Numerical Investigation of Heat Transfer Enhancement in A Tube With Hexagonal Cross Sectioned Coiled Wire
A numerical investigation on heat transfer enhancement in a constant heat-fluxed tube inserted with hexagonal cross-sectioned coiled wire inserts was performed.The computations were carried out by consideration of with three different pitch ratios (P/D=1, P/D=2 and P/D=3) and three different hexagon edge length ratios (a/d=0.08, a/d=0.1, a/d=0.12) for Reynolds numbers between 5000 and 17000, using air as a working fluid. The plain tube results were compared with the works available in literature for confirmation of the used numerical method. The usage of coiled wire inserts yielded a significant increase in heat transfer rate and flow friction over the plain tube. Numerical results revealed that Nusselt number and friction factorrise with the reduction of pitch ratio (P/D) and increment of hexagon edge length ratio (a/d). Eventually, the maximum thermal enhancement factor of 43% wasprovided for the wire with a/d=0.12 and P/D=1 at Reynolds number of 17000.
Index Terms—coiled wire, flow friction, heat transfer, thermal enhancement factor.