Experimental study of moisture removal rate in Moringa leaves under vacuum pressure in closed-loop heat pump dryer

Abstract

Herbal industries are facing challenges while processing the herbal leaves. Herbal leaves are processed using various methods such as convection drying, chemical drying, vacuum drying, microwave drying, etc. The common issues encountered during the time of drying the herbal leaves are lost in phytochemicals, nutrients and colour. Heat pump drying is an important method by which the drying can be made without influencing of environmental condition and by controlling the drying properties without loss in phytochemicals, nutrients and colour. In this proposed work the experimental device, namely closed-loop heat pump dryer is designed and developed for conducting experiments. For this study, Moringa leaves were considered as herbal leaves. The vacuum is introduced in the heat pump dryer and the Moisture Removal Rate (MRR) is calculated under this condition. The experiments were conducted with vacuum pressures of 0.9 & 0.8 bar and the air velocities of 1.1 m/s & 1.4 m/s respectively. In this study, the experiments were conducted under the above-said conditions for several periods with temperature transients. Based on the experimental study it is observed that the moisture removal rate is increased significantly under low pressure with high temperature and velocity.