Effect of flow configuration on the performance of spiral-wound heat exchanger

The effects of flow configuration on the heat transfer performance of a spiral wound heat exchanger were experimentally investigated. The spiral-wound heat exchanger was made from stainless steel tubes of 6 mm outside diameter and consisted of 4 helical coils centrally connected in series, with a longitudinal and transverse pitch of 12 mm. Three air flow configurations were tested, namely axial, radial, and mixed axial-radial flows. The overall heat transfer coefficient was determined from the experimental data and the shell-side convection heat transfer coefficient was calculated from the tube-side convection heat transfer coefficient and the total thermal resistance. The measurements were conducted for tube-side Reynolds number in the range of 9000-10,000 (for water flow inside the tubes) and shell-side Reynolds number in the range of 500-6000 (for air flow outside the tubes based on maximum velocity). The results showed that the mixed axial-radial flow configuration has the highest heat transfer coefficient and pressure drop followed by the axial and radial flow configurations. Correlations of Nusselt number, Colbum-j factor, and friction factor were developed for the different flow configurations and a comparison with the Nusselt number correlations for heat transfer over bank of tubes was presented. The correlations are in good agreement with experimental data and has correlation coefficient in the range of 78-98%.