Enhancing Thermal Performance of Hot Storage Tanks through Chimney-Type Electric Heating and Natural Circulation

This study goes on the enhancement of thermal performance of a chimney type electrically heated hot storage tanks (HST) in static mode. The different natural circulation areas (chimney areas) were used with different di - ameter of large (9.5 cm), medium (2.5 cm) and small (1.5 cm) to find the effect of natural circulation on HST performance. Being part of real system, the performance of chimney insulated and without chimney insulation was also studied. The experiments showed that the chimney significantly affects the thermal stratification within the tank. Different chimney contact diameters (9.5 cm, 2.5 cm and 1.5 cm) were tested giving varying degrees of thermal stratification. It was found that the smaller chimney contact diameters led to higher thermal stratification that gives a more rapid heating of the top layer temperatures. The impact of insulation on thermal performance was inconclusive as top layer temperatures of the tank were still rising, showing the need of a more effective insulation as well as further investigation into the dynamic mode of operation. It is also noted that the top outer layer had the higher rate of temperature rising to the larger diameter, giving the sign of the importance of the chimney type electrical heater in the hot storage tank.