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Ordinary Heat Pump Operating Under Low Temperature Why Difficult? Jul 12, 2017

  Ordinary heat pump operating under low temperature why difficult?

  We first said that ordinary heat pump in low temperature conditions, what are the main problems.

  The first is the heating capacity. Compressor suction flow and evaporation temperature is proportional to the lower the ambient temperature, the lower the inspiratory flow, the worse the heating capacity. In addition, when the evaporation temperature is reduced, the motor heat is constant, or so much, while the system mass flow is declining.

  If the evaporation temperature at -5 ℃, the mass flow is 50KG / S, when the evaporation temperature dropped to -30 ℃, the mass flow may be only 20KG / S. At this time the heat of the motor is almost no change, but the flow of refrigerant used to cool the motor is reduced, the corresponding amount of refrigerant per kilogram of refrigerant will increase, so the exhaust temperature will rise. The density of the inspiratory heat will drop, which is equivalent to the fact that the refrigerant flow rate drops more, which is why the lower the temperature the heating capacity will get worse.

  Followed by reliability. Just said the lower the evaporation temperature of the compressor when the suction flow is reduced, this time the exhaust temperature will rise, the compression ratio becomes larger, when the compressor lubricants easily puffed, and then sticky decline, so It will lead to the disc will become serious wear and tear, thus affecting the host of stable and reliable operation.

  There is running width. Any product in the design of a security interval, that is running in this interval is safe, and once beyond the range of this range, there may be accidents. Conventional heat pump compressors are also designed to have a safe operating range, and if they are operated in a lower evaporative temperature environment, a cool down may not work immediately. This is not just a matter of reliability, but a question that can not be used.

  How do low temperature heat pumps solve these problems?

  Low temperature heat pump is able to run at a lower ambient temperature, is to solve the corresponding conventional heat pump encountered several problems - due to low evaporation temperature, suction flow, compression ratio, high exhaust temperature caused by the system Lack of heat, low COP and unstable operation.

  The first is the internal structure design. The lower the evaporation temperature, the greater the compression ratio, and if you want to work at a lower evaporation temperature, the compression ratio is greater. Therefore, the low-temperature heat pump compressor scroll plate design will be larger. May be ordinary heat pump compression ratio is only 2.3 or so, but the low temperature heat pump will do higher. This means that in the case of lower evaporation temperature, low temperature heat pump can get higher efficiency, but also can have a lower evaporation temperature of the working range, to adapt to the larger temperature difference between the working environment.

  Followed by the use of jet enthalpy technology. The enthalpy of the jet is equivalent to the introduction of the refrigerant through the external refrigerant when the evaporation temperature is particularly low, and the branch of the condenser is divided into two streams - all the way to cool the main circuit of the refrigerant, increase the degree of subcooling, The temperature of the heat transfer temperature difference, to enhance the heat; another way to cool the main circuit of the refrigerant, reducing the compression ratio of the scroll. This can reduce the actual suction pressure of the compression chamber by the new pressure injected, and the compression ratio is reduced, so the power consumption, exhaust temperature and power will be significantly reduced. At the same time, the heat will increase, because the heating capacity from the main circuit to increase the degree of subcooling.