Performance studies of a built-in-storage type solar water heater at Dhaka in the month of January-March

Abstract

A Built-in-Storage Type Solar Water Heater (BSWH),115 litres in capacity, 1.25m2 of collector surface area, and 92 mmin depth was studied at Dhaka during the months of January, February, and March, 1992. In four hours starting at 8 AM, the BSWHcan heat 115 litres of water to a temperature of 50°C absorbing 0.743 kW/m2 in February and to 61°C absorbing 0.979 kW/m2 in March. From February to March the energy is increased by 32 percent but the water temperature is increased by 22 percent. The monthly average heat energy absorbed by BSWHis 0.240 kW/m2 with 59 percent efficiency in February and 0.270 kW/m2 with 54 percent efficiency in March. From February to March, the average heat energy absorbed by water increased by 12.5 percent but efficiency reduced by 8.5 percent. This differences in heat energy absorption is because of the fact that loss of heat increases rapidly with the rise of water temperature in March. On very dear bright sunny days, the maximum efficiency of 70 percent can be obtained with a mean water temperature of 56°C in February and 58 percent efficiency with a mean water temperature of 63°C in March.