Comparative Study for Thermal and Fluid Flow Peculiarities in Cascading Spiral Inner Tube Heat Exchanger with or without Diverse Inserts over Spiral Tube

Abstract

Present work deals with experimental analysis in which various observation takes place related to performance characteristics like HTR, effectiveness and fluid flow peculiarities like Nu, Re, f, NTU, TPF etc in a cascaded spiral concentric tube type heat exchanger consisting of a GI shell and a cascaded spiral copper inner tube having conical shape inserts, hemispherical insert and plane profile unit for parallel flow. Five spiral cascades with three turns in each are used for the inner side copper tube unit. Water enters at 304°K from the innermost turn along the cascaded spiral tube, and leaves at the outermost turn. The hot fluid inlet for heat exchanger is from bottom of one end of the shell at 333°K, flowing radically across the cascades, and then leaving the exchanger from the top of another end. This paper based on comparative experimental study of the behavior of such system for parallel flow with different shape of inserts, and then compared with the simulation results for same. In this analysis comparative approach is considered for evaluating optimum fluid flow and thermal properties on the basis of geometrical parameters. The results predicted that out of three profiles of insert, plain, conical and half cut elliptical profile, which located over inner copper tube of exchanger, half cut elliptical profile insert shows best results on fluid flow and thermal peculiarities, for mass flow rate range 0.012 to 0.049 Kg/s and Reynolds number range 4236 to 18540, heat transfer rate varies from 1128.06 to 2374.77, Nusselt number varies from 75.15 to 144.05, Friction factor varies from 0.00376 to 0.00305 and effectiveness varies from 0.77 to 0.40 and Number of transfer unit varies from 2.08 to 0.68 for half cut elliptical profile.