Abstract: Water-source heat pump is a system or group of systems that uses water as a medium to extract energy for heating and cooling. This article describes the water source heat pump working principle and advantages. Key words: Water source heat pump principle Advantages 1. Water source heat pump definition Water source heat pump is based on water as a medium to extract energy to achieve heating and cooling of a system or a group. For water source heat pump units, low-grade heat, which can not be directly utilized in surface water, is extracted by consuming a small amount of high-grade energy and becomes a high-grade energy device that can be directly used. Water source heat pump is the use of solar energy and geothermal energy for cooling, heating, it should be said that it is a heat pump in the "ground source heat pump" one. After rigorous testing and application examples of heat pumps in different regions, water-based heat pump heating coefficient of performance in the 3.3-4.4 between the cooling coefficient of performance in the 4.1-5.8. 2. Water source heat pump working principle Shallow water sources on the surface of the Earth, such as groundwater, surface rivers, lakes and oceans with depths of 1,000 meters, absorb the solar radiation entering the Earth, and the temperature of these water sources is generally very stable. The principle of water source heat pump unit is to transfer the heat in the building to the water source in the summer. Since the temperature of the water source is low, the heat can be efficiently taken away, and in winter, the energy is extracted from the water source by the heat pump principle and is cooled by air or water Agent to raise the temperature to the building. Usually water source heat pump pumps consume 1kW of energy, users can get more than 4kW of heat or cold. Water source heat pump according to the different ways of using water can be divided into two kinds of closed system and open system. Closed system refers to the water side of a group of closed loop heat exchange coil, the group of coils are generally buried horizontally or vertically in the lake or sea water, heat transfer with the lake or sea water to achieve energy transfer The system in which the pipe is directly buried in the soil is called a ground-source heat pump and is also a type of ground-source heat pump. The open system refers to a system that discharges directly from a ground or a surface through a heat exchanger. Water source heat pump both in the heating or cooling process are water as a heat source and cooling medium, that is, with switching refrigerant circuit to achieve heating and cooling operation. However, it is more convenient to complete the three-way valve in the water circuit. Although the water source heat pump system diagram shows the direct entry of water into the evaporator (condenser for cooling purposes), in some cases, in order to avoid contamination of the closed cold water system (usually treated), an indirect heat exchanger To supply water; another way is to use a closed loop condenser water system. Water as a heat pump heating, cooling medium, to meet the following two conditions can be used: First, the water temperature between 7 ℃ ~ 30 ℃, the second is the amount of water to be adequate. Water source water can be a variety of industrial wastewater, domestic water, sea water, river, river, etc., and even a variety of industrial waste heat. Extraction of water in the hot (cold) volume is relatively easy way to dig wells, the use of well pump groundwater extraction as a recycling medium. As the water source heat pump technology uses surface water as the hot and cold air conditioning unit, so it has the following advantages: Significant environmental benefits Water source heat pump is the use of surface water as a source of cold and heat, energy conversion heating and air conditioning system. When heating, the boiler room system of coal, gas, oil and so on is eliminated, there is no combustion process, and pollution such as exhaust smoke and sewage is avoided; the cooling water tower is omitted when cooling, and the noise, mold pollution and cooling of the cooling tower are avoided Water consumption. So, a water source heat pump uses a technology that is clean and renewable. Efficient water source heat pump units available water temperature in winter is 12 ~ 22 ℃, the water temperature is higher than the ambient air temperature, so the heat pump cycle evaporation temperature increases, the energy efficiency ratio also increased. The summer water body is 18-35 ° C, and the temperature of the water body is lower than the ambient air temperature. Therefore, the condensation temperature of the cooling decreases, making the cooling effect better than that of the air-cooling and cooling towers, and the unit efficiency is improved. According to the EPA of the United States Environmental Protection Agency, the design and installation of a good water source heat pump can save 30-40% of the heating and cooling air-conditioners on average. Electricity used by energy-saving water heat pumps is a clean energy source, but consumes primary energy and generates emissions of greenhouse gases such as pollutants and carbon dioxide when generating electricity. Well-designed water-source heat pump units, compared with air-source heat pumps, are equivalent to reducing power consumption by more than 30%, which is equivalent to reducing power consumption by more than 70% compared to electric heating. Therefore, the water source heat pump energy saving at the same time also reduces and reduces the generation of electricity generated during primary pollution emissions and greenhouse effect. Wide range of applications Can be widely used in hotels, office buildings, schools, shopping malls, villas, residential district central heating and cooling, and other commercial and industrial building air conditioning, and can be used for swimming pools, dairy processing, beer brewing, cold Rolled forging, cold storage and indoor cultivation and constant temperature farming and other industries. Multi-purpose use of a machine for a cold, but also for heating, but also provide hot water. For air-conditioning system, a heat pump provides two heat sources, saving one-time investment, the total investment is only 60% of traditional air-conditioning systems, and easy to install, installation work less than other air-conditioning systems, short installation period, Change the installation is also easy. High degree of automation High water source heat pump unit due to stable conditions, so you can design a simple system; fewer components, a high degree of automatic control. There are no contaminated water source heat pump technology used in the refrigerant can be R22 or R134A, R407 and R410A and other alternatives. Water source heat pump unit operation without any pollution, no combustion, no smoke, does not produce any waste, waste water, waste gas and soot, so that the environment more beautiful. Can be built in residential areas, do not need to pile up fuel waste sites, and do not have long-distance transport of heat. Stable, reliable, easy to maintain Water temperature is relatively stable throughout the year, the scope of its fluctuations is much smaller than the air changes, is a good heat pump heat source and air-conditioning cold source. The constant temperature of water body makes the operation of heat pump unit more reliable and stable, and also ensures the high efficiency and economy of the system. There are no difficult problems such as winter defrosting of air source heat pump. As the system is simple, less crew components, simple operation, stable, relatively speaking, much lower maintenance costs, the service life can be longer than 20 years. special reminder Reasonable use of groundwater resources for heat pump air conditioning, there are two problems in the design and use should be concerned about. (1) Groundwater source selection Groundwater source heat pump, the principle of selecting the water source should be: adequate water, water temperature is appropriate, good water quality, water supply and stability. In the case of a project, the availability of underground water sources should be judged on the basis of the local conditions. The amount of water required for a project depends mainly on the cooling load and the groundwater temperature of the project. The suitable groundwater source conditions are , Hydrogeological features of sand, pebbles, gravel and fissure zone; aquifer thickness greater than 5m, winter groundwater temperature not lower than 10 ℃. In addition, pay attention to water quality, including sand content and turbidity, as well as the chemical properties of water. Therefore, the sand content of groundwater source should be less than one hundred thousandth, and the turbidity of recharge water to underground aquifer should be less than 20 Mg / l; the total salinity is less than 3 g / l, the water Cl is less than 100 mg / l, SO4 2- is less than 200 mg / l, Fe2- is less than 1 mg / l, H2S is less than 0.5 mg / l, Conditions not up to requirements, the water source heat pump system should consider anti-corrosion measures. </ P> (2) Artificial recharge There is a lack of water resources in our country. The competent authorities strictly regulate the exploitation of groundwater and stipulate that unless there is a large demand for water, users must recycle water. Of course, in order to ensure the long-term normal operation of the underground water source heat pump air conditioning system to supplement groundwater sources, regulate the water level and maintain reserves balance. In order to avoid the water that is recharged to the ground after cooling or heating in the heat pump, it is withdrawn due to the short circuit and the distance between the recharge well and the intake well should be as far as possible. At present, although there is no national standard for water quality recharging, the quality of the returned water should be at least equal to that of the original groundwater so as to ensure that the local water quality will not be polluted after the recharge. Therefore, the following provisions should be observed: (1) Groundwater should be transported in a closed system; (2) Parts of the heat pump air-conditioning system that come into contact with groundwater should be made of corrosion-resistant materials; (3) The water intake and return pipelines shall be fitted with stopcocks for the collection of water meters and water samples; (4) Conducting regular laboratory tests on groundwater and submitting the test results to the relevant departments for the record; (5) If abnormal underground well water is found, especially if there is any chemical substance or other irrelevant substance in the water, it shall timely contact the relevant department and take measures. There are three ways to recharge groundwater, namely: vacuum recharge, gravity (gravity) recharge and pressure recharge. Vacuum filling: Vacuum filling is the use of low static water level (below the ground 10m) to form a vacuum for irrigation. Aquifer permeability is good. As the recharge, the impact of the well water layer is not strong, so it is suitable for the old wells. Vacuum recirculation is adopted. For fine-grained aquifer, the amount of recirculation is generally 1 / 3-1 / 2 of the water intake; for coarse-grained aquifer, the amount of recirculation can reach 1 / 2-2 / 3 of that of water. Gravity recharge: relying on natural gravity of irrigation is also suitable for low water level and permeability of aquifers, this method has the advantage of the system is simple. For sand and gravel aquifer, the amount of water returned is generally 50%; for good permeability of gravel layer, the amount of water up to 75-90 ℃. Pressure recharge: Pressure recharge is used in high water and low permeability aquifers. The disadvantage is that when recharged, the impact on the well and the aquifer is strong. Shanghai has widely used this method to recharge. In order to prevent well tube plugging, timely removal of impurities blocking the aquifer and well tube, after the recharge, often open the pump to exclude over-plugging in the recharge well water, that is, back. The number of recharge cycles and the duration of recharge in a recharge well depend primarily on the particle size and permeability of the aquifer. In karst fissure aquifer recharge wells, the long-term non-rebound, the ability to recharge can still remain unchanged in the loose coarse-grained aquifer recharge wells 1-2 times a week back in the fine particles Recirculation wells in aquifers should be further shortened by bayonet spacing, and regular return is particularly important for recharge wells in fine-grained aquifers. Therefore, after the system commissioning is completed and normal operation, in order to prevent well tube plugging, timely removal of impurities blocking the aquifer and well tube to ensure the reliable operation of the system, the injection wells and pumping wells need to be cleaned once a year at a cost of Eye 5000 yuan or so.