Study of the Effect of Fin-and-Tube Heat Exchanger Fouling on its Structural Performance

This paper presents the thermal and structural analysis of high temperature fin-and-tube heat exchanger. Water flowing in tubular space and flue-gas flowing in the intertubular space, were considered as working fluids. The effect of limescale fouling on thermal and structural performance of heat exchanger was studied. The analysis considered an industrial heat exchanger, which failure occur from time to time. The expert inspection, after the failure indicated the existence of fouling layer within the heat exchanger tubes. In order to understand the reasons of heat exchanger failure, a detailed fluid flow analysis (both in the tubular and intertubular spaces) was performed. The analysis indicated that the silicate limescale fouling layer with thermal conductivity of 0.35W/(mK) and thickness up to 1.5mm existing in the tube, may increase the tube wall temperature even more than 150 degrees C. The study also includes the impact of outer tube wall surface fouling with thickness of 0.2mm and heat transfer coefficient of 2W/(mK). As a result, the compressible stresses may increase over three times compared to the situation where the tube wall fouling does not exist.