Numerical Investigation on Circumferential Overlap Trisection Helical Baffle Heat Exchanger

Abstract

The circumferential overlap trisection helical baffle shell-and-tube heat exchanger (cothSTHX) is a modification one based on the quadrant helical baffle one to improve the heat transfer performance. The model of cothSTHX has 34 tubes and 3 rods with tube layout of equilateral triangle and a baffle inclined angle of 20°, and the numerical simulation of flow and thermal performances was conducted using the commercial CFD software FLUENT. The distributions of temperature, pressure and velocity, and temperature, pressure or velocity nephograms with superimposed velocity vectors for special slices can provide access to important implicit information in the simulation results. The Dean vortex secondary flow, which is one of the key mechanisms of enhancing heat transfer in heat exchangers, is clearly depicted, and it shows that the fluid in spiral channel flows outward under the centrifugal force, then flows back to the axis under radial differential pressure, thus a single vortex is formed in each baffle pitch cycle. The unfolded concentric hexagonal slices are designed to make up for the defect that the shortcut leakage flow in the V-notch zone of the adjacent baffles could not be depicted along the longitudinal slices. Moreover, the shortcut leakage flow is restricted with the damper effect of the structure that a row of tubes in the circumferential overlap area of adjacent baffles.