Performance Testing Of The Whole Solar Dryer Of Wood And Simulation Optimization Of Flow Field

Drying kiln powered only with solar was designed in this paper and several tests of light-electricity and light-heat were implemented to this kiln. Besides, the FLUENT was applied to simulate and optimize the homogeneity of inner fluid distribution, and to determine the effects of airflow velocity, airway width, thickness of parting stop, the relationship between wind screen and timber pile and the guide plate on the homogeneity of fluid distribution. Finally, a contrast of pre-drying performance was made between the optimized and non-optimized kiln, the model was fitted on the basis of the relationship between drying rate, solar daily radiation and the moisture content. The main research results are the following:(1)The total monthly electric energy production of the photovoltaic power generation system was 221.37kW·h which was enough for the equipment; the gross generating capacity was 221.37 kW·h which was enough to meet the requirements. When the device was under sunny and cloudy days, the highest temperature was 73.6℃ and 60.8℃, and the average temperature of no-load dryer was 51.2℃ and 48.6℃, respectively. The daily total radiation was 20.7 MJ/m2 and 14.3 MJ/m2, and the photovoltaic power generation capacity was 9.44k W·h and 5.99kW·h. Compared with natural convection drying, the temperature distribution was more uniform in forced convection drying condition, but the entire temperature of the drying room was decreased.(2)The effects of airflow velocity, airway width, thickness of parting stop, the relationship between wind screen and timber pile on the homogeneity of fluid distribution were sorted as airway width> airflow velocity> the relationship between wind screen and timber pile> thickness of parting stop. The optimized factor combination applied to this kiln was airflow velocity of 2.5m/s, airway width of 0.4m, parting stop thickness of 0.04m and the wind screen 0.2m shorter than the timber pile.(3)The guide plate was benefit for the homogeneity of fluid and temperature distribution, but the improving extent was closely related to the angle of the guide plate. The fluid and temperature distribution could achieve the greatest homogeneity when the angles of horizontal and vertical plate were 90° and 60°, respectively.(4)Compared with natural drying, the solar kiln in this paper could significantly accelerate the drying rate. Drying with natural convection could increase the drying rate by 41.4% while the drying with forced convection could improve the rate by 116.3%. Additionally, the solar drying obtained remarkable effect on improving the uniformity of the wood moisture content distribution, reducing wood drying stress.