Experimental Studies on Natural Circulation Solar Water Heating System Fitted with Helical Screw Tape Inserts

Experimental investigation of heat transfer and friction factor characteristics of thermosyphon solar water heater with helical screw tape of various twist ratios(Y=3, 4, 5 and 6) has been studied. Compared to other twist ratio, the minimum twist ratio 3, offers higher Nusselt number, friction factor and Thermal performance. The average Nusselt number, friction factor and thermal efficiency for helical screw tape collector with minimum twist ratio 3 are 13.86, 0.111 and 63.62% respectively. Whereas the increasing twist ratio decreases the above performance. The heat removal factor for screw tape collector with twist ratio 3 has 54.4% higher than plain tube collector. Correlations developed for friction factor and Nusselt number has been verified and deviation falls within ±13%.