Working principle of heat pump hot water machine
[2] Heat pump hot water system realizes heat transfer from low temperature to high temperature by inputting a small amount of high grade energy (such as electric energy). Throughout the year, the heat pump hot water system uninterrupted the air, groundwater, surface water heat "take" out, heating tap water to a certain temperature after the supply of users as domestic hot water use. The outdoor air temperature fluctuates greatly with the seasonal change, while the air temperature inside the underground building fluctuates little. Groundwater water temperature or soil temperature varies with the natural geographical environment, geological conditions and circulation depth. Near the surface, it is a variable temperate zone, and a certain depth below the variable temperate zone is a constant temperature zone. The underground water temperature or soil temperature is not affected by solar radiation. Different latitudes have different depths of thermostatic zone and water temperature ranges from 10 ℃ to 22℃. The temperature increases with the increase of depth, and the increase depends on the geothermal warming rate of different regions and different lithologies. Usually the heat pump consumes 1kW of energy, and the user can get more than 4kW of heat or cooling.
Principle of heat pump hot water system
The basic system scheme of heating water with heat pump has direct heating and indirect heating.
Scheme 1, direct heating mode, is to heat the heat pump condenser directly in the water tank to heat cold water, compared with scheme 2, there is less a heat exchange equipment, so the heat exchange efficiency is relatively larger, the highest water temperature can be reached is also a little higher. The heat storage tank must be combined with the heat pump, which is not suitable for the modification of the existing heat pump. The supply of hot water needs to be powered by a pump, which increases the power consumption and noise of the system to a certain extent.
Scheme 2, indirect heating mode, is to first transfer the heat of the condenser to the intermediate medium - circulating water, and then the circulating water through the coil heating water tank. The system has an additional heat exchanger. Indirect heat transfer has heat loss, which reduces the heating efficiency of the whole system to a certain extent.

Scheme three, the hybrid heating mode, with a pump to force the water in the water tank to circulate through the condenser, enhance the heat transfer efficiency.