Wall temperature spectrum determination for high temperature heat exchangers (HTHE) with extended surfaces

摘要

The extension of the heat transfer surface is intended mainly to limit the temperature of the metallic wall, looking to generate the possibility of using the least refractory steel and therefore to minimize the material and processing costs. The constructive solution for "corrugated chimney" consists of a flue gas channel that has welded longitudinal ribs on the outside, everything being wrapped in a metal casing. Between the metal housing and the corrugated chimney are generated flow channels limited by two consecutive ribs, the flue gas duct and the metallic housing. The calculation methodology sets upon a verification calculation of the performances of the heat transfer along with the wall temperature determination. The calculation is performed with longitudinal sections meshing, for each individual element being defined as variables the temperatures of the fluids and the temperatures of the HTHE elements. The main input parameters for each computational session refer to the flue gases origin (fuel type and burning conditions), flue gases debit, air debit, inlet temperatures for the fluids, chimney steel pipe dimensions (diameter, length) and rib geometry (height, thickness and spacing).