[Abstract] The technology of using heat pump to convert the heat energy of air or air-conditioning water into the heat energy of domestic hot water has been well applied in developed countries. This paper introduces the structure and working principle of heat pump, Application example. [Key words] heat pump hot water heat exchanger air conditioner 1 Foreword To protect the natural environment and improve people's living standards, the development and utilization of green energy (non-polluting natural energy, such as solar energy, geothermal, etc.) should be actively promoting the construction of hot water discipline New technology. Discussed in this article is through the heat pump using air or air conditioning water heat as a living hot water heat source technology. 2 heat pump working principle Heat pump work is the use of "air conditioning" principle, the air or water heat transfer out, but with the air conditioner is not the heat emitted to the outside but transferred to the water, to achieve the purpose of heating water, at the same time Create air-conditioners (or cold water) to remove excess moisture in the air. The amount of heat provided by the heat pump during operation is greater than the amount of heat it takes from air or water because the air compressor of the heat pump also converts electrical energy into heat output without contamination of the fuel or gas heating equipment. Heat pump development and application in the United States has more than two decades of history, more than 50,000 systems in use. Applications in Hong Kong have more than a decade of history and are used on multiple systems. In recent years, Shenzhen has also been applied. According to the different sources of energy, heat pump can be divided into water - water series, gas - water series and other types. Figure 1 shows the structure and working process of heat pump with air as energy source. The figure after the refrigerant gasification compressor pressurized by the three-way valve to the pool water heat exchanger (this type of heat pump is generally used for pool water heating and air dehumidification), high temperature gas refrigerant after cooling by pool water and liquefied Re-flow to the collector. The liquid refrigerant evaporates in the low-pressure evaporation coil through the expansion valve. When the refrigerant evaporates, it absorbs a large amount of heat energy and cools the air flowing through the outside. After the refrigerant is gasified, it is pressurized by the compressor and then flows through the three-way valve to the pool water heat exchange Device. This movement cycle cooling or heating. Figure 2 is the air conditioning chilled water as the energy source of heat pump structure and working process. Air-conditioning chilled water into the evaporative heat exchanger, liquid refrigerant in the low-pressure evaporation coil evaporation, absorption of frozen water heat and chilled water temperature will be reduced. The gasified refrigerant is pressurized by the compressor and returned to the condensing heat exchanger, liquefied in the condensing coil to release the heat and heat the domestic water. 3 Engineering Application Figure 3 for the water - water heat pump system diagram. Table 1 for the water - water heat pump parameters. Figure 4 for the water - water heat pump appearance. On the evaporative heat exchanger side, the chilled water is returned to the heat pump via the circulating pump, reducing the temperature by 4 ° C for each cycle. In the evaporation heat exchanger side, hot water is also circulated through the pump into the heat pump, each cycle can make the water temperature increased by 5 ℃. When the hot water tank temperature reaches 65 ℃, the compressor stops working. To increase the efficiency of the heat pump, the first hot water tank is used as the preheating tank, and the heat pump only provides the basic heat load. The second hot water tank with heating elements serves as the last means of heating the water. The volume of the second hot water tank should be calculated according to the amount of heat required by the entire building for heat pump or air conditioning system maintenance. Figure 5 shows the hot water system of the Gold Coast Hotel in Hong Kong. This hotel is a five-star hotel, originally designed with oil-fired hot water boiler, after the Hong Kong Department of Environmental Protection and power sector requirements using heat pumps and volume electric heaters combined heating. Four hot-water pumps are used in the hot water of our hotel. Two of them are installed in tandem, and the original heat exchanger (three for guest rooms and two for kitchen) is used as the second-level hot water storage tank. Total demand by the hotel total heat capacity of 5 sets of electric water heaters. Due to the space constraints of underground equipment, the total heating capacity of 4 heat pumps can not meet the total demand. During the peak water supply, 2-3 electric water heaters need to be put into operation. The hotel has embarked on the second phase of the transformation, and then install the four gas - water series of heat pumps for swimming pool water heating and air dehumidification, and to supplement the shortcomings of domestic hot water heat pump. 4 Conclusion Heat pump as a non-polluting new environmental protection equipment, has been widely used in developed countries and regions, China has joined the WTO and successfully bid for the 2008 Olympic Games, green Olympics, science and technology Olympics as our basic policy has been the International Olympic Committee Will be recognized. In the next seven years of construction, heat pumps in the hot water system and air conditioning system will be widely used.