Feasibility Discussion on Water Source Heat Pump Popularized in Hunan Province

With the economic development in our country and the improvement of living standards of the people, the air conditioning equipment is becoming more and more popular. There is a huge demand for air conditioning in the society. China's winter cold and hot areas such as Hunan need cooling in summer, heating in winter. At present, most of the heating and cooling equipment used in these areas are electric heaters and air conditioners that are widely distributed among users and consume a large amount of power. With the sustainable development and people's awareness of environmental protection, environmental protection and energy saving have become the primary research issues in the development of building air conditioners. Because water source heat pump system has the advantages of energy conservation, environmental protection, stable performance and cleanliness, we have reason to believe that water source heat pump Hot summer in Hunan Province is the most promising energy-saving air-conditioning installations and systems.

Water source heat pump is a water-based heat pump cooling / heating cycle can be a heat pump water-air air-conditioning unit. Water quality, heat capacity, heat transfer performance is good, the amount of water required to transfer a small amount of heat, the size of the heat exchanger can be smaller. Therefore, water is an ideal source of heat in areas where a large amount of relatively stable temperature water is readily available. Surface water such as groundwater and rivers, lakes and seas have little temperature change within a year and are all water sources that can be used as heat sources. There is also no problem of frosting on the surface of evaporators when using water as a heat source. However, water as a heat source, the water system is more complex, but also need to consume the pump power, if the water hardness, but also cause heat exchanger surface scaling, the heat transfer performance of equipment, if the water contains large amounts of chloride ions, Will cause corrosion of equipment.

Water source heat pump air conditioning systems include [ 1 ] : a water loop heat pump system that utilizes a circulating water loop as a source of heat and heat, a groundwater source heat pump system that uses groundwater, surface water from lakes, streams or channels in the vicinity of a building Surface water heat pump system; a closed-loop, surface-water heat pump system using a closed water or brine circuit, including a pipeline submerged in surface water (river, lake or pond); a closed water Loop buried underground, with soil as heat source and heat source closed loop soil heat pump system.

2.1 Hunan climate conditions

Located in the south of the middle reaches of the Yangtze River and the north of Nanling, Hunan Province is located in the subtropical monsoon humid climate at latitudes 24 ° 39 '~ 30 ° 08' and longitude 108 ° 47 '~ 114 ° 15'. In the winter, it is often controlled by cold regiments south of Siberia and the People's Republic of Mongolia. The northern cold are frequently southward, and the wet and cold are frequent and the climate is chilly. In the summer, it is mostly surrounded by warm and humid air masses in the ocean, with high temperature and humidity, and high temperature in midsummer. Therefore, the change in the area during the year is relatively large and belongs to the typical winter, cold and hot areas. The annual average temperature in Hunan Province is between 16 and 18 degrees centigrade, the coldest month in January and the average monthly temperature between 4 and 7 degrees centigrade in July and the hottest month in July with an average monthly temperature of 27 and 30 degrees centigrade. Poor generally greater than 23 ℃ [2 ] . Throughout the annual climate in Hunan, can be summarized in its main features are: a warm climate, four seasons; adequate heat, rainwater concentration; spring temperature changeable, more drought in summer and autumn; cold period is short, long summer heat.

2.2 Water Resources in Hunan Province

The average annual precipitation in Hunan is 1200-1700mm, belonging to rainy areas. The precipitation in April-September accounts for about 65-70% of the whole year, and the annual precipitation days are 140-180 days [ 2 ] . In 2001, the highest water temperature in Xiangjiang River was 32.5 ℃ (July 31) and the lowest water temperature was 6.8 ℃ (January 2), with only 1 day below 7 ℃ and 7 days below 8 ℃ .

2.2.1 Total water resources

The total amount of water resources used to assess the formation of surface precipitation within the region, the total amount of underground water production, excluding transit water, by the amount of surface water resources, groundwater resources deduct the amount of double counting. Data show that Hunan is very rich in water resources.

2.2.2 The main rivers water quality conditions

(1) Xiangjiang River: Type II and III water quality rivers account for a long river of assessment, with a flood season of 70.0% and a non-flood season of 62.7%. The main pollutants are total mercury, ammonia nitrogen, total cadmium, total arsenic, petroleum, total coliform bacteria and so on.

(2) Zishui: Grade II and III water quality rivers accounted for 51.0% of flood season and 51.0% of non-flood season. The main pollutants are ammonia nitrogen, phenol and other points.

(3) Yuanjiang: Type II and III water quality rivers account for a long river of 86.1% in flood season and 83.7% in non-flood season. The main pollutants are total mercury, phenol degradation, ammonia nitrogen, five days of biochemical oxygen demand.

(4) water: good water quality, have reached II, III water quality standards.

2.3 water source heat pump system on the water system requirements

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. Water source heat pump system on the water system requirements are: adequate water, moderate water temperature, water quality, water supply stability. Specifically, the amount of water in the water source should be sufficient enough to meet the heating load or cooling load requirements of the user. The water temperature of the water source is moderate and suitable for the operating conditions of the unit. According to the American Society of Refrigeration ARI320 standard [ 3 ] , the open system water source heat pump The water temperature requirement is 5 ~ 38 ℃, when the water temperature is between 10 ~ 22 ℃, the energy efficiency is relatively high.

3.1 County Hotel in Hunan Province groundwater source heat pump system

3.1.1 Project Overview

The system is located in Juxian County in the northwest of Hunan Province, near the Dongting Lake in the Yangtze River. The groundwater is rich and the average groundwater level is 8m. Geological structure: 0 ~ 7m for the soil layer, 8 ~ 16m sand and gravel mixing layer, 17m below the clay layer. Groundwater temperature was essentially constant at 18.5 ° C throughout the test period, independent of run-time. Geological conditions: 0 ~ 7m soil layer, 8 ~ 16m is a mixed layer (free aquifer), 17m below the soil layer. The system consists of two good special heat pump units Ⅰ, Ⅱ parallel operation, the nameplate heat were 100KW, 40KW, rated input power of 20.1KW, 12.6KW, the refrigerant is R22. The water source system has two deep wells with diameters of 160cm and 140cm respectively, one for one time and about 30 meters apart. Water supply and return wells at the groundwater pressure, pitot tube and micro-pressure meter measured 37pa, water supply wells higher than the return wells.

3.1.2 groundwater source heat pump and several other commonly used energy-saving heating mode factor comparison

Although the heat pump has a heating coefficient greater than 1, but only to determine the heating economy is not enough. In the electric heat pump heating and other heating methods are compared, you should also consider another economic indicator - energy efficiency factor E. Energy efficiency factor E is defined as the ratio of primary heat source to consumed energy [ 4 ] . In addition to reflecting the level of the heating coefficient, it also takes into account the heat pump to use primary energy (fuel) efficiency, which includes power generation efficiency and transmission efficiency.

It can be seen from Table 3 that among the types of heating methods listed in the table, the maximum energy utilization coefficient of the water source heat pump is the highest, reaching 1.4, which shows that the water source heat pump heating mode is the most energy-saving and most economical.

3.2 Xiangtan City, Hunan Province, a project of surface water source heat pump system

3.2.1 Project Overview

The first phase of the water source heat pump system in Xiangtan downtown area includes the municipal government building, radio and television center, grand theater and underground mall with a total construction area of ​​75,000m 2 . Central Park Huxiang will build a total area of ​​120 acres of artificial lake, the use of the artificial lake as a water source heat pump unit of winter heat source and summer cold source. Selection of Hunan Ling Technology Co., Ltd. production of LD-BL-1000 modular geothermal central air conditioning unit 15 units; unit total cooling capacity of 13410KW, the total heating capacity of 15030KW; cooling rated power 2682KW, heating rated power 3330KW. The total installed power of the heat pump unit and pump in the equipment room is about 3262KW. If the transformer is set separately, the required transformer capacity is 4338KVA.

3.2.2 water system specific parameters

(1) water temperature

Xiangjiang water temperature varies with the seasons, latitudes and altitudes. According to the 2001 Xiangjiang River water resources data, Xiangjiang River water temperature in winter and summer in Xiangjiang River between 6.8 ~ 32.5 ℃, basically meet the water source heat pump system on the water temperature requirements.

(2) water quality

The summer cooling time in Xiangtan is from July to September, and the heating time is from December to February. During this period, the water quality in the Xiangjiang River is relatively clear with less sediment content. From the Xiangjiang River to the sedimentation tank after pumping, and then into the artificial lake clarified filter for the water source heat pump heating or cooling. As the system design condensing pressure of 28bar, the corresponding temperature is below 60 ℃, so it will not scale.

(3) water flow

The actual demand of water source in winter and summer should actually be related to the selected unit performance, water temperature, circulating temperature in the building, cooling load, and heat exchanger type. After calculation, the amount of water required for cooling is 712.1t / h, and the amount of water required for heating is 558.1t / h. Visible, summer cooling required flow should be the minimum flow of water required.

3.2.3 program feasibility analysis and possible solutions to the problem

Surface water systems may be the most energy-efficient and economical air-conditioning system if there is an available sea, lake or pool and man-made lake near air-conditioned buildings. According to the calculation and analysis, except for extreme temperatures, water diversion and storage efficiency of the water source heat pump in the Xiangjiang River is reduced. Most of the water source heat pump units have high energy efficiency ratios. According to the lake with the minimum artificial lake capacity of 210,000 m 3 , the heat absorption or discharge heat up to 244186KW when the temperature is increased or decreased by 1 ℃ is 34 times of the system's hourly cooling capacity and 56 times of the heat supply. In other words, the heat pump heat for 34 hours, only to make the water temperature increased 1 ℃; or continuous heat 56 hours, only to reduce the water temperature 1 ℃. Visible, water lake has enough capacity for system use.

However, the temperature of the lake is different from the temperature of the Xiangjiang River, which is greatly affected by the weather. In extreme cases, it does not exclude exceeding the threshold. For solutions beyond this value, the following solutions can be taken:

(1) When the temperature of the lake is too high in summer, a fountain-type spraying method may be used to make the water spray around the lake or the lake to reduce the water temperature so that the water temperature remains below 32 degrees Celsius,

(2) When the winter lake temperature is too low, the buried water pipe connecting the Xiangjiang River and Shui Lake can be used as the extraction device of geothermal energy; meanwhile, when the summer lake temperature is too high, the system can also be used to distribute the heat of condensation;

(3) In winter, the water in the water tank is heated by the trough electricity at night to heat the system after the water is heated in the daytime.

Hunan's winter and summer seasons account for 67% of the annual total, and the winter damp and cold in summer, hot and hot in high temperature. In Hunan, water sources are guaranteed and the price is low, and the water quality basically meets the requirements of water source heat pump units. Reliability and take appropriate measures (such as in the unit before the decontamination to separate solids in the water; install water softener to improve water quality to further improve water quality; or the use of intermediate heat exchanger), in Hunan to promote water source heat pump air conditioning System is entirely feasible. The use of water source heat pump in Hunan Province will greatly reduce the energy consumption of air conditioning and heating, reduce peak load of electricity, reduce emissions of coal-fired power generation, improve the atmospheric environment and urban ecological environment, in line with the requirements of sustainable development in today's world, you can As the long-term winter cooling in Hunan Province in the long-term good policy. The analysis of this article can also provide reference for handling the building environment and building energy conservation issues in the winter and summer and hot summer areas such as the Yangtze River Basin.