Study On Control Method Of Heat Transport Process Of Solar Air Collector

Passive solar houses with Trombe-wall have been widely used in rural areas in northern China.In order to deal with the over-heating problem in summer,to facilitate the building reconstruction,as well as to meet the living standard of urban buildings,some new solar air collectors have been developed.But most researches mainly focus on thermal performance of the single solar collectors,which results in high heat efficiency of the single solar collectors but poor heating capabilities.It is indicated that optimal transport method has to be considered to obtain ideal indoor environment.In addition,effective control of the whole system is required to not only allocate the energy optimally and create comfortable environment,but also provide a simple operation pattern for the actual use.In this study,the self-developed heat supply system with solar air collectors is studied by experiment and numeric simulation to investigate the effect of circulation strategy on the heating effect.The main work includes:1) determining the optimal air circulation and flow rate.2) Proposing strategies of vent control and heat distribution method.3) The control methods of valves can effectively aid the reasonable distribution of solar energy,and then provides data for the integrated design of solar energy collection system in buildings.Conclusions obtained from two years' in-situ measurement and theoretical calculation can be summarized as:(1) The disruption of airflow through solar collectors With holes is much more intense than that in the solid collectors,which leads to quick temperature rise.The temperature difference in the two cases can reach 8～10℃in natural circulation.(2) Proper enhancement of air flow rate promotes both the quality and the quantity of heat supply,and stabilizes the solar collecting efficiency even under variable outdoor climate.However, uncontrolled flow rate will harm the system performance.The optimal air flow rate is approximately 0.025 kg/s from the experimental results.(3) Performance of intermittent operation is higher than that under the constant operation,while varied time division under intermittent operation is favorable than that under the constant time division.The operation extension changes with solar radiation intensity.(4) Predicted temperature distribution with a theoretical calculation formula is validated well against experimental data for solid plate collectors.The outlet air temperature in the module can be used as a control parameter.(5) The relation between air layer and convective heat transfer is regressed,which can accurately predict the heat transfer rate into buildings,and provides references for optimal design of solar collectors.