| The whole world now is facing a serious energy crisis. More and more countries gradually realize the importance of the energy for the global economic development and social harmony and stability, hoping to solve the current energy crisis by renewable energy.The solar energy as a new type of renewable energy goes into people’s vision. It is environmental friendly, abundant, persistent and widespread, which will be very important in the future. Solar air collector is an important part for the solar energy heat utilization and has been widely used in agricultural and sideline products building integrated solar drying and solar heating and other fields, which makes a positive role for the promotion and application of solar energy. Therefore, the design and promotion of solar air collector with higher efficiency and lower cost has a profound influence on the development of solar energy.This paper mainly research three kinds of design of new type solar air collector,including the solar air collector with finned absorber, solar vacuum tube air heater with11 the Baffle and a new straight vacuum tube solar air heater. The advantages of them have been pointed out and the three new solar air collectors have been made. Then the thermal performance of them are measured. The mathematical model of solar air collector with fins was established and the gained theoretical values are compared with the experimental values. The results show that the test error of solar air collector with fins under different inclinations is less than 3.5%. The internal air mass flow rate change of collector is tested.The instantaneous efficiency and mass flow rate present a proportional relationship in a certain range, and the error between theoretical value and experimental value is only 8%. If the flow way of solar air collector with fins is changed, the instantaneous efficiency is higher than that of under the positive pressure when internal working medium of air collector is under the negative pressure condition, and the average instantaneous efficiency can be higher than 5%. For the model with the vacuum tube solar air heater, the thermal performance was significantly higher than that of general type straight vacuum tube solar air heater. The instantaneous efficiency difference between the two different types of heater is 16.4%, while the instantaneous efficiency of new straight vacuum tube collector can reach up to 72.9%. However, the experimental tests show that the number of new straight vacuum tube solar air heater pipe should not be too much and should be controlled within15. The thermal performance of baffle type vacuum tube air collector is also higher thanthat of interpolation type vacuum tube air collector, and the average instantaneous efficiency is higher above 6%, The maximum instantaneous efficiency of baffle type vacuum tube air collector is 80.1%, and the temperature difference between the import and export of collector can up to 113.1 ℃. Similarly, the air heat collector has relatively increase the internal air resistance. Consequently, we suggest that the air collectors in series should be less than 10 vacuum tubes. According to the researches on designing, testing and analyzing for the air collector, some advises can be provided for the future solar air collector,extending the improvement and optimization of solar air collector.A solar air collector combined with heat pump system has been designed, the drying experiments are conducted under two conditions. On one hand, only the solar air collector is used as the heat resource to dry. On the other hand, the solar air collector is used as the primary heat resource which is combined with the heat pump as the supplementary heat resource. The drying process is tested under different temperature and different material quality. The dehydration rate of material is tested and obtains the physical drying characteristic curve, which may provide certain reference value for solar drying. |
PDF Full Text Request