The selection and matching of expansion valve plays an important role in the system characteristics of all air compressors.
The proper selection of expansion valve of air conditioner will greatly apply the evaporator of air conditioner and make the evaporator consistent with the heat load from the beginning to the end.
When the expansion valve of air conditioner cannot match with the system
When the cause of mismatch, the refrigerant flow of the system will be more or less, which will lead to thermal air conditioning expansion valve
The professional ability of refrigeration varies from big to small.
1. When the opening of the expansion valve of the air conditioner is too small, the delivery of refrigerant will be insufficient and there will be no sufficient refrigerant
Evaporates in the air conditioning evaporator, so that the refrigerant evaporates in a circulating manner in the air conditioning evaporator tube.
After that, there is no liquid refrigerant evaporation in the air conditioning evaporator pipe, only the steam is overheated. So,
A large number of air-conditioning evaporators can not make full use of their high efficiency, resulting in the lack of refrigeration professional capacity,
This reduces the expected cooling rate of the central air conditioning system, resulting in a negative effect.
2. If the opening of the expansion valve of the air conditioner is very large, that is, the supply and demand of the expansion valve of the thermal air conditioner is in contradiction with the evaporator of the air conditioner
If the liquid volume exceeds the load of the air conditioner evaporator, some liquid refrigerant will be in the air conditioner evaporator
Evaporation and lifting to the refrigeration unit together with the vapor refrigerant results in liquid hammer (wet schedule),
Even cylinder destructive safety production accidents, and damage to the refrigeration unit. In addition, when cooling
When the professional ability is too high, it will lead to fluctuation and intermittently deliver too much liquid to the air conditioner evaporator,
As a result, the suction pressure of refrigeration unit fluctuates greatly. In addition, the expansion valve of the air conditioner is too open,
This increases the evaporation temperature, reduces the cooling capacity of the air conditioner and increases the output power of the refrigeration unit,
The output power is increased.
How to choose the expansion valve of air conditioner
The selection of the expansion valve of the air conditioner depends on the refrigerant type and evaporation temperature of the refrigeration unit
Level and specification of overheat load of air conditioner evaporator. The following points must be established when choosing:
1. Establish the air pressure of the valve.
The deviation between the cooling pressure and the evaporation pressure. Subtract all other pressures from this deviation
Hazard to obtain the net gas pressure of the valve. However, full consideration should be given to all potential gas pressure sources
(1) Friction hazard when passing through the air conditioning duct including cooling tower and air conditioner evaporator,
(2) Gas pressure when passing through liquid pipe fittings (e.g. automotive relays and air dryers),
(3) The tip discharge liquid tube is perpendicular to the gas pressure (rise) caused by the lift (decrease), and
(4) According to the gas pressure of the refrigerant controller (if the controller is used).
2. Select a range of air conditioning shut-off valves from a range of products.
According to the evaporation temperature and the gas pressure of the available stop valve, if,
The air conditioning cooling capacity of the stop valve should be equal to or slightly larger than the design level of the scheme. System. With
For many air conditioning evaporator systems, each stop valve should be selected according to the refrigeration professional capacity of each air conditioning evaporator.
3. Establish the refrigerant type of the system.
4. Establish the evaporation temperature level of air conditioning evaporator.
5. Be sure to establish whether the outer tube is balanced.
The inlet of the valve and the temperature chamber are attached to a part of the air pressure in the middle, which will determine whether the external balance pipe is necessary.
6. Air conditioning cooling capacity.
7. The pressure difference between the safe passage of the expansion valve and the inlet.
8. Internal or external pressure balance mode.
9. Specification and model connection.