Vortex generators in a tube for thermal enhancement

Vortex generators/turbulent promoters generate the vortices which reduce the boundary layer thickness and introduce a better mixing of the fluid to enhance the heat transfer. In this research, thermal performance of winglets vortex generators (VGs) is investigated experimentally. Delta winglet VGs of different heights and attack angles were inserted inside a copper tube. The experiments were conducted with VGs for an air flow range of Reynolds numbers from 6000 to 33000. The influence of the winglet VGs on heat transfer and pressure drop was investigated in terms of the Nusselt number and friction factor. Vortex generators were arranged repeatedly inside the tube of 12 rows (N) with same pitch distance (P = L N) and each row consists of 4 VGs in a circular pattern on the inner surface of the tube. So relative pitch ratio (PR = P D) is 1.6 and three winglets blockage ratios (B = H D) are 0.1, 0.2, 0.3 with respect to three winglets heights (H = 5mm, 10mm and 15mm). Attack angles of the VGs were maintained 0°, 15°, 35° and 45° for B = 0.3. Based on the experimental results, Nusselt number increased 2 times higher than that of the smooth tube. Friction factor decreased with Reynolds number from 0.13 to 0.06.