Mathematical modeling and performance analysis of thin layer drying of bitter gourd in sensible storage based indirect solar dryer

• Performance of the sensible heat storage based indirect solar dryer was studied for drying bitter gourd slices.
• The thin layer drying behaviour explained with drying models for the indirect solar dryer and under open sun drying.
• Probably, first time, the drying models were reported for bitter gourd drying in the indirect solar dryer.

An indirect forced convection solar dryer integrated with porous sensible heat storage medium was developed. The effect of porous thermal storage and mass flow rate of air on the performance of the system for drying bitter gourd was studied. The experimental setup consists of a blower, solar flat plate collector with corrugated absorber plate (2 m2) and a drying chamber. The thermal storage medium (pebble) is placed below the corrugated absorber plate, in the air passage as a porous medium. The experiments have been carried out with various mass flow rates of air and different drying models have been used for explaining the drying behaviour of sliced bitter gourd. The result shows that, (i) the initial moisture content 92% (w.b) of bitter gourd was reduced to 9% (w.b) in 7 h in the proposed drying system, while it was 10 h for open sun drying, (ii) the maximum specific moisture extraction rate was observed as 0.215 kg/kWh at the mass flow rate of 0.0636 kg/s and the corresponding specific energy consumption was 4.44 kWh/kg, (iii) the collector and drying efficiency of the system were 22% and 19% respectively. The two term model and Midilli–Kucuk model are most suitable for indirect solar dryer and open sun drying in terms of statistical parameter respectively. The drying inside sensible heat storage based indirect dryer was more consistent and produced better quality product as compared to open sun drying.Industrial relevance
• Every year post harvest losses are increasing rapidly due to the lack of storage facilities.
• Solar dryers are the most suitable technology that can be easily availed at low cost and in small scale and it can be used as an income generation option for farmers and women in rural areas.
• The role of solar dryers in food processing industries is significant especially in developing countries in the following areasoFor preserving fruits and vegetablesoDairy industriesoAgricultural crop dryingoTimber dryingoIndustrial waste drying
• The utilization of thermal storage medium in the solar dryers is being focused much for the reasons of extending the availability of the system for operation and to achieve better quality of the products.