Performance of an improved design for storage-type domestic electrical water-heaters

Performance of an improved design for storage-type domestic electrical water-heaters (EWHs) was experimentally investigated for energy conservation. The results were compared with those of conventional design EWHs having the same tank size and power rating. Data were obtained for two tanks with aspect ratios of 1 and 2, two draw-off rates of 5 and 10 l/min, and using three heating elements of different heights. It is found that improved design EWHs provide more hot water at almost constant temperature in the first mean residence time, which is of prime concern for the user. Thus, they exhibit higher discharging efficiencies due to better thermal stratification inside the heater storage tank. Also, thermal performance is enhanced with increasing tank aspect ratio and decreasing draw rate. These characteristics have a direct impact on energy consumption and result in lower electricity bills. The design improvements are simple to adapt as they only require minor modifications to be made to existing EWH models.