Experimental investigations of fouling reduction in an ultrasonically-assisted heat exchanger

The aim of this study is to investigate the potential use of ultrasonic waves directly applied to a heat exchanger structure in order to clean some fouling layers. The heat exchanger is a double pipe configuration where the central pipe is removable. Glass and stainless steel central pipes were tested after being painted with spraying paint to simulate some fouling layers. The fouling reduction, or paint removal, can be illustrated visually or by plotting the evolution of either the overall heat transfer coefficient or the fouling thermal resistance with time as the paint is removed. Results are very encouraging since the fouling layers can be removed both from the external side of the pipe and, with more difficulties, from the internal side. Therefore, the overall heat transfer coefficient, previously decreased by the thermal resistance of the paint thickness, can be found again up to its initial value, corresponding to that of a clean tube.

► Fouling reduction by 35 kHz ultrasound in a double tube heat exchanger is possible.
► The fouling layer was simulated by a thermally and mechanically resistant spray paint.
► Removal of the fouling layer is possible on both surfaces of the central pipe.
► The overall heat transfer coefficient can be found up to its initial value.