Heat and mass transfer parameters in the drying of cocoyam slice

Abstract

The paper investigates some heat and mass transfer parameters (HMTPs) of three varieties of cocoyam slice and their vitamin B retention level in convective drying. The varieties include Colocasia esculenta (COE) and xanthosoma sagittiffolium (white flesh – NX01, red flesh – NX02). The objective is to generate HMTPs for process model development, applied in dryer design. The oven and sun drying procedures were employed where temperatures were maintained between 50 and 70 °C (oven drying) and sun drying, the readings were observed at every one hour. The results obtained show that the mass transfer coefficient for the three varieties lies between 1.01044×10−6 and 3.44876×10−6 m/s while the heat transfer coefficient ranged from 1.17973 to 3.58284 W/m2 K. The specific energy consumption for drying was estimated at 14.15, 25.16 and 35.07 kWh/kg for NX02, NX01, and COE respectively, at drying temperature (DT) of 60 °C. However, at DT range between 50 and 70 °C the moisture extraction rate was varied from 0.047 to 0.185 kg/kWh, for NX02, 0.070–0.258 kg/kWh for NX01 and 0.099–1.42 kg/kWh for COE, with vitamin B retention level ranging from 70.13% to 100% at all DTs for the varieties.

Keywords

• Cocoyam drying
• Vitamin B
• Energy consumption
• Heat transfer coefficient
• Volume shrinkage