Design and experimentation on domestic solar water heaters using kenics twist inserts

Passive thermal augmentation is preferred in the design of compact and energy efficient domestic solar water heating systems (DSWH). Current study investigates the impact of modified DSWH with Kenics insert brazed with rod and spacer sequentially on the heat augmentation, and flow pressure, and frictional attributes. The thermal performance and flow friction characteristics have also been analyzed for different rod and spacer lengths such as 0.125, 0.25, and 0.5 m for twist designed with a stable twist ratio of 3. Experimental results reveal the drop in Nusselt number when the rod and the spacer span increase; and the flow pressure drop (Δ P ) decreases significantly while extending the same in comparison with full kenics twist. Further, the increment in pressure drop and heat removal was observed significantly in twist and rod inserts of minimum twist ratio and rod length compared to twist and spacer combination. Interrelationships developed for Nusselt number (Nu) and Friction factor (ft) show close agreement between estimated and experimental values.