Performance analysis of heat exchanger- evacuated tube assisted drying system (HE-ETADS) under unload condition

Abstract

A prototype heat exchanger-evacuated tube assisted drying system (HE-ETADS) has been fabricated and tested under unload conditions in active mode at different water flow rates (10, 20, and 30Ltr/hr). Experimental work was conducted in three different categories. Category-I: drying system in stagnation condition, Category-II: all fans are in operating condition and Category-III: ventilation window is open. Coefficient of performance, heat consumption factor, convective heat transfer coefficient (CHTC) and diffusion coefficient have been calculated in thermal performance analysis of advanced system. Highest coefficient of diffusivity (0.19) was on third day of experimentation under Category-III at 30Ltr/hr water flow rate. Maximum heat consumption factor (0.60) was calculated during the second day for Category-I at 20Ltr/hr and for Category-II it was 0.775 during third day of experimentation at 30Ltr/hr, whereas in Category-III it was 0.782 at 10Ltr/hr water flow rate during first day of experiment. Higher coefficient of performance was 0.902 on third day of experiment for Category-I at 30Ltr/hr water flow rate whereas 0.940 was on first day of experimentation for Category-II at 10Ltr/hr flow rate. Category-III achieved 0.97 at 10Ltr/hr water flow rate during first day of experiment. CHTC of north wall insulated greenhouse dryer (NWIGHD) for ground to drying cabin air was 46.622 W/m2℃, while for advanced HE-ETADS it was found 47.542 W/m2℃, which is 1.98% greater than NWIGHD. Hence, HE-ETADS has potential to enhance drying rate and reduce payback period.