Drying kinetics and thermal analysis of turmeric blanching and drying using solar thermal system

Abstract

This paper presents an experimental investigation and mathematical modelling of turmeric blanching and drying in the solar cabinet dryer (SCD) using solar thermal energy. Steam generated from the Scheffler system is used for turmeric blanching, and an average blanching efficiency obtained is 19.93%. Also, SCD used the steam generated from the Scheffler system for drying of turmeric, and the drying efficiency of SCD was found to be 1.62%. Further, turmeric dried in SCD without connecting it with the Scheffler system (without steam). The efficiency of SCD without steam is found to be 49.76%. Initial and final moisture content is calculated by measuring turmeric's weight at a regular interval of time. Turmeric's moisture content is reduced from 77% to 15% in open Sun drying (OSD) and the SCD when it is connected to steam and without steam. The time required for the drying in SCD with and without steam was 63.88% and 52.77% less than the open Sun-drying (OSD) process for the same moisture content reduction. Convective heat transfer coefficient (CHTC) and evaporative heat transfer coefficient (EHTC) play a vital role in the thermal performance of the SCD. Correlation between the Nusselt number, Reynold number, and Prandtl number is formulated using the experimental data to evaluate CHTC and EHTC. An average value of 1.2468 W/0C-m2 for CHTC and 28.8841 W/0C-m2 for EHTC is found for SCD connected to steam, whereas for SCD without steam, it is an average value of 0.8779 W/0C-m2 and 15.7462 W/0C-m2 is observed. Mathematical modeling of thin layer drying turmeric was done to predict the moisture ratio. Among the different mathematical models used for prediction, the Page model is best suitable for turmeric drying in OSD and SCD.