Characteristics of local deposition of CaCO3 fouling on rough wall surfaces of heat exchanger channels

Abstract

The corrosion of the heat exchanger in the actual operation process will make the heat exchange wall rough, and the rough heat exchange wall will cause local fouling deposition in the channel. Based on the constructed local crystallization fouling model, this study compares the local fouling deposition of smooth channel and triangular roughness element channel, and analyzes the relative spacing of triangular roughness elements and the effect of different working condition parameters in detail. Results indicate that compared to smooth channels, triangular roughness elements significantly influence fouling deposition, appearing an extreme value in local fouling resistance. As the relative spacing decreases, the average value of the local fouling resistance initially decreases, reaching its minimum at a spacing of 0.125, before slightly increasing and stabilizing. For the average value of fouling resistance, the increase of inlet velocity or the decrease of calcium carbonate concentration will reduce it; an increase in wall temperature will increase it. Additionally, the thickness of the fouling layer decreases with increasing inlet velocity, decreases with lower concentration of calcium carbonate, and increases with rising wall temperature, both in the smooth zone outside the roughness element and in the roughness element affected zone.