Abstract: This paper summarizes the development and current situation of water source heat pump, analyzes the problems existing in application of water source heat pump unit and puts forward an energy-saving structure of water source heat pump unit, which plays an important role in the application and development of water source heat pump in our country. Indoor Trampoline,Bowl Trampoline,12Ft Trampoline,Mini Trampoline Jiangsu Baoxiang Sports Equipment Co., Ltd , https://www.skyboundsports.com
Keywords: water source heat pump energy-saving dual-evaporator series parallel I. Overview:
Increasing energy consumption and environmental pollution are two major problems plaguing human society and have drawn great attention from all countries in the world. According to statistics from the IEA Heat Pump Center and the European Heat Pump Association (EHPA), there are currently 4.5 million heat pumps in Europe for residential use, 1.5 million heat pumps for the tertiary industry, and 2.5 to 30,000 heat pumps For industry. EHPA's goal is to have at least 15 million heat pumps in Europe by 2010 for residential use, equivalent to saving 100 TWh of energy annually and reducing 40 million tons of CO2 emissions. By 2002, the heat pump in Switzerland accounted for more than one-third of new houses and Japan's buildings had a heat pump share of 20%. However, the application of heat pumps in our country only enjoyed rapid development after 1990, reaching 11.4 million units in 1997 , But also the momentum of rapid development.
The use of oil-fired boilers is also being limited to a certain extent, thus giving tremendous room for development for heat pump applications. The heat pump unit is mainly divided into air source heat pump and water source (ground source) heat pump. Because air source heat pump is greatly affected by environment and climate, its application has been greatly restricted, while the groundwater temperature has little change in winter and summer. Therefore, Cold and heat source water source heat pump system so that this issue has been effectively resolved. It has been widely welcomed by all walks of life due to many advantages such as less energy consumption, utilization of renewable energy sources, non-consumption of water resources, non-pollution of the environment and compliance with the requirements of sustainable development.
Second, the status of water source heat pump:
The biggest problem of water source heat pump application is to provide a stable source of water according to the actual situation. At the same time, it is necessary to solve the problem of recharge of groundwater and how to maximize the use of the energy contained in water in winter. At present, the application of such projects generally takes natural recharge. Since natural recharge is only gravity, and water is power, it is necessary to maintain the balance of the water system and ensure that the water taken out is fully recharged. The proportion of wells to recharge wells is normal Take 1: 2 or 2: 3. This not only increases the investment but also the utilization of the recharge well at part load. Therefore, whether it can solve the problem of reducing investment and saving operating costs while ensuring 100% recharge will directly affect the application and development of water source heat pumps. Therefore, the research and development of a water-saving and energy-efficient water source heat pump unit is helpful for the application and promotion of water source heat pump, and will have a good market prospect.
Third, energy-saving water source heat pump unit:
In order to overcome the heat pump temperature conditions to increase the temperature caused by many technical problems, we have conducted a study on the unit structure and exploration. Its structure is the unit uses two small evaporators, each evaporator and one or more compressors and condensers, expansion valves and other components of the independent refrigeration cycle. Between the two evaporator inlet and outlet pipes through the valve control to achieve two evaporator water system in series or in parallel. The valve between the two evaporator pipes opens in the summer cooling condition, and the backwater of the end system of the air conditioner enters two evaporators at the same time in two paths at the same time. After the outlet of the evaporator joins the end of the air conditioner, that is to say, the cold water flows in parallel Two evaporators. The cooling capacity of the system is realized by two evaporators. The inlet and outlet water temperature of each evaporator is 12/7 ° C (Δt = 5 ° C). In winter heat pump operation, Between the closure of the valve, as a heat source of groundwater flow through the two evaporators, which means that the two evaporators water in series, as the source of groundwater through two evaporators to achieve Δt = 10 ℃ temperature drop. Compared with the parallel flow of water through the evaporator, the flow area of ​​the water through the evaporator decreases in tandem to make up for the effect of reduced flow on the flow rate, so that the flow of water through each evaporator, the flow rate, and the summer operating conditions When the same, the heat transfer performance of the smaller, both to achieve the purpose of saving groundwater, without affecting the heat transfer performance.
Fourth, project application example:
The following is a unit of office buildings using the new energy-saving water source heat pump unit as a cold and heat source design examples:
1, office building area: 4600m2, the indoor end of the embedded wind tray, calculated by the required cooling load Q0 = 460kW, the required heat load Qh = 506kW.
2, water conditions: single well water volume 50 ~ 60m3 / h, water temperature: summer 16 ℃, winter 15 ℃.
3, choose four 40HP semi-sealed piston compressor, two compressors and an evaporator, a condenser composed of two independent systems.
4, design conditions:
Refrigeration conditions: the evaporator 1,2 water system in parallel, the fluorine system is independent, the inlet and outlet temperature 12/7 ℃, evaporation temperature 2 ℃; condenser 1, 2 water system in parallel, the fluorine system independent, its inlet and outlet temperature 16 / 26 ℃, condensing temperature 31 ℃.
Heating conditions: evaporator 1, 2 water system in series, independent fluorine system, evaporator inlet and outlet water temperature 15 / 9.5 ℃, the evaporation temperature 5.5 ℃; evaporator 2 inlet and outlet water temperature 9.5 / 5 ℃, evaporation temperature 1 ℃; Condenser 1,2 water system in parallel, the fluorine system is independent, the inlet and outlet temperature 40/45 ℃, condensing temperature 50 ℃.
5, the calculation results are as follows:
â‘ refrigeration conditions:
Total system cooling capacity: Q0 = 466kW,
Total system power: Pi = 89.5kW
System cooling factor: Cop = 5.2
Well water (water system in parallel) to take water: 47.2m3
â‘¡ heat pump conditions:
Total system heat: Qk = 511kW,
Total system power: Pi = 121.7kW
System heating factor: Cop = 4.2
Well water (water system in series) to take water: 34m3
After a winter and summer operation results show that the two wells in the local water conditions can be safe and reliable operation of the unit, cooling and heating effects to fully meet the requirements of users. Reduce the initial investment and operating costs, received a very good economic returns.
Fifth, conclusion:
Adopting this structure, the heat transfer performance of the evaporator is basically the same regardless of whether the temperature of the evaporator inlet and outlet is 5 ° C. during cooling or 10 ° C. during the heating. In other words, the heat transfer area of ​​the evaporator is in the winter, Xia two conditions have been fully utilized. At the same time, heat pump operating conditions, the water decreased by 20%, the system's heating capacity increased by about 10%, Cop increased by about 7%.
In summary, by improving the structure of the heat pump unit, changing the series and parallel of the evaporator water system, not only to achieve the saving of groundwater intake, reduce the number of wells and recharge wells, and rational use of the evaporator heat transfer Area, while increasing the system of heating and energy efficiency ratio. This will not only reduce the initial investment, but also reduce operating costs, with significant economic and social benefits, the application of water source heat pump in our country and development will play a catalytic role.