Solar rack dryer with supplementary heat storage and evaluation of dried food quality

Performance of a solar rack dryer augmented with heat storage materials was evaluated in terms of temperature and humidity developments as well as quality characteristics of dried foods. Granite chips and granite rubbles were used as sensible heat storage materials. Also paraffin wax in aluminum trays and enclosed in PVC pipes were integrated into the collector as sensible and latent heat storage. Trials were carried out under natural and forced air draft conditions. Results showed that the solar rack dryer coupled with flat a plate collector containing granite rubbles, granite chips and paraffin wax collectively stabilized drying air temperature during the day time at 50C, thus increasing the effective drying hours. However, marginally acceptable organoleptic quality of dehydrated foods indicated that the dryer further requires additional heat source to supply necessary heat during nights, and whenever necessary during daytime to obtain optimum product qualities.