Development and evaluation of mini heat pump dryer for slice banana

Abstract

The purposes of this research were to develop and to test performance of mini heat pump dryer for slice banana. Drying chamber of 0.48×0.47×0.39 m3 was designed and it could contain three trays. The three trays had dimension of 0.33×0.409 m2. A blower with 174.6 W motor of air condition was modify and could adjust flow rates of three levels for air cycle system in dryer. The air system had bypass air at evaporator. The refrigerant of R-134a and four main parts were used in the heat pump system. The four main parts were a 497 W hermetic compressor, a 1,800 W condenser, an expansion valve and a 1,300 W evaporator. Experiments for test performance of the mini heat pump dryer used close loop air system, an evaporator bypass air of 60 %, a temperature of 60 oC and various flow rates of 0.117, 0.128 and 0.140 m3/s. Slide bananas of 400-500 g had an initial moisture content of 244-281 %dry basis and were dried until final moisture content lower than 6.24±0.007 %dry basis. It was found that the flow rates of 0.117, 0.128 and 0.140 m3/s had coefficients of performance (COPh) of 3.32±0.066, 3.88±0.031 and 4.24±0.08, respectively and had specific moisture extraction rates (SMER) of 184.5±11.85, 186.2±8.17 and 200.1±21.34 g/kWh, respectively. The flow rate at 0.140 m3/s was the best condition because it had high specific moisture extraction rate.