Macro encapsulated pcm cluster integrated air heater driven multi tray solar dryers

Abstract

Rapid economic growth boosts the demand for energy, and postharvest losses threaten the food security of the world. These two aspects serve as the motivation for the present research work. This work attempts to address and resolve the challenges dealt with the intermittency of solar radiation and sustaining the thermal response of a solar air heater by the thermal lag of phase change material (PCM). Additionally, the study investigates to determine and remedy the problems encountered in multi-tray solar cabinet drying, namely, the drying uniformity per batch, the choice between different preliminary preparation considerations, and the user-flexibility in product selection. The present research work comprises of mainly four stages, with comprehensive experimental and computational analysis pursued up on a sequential order. The first stage deals with the design, fabrication, and thermodynamic performance evaluation of the double-pass solar air heater with a channel depth ratio of 1.5. The outdoor experimental study assesses the thermal response of the air heater under different influencing parameters, such as mass flow rate, channel depth, pressure drop, and thermophysical properties of the working fluid. The second stage proposes a cost-effective method of integration of thermal energy storage (as a cluster of macro-encapsulated metallic containers filled with PCM) within the solar air heater. The second stage analysis consists of three subsets, namely, (i) the determination of the influence of geometry and location of the macro-encapsulate containers, (ii) the generalization of the impact of elementary heat transfer aiding for the phase transition of PCM enclosed within a thin cylindrical macro-encapsulate container introduced in an air duct, and (iii) studying the influence of critical factors like heat input, flow velocity, melting temperature, and quantity of PCM on the phase change characteristics of a cluster of discrete macro-encapsulated PCM incorporated in the airflow pathway of a solar air heater.