Numerical simulation on flow field in circumferential overlap trisection helical baffle heat exchanger

A novel helical heat exchanger structure consisting of circumferential-overlap trisection helical baffle shell-and-tube heat exchangers (cothSTHXs) is proposed as a means of overcoming the limitations imposed by non-uniformity of the quadrant baffle sectors with natural intervals used in helical baffle heat exchangers with equilateral triangle tube layouts. The cothSTHXs also exhibit anti-shortcut protection by using one row of tubes in each gap between adjacent circumferential overlap baffles to damp the shortcut leakage. A numerical model was used to determine the flow field in a cothSTHX of the same geometric size as the test exchanger. A figure showing the pressure nephogram with superimposed velocity vectors is presented. The Dean vortex secondary flow field, which is one of the key mechanisms of enhancing heat transfer in heat exchangers, is clearly depicted. The unfolded concentric hexagonal section charts demonstrate that the shortcut leakage flow is restricted and that the flow pattern in the cothSTHX is very nearly "plug flow". (C) 2012 Elsevier Ltd. All rights reserved.