Transient thermal efficiency of natural hybrid dryer system on chimney height variation of exhaust moist air

In developing countries, the sun and biomass are very important as the alternative and renewable energy sources that is very necessary the effort for utilizing them maximally. This study has developed a natural hybrid dryer system utilizing the heat energy was generated from the biomass stove and the solar collector. This dryer system has been tested on the chimney height variation of exhaust moist air, namely: 2m, 4m, and 6m. For assessment of thermal efficiency, several variables of experimental data was collected consist of: several point of air flow temperatures, the ambient temperature, air flow velocities, mass of material which was dried, and solar radiation. Further, the efficiency of solar collector, the efficiency of biomass stove, the efficiency of drying chamber, and the total efficiency of system against the time as the purpose of this study. The result showed that with increased of chimney height of exhaust moist air caused the increase of air mass flow rate, and further caused the increase of heat transfer rate in the biomass stove and solar collector against the time. It caused the increased of transient thermal efficiency of biomass stove and solar collector against the time and it was influencing the increase of evaporation rate. Thus, the drying speed was increasing and with chimney height of 6m was the fastest with the drying time was 7 hours, while 7.5 hours and 8 hours were for height of 4m and 2m respectively. With increased of chimney height of exhaust moist air caused the efficiency of the drying chamber was decreasing and the total efficiency of system was increasing slightly, each was decreasing against the time due to decreasing of mass.