In order to achieve sustainable development, pollution-free renewable energy has become the first choice for human energy. Among the energy consumption of countries all over the world, the heat consumption is the largest. In the process of converting primary energy into thermal energy and then converting it into various forms of energy, a large amount of energy is lost in the form of exhaust heat such as exhaust gas, steam, and low-temperature hot water (below 100 ° C). The development of water source heat pump technology provides a powerful means of utilizing these heat sources. Water source heat pump technology is a low-level thermal energy resource formed by using these exhaust gas energy or solar energy and geothermal energy absorbed in shallow water (such as groundwater, geothermal water, surface water, seawater, etc.) on the surface of the earth, and adopts the principle of heat pump to consume a small amount. Electrical energy, a technology that enables the transfer of low-level thermal energy to high-level thermal energy. Heat pump technology Since 1824, French physicist S Carnot first proposed the theory of thermodynamic cycle, and in 1852, the British Kelvin (LordKelvin) specifically proposed the design idea of ​​heat pump. It has experienced more than a century of development in Russia, Japan, Australia and some European countries. Developed countries have invested a large amount of funds in the development and application of newer and more advanced heat pumps. China's research and development is relatively slow. The research and application of heat pumps began in the 1980s, and some achievements have been made. With the success of Beijing's Olympic bid, the development and research of energy-saving and environmental protection technologies with the theme of green Olympics has received extensive attention from the society. The research team of this paper began to track the development of foreign heat pump technology in 1997 and developed a series of water source heat pumps suitable for the Chinese market. It has achieved good economic and social benefits in engineering applications. Energy-saving principle of water source heat pump The water source heat pump unit is mainly composed of a compressor, an evaporator, a condenser and an expansion valve. The compressor plays the role of compression and conveying circulating working medium from low temperature and low pressure to high temperature and high pressure, and is the heart of the heat pump system; the evaporator evaporates the refrigerant liquid flowing in through the throttle valve to absorb the heat of the cooled object. The purpose of refrigeration; the condenser transfers the heat absorbed from the evaporator together with the heat converted by the compressor's work consumption to the cooling medium to achieve the purpose of heating; the expansion valve acts as a throttling and depressurizing effect on the circulating working medium, and adjusts According to the second law of thermodynamics, the work (electric energy) consumed by the compressor plays a compensating role, so that the circulating working fluid continuously absorbs heat from the low temperature environment and releases heat to the high temperature environment. Engineering application of water source heat pump system, technical and economical water source heat pump of water source heat pump Compared with other heating and cooling systems, it has unique characteristics from principle to application and has distinct technical characteristics. First, the water source heat pump technology uses water as a carrier to extract heat from the soil and water. Surface soils and water bodies receive hundreds of times more solar energy per year than humans use each year. Some of these energy is transmitted to the groundwater through the soil. At the same time, the water is directly or indirectly supplemented by solar radiation, which is equivalent to indirect use of near-infinite Solar energy can be said that water source heat pumps use clean renewable energy. Secondly, water source heat pump technology is an efficient environmental protection and energy saving technology. The water body temperature of the water source heat pump unit can be maintained at 10 ° C ~ 25 ° C for many years. In winter, the water body temperature is higher than the ambient air temperature, so the temperature T in the heat pump cycle is increased, and the energy efficiency ratio is also improved. In summer, the water body temperature is lower than the ambient temperature, so the cooling temperature is lowered, so that the cooling effect is good and the cooling efficiency is high. The water source heat pump unit eliminates the traditional boiler room system when heating, and does not have a combustion process to avoid dust pollution; when cooling, the cooling tower noise and mold pollution and the heat island effect caused by heat emission to the atmosphere are eliminated. Is a true energy-saving and environmentally friendly green product. Water source heat pump technology has good economics. Although there are many factors affecting the economics of water source heat pumps, such as water source investment, electricity price, user or resident behavior, climatic conditions, etc., the quantitative assessment of its economy is still uncertain, but according to the existing application examples, the design The well-installed water source heat pump can save more than 1/3 of the operating cost of the user compared with the traditional heating and cooling system. The Ministry of Construction and the Air Conditioning Institute of the Research Institute use different heating modes for a residential building in Beijing. The cost was measured and the combined cost of the water source heat pump system and other common heating and cooling modes were compared. The optimal design of the water source heat pump system is a developing technology, and the optimal design of the water source heat pump system is very important. While tracking the advanced technology of international heat pumps, the author has developed a variety of water source heat pumps in recent years. The heat pump uses the company's latest production of scroll compressors. In order to solve the problem of small power of a single compressor, the author developed four parallel compressors. The four compressors can be used at the same time or in a single machine depending on the energy requirements. Tested by the China Institute of Metrology, its energy efficiency ratio COP reached 4.6. Currently, this type of heat pump is used in some units of Zhongyuan Oilfield, Shandong Dezhou and Beijing. The user's response not only achieves the goal of energy conservation and environmental protection, but also opens up new fields for the application of new energy sources and has achieved good social benefits. In terms of control, the water source heat pump control system must complete the automatic operation of the entire unit, and at the same time achieve various protections for the unit. The system detects the water temperature through the temperature sensor, and starts the compressor and the water pump according to the temperature change, so that the outlet water temperature is stable within the set range. For the safety of the compressor, it must be ensured that the compressor does not start frequently. When there is water interruption, the compressor pressure is too high or too low, and the water temperature is too high or too low, the automatic protection is stopped. At the same time, because the compressor is expensive. For high-power devices, some current protection, voltage protection, and phase protection devices must be added to the design. In design, reasonable design of main and control electrical circuits should be designed according to the required working conditions, pump motors and compressors that need to be controlled. In the application of water source heat pump engineering, it is indispensable to explore technical and economic indicators according to the actual environment. The water source heat pump used in parallel with one of the four scroll compressors developed by the author is given. The heat pump has advanced compressor models, safe and reliable control system, and overall design optimization. For the application of open groundwater, a series of technical measures such as cost reduction and efficiency-free maintenance are adopted in the design of heat exchangers. Performance indicators have met the actual requirements. 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