Heat transfer analysis of hybrid active greenhouse solar dryer attached with evacuated tube solar collector

Abstract

The objective of the paper is to carry out the heat transfer analysis of novel designed hybrid active greenhouse solar dryer (HAGSD) attached with water-in-tube type evacuated collector. The experimentation is carried out to investigate the performance of dryer with and without evacuated tube collector (ETC) under active mode. Three high moisture seasonal crops namely tomato, ginger and bottle gourd have been dried inside the dryer for the two cases and also in open sun drying. Also the drying kinetic of crops has been fitted with ten drying rate models given by researchers. A new drying rate model is also obtained which gives a very close fit with experimental drying rate. The average values of convective heat transfer coefficients for dryer with ETC are 153%, 3.8% and 305.4% higher than the dryer without ETC for tomato, ginger and bottle gourd respectively. The drying time in case of dryer with ETC for tomato, ginger and bottle gourd is 9, 12 and 6 h respectively less than the dryer without ETC. The overall efficiency of the dryer for the three crops varies between 14.22 and 27.99% for dryer with ETC, while for dryer without ETC, it varies between 9.63 and 24.88%.