greater than the load of the evaporator, some liquid refrigerant will evaporate in the evaporator and enter the compressor together with the gaseous refrigerant, resulting in Liquid hammer (wet stroke), even cylinder impact accidents, and damage to the compressor. In addition, when the cooling capacity is excessively large, oscillation is caused, and excessive liquid is intermittently supplied to the evaporator, causing the suction pressure of the compressor to fluctuate drastically. At the same time, the opening of the thermal expansion valve is too large, which increases the evaporation temperature, reduces the cooling capacity, increases the power consumption of the compressor, and increases the power consumption.

Regarding the choice of thermal expansion valve, we need to make reference judgment according to the refrigerant type, evaporation temperature range and evaporator superheat load of the refrigeration system. The following points are needed to determine when choosing:

1. Determine the pressure drop of the valve.

The difference between the condensing pressure and the evaporation pressure. The net pressure drop of the valve is obtained by subtracting all other pressure losses from the difference. However, all possible sources of pressure drop should be considered: (1) frictional losses through the refrigerant piping including the condenser and evaporator, and (2) flow through the liquid piping fittings (such as solenoid valves and overdriers) The pressure drop at the time, (3) the pressure drop (rise) caused by the vertical lift (fall) of the electrostatic liquid tube, and (4) the pressure drop across the refrigerant distributor (if a dispenser is used).

2. Select the valve from the cooling capacity reference table for each valve series.

Depending on the designed evaporation temperature and the pressure drop of the available valve, if possible, the valve's cooling capacity should be equal to or slightly greater than the design level. system. For systems with multiple evaporators, each valve should be selected based on the cooling capacity of each evaporator.

3. Determine the type of refrigerant in the system.

4. Determine the evaporation temperature range of the evaporator.

5. Determine if an external balance tube is required.

The pressure drop between the valve outlet and the portion of the temperature pack will determine if an external balance tube is required.

6, cooling capacity.

7. The pressure difference between the inlet and outlet of the thermal expansion valve.

8. Internal or external pressure balancing method.

9, take over the caliber specifications.