Numerical simulation of CaSO4 crystallization fouling in a rectangular channel with vortex generators

Abstract

Use of passive vortex generators (VGs) is an efficient heat-transfer enhancement technique, which utilizes a special type of extended surface that mainly generates vortices parallel to the flow direction to not only improve the heat transfer performance of the heat exchangers, but also prevent the formation of fouling. In order to study the growth characteristics of fouling on the rectangular channel with different VGs, three types of VGs with the same frontal area were used in the present study and the deposition process of calcium sulfate (CaSO4) fouling was studied by numerical simulation method. First, the effects of the changes in inlet velocity from 0.5 to 0.8 m/s, concentration of CaSO4 from 2.0 to 3.5 kg/m3, and surface temperature from 320 to 350 K on fouling characteristics were investigated. Then, the Performance Evaluation Criterion (PEC) was used to evaluate the heat transfer characteristics and fouling characteristics on a channel with different types of VGs. The results showed that the fouling resistance of the three types of VGs followed the same trend. The value of asymptotic fouling resistance decreased with the increase of the velocity, and increased with the increase of the concentration and surface temperature, respectively. For the rectangular channels with three different types of VGs, when the flow resistance was taken into account, the Performance Evaluation Criterion with fouling (PECf) of the half-cylinder VG was found to be the best among the three different types of VGs.