Studies On The Effects Of The Variation Of Key Parameters Of A Flat-Plate Solar Collector On Its Heat-Collecting Efficiency

With the economic and social development and the improvement of people's living standard,the demands and consumption for energy grow increasingly.In addition,the environmental pollution problem from using traditional fossil fuel is becoming more serious with each passing day.Therefore,it is necessary to implement the development and utilization of new energy.Solar energy has been widely studied and applied in the field of building energy conservation because of its universal,cleaning,and renewable advantages.Moreover,the flat-plate solar collectors are one of the important heat-collecting devices in thermal collection and utilization of solar energy systems in buildings.In order to reduce the proportion of the traditional fossil fuel to the building energy supply system,improve the utilization rate of solar energy and meet the requirements of energy conservation and environmental protection,a flat-plate solar collector with single-layer glass board is considered as a studying objective in this paper,and its heat-transfer model with one-dimensional steady state is set up as well.In addition,a numerical simulation and analysis of the effects of the variation of key parameters of this kind of solar collector on its heat-collecting efficiency is carried out.At the same time,the heat-transfer model and the corresponding numerical simulation program are verified by the related experiment.The main results in this research are as follows.1.Based on the method of mechanism analysis,the composition,structure,and operation mechanism of a flat-plate solar collector are represented.2.For the studying objective,i.e.,a flat-plate solar collector with single-layer glass board,its heat-transfer model with one-dimensional steady state is firstly set up.Accordingly,the effects of the variations of key parameters of this flat plate solar collector,including environmental parameters(solar irradiance,environmental temperature and wind speed),structure parameters(the spacing and the inner diameter of heat-collecting tubes and absorber plate thickness)and operational parameters(the inlet temperature and the mass flow of working media)on its heat-collecting efficiency are mathematically described in terms of heat transfer mechanism.3.By MATLAB software,an iterative numerical simulation program considering the board temperature,the average temperature of heat-collecting panels,and the average temperature of working media in heat-collecting tubes as the criterion,the variations of the spacing and the inner diameter of heat-collecting tubes and the inlet temperature and the massflow of working media as the input parameters,instantaneous efficiency as the output parameter,respectively,is designed and compiled and then the numerical simulation and analysis of the effects of the environmental,structural and operational parameters on its instantaneous efficiency are carried out.4.The related theory and method for the experimental measurement system to verify instantaneous efficiency of this kind of flat-plate solar collector are introduced in detail.Based on this experimental measurement system,the instantaneous efficiency of the flat plate solar collector with a single glass cover plate decreases with the increase of the normalized value of temperature difference,and the corresponding comprision and analysis of efficiency curves and efficiency equations obtained from the experimental measurement with those from the numerical simulation are executed,respectively.The results show that the established heat-transfer model with one-dimensional steady stat for this kind solar collector is correct in theory and the proposed iterative numerical simulation program of the effects of the variation of key parameters of this kind of solar collector on its instantaneous efficiency is feasible.