Abstract
A proposed solar system for drying agricultural waste sludge was tested on its collecting performance of solar thermal energy. The system has a simple solar housing and a rotating drum inside the housing, and its manufacturing cost is very cheap. One of the characteristics of the proposed system is that it collects solar heat in the solar housing and drying operation is run in the housing simultaneously. The experiments on collecting solar thermal energy brought the following results.
1. Hot air about 40-50°C is obtained for 6 hours on a fine day in the summer. There is a temperature gradient in the solar housing. The air temperature on the floor is lower than that of exhaust air and the air warmer than the exhaust air remains above the rotating drum inside the housing.
2. The collecting characteristic of solar heat is described with a state model. The exhaust air temperature is simulated approximately by the state differential equation which has a system heat capacity and two variables, solar radiation and inlet air temperature.
3. The collected solar heat is influenced with exhaust/inlet air flow rate. The more the exhaust air flows, the lower the air temperature increases, however, the higher the total collecting efficiency becomes.
4. Simulation results show that about 5°C warmer air was obtained in winter noon time of Tokyo in case of the exhaust air rate 0.02m3/s than in case of the exhaust air rate 0.06m3/s, but they induced almost same removed water by drying.
