Introduction: Two issues, increasing energy consumption and environmental pollution, have plagued human society and attracted worldwide attention.
Heat pump According to statistics from the International Energy Organization (IEA's Heat Pump Center) and the European Heat Pump Association (EHPA), 450 million units, European residential heat pumps, 1.5 million yuan heat pumps in the tertiary industry, and 2.5 to 3 million heat pump equipment industries. EHPA's target is to have at least 15 million units in Europe by 2010, with heat pumps as residential units, which is equivalent to saving energy and reducing carbon dioxide emissions by more than 400,000 tons per year. In 2002, the number of heat pumps in Switzerland exceeded 1/3 in new housing, and the share of heat pumps in buildings in Japan was 20%. However, the heat application after 1990 has been rapidly developed. By 1997, the market share was 114,000 units, indicating that it has been installed and developed rapidly. The momentum.
With China's entry into the WTO and its successful bid for the 2008 Olympic Games, China's urban centers are gradually banning the simultaneous use of coal-fired boilers, and the use of oil-fired boilers has also been limited to a certain extent, so there is huge room for development of heat pump applications. Heat pump air source heat pumps are divided into water (ground source) heat pumps and air source heat pumps. Due to the large environment and climate, its application is limited to a large extent, but water temperature changes in summer and winter are not much different, so do not cold The hot water and groundwater source heat pump system makes this problem effectively solved. This is energy consumption, the use of renewable energy, does not consume water, does not pollute the environment, meets many advantages such as sustainable development, and is widely consistent with popular requirements.
Second, the current situation of water source heat pumps: In the application of water source heat pumps, the biggest problem lies in the actual situation, providing stable water supply and groundwater recharge at the same time to solve the problem and how to maximize the use of hidden energy in water resources in winter. The current application of this work usually adopts natural replenishment. Natural replenishment is only due to gravity and water is power to maintain the balance of the water system to ensure that the water coming out is fully charged. The general ratio of the number of access wells and recharge wells is 1. : 2 or 2: 3. This not only increases investment, but also has a low utilization rate in part-load recharge wells. Therefore, it is necessary to reduce the investment that can be solved, and also save operating costs, while ensuring 100% charging, which is directly related to the development of applications and water source heat pumps. Therefore, research and water-saving, high-energy water source heat pump heat pump units will help to develop and promote the efficiency of application and promotion, and have good market prospects.
Third, energy-saving water source heat pump unit: Song Taizu In order to overcome the temperature difference related to the working conditions of the heat pump and increase some technical problems, our unit structure was studied and discussed. Its structure is an independent small unit with two evaporators, an evaporator, each or several compressors and condensers, an expansion valve and a refrigeration cycle system. Two serial or parallel water system evaporators are realized between the two coming out of the evaporator through a valve to control the water. In summer, evaporative cooling conditions, the opening of the pipeline valve between the two, the operation of the air-conditioning return water system, and the end of February to the two evaporator routes, after which the end of the flow of cold horizontal lines converged through the outlet to evaporate the two evaporators into the air. The cooling capacity of the system is realized by two evaporators, the temperature of various inlet and outlet evaporators is 12/7 ° C (the temperature difference between the inlet and outlet water Δt = 5 ° C), and the valves of the two tube evaporators are closed under the conditions of the heat pump operation in winter. As a groundwater source that turns to flow, through these two evaporators, water is two series of evaporators. The evaporator passes two as groundwater sources to achieve a temperature drop of Δt = 10 ° C. The area ratio of the water evaporator flowing through the evaporator parallel to the series of water flows is reduced in parallel to make up for the water flow velocity to reduce its impact, so that water flows through each evaporator, the flow rate flows to the conditions and running summer when the same heat is small, the Thermal performance, not only to achieve savings without affecting the heat transfer performance and use of water.
4. Engineering application: The following is a new building energy-saving water source heat pump unit as an example of cold and heat design. The application unit:
1. Office building area: 4,600 square meters, with embedded disks for indoor air terminals. Calculate the required cooling load Q0 = 460kW, and a quick description of the required heat load = 506kW.
2. Water conditions: single well water 50 to 60 cubic meters / h, temperature: 16 ℃ in summer and 15 ℃ in winter. 4. Design conditions:
Cooling conditions: 1,2 water system parallel evaporator, fluorine system is independent, its water temperature is 12/7 ℃, evaporation temperature is 2 ℃; cooling water system is parallel 1,2, fluorine system is independent, and its outlet temperature is 26 minutes It is 16 ° C and the condensation temperature is 31 ° C.
Under heating conditions: 1,2 evaporator series water system, fluorine system is independent, 1 15 / 9.5 ℃ in and out of the evaporator, evaporation temperature is 5.5 ℃ water temperature 2 water temperature of the evaporator 9.5 / 5 ℃, evaporation temperature 1 ℃, 1,2 Parallel cooling water system, F system is independent, when the water temperature is 40/45 ℃, the condensation temperature is 50 ℃.
5. The results are as follows:
① Cooling conditions:
Total cooling capacity of the system: Q0 = 466kW,
Total system power: pico = 89.5kW
System cooling factor: Contracting Party = 5.2
Well water (parallel water supply system) taken water: 47.22 cubic meters
② Thermal conditions:
Thermal capacity of the entire system: to Qk = 511kW,
Total system power: pico = 121.7kW
System, heating factor: Parties = 4.2
Well water (water system connection): 34 cubic meters
After a winter and summer operation, it is shown that the unit can operate safely and reliably under the conditions of the two wells supplying local water, and the cooling and heating effects fully meet the user's requirements. Reduced initial investment and operating expenses, good value for money already received.
V. Conclusion: This structure makes the water from the evaporator at 5 ℃, the cooling temperature or heating 10 ℃, the heat transfer performance of the thermal evaporator is basically the same when the temperature difference, that is, the evaporator heat in the winter transfer area and summer two Conditions are fully utilized. Under the condition that the heat pump is operating at the same time, when the water volume is 20%, the increase of the system heating capacity by about 10% is reduced, and poverty reduction is increased by about 7%.
In short, by improving the structure of the heat pump unit and the evaporator of the water system in series and in parallel, it has realized the accumulation of groundwater, condolences and reduced the number of recharge wells, as well as the reasonable use area of the heat transfer of the evaporator. Thermal capacity and energy efficiency. This will not only reduce the initial investment, but also reduce operating costs with significant economic and social water source heat pump application and development benefits in China, which will play a catalytic role.