Last Updated on January 29, 2024 by Shawn Lee
The products are based on different standards. The interim standards for ultra-low temperature heat pumps are heat pump (chilled water) units for industrial or commercial use and similar purposes.
The difference between commercial and household use is the energy size, about 50KW for commercial use.
The standard for air-cooled heat pumps is: chilled water (heat pump) units for industrial, commercial and similar purposes
Vapor compression cycle chilled water (heat pump) units, chilled water (heat pump) units for household and similar purposes.
It is also distinguished by the size of the cooling capacity. The cooling capacity is less than 50KW for household use, and the cooling capacity greater than 50KW is for commercial use.
Product design conditions are different. The design conditions of the two are different, that is, the design working conditions are different. Let’s take the nominal working conditions as an example to illustrate.
The nominal working condition is the working condition when the rated heating capacity (refrigeration capacity) indicated on the product nameplate is measured. It is generally the most common and commonly used working condition of the unit.
The nominal heating working condition of the low-temperature heat pump, the air side temperature is “-12℃”; the nominal heating working condition of the air-cooled heat pump, the air side temperature is “7℃”. The main design working conditions of low-temperature heat pump heating are below 0℃, while all the design working conditions of air-cooled heat pump heating are above 0℃.
The application scenarios and operation modes of the products are different. Low-temperature heat pumps are used in low ambient temperature scenarios, while air-cooled heat pumps are used in normal temperature scenarios.
The main function of low-temperature heat pumps is heating, and most of them are used in this way; air-cooled heat pumps focus on cooling and heating.
The ends of low-temperature heat pumps are mainly floor heating, radiators, and fan coils; the ends of air-cooled heat pumps are basically fan coils, without floor heating or radiators. The operating characteristics of floor heating and radiators are small flow rates and large temperature differences. The operating characteristics of fan coil units are small temperature difference and large flow rate.
Therefore, the design concepts of low-temperature heat pumps and air-cooled heat pumps are different. The air-cooled heat pump is based on the premise that the end is a fan coil unit. The two devices are too small and the water pump is too large. The operating characteristics of floor heating are not considered, so the traditional air-cooled heat pump The energy-saving advantages of heat pump and floor heating are not obvious.
The core components used are different. The compressor used in the low-temperature heat pump is a special low-temperature jet enthalpy-increasing compressor for the heat pump, while the air-cooled heat pump uses an ordinary compressor.
In addition to the traditional air conditioner compressor, condenser, throttling components, and evaporator, low-temperature heat pumps generally add an intermediate economizer or flash evaporator to provide low-temperature and low-pressure refrigerant “jet” to the “jet enthalpy increasing” compressor.
When the ambient temperature of a general heat pump unit is very low, the evaporation temperature is very low, resulting in a very low evaporation pressure. Therefore, the compressor pressure is low, the refrigerant circulation volume is small, and the heating capacity is very small.
The low-temperature heat pump adds an economizer or flash evaporator, which introduces part of the refrigerant vapor into the compressor, increases the suction pressure, increases the refrigerant circulation volume, and increases the heating capacity.
At the same time, the main refrigerant passing through the economizer or flash evaporator is subcooled, which increases the heat exchange enthalpy difference and also increases the heating capacity. Therefore, it is called “jet enthalpy increase”.