Numerical Analysis of Termo-in Shell and Tube Heat Exchangers with Continues Helical Baffles and Emphasis on the Geometrical Ratios of Shell and Pipe Diameters and Baffle's Pitch

Nowadays, substitution of the heat exchangers equipped with continuous helical baffles is a new methodology to improve of the heat exchangers efficiencies. In this paper, heat and fluid flow fields through the heat exchangers equipped with segmental and continuous helical baffles are analyzed numerically using the computational fluid dynamics. Comparison of segmental and continuous helical baffles shows lower pressure drop and upper temperature differences for heat exchangers equipped with the later baffles. Also the effects of two major geometrical ratios: the shell to pipe diameters, D/d, and the baffle pitch to shell diameter, B/D, on the efficiency of the heat exchangers are studied. Numerical methodology of solution and governing equations is validated by iterative numerical analysis of a heat exchanger that had experimental data for comparison. Consistency between the numerical and experimental are occurred. The results show that for D/d near to 11.5, the variations of both parameters, temperature difference between output and input of the shell and the pressure drop with respect to D/d, changes from decreasing manner to increasing manner. Similar results also occurred near the ratio of the baffle pitch to shell diameter, B/D of about 2. Post processing of the results also shows the thermal performance index of the heat exchanger has its maximum value for D/d ratio greater than about 16 and the B/D ratio lower than one.