A medium-size greenhouse solar dryer for drying eco-friendly handmade papers: Performance analysis and drying kinetics

In the presented experimental study, a medium-sized industrial greenhouse solar dryer (MSGSD) of floor area 1.82 x 1.52 m2 was developed using low-cost, locally available materials and tested in the winter season (November- December 2022) for eco-friendly handmade paper drying. The handmade papers having initial moisture content of 60 % (w.b.) were dried to a moisture content of 8–10 % (w.b.), and time taken to dry these papers varied from 3 to 8.5 h depending upon the paper type (off-white or coloured), paper thickness (100–200 GSM) and number of papers (75–150) dried inside the dryer. However, drying in the open sun and shade took 4 to 10 h and 19 to 29 h, respectively, to achieve a moisture content of 8–10 % (w. b.). The instantaneous thermal loss efficiency factor of the developed dryer was calculated for forced and natural convection modes of operation and found to be in the range of 13.1 % − 23.5 %. Ten theoretical models were investigated for characterizing the drying process, out of which the Midilli-Kucuk model was observed to be the best fit with experimental data. The economic analysis revealed a payback period of 0.61 years.