| Along with the progress of the Western Development Strategy, winter heating inwestern plateau regions represented by Lhasa is highly valued and supported by thecommunity, and the government has been carrying out heating services constructionvigorously in the Twelfth Five-Year period. Lhasa belongs to the plateau cold areas,with dry air, plenty of solar radiation, fragile ecological environment and scarce fossilenergy.These climatological, resource and environmental characteristics requires thatbuilding heating in Lhasa needs a suitable solution and should not copy the experienceof the inland.Air Source Heat Pump is applied in a large number of projects in Lhasa for itsenergy efficiency, environmental safety and simple equipment, and low air humidity inthe winter of Lhasa helps keeping the heat pump units from evaporator frosting.However, the low atmospheric pressure, low air density and other factors adverselyaffect the operation of air source heat pump. In this regard, this thesis carried out aresearch on the application of air source heat pump for heating in the plateau cold areasrepresented by Lhasa.Firstly, according to the weather conditions and geographical features of Lhasa,local air physical parameters was calculated. And the influence of the plateauenvironment on the heat transfer performance of evaporator was analyzed based on thestructural parameters of evaporator of air source heat pump water chillers. Theprinciples of evaporator frosting process and its predication strategies are introduced,and by theoretical analysis it is concluded that frosting is not frequent in heatingoperation of Air Source Heat Pump in Lhasa’s low humidity environment.Mathematical models of air source heat pump water chiller and its componentswere established, the algorithmand calculation steps of which weredescribed.MATLAB was used for the programming and simulation of the models inboth Lhasa and plain regions. Comparative analysis of the simulation results showedthat without considering the impact of evaporator frosting, heating capacity andcoefficient of performance of heat pump in Lhasa would decrease by16.2%~19.8%and9.5%to12.5%, separately.Field test has been carried out in anair source heat pump heating project in Lhasa,to analyze the influence of outdoor air temperature andoutlet water temperature on system heating capacity and coefficient of performance. The measured and simulatedvalues were compared, which verified the accuracy and feasibility of the model.According to the results of the simulation, a correction coefficient of0.80～0.84wasproposed for calculating the actual heating capacity of Air Source Heat Pump in plateauregions. The actual heating capacity was compared with that of the plain regions,indicating that heating capacity of Air Source Heat Pump in Lhasa is larger than that ofthe inland plain cities with low temperature and high humidity.The simulation software DeST was used to calculate the hourly heating load of abuilding in Lhasa, and variation of the heating load were analyzed. Using BIN method,the energy consumption, energy saving and environmental performance of severalhybrid heating systems in which air source heat pump predominates were compared andanalyzed. The results showed that in the heating season of Lhasa, air source heat pump+solar heating system has the lowest energy consumption and the best environmentalbenefits, and should be promoted in heating projects in Lhasa. |
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