Water system, water temperature, water quality and water supply stability of water source heat pump system is an important factor in the operation of the effect. The application of water source heat pump, the principle of the water system requirements are: adequate water, moderate water temperature, water quality, water supply stability. Specifically, the water source of water should be sufficient enough to meet the user heating load or cooling load needs. If the water is not enough, the unit's heating capacity and cooling capacity will be reduced, failing to meet user's requirements. Water temperature should be moderate, suitable for unit operating conditions. For example, Tsinghua Tongfang GHP type water source central air-conditioning system in the heating operation conditions, the water source temperature should be 12-22 ℃; cooling operating conditions, the water source temperature should be 18-30 ℃. The water quality of the water source should be suitable for the materials of the system unit, pipeline and valve without causing serious corrosion damage. Water source system to ensure high water supply, water supply function with long-term reliability, to ensure water source heat pump central air conditioning system long-term and stable operation. First, water In principle, any water, water temperature to meet the needs of the user heating load or refrigeration load, the water quality of the unit equipment does not produce corrosion damage to any water source can be used as water source heat pump system, either renewable water source , Can also be a natural source of water. 1. Recycled water source refers to the water discharged from man-made but treated urban domestic sewage, industrial waste water, mine waste water, oilfield waste water and thermal power plant cooling water, etc. Users who make use of recycled water source conditionally can turn waste into profits and reduce initial investment , Save water resources. But for most users, the water of choice in nature is available. 2. Water in Nature Water in nature is found in the atmosphere, the Earth's surface and crustal rocks, called atmospheric, surface and groundwater, respectively. Surface water and groundwater on land come from precipitation in the atmosphere. Surface water accounts for about 96.5% of the total natural water reserves. The coastal city of the conditional use of seawater, foreign application of seawater as an example of heat pump water. Some coastal cities in China have used sea water for industrial cooling water sources for many years. In recent years, there is a useful sea water for heat pump water research, but the practical application of seawater source heat pump technology still needs time. Surface water on land, that is, rivers, rivers, lakes and reservoirs has a lower degree of salinity than seawater and groundwater, but there are more organic matters such as sediment and other solid particles, colloidal suspensions and algae, and sand content and turbidity are more High, subject to necessary treatment before heat pump water. Groundwater refers to the body of water that is buried and transported in aquifers below the earth's surface. Groundwater is widely distributed, water quality is better than surface water, water temperature with surface water than climate change is small, is the water source central air conditioning can use more ideal source of water. 3. The choice of water quantity and water quantity The water quantity is the key factor that affects the working effect of the water source heat pump system. The amount of water required for a project is determined by the load of the project and the performance of the unit. The selected amount of water source and water should meet the load requirements. If other conditions are available, but the water slightly less than the gap can take some remedial measures to make up. If the water gap is large, can not meet the load requirements, it should consider other options. For a specific project, we should proceed from the actual situation to determine whether there is available water source. Different projects of the site environment and hydrogeological conditions vary widely available sources of water should be selected according to local conditions suitable for water. When there are different water sources to choose from, they should be technically and economically analyzed and compared to determine the optimum. Second, water quality Water in nature in endless cycle of movement, and constantly with the atmosphere, soil and rock and other environmental media contact, interact with each other, it has a complex chemical composition, chemical and physical properties. Application of water source heat pump, in addition to water should be concerned about the amount of water, but also should be concerned about the water temperature, chemical composition, turbidity, hardness, salinity and corrosion and other factors. However, there is no relevant regulation on the water quality of the water source heat pump at present. The data presented in this paper refer to the relevant provisions of the cooling water quality standards and some groundwater recharge quality. 1. Temperature Surface water temperature varies with season, latitude and elevation. North of the Yangtze River and the plateau, winter surface water freezing, can not be used for heating. Summer water temperature is generally below 30 ℃, can be used for refrigeration and air conditioning. Groundwater temperature varies with the physical and geographical environment, geological conditions and depth of circulation. Near the surface of the variable temperature zone, variable temperature zone for a certain depth of constant temperature, the groundwater temperature is not affected by solar radiation. Different latitudes have different depths of temperature, water temperature range 10-22 ℃. With the temperature decreasing, the groundwater temperature increases with the increase of depth, and the increase depends on the geothermal warming rate in different regions and different lithologies. The average geothermal warming rate of the crust is 2.5 ℃ / 100m, which is greater than this value for geothermal anomalies. Geothermal anomalous area rich in groundwater can form geothermal field. According to 1997 statistics, more than 3,200 geothermal spots have been discovered in the country, 130 geothermal fields have been exploited and utilized, and 345 million cubic meters of geothermal water have been mined annually. At present, many geothermal users discharge high temperatures (about 40 ℃). Application of water source heat pump can be discarded in the 30 ℃ temperature difference be reused, greatly improving geothermal energy utilization. 2. Sand content and turbidity Some water contains sediment, organic matter and colloidal suspended solids, the water becomes turbid. The high sand content of water can cause wear to the unit and the valve. Sand with high turbidity and water used for groundwater recharge can cause aquifer plugging. Water source for heat pump system, sand content should be <1/20000, turbidity <20 mg / liter. If the water source heat pump system is equipped with a plate heat exchanger, the particle size of solid particles in the source water should be <0.5 mm. 3. The chemical composition of water and its chemical nature Water dissolved in different ions, molecules, compounds and gases, making the water has a chemical nature of pH, hardness, salinity and corrosive, have a certain impact on the unit material. PH pH value of water is less than 7, acidic, whereas it is alkaline. Water source heat pump water source pH value should be 6.5-8.5. Hardness The total amount of Ca2 + and Mg2 + in water is called total hardness. Hard, easy to scale. Water source heat pump water CaO content should be <200 mg / L. The total amount of various ions, molecules and compounds contained in the volume of water per unit of salinity is called the total salinity. The salinity of the water source water used in the water source heat pump system should be <3 g / L. Corrosive water Cl-, free CO2 are all corrosive, the presence of dissolved oxygen to increase the corrosion of the metal pipe corrosion. Application of water source heat pump system, the corrosive, high hardness water source should be installed in the system anti-corrosion stainless steel heat exchanger or titanium plate heat exchanger. Third, water structures from water sources to water source heat pump room water supply, water structures to be built. According to different water sources, water intake structures can be divided into two categories: surface water intake structures and groundwater water intake structures. 1. Surface water intake structures by structure Surface water intake structures can be divided into two kinds of activities and fixed. Active surface water intake structures floating pontoon and active cable car. More commonly used is the fixed surface water intake structures, which are more types, but generally include water intakes, aqueducts (or horizontal headers) and water collection wells. Surface water intake structures are greatly affected by water flow, velocity and water level, Construction is more complex, to choose the construction plan for the specific circumstances. 2. Groundwater abstraction structures Groundwater abstraction structures include tube wells, large wells, combination wells, radial wells and seepage channels. Table 1 lists the types and application ranges of groundwater intake structures [1]. In practical projects, different forms should be selected according to the depth of groundwater, the thickness of aquifer, the amount of water discharged, and the technical and economic conditions. 3. Tube well water intake structures in the most common type of tube wells, generally by the borehole, borehole pipe, drainage pipe, sinking pipe composition. The well bore is drilled by a drilling machine. The well wall pipe is installed at a non-aquifer to support the hole wall of the well bore so as to prevent collapse. The well pipe and the porthole are sealed with impervious materials such as clay or cement to prevent the seepage of the ground water. Water pipes installed in the aquifer, in addition to the role of the shaft wall outside its main role is to filter water and sand; the bottom of the tube for the sinking pipe, used to sediment sediment in water to extend tube life. Fourth, the water system design and construction should pay attention to the issue 1. Feasibility study of water supply water source water source heat pump system is intended to be investigated, the first survey of water supply conditions of the project site to the local water management consulting or professional teams to carry out the necessary Hydrogeological survey or hydrogeophysical survey to find out whether there is a suitable source of water for the heat pump to use and to conduct a feasibility study to determine the scheme of water supply using surface water or groundwater. 2. Surface water source engineering design and construction Elected surface water, the design of water intake to take into account the water temperature and water requirements of the guarantee rate, water intake structures
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