Development of Nusselt number and friction factor correlations for the shell side of spiral-wound heat exchangers

Abstract

This research aims to investigate the thermo-hydraulic characteristics of flow in the shell side of spiral-wound heat exchangers with consistent shell geometry. To achieve this end, three-dimensional computational fluid dynamics is employed. Geometrical configuration of spiral-wound heat exchangers can be completely determined by knowing six primary parameters including start factor, tube outside diameter, number of tubes in the first layer, number of layers, longitudinal pitch, and radial pitch. Dividing the longitudinal and radial pitches by tube outside diameter, the six primary geometrical parameters reduce to five non-dimensional parameters. The effects of number of tubes in the first layer, number of layers, longitudinal pitch to tube outside diameter ratio, and radial pitch to tube outside diameter ratio referred to as four main non-dimensional parameters on flow and heat transfer are numerically studied by modeling 64 different geometries. The results indicate that the number of tubes in the first layer is the only parameter among four main non-dimensional parameters that does not have any influence on the flow characteristics. Based on the numerical simulation results, multivariate correlations for average Nusselt number and friction factor have been developed taking into account the three remaining main non-dimensional parameters, i.e. the number of layers, the longitudinal pitch to tube outside diameter ratio, and the radial pitch to tube outside diameter ratio. The average deviation of developed Nusselt number and friction factor correlations from numerical simulation results are 5.4% and 7.0%, respectively.