EXPERIMENTAL PERFORMANCE ANALYSIS OF HEAT EXCHANGER-EVACUATED TUBE ASSISTED DRYING SYSTEM (HE-ETADS) UNDER VARIOUS OPERATION CONDITIONS

Abstract

Food is one of the essential needs of human for their existence. With the increase in population, the food requirement also increases. The food requirement can be met either by growing more food or by conserving the produced one. The edible items (fruits, vegetables, cereals, etc.) mostly get spoiled due to high moisture content in them. The effective method to preserve the crop from being deteriorated is drying it up to a safe moisture level. Solar drying is considered an efficient method of using solar radiation. Solar drying of crops prevents crop deterioration and helps in storing it for longer time. The dried produce has various advantages like better quality, low after harvest losses and longer storage time. To fulfill these criteria an advanced heat exchanger-evacuated tube-assisted drying system (HE-ETADS) has been fabricated at the rooftop of Madhav Institute of Technology and Science, Gwalior (26° 14' N, 78° 10' E) and tested under unload conditions in active mode at different water flow rates (10, 20, and 30Ltr/h). The purpose of testing in unload conditions is to record the maximum temperature and dehydrate the agricultural product that has moisture content in the range of 90 ± 5% to 70 ± 5%. Maximum heat consumption factor (0.775) was calculated during the third day for Category-III (ventilation window is open) at 30Ltr/h. Higher coefficient of performance was 0.902 on third day of experiment for Category-I at 30Ltr/h water flow rate whereas 0.940 was on first day of experimentation for Category-II at 10Ltr/h flow rate. Category-III achieved 0.97 at 10Ltr/h water flow rate during first day of experiment. Response surface methodology (RSM) is applied in the optimization of drying parameters i.e. drying chamber temperature (◦C), water flow rate (Ltr/h), and geometry (cm2 ). Optimal operational parameters are observed 89.99℃ (drying cabin temperature), 14.0 Ltr/h (water flow rate), 0.9998 (circular geometry), and 0.24004 kg (product mass). Optimum responses were 7.55% db. (moisture content), 5.54 kW/h (energy consumption), and 69.54% (shrinkage). Highest value of drying rate is 1.48 kgH2O/kg dry solid/h and the maximum efficiency of solar collector and solar dryer is 43.62% and 55.28%, respectively, at 30 Ltr/h water flow rate. Garlic dehydrated from 70% to 8% (wb) moisture content. The maximum exergy efficiency and minimum exergy loss were 57.64% at 30 Ltr/h water flow rate and 4.58 W at 10 Ltr/h water flow rate. Future, investigations carried out in three different drying methods named HE-ETADS (Heat exchanger- evacuated tube assisted drying system), greenhouse solar dryer (GHSD), and open sun drying (OSD) to compare thin layer drying kinetics, concept of mass transfer, and quality assessment of banana slices. Initial moisture content of banana slices was obtained 78 ± 2.0% (wb), which decreased to 23.2 ± 2.0% (wb), 25.6 ± 2.0% (wb), and 28.8 ± 2.0 % (wb) in all three drying systems respectively in 9hours of drying time. Weibull model (WM) defines thin layer drying kinetics of banana slices in all three drying processes. Maximum hardness and shrinkage factor of dried banana slices were obtained as 373.6g and 75%, respectively, in HE-ETADS. Effective moisture diffusivity, activation energy, and mass transfer coefficient were computed as 1.11E 07 to 2.48E-07m2 s -1 , 30.25kJ/mole, 3.21E-04 to 1.0E-04m/s, in HE-ETADS. System mitigates 77, 45.52, and 126 tons of CO2 & 42.68, 24.62, and 39.21 tons of CO2 in its lifetime for Case-I and Case-II for garlic cloves, banana slices and peppermint leave correspondingly. Energy payback time for garlic cloves, banana slices, and peppermint leaves is 0.85, 1.1 and 2.45 years less in Case-I compared to Case-II. The drying system is more sustainable in Case-I, with a higher Environmental Sustainability Index (ESI) value of 2.92, while in Case-II, the drying system has a lower value (1.25).