Analytical modeling and performance analysis of a solar cooker cum dryer unit

Abstract

ABSTRACT In this work, analytical modeling and theoretical analysis of a recently developed unique design of a solar cooker cum dryer (SCCD) have been conducted to predict its thermal characteristics under a given set of input parameters. The energy balance equations of the main components of the cooking compartment are iteratively solved to determine the unknown temperatures of the SCCD unit when it operates as a pure cooker and when the same acts as an air heater for the food drying compartment. The influence of design parameters such as air velocity, glazing thickness, spacing between glazing, back reflector, and surface coatings of the absorber plate has been studied and quantified. The analytical model has been tested by simulating and validating the modeling results with the experimental data for different days of the year Moreover, further experiments are conducted on the SCCD in drying mode to quantify its thermal performance in natural versus forced convection of the airflow through the SCCD and to demonstrate its effectiveness in comparison to open sun food drying. The obtained results show that the SCCD unit attain cooking and drying temperatures in the suitable range of 80–135℃ and 50–70℃, respectively. The experimental results of the SCCD unit as a food dryer revealed that the Page model with higher adequacy is found to be the best fit for all three modes of food drying in the SCCD unit. It is found that in comparison to drying of tomatoes in the open sun which took ⁓13 hrs, forced convection of airflow in the SCCD unit resulted in the least time of ⁓7.5 hrs to achieve the desired level of moisture content. The energy and exergy efficiency of the SCCD in cooking mode was estimated to be in the range 2.1–15.5% and 1.1–5.6%, while it was 7.5–16.5% and 26.6–50.7% in drying mode, respectively.