Application of Response Surface Methodology for Energy Analysis of Thin Layer Drying of Physic Nut (Jatropha Curcas)

Abstract

A central composite design was used to analyze the effects of temperatures, air velocities and drying time on energy analysis of drying process of physic nuts. The data obtained from the drying kinetics were fitted into energy equations to obtain the energy utilization (EU), energy utilization ratio (EUR) and heat transfer rate due to evaporation (Qevap). Response surface methodology was used to generate mathematical models for the energy responses and a quadratic polynomial equation was obtained for energy parameters by multiple regression analysis. Verification experiments confirmed the validity of the predicted model. The analysis of variance (ANOVA) depicted that the quadratic model was suitable for all responses. The predicted and experimental values of responses were in reasonable agreement with each other. An analysis of variance indicated that EU and EUR increased (p< 0.05) with the increasing in air temperature from 40 to 80 oC while Qevap decreased (p<0.05) with the increasing in air temperature and velocity. The optimum value of EU was 5.468 J/s at 80 oC and 5.0 m/s while that of EUR was 0.85 obtained at a drying air of 80 oC at air velocity of 1.0 m/s. Maximum and minimum values of Qevap were 17.1 J/s and 3.979 J/s while drying at 80 and 40 oC and at air velocity of 1.0 and 5.0 m/s respectively. The respective values of regression coefficient (R2) and Adj. R2 of the responses are; EU (0.9638, 0.9379), EUR (0.9636, 0.9376), Qevap. (0.9575, 0.9271). Energy was maximally utilized in the drying process of the physic nuts.