Performance improvement studies in a solar greenhouse drier using sensible heat storage materials

Experiments were conducted in a natural convection solar greenhouse dryer using different sensible heat storage materials (concrete, sand and rock-bed) in order to study their thermal performance. For both sand and rockbed, 4 '' thickness was found to be optimum as it provides better drying environment both during day and night. The dryer reduced the moisture content of coconuts from 52 (w. b.) to 7 % (w. b.) using concrete as heat storage material in 78 h saving 55 % of drying time compared to open sun drying which takes 174 h for reducing the moisture content to the same level. The sand took 66 h saving 62 % of drying time whereas rock-bed took only 53 h thereby saving 69 % of drying time compared to open sun drying. The efficiency of the dryer was found to be 9.5, 11 and 11.65 % using concrete, sand and rock-bed respectively.