Experimental analysis of convective heat transfer on tubes using twisted tape inserts, louvered strip inserts and surface treated tube

This paper analyses and compares the effects on outlet water temperature, heat transfer rate and its thermal efficiency of three different types of tubes such as twisted tape inserted tube, louvered strip inserted tube and a surface treated (laser peened) tube are dealt with different operating parameters, viz., solar insolation, water temperature at the inlet and ambient temperature. Non-concentrate collector (flat plate) is used. A plain or normal tube (non-surface treated) was also tested for comparison. Polystyrene and acrylic glasses were used for reduced heat loss. It is observed that the heat transfer rate and its thermal efficiency tend to increase with the increased ambient temperature and solar insolation with the louvered strip inserts had given the best thermal performance in comparison with the other types.