Heat transfer enhancement for laminar flow in tubes using curved delta wing vortex generator inserts

The results of an experimental study for heat transfer enhancement in a circular tube fitted with a curved delta wing vortex generator insert are presented here. Local heat transfer coefficient and overall pressure drop measurements in the laminar flow regime with water as the working fluid are presented. Curved delta wing vortex generators were attached on the opposite sides of a central rod at specific axial locations to form the insert. The thermo hydraulic performance of these inserts with different geometrical parameters viz. pitch to projected length ratio (p/pl), angle of attack (a), and circumferential contact length to tube inner diameter ratio (bid) was studied. The local heat transfer measurements for both smooth and rough surface sides of the tube are reported with the tube Reynolds number (Re) varying between 250 and 1500. The average Nusselt number ratio with and without the insert (Nu(a)/Nu(s)), at equal Reynolds number (Re) is found to be in the range of 5.0-15.0. The performance ratio R3, (Nu(a)/Nu(c)), based on equal pumping power and constant heat transfer area, is found to be in the range of 1.0-6.0. (C) 2016 Elsevier Ltd. All rights reserved.