Utilization of waste heat for energy conservation in domestic dryers

Abstract A physical means of dehumidification was used in this study to recover and reuse waste heat emitted from tumble dryers to increase drying efficiency and decrease power consumption. An experiment was conducted; waste heat from a dryer was dehumidified in a heat exchanger, and some heat was reclaimed to preheat external air. After the optimal mixture ratio of external and re-circulated air had been determined, that optimal air mixture was introduced into the dryer through the recirculation air ducts designed in this study. Experimental results showed that the improved dryer, operated at a 60% recirculation ratio produced the highest energy efficiency, resulting in 18% less power consumption than a standard dryer. In addition, this configuration produced the lowest specific moisture extraction rate (1.099) and the highest drying efficiency (60.6%). This efficiency was higher than that of the dryer (50%) and the proposed heat exchange system was thus more energy efficient than was the dryer. The theoretical mathematical model derived in this study matched experimental results. The average error values between the theoretical and experimental values for the drying efficiency and the specific moisture extraction rate were 0.7% and 0.6%; the largest error values were only 1.5% and 1.2%.