What is the role of the evaporator in the air energy heat pump？

What is an evaporator? It is a very important part of the refrigeration four parts, low temperature condensate liquid through the evaporator, heat exchange with the outside air, gasification heat absorption, to achieve the effect of refrigeration.

Throttling is one of the four essential processes in the compression refrigeration cycle. The throttling device depresses the pressure of the refrigerant high-pressure liquid coming out of the condenser to reach the evaporation pressure, and adjusts the quantity of the refrigerant liquid entering the evaporator according to the change of the system load. Commonly used throttling devices include manual expansion valve, floating ball expansion valve thermal expansion valve, flow resistance expansion valve (capillary) and electronic expansion valve. The basic principle of the throttling device is that the high-pressure liquid refrigerant is forced to pass through a small cross section and produce a suitable local resistance loss (or along the way loss) after the pressure plummets. At the same time, the refrigerant after throttling becomes a low-pressure and low-temperature state, and part of the liquid refrigerant is vaporized and absorbs the latent heat in the air.

Air energy heat pump evaporator is mainly composed of heating chamber and evaporation chamber. The heating chamber provides the liquid with the heat needed for evaporation, and causes the liquid to boil and vaporize. The evaporation chamber separates the gas and liquid phases completely.

The inside of the evaporator is an interwall heat exchanger with refrigerant and the outside is air or water. The boiling heat transfer in the phase transformation heat is carried out inside the evaporator. Heat pump units of the finned tube is brass + aluminum fin structure way more, aluminum fin on the window or pressed into corrugated shape is better able to strengthen the disturbance airflow, has "ribs" effect to the outer edge of the copper tube, can increase the heat absorption area, with refrigerant in the evaporator is in low pressure low temperature condition, usually work pressure is close to atmospheric pressure.

Air energy heat pump evaporator (finned tube heat exchanger) is the air source directly complete the absorption of heat from the air device. Refrigerant in the evaporator tubes flow absorption of latent heat and boil in the air, but due to the air side heat transfer coefficient is low, in order to satisfy the heat capacity, without any increase in heat transfer temperature difference of the premise condition, only increased heat transfer coefficient, heat transfer area and the installation of the fan to increase air flow speed, to improve the heat transfer ability of the evaporator.

The air energy heat pump evaporator is composed of copper tube + aluminum fin structure, which can improve the heat absorption coefficient and heat transfer capacity of the evaporator. When the four-way valve is opened in the defrosting condition in winter, the evaporator plays the role of condenser. Air energy heat pump evaporator has mature manufacturing technology, fast production and reasonable cost.