The mathematical model developed for solar dryer on the basis of energy balance of solar radiations falling
on transparent cover, to give air temperature at the outlet of the collector. The collector is a most important part of the
solar dryer. An absorber plate and top enclosure cover forms the entire collector. The performance of collector is the
key factor in deciding total efficiency of solar dryer. Various convection heat transfer coefficients are associated with
solar collector. Heat loss from the top is the function of re-radiation of absorbed heat from solar absorber. Side loss
and bottom loss are also associated with collector of solar dryer. Thus careful design of collector is necessary to absorb
more solar radiations and to increase heat absorption rate. Figure 3 describes modelling variables and losses incurred.
Compared to top loss, side loss and bottom loss are negligible. Hence during model development they are assumed to
be neglected. An aperture factor is defined on account for some area of cover is closed with black absorber enclosure.
Ratio of Open area of cover to absorber area is the aperture factor.