The radial flow layout results in a more compact design for a given pressure loss and heat transfer duty
Compact design. The radial flow layout results in a more compact design for a given pressure loss and heat transfer duty. The radial geometry achieves true, uniform perpendicular flow resulting in effective use of all heat transfer surfaces. This significantly reduces heat transfer area requirements in comparison to segmental baffle exchanger designs. Fewer tubes are required thus resulting in smaller shell diameters. The CECEBE RF exchanger is also offered in a split flow design. The shell side inlet flow for this type of unit is split between two nozzles located on the top and bottom vestibules respectively. This arrangement further reduces the required shell diameter for a given shell side flowrate. In most cases, CECEBE RF exchangers can be shop fabricated, resulting in better quality control and reduced costs.
Ease of tube bundle fabrication. Polygonal tube arrangements provide a compact tube bundle design that facilitates tubesheet lay out and fabrication. This reduces shop labour costs and fabrication duration.
Minimal differential thermal stress. All tubes are located circumferentially such that the gas flows radially across the tube bundle between an open outer annulus and open core. This symmetrical arrangement results in even flow distribution, minimising differential thermal expansion between individual tubes thus reducing tube and attendant tubesheet stress. The reduction in mechanical stress results in an extended service life.
Lower shell side pressure loss. For a given gas flowrate, the radial flow layout results in a lower shell side pressure loss in comparison to similarly sized segmental baffle exchanger designs. This is achieved by the uniform dispersion of the shell side flow around the open annulus coupled with the uniform collection of the flow in the open core. The efficient dispersion of the gas flow from the annulus to the core minimises the effect of flow restrictions thus pressure loss is reduced. Reductions in the shell side pressure loss contributes significantly to savings in blower operation cost or, alternatively, available increases in blower capacity.
Freedom of nozzle orientation. The radial flow layout permits 360° orientation of nozzles on both the shell and tube side inlets and outlets. This facilitates the layout of ducting, or matching of existing ducting.
Effective control of tube and tubesheet temperatures. The split flow option of the CECEBE RF heat exchanger allows effective control of the tube and tubesheet temperature at the cold or hot end of the exchanger. This is achieved by proportionally splitting the shell side inlet flowrate to each end of the exchanger to achieve the desired temperature level required at the specified end. In cold exchangers, condensation in the tube side is often a problem at the cold end of the exchanger. The split flow design provides a small warming flow of shell side hot gas to be directed at the cold end tubes thus eliminating possible corrosive gas condensation. For air preheater exchangers, the split flow radial design provides a small flow of shell side cold gas to cool the hot end of the exchanger thus reducing the thermal stresses in the hot end tube to tubesheet connection which is directly exposed to extremely high furnace gas temperatures.
Noram Engineering and Constructors Ltd., Granville Square, 400-200 Granville St, Vancouver, BC V6C 1S4. Tel: 604-681-2030; Fax: 604-683-9164.