Effect of inlet design on the performance of storage-type domestic electrical water heaters

The effect of inlet design on the performance of storage-type domestic electrical water heaters (EWHs) was experimentally investigated for energy conservation. Three different side-inlet geometries; namely wedged, perforated, and slotted pipe-inlets; were tested using two 50 L capacity EWHs of aspect ratios 1 and 2 and two discharge rates 5 and 10 L/min. The three inlet designs are successful in promoting good thermal stratification inside the storage tanks of the EWHs. However, the degree of mixing produced by each design is found to have a significant impact on the performance. Thermal performance is quantified in terms of discharge efficiency, extraction efficiency, and fraction of heat recoverable. The results show an excellent performance for the slotted inlet. Although performance measures of perforated inlet are slightly less, the slotted inlet is attractive as it is simpler to manufacture and the extra cost associated with adopting it inside the existing EWH models is justified by the substantial savings in electricity and water consumptions, which ultimately concern the users. (C) 2006 Elsevier Ltd. All rights reserved.