The prime objective of the present numerical study is to obtain relatively more realistic values of performance parameters of a sheet and tube type solar flat plate collector of fixed collector area and number of tubes. Considering temperature dependent thermal conductivity and overall loss coefficient and assuming cubic temperature profile along the tube, pseudo-transient form of two-dimensional, nonlinear partial differential equation governing the steady state temperature distribution in the absorber plate fin is solved using Alternating Direction Implicit finite difference scheme. Numerical results are presented and discussed for wide range of values of aspect ratio of the absorber plate, overall loss parameter, and dimensionless fluid outlet temperature. On the basis of discussion of these results, it is concluded that assumption of constant thermal conductivity and overall loss coefficient results in overestimation of the total entropy generation rate with substantial error. It is also concluded that for any fixed set of values of dimensionless fluid outlet temperature and overall loss parameter, total entropy generation rate increases linearly with increase in aspect ratio of absorber plate. Further, it is found that total entropy generation rate increases with increase in overall loss parameter, the rate of increase being somewhat higher for lower values of overall loss parameter and a decrease in fluid outlet temperature results in an appreciable increase in total entropy generation rate. (C) 2014 Elsevier Ltd. All rights reserved.