Solar assisted heat pump drying system

Rahman SMA, Lambert Academic Publishing (LAP), Theodor-Heuss-Ring 26, 50668 Koln, Germany , 2010

A solar assisted heat pump drying system was designed, fabricated, and tested under the meteorological conditions of Singapore. Experimental results were analysed to evaluate the effect of different parameters on the system performance and, finally, compared with simulation results. Drying characteristics of green beans, grams, and paddy have been investigated. For the condition considered in this study the diffusion coefficient of green beans, paddy and grams was found to be about 9.61x10-11 m2/s, 1.075x10-10 m2/s, 1.08x10-10 m2/s, respectively. The range of efficiency of air collector, with and without dehumidifier, ranged between 0.72 - 0.76 and 0.42 - 0.48, respectively. Maximum evaporator-collector efficiency of 0.87 against a maximum air collector efficiency of 0.76 was obtained. A COP value of 6.0 for a compressor speed of 1200 RPM and solar fraction value of 0.81 for a drying temperature of 550C were obtained. A series of numerical simulations have been performed for different operating conditions to optimise the system and to carry out the economic analyses. The optimum combination of air collector area, evaporator-collector area, drying temperature, and air mass flow rate was about 1.25 m2, 2 m2, 500C, 0.036 kg/sec, respectively, which provided around 89% of the total load. Economic analysis showed a minimum payback period of about 4.37 year.