Novel dryer cum grinding unit: A thermal analysis of herbs drying

Abstract

The herbs are being extensively used in Indian families as medical purpose in dried state. Many a time, it is open sun dried or control oven dried. But, open sun drying is unhygienic and inefficient process for herb drying. Further, the aroma of the herbs is get compromised at times in control oven drying. The present work discusses the herb drying process cum grinding in controlled sun drying with persevering the aroma and quality of the herb to be dried. The study shows the effect of collector area exposed to sunshine and the useful heat gain at collector end, and in the drying chamber, further the instantaneous thermal efficiency is evaluated. The various heat losses in the cabinet and their effect on the system efficiency are calculated. The area of collector is exposed to sunshine (Ac) (ranging from 0.6 to 1 m2) for the study. The maximum thermal efficiency obtained is around 85.22%. It is observed that at lower temperature difference, i.e. at 5 °C, the instantaneous thermal efficiency is higher as compared to the 7 °C. Further, total 246 W-h is sufficient for grinding 20 kg dried herbs leaves. This study helps to find out the optimum conditions at which the drying process needs to be performed which would result in improved dryer performance.