Generally speaking, a newly matched air conditioner has a reference model, and the performance indicators of the newly matched air conditioner have a significant impact on the selection of compressors, condensers, and evaporators. The motor rotational speed, air volume, and noise of outdoor and indoor units should first be thoroughly understood.
1. Compressor selection
Choose the compressor type according to the actual situation: piston type, rotor type, scroll type, and power supply specifications. Generally speaking, piston type air conditioners are rarely used in household air conditioners, while T3 type air conditioners generally choose piston type compressors. Currently, most household air conditioners below 3P are rotary compressors. Rotor compressors are divided into single rotor and double rotor compressors. Household air conditioners above 3P generally use scroll compressors. The size of the compressor is selected based on the cooling capacity of the air conditioner. Generally speaking, the customized cooling capacity of the air conditioner is 90% of the monomer capacity of the compressor. The capacity of each displacement (1 cc) of the compressor is approximately 175W.
2. Selective condenser
Long U-tube diameter, internally threaded tube or plain tube. Within the normal range, the smaller the tube diameter, the greater the heat transfer coefficient, and the greater the pressure resistance, but the greater the flow resistance. The heat transfer coefficient of internally twisted tubes is higher than that of plain tubes, and the heat transfer coefficient of different types of internally twisted tubes is also different. The research on small diameter condensers and new types of internally twisted tubes is an important direction. Choose non hydrophilic aluminum foil (ordinary aluminum foil) or hydrophilic aluminum foil, choose whether the sheet type is flat, punched, or corrugated, and choose the sheet pitch
Choose other types of condensers, and efficient condensers include all aluminum condensers, all copper condensers, and so on.
3. Evaporator selection
Long U-tube diameter, internally threaded tube or plain tube. Generally speaking, the long U-tube diameter of the evaporator can be small. Choose hydrophilic aluminum foil. Generally, choose punched sheets, with a minimum sheet spacing of 1.3mm.
4. Estimated refrigerant charge
Referring to the refrigerant charging capacity of the model, under normal conditions, about 60% of the refrigerant in an air conditioner will be in the condenser on the outside of the room, and about 40% of the refrigerant will be in the evaporator on the inside. Based on the reference model, calculate the proportion of increase (or decrease) in the internal volume of the condenser and evaporator, and estimate the approximate refrigerant charge amount. For example, for the reference model, the filling amount is 1000g, while the internal unit remains unchanged. The outdoor unit condenser changes from a single row to 1.5 rows. The estimated filling amount for the side is: 1000 * 0.6 * 1.5, 1000 * 0.4=1300 (g). Generally, the estimated filling amount is slightly more than the final one. This can only be mastered through experience. The estimate can only provide a rough estimate.
5. Matching refrigeration system
The following points are for general purposes, and the following data are for reference. "To match the refrigeration conditions, the" increase in refrigerant "in the following countermeasures is only a last resort, and this method should be avoided as much as possible.". Target matching under standard refrigeration conditions:
1) Exhaust temperature target value: 85-90 ℃
If it is higher than the target value, the capillary tube should be shortened, the air volume of the outdoor unit should be increased, or the refrigerant should be added. If it is lower than the target value, the capillary tube will be lengthened to reduce refrigerant. If it is a specially matched high-efficiency refrigeration system, the exhaust temperature is relatively low, generally between 70-80 ℃.
2) Target temperature value in the middle of the condenser: about 45-50 ℃, and target subcooling value: about 5-10 ℃
The minimum temperature at the condenser outlet is 37-38 ℃. If it is too low, the temperature difference with the ambient temperature of 35 ℃ is too small, and the heat exchange is very small
If the temperature in the middle of the condenser is higher than the target value, the capillary tube should be shortened, the air volume of the outdoor unit should be increased, or the condenser should be increased.
If the temperature in the middle of the condenser is lower than the target value, the capillary tube should be lengthened and refrigerant should be added.
3) Target temperature value in the middle of the evaporator: about 8-12 ℃, and target superheat value: about 0-1 ℃
If the temperature value in the middle of the evaporator is higher than the target value, the capillary tube will be lengthened.
If the temperature value in the middle of the evaporator is lower than the target value, shorten the capillary tubes, increase the indoor unit air volume, or increase the evaporator.
If the superheat value of the evaporator is higher than the target value, the capillary tubes will be shortened and the refrigerant will be increased.
If the superheat value of the evaporator is lower than the target value, lengthen the capillary tubes, increase the indoor unit air volume, reduce the refrigerant or increase the evaporator.
4) The return air temperature of the compressor can be 1-2 ℃ higher than the outlet temperature of the evaporator.
If the return gas temperature is higher than the outlet temperature, for example, the outlet temperature is 10 ℃, while the compressor return gas temperature is 20 ℃, this is the reason for the compressor exhaust temperature rise. Therefore, the capillary tube should be shortened or the refrigerant should be increased. If the return air temperature is much lower than the outlet temperature, such as 10 ℃ at the outlet and 5 ℃ at the compressor return air, this is the reason why the compressor exhaust temperature drops. At this time, the refrigerant cannot fully evaporate in the evaporator, resulting in insufficient capacity. Therefore, it is necessary to lengthen the capillary tube or reduce the refrigerant.
5) Under refrigeration overload condition.
If the OLP is activated, the outside air volume should be increased, the refrigerant should increase, and the compressor load should increase. If possible, shorten the capillary tubes, reduce the refrigerant, or increase the condenser.
Ensure that the pressure at the high-pressure side does not exceed 26.5 bar, which corresponds to a temperature of about 65 ℃ in the middle of the condenser.
The compressor exhaust temperature should generally be below 115 ℃, not exceeding 125 ℃. The coil temperature of the compressor motor is about 10 ℃ higher than the exhaust temperature. If the temperature is too high, the coil may burn. When the exhaust temperature is too high, the capillary tube can be shortened or the condenser can be enlarged or the refrigerant can be increased (note that shortening the capillary tube may reduce the capacity under standard operating conditions)
6) OLP (Over Load Protector) action
The overload protector is controlled by both current and temperature.
There are two representations of OLP graphs. When the current is I1, as long as the compressor temperature is less than t1, the OLP of the compressor will not operate. Alternatively, when the compressor temperature is t1 and the compressor current is less than I1, the OLP will not operate.
7) Under the minimum refrigeration condition.
The temperature of the evaporator should not be lower than 0 ℃. When it reaches below 0 ℃, the dehumidifying water attached to the evaporator will start to freeze and cannot be cooled. When ice falls into blocks, the wind turbine will be damaged.
The anti freezing function of the air conditioner stops the compressor from working when the temperature T2 of the evaporator is detected to be lower than a certain temperature value for a continuous period of time.