Second law analysis of transient heat transfer for turbulent flow in a circular tube with baffle inserts

This paper presents the results of an experimental investigation of transient forced convective heat transfer for turbulent flow of nine circular tubes with baffle plate inserts using different pitch to tube inlet diameter ratios and baffle orientation angles in the range of Reynolds number 3000 <= Re <= 20000 in the case of constant heat flux. The characteristic parameters of the tubes are: pitch to tube inlet diameter ratio H/D = 1, 2 and 3; baffle orientation angle beta = 45, 90 and 180 degree. Air, having a Prandtl number of 0.71 was used as the working fluid, while stainless steel was considered as the pipe material. The data show that unsteady entropy generation numbers for the baffled tubes are higher than those from the steady one. A generalised correlation for the unsteady entropy generation number relative to the steady dimensional entropy generation number for the baffle inserted tubes has been developed.