Study on Optimal Operation Strategy of Solar Air Collector

Solar air collector system have been developed for 30 years, and it has a very perspective to employed in solar heating area for the advantages that has low cost,simple structure, no moisture condensation or frost phenomenon and rapid response for adjusting indoor air temperature. As to our country, most of the residential buildings are multi-storey, therefore the research on solar air collector using south external wall has become the key program of national” the Eleventh Five-Year Plan Period” in development of renewable energy. The thermal performance of single solar air collector have made progress recently. However, the control strategies on heat transfer process still are issues, and those are also critical to the practical engineering design.In this study, the heating system with solar air collector (Mode for short) which was developed by ourselves is studied by means of experimental research, theoretical analysis and simulation.In this study, the heating system with solar air collector (Mode for short) which was developed by us is studied by means of experimental research, theoretical analysis and simulation. In this paper, the module thermal capability and heating effect under different operating modes of the fan, the climate adaptation of the module heat capacity and the impact of the module thermal cycling velocity on the module thermal efficiency and indoor temperature distribution have been systematic studied. The module macro-physical model and the mathematical model of test room environmental control systems have been established, and the control system of auxiliary heating source have been simulated in the TRNSYS.Content and conclusion:(1) The heat exchange intensities, heat supply rates, heat efficiencies and heating effects under different operation were experimentally studied. It can be determined that the total heat exchange rate is 1.3-1.5 times of the sensible heat exchange rate, and the latent heat exchange can be neglected. The heat supply rates and average heat efficiencies under continuous operation are bigger than that under intermitted operation, but the transient heat efficiency is higher as the fan is running. The fluctuation of indoor air temperature at non-equal interval time is smaller than that at equal interval time, and that under continuous operation is between the two stated above.(2) The level analysis method was introduced to evaluate the climate adaptation for the module under different climates. The factors that affect the climate adaptation include the sunlight rate, total solar intensity, sunlight hour, the average lowest outdoor air temperate and average outdoor air temperature during heating season with the weighting factors of 0.177,0.465,0.233,0.046and 0.079. The method is used to evaluate the climate adaptation of the module in eight typical cities in heating area.(3) Both experimental and theoretical methods were used to study the heat supply rate and heat efficiency under different airflow velocities, and the relationship between heat efficiency and airflow velocity. The module ventilation mode was built with Airpak to investigate the effect of different outlet air velocity on indoor air temperature field. It can be found that the outlet air velocity gets bigger with an increase of airflow rate.(4) The formula of outlet air temperature was derived using the module heat exchange model. In addition, the auxiliary heat source control model for the test room was built with TRNSYS, and the indoor air temperature can be steadily kept at 18℃by regulating proportional constant, integration time and differentiating time of the PID controller.