Technical points of air energy heat pump compressor

Technical points of air energy heat pump compressor

In the actual system design, the rules of heat pump operation must also be followed, so that the function of the heat pump special compressor can be truly utilized. Specifically, the following aspects should be noted:

　　 1. The throttling device must ensure a wide range

　　 Whether it is a split type or an integrated heat pump water heater placed outdoors, its evaporation temperature is very wide. In order to effectively throttle in a wide range, it is recommended not to use a single capillary tube, but to use an expansion valve or multiple sets of capillary tubes to cope with changes in ambient temperature and ensure that there is suction superheat under all operating conditions. At the same time, avoid the direct entry of liquid into the compressor, especially in winter.

　　 2. Observe the phenomenon of liquid hammer and immersion, and assess the risk

For static heating storage heat pump water heaters, "refrigerant migration" is an unavoidable problem: that is, after the compressor stops working, the condenser is in a high water temperature environment, the compressor/evaporator is gradually cooled, and the temperature difference causes the refrigerant to gradually migrate to evaporation And compressor.

　　 The refrigerant "accumulates". When the compressor restarts, the refrigerant accumulated in the evaporator is likely to enter the compressor directly. In other words, the degree of liquid shock in the heat pump water heater is much more serious than that of the air conditioner. This phenomenon has been verified through many experiments. This is also one of the reasons why the heat pump special compressor adopts a super large-capacity arc-shaped accumulator (to relieve liquid hammer and increase suction superheat). Therefore, when developing heat pump water heaters, it is necessary to observe the phenomenon of liquid hammer and immersion and assess the risks. For example, Ariston, Gree and other companies have carried out detailed observations in the development of heat pump water heaters, confirmed the reliability of the system design, and did a professional job.

　　 Three, pay attention to the problem of overheating at the bottom of the compressor

　　 This point is easily overlooked in system design, but it is extremely important. The so-called compressor bottom superheat is defined as: compressor bottom temperature-condensation temperature. If the value is zero or less than zero, the compressor body becomes a "condenser" at this time, and the refrigerant will slowly condense into liquid in the compressor shell and deposit at the bottom of the compressor, which is pumped as "lubricating oil" Each sliding surface of the compressor pump body. Liquid refrigerant has no lubrication function. As a result, the friction couple of the compressor pump body wears out. It is only a matter of time before "cylinder blockage" occurs.

　　 When the compressor is running in winter, if "intake liquid" occurs, the liquid refrigerant entering the compressor will quickly reduce the temperature of the compressor body, and the low ambient temperature will cause the bottom temperature of the compressor to drop relatively low. Since the heat pump water heater needs to produce higher temperature hot water, the condensing temperature is relatively high, and it is easy to happen that the temperature at the bottom of the compressor is lower than the condensing temperature. The system experiment shows that when there is liquid inhalation, when making 55 degrees hot water, the bottom superheat will be less than zero when the ambient temperature is about 5 degrees. The lower the ambient temperature, the more serious.

　　 Ordinary air-conditioning compressors are prone to "motor overheating" when there is suction superheat, especially when running at a high compression ratio. This is exactly what the heat pump dedicated compressor needs to solve. At a high compression ratio, the heat pump dedicated compressor can still operate reliably.

　　Four, the condensing side heat exchange leaves a safety margin

　　 Regardless of the type of heat pump water heater, after long-term operation, the heat exchange effect on the water side (condensing side) will decrease (scaling, loosening, aging, etc.), and the heat exchange temperature difference will increase. Therefore, at the beginning of the design, it is considered how the temperature difference of the condensing side may change in the future, leaving a certain safety margin to ensure that the compressor operates within a safe range for a long time.