Influence of thermal shock on the mitigation of calcium sulfate crystallization fouling under subcooled flow boiling condition

Fouling is a common and high cost problem in various heat transfer equipment. Different on-line and off-line solutions were recommended for fouling mitigation in the recent years. Thermal shock technique which is performed by sudden decrease or increase in heated surface temperature is known as one of the on-line ways to mitigate fouling. In this research, several experiments performed in order to investigate the effects of thermal shock on the fouling mitigation in a vertical upward annulus under subcooled flow boiling conditions for calcium sulfate (CaSO4) aqueous solution. The experiments conducted at different levels of operating conditions such as fluid bulk temperatures (55-75 degrees C), volume flow rates (2.5-5.5 l/min), heat fluxes (8-95 kW/m(2)), and calcium sulfate aqueous solution concentrations (1.75-2.2 g/l). The results revealed that at higher fouling resistance approximately above 0.1 m(2) K/kW, thermal shock could successfully disintegrate and deteriorate the fouling layer, and return the heat transfer surface to its initial condition.