Family size solar dryer for an estimation of the heat transfer coefficient

Knowledge of the heat transfer coefficient is believed to be of great contribution in the course of a full design of a solar dryer. To find an expression for the heat transfer coefficient, the general logarithmic velocity profile for turbulent flow is used for the analysis. It is assumed that the fluid is air at atmospheric pressure, and that the thin wall laminar sublayer has a small or negligible effect on the value of the fluid bulk temperature. The final form of the correlation equation gives a relation between Nusselt number and Reynolds' number, and is given in a form which is easy to remember by the solar dryer designers. Comparison of the predicted values indicates that the correlation can predict values to within +/- 6% of experimental values reported in literature. Expected errors of nearly +/- 25% were observed when the correlation predictions compared with well known correlations found in literature and in text books.