Development of Heat Storage-based Greenhouse Dryer - A Comprehensive Assessment of the Dryer
Abstract
Different agricultural produce is dried using various drying sources and processes. Fossil fuel based dryers are more efficient but polluting and costly. In third world countries primary processing systems are scarce in all production catchment. Present study develops heat storage-based greenhouse solar bulk drying system for process standardization and value addition of produce.Among several cost-effective bulk drying systems, the Poly-house heat storage-based greenhouse dryer stands out because it considers meteorological conditions and physico-chemical characteristics of harvested agricultural produce. This dryer is suitable for spices like ginger and turmeric and minor fruit like elephant apple and Indian gooseberry. Structural design dimensions are improvised and the system is smart to achieve improved hot air circulation, thermal efficiency, and economic return.The structural system of the dryer is standardized into hemi-cylindrical section ofspan 10.2m and radius 2m of capacity 1000 kg (with racks), flat plate collectors in inlets, insulated heat storage base and improvised forced convection system.Under no load test, the system generates hot air ranging from 42.70 to 54.32˚C at an ambient temperature of 28.50 to 34.60˚C.The primary drying is predominantly natural convection with an air residence time of 36 seconds, supplemented by humidity sensor-induced forced convection. Initial and final moisture content of 640 kg turmeric dried in one batch range from 85 - 89% to below 11% respectively. At average solar radiation 521.46 watt/m2, thermal efficiency of the dryer is 28.49%.
