Experimental analysis of a CO2 closed heat pump drying system combined with rotary dehumidification for drying banana slices drying

Abstract

A CO2 closed heat pump drying system combined with rotary dehumidification (HPRD) was investigated using both experimental and theoretical approaches. The advantages of HPRD over traditional CO2 closed heat pump drying systems (THPSs) for drying banana slices were analyzed. After drying, the drying kinetics and quality of banana slices were investigated. The results demonstrated that HPRD reduced the banana slice drying time during low-temperature processing while retaining more color and vitamin C content than THPS. In particular, HPRD increased the drying rate of banana slices dried at low temperatures by up to 41 % compared to the rate obtained by THPS. In addition, it increased the vitamin C content by an average of 12 % and reduced the total color difference by an average of 16 %. And the specific moisture extraction rate of HPRD increases by 26 % compared to THPS. The highest-quality banana slices, which were 3 mm thick and dried by HPRD at 43 °C, maintained a high drying rate and high drying quality. The optimal model of Henderson & Pabis predicted the drying behavior within the experimental range. The results indicated that the drying rate and quality of banana slices dried at low temperatures using HPRD were superior to those dried using THPS.