Impact of perforated shapes in delta type hindrance promoter on thermo-hydraulic performance of solar water heating system (An experimental study)

Abstract

In this investigation, the influence of the non-circular type of holes in perforated delta-winglets on the thermo-hydraulic performance is studied. The copper strip having perforated delta-winglets attached on both sides (top and bottom) is inserted into the absorber tube of the solar water heating system. Distinct parameters of the perforated delta-winglets which are varied in present investigation are Circularity (ψpw), Pitch ratio (Ppw), Angle of attack (αpw), Spacer length (Spw) and the Reynolds number (Re). The circularity (ψpw ) varies from 1.0 to 0.75, Pitch ratio (Ppw) varies from 2.0 to 0.5, Angle of attack (αpw) varies from 15o to 60o, Spacer length (Spw) varies from 0 to 450 mm and the Reynolds number (Re) of the flow varies between 200 and 1200. The experimental examination shows that the high non-circularity of perforation holes causes maximum thermal enhancement of Nusselt number (Nupw), while perfectly circular type of perforation holes in delta winglets have considerable lower impact on the thermal enhancement of Nupw. The experimental outcomes show that the perforated delta-winglets with Circularity ψpw = 0.86, Pitch ratio Ppw = 0.5, Angle of attack αpw = 450 and Spacer length Spw = 0 mm have optimum influence on Nupw and friction factor (fpw) of the solar water heating system.