Abstract :

The thermal profile of an exhaust gas waste heat recovery (WHR) crop dryer is presented. The dryer uses a parallel flow heat exchanger to recover the exhaust gas waste heat of a diesel engine generator for the drying of food crops. No-load tests of the assembled test rig were conducted to study the temperature profile and heat transfer rates in the dryer at varying inlet ambient air velocities. The results of the no-load tests revealed that the higher the airspeed through the WHR heat exchanger, the faster the rate of heating of the drying chamber. It was observed that the drying chamber initially at 32.3?, was heated to a maximum temperature of 116.1 ? after only a period of 39 min at an air velocity of 2 m/s. The values of the heat transfer rate obtained at selected drying chamber temperatures showed that the higher the drying chamber temperature, the lower the value of the heat transfer rate. The dryer was successfully used to dry freshly harvested maize grains and blanched yam samples at varying drying air temperatures and velocities. The results obtained will be very useful in the design and development of eco-friendly commercial dryers powered by recovered waste heat from available sources.