Cleanabilty study of a Scraped Surface Heat Exchanger

Scraped Surface Heat Exchangers (Contherm SSHE model 6 × 3) are widely used industrially. In this kind of heat exchanger, the inlet and the outlet are difficult to clean due to their particular geometry and the presence of seals. A specific study was conducted on the inlet bowl of a SSHE, whose design has been optimized by the manufacturer in order to minimize risk of deposition by eliminating hydrodynamic dead zones. For this purpose, measurements of wall shear stress were made by an electrochemical method, for different hydrodynamic conditions. On the other hand, cleanability measurements were also performed. The bowl geometry tested presented no dead zones. However, the available space for flow significantly reduces the Reynolds number and turbulence intensity. As a consequence, three areas of increasing contamination appeared throughout the bowl due to the low mean and fluctuating shear stress values. The use of a pulsating flow increases these fluctuations, and thereby reduces the residual contamination.

► The cleanability of a new Alfa Laval SSHE inlet bowl was assessed.
► Pulsating flows induce an increase of the local velocity gradient at the wall.
► For open surfaces, the effect of pulsations is less evident.
► The cleanability of the system is improved using pulsating turbulent flows.