Deposition of CaSO4 on structured surfaces during convective heat transfer for utilization in micro heat exchangers

Abstract

ABSTRACT Micro heat exchangers are characterized by their high surface-to-volume ratio of up to 100,000 m2/m3. Due to superior heat transfer performance, their utilization for pure fluids is gaining increased attention. One major drawback though is the unwanted deposition on their surfaces when subject to fluids which tend to foul. To address this, a better understanding of the deposition process in these devices looks imperative. In this study, the crystallization fouling of calcium sulfate on micro-structured surfaces during convective heat transfer has experimentally been studied. The experimental specimens of stainless steel with rectangular micro-channels were subjected to CaSO4 solution with a concentration of 4 g/L. The impact of channel dimension and direction with respect to fluid flow has also been investigated at a given velocity of 0.17 m/s. In addition, the comparison of finned and grooved structured surfaces was made. The results showed that as the groove’s width increases, the propensity of deposition is expected to decrease as such that fouling rate and fouling resistance decreased as much as 30% and 15%, respectively. Moreover, the crossed grooves increased the turbulence more than the longitudinal ones. It was also attained that the disturbance promoters, i.e. fins, would have positive impact on heat transfer coefficient compared with those of grooves.