Mineral scale control in polymer film heat exchangers

Single salt deposition of CaSO4 and CaCO3 is studied on various polymeric heat transfer surfaces to gain a sound basis for novel polymer film heat exchanger (PFHX) design. Even at high overall heat transfer conditions (possible due to small wall thickness) the scaling quantity was found to be very low compared to a stainless steel surface and strongly dependent on the interfacial energy difference between polymer surface and deposit. The comparatively low scaling quantity is explained by an investigation of the CaCO3-deposition kinetics, which reveals an activation energy that is 40% higher for the polyether ether ketone (PEEK) surface compared to stainless steel. The developed correlations for the quantity of crystallization fouling as a function of supersaturation and flow conditions can be applied in PFHX design and operation with regard to scaling mitigation. A breakup of the falling film results in significant crystallization fouling enhancement and should be avoided during heat transfer operation. The presented cleaning in place strategy for the PFHX concept is very promising and easily applicable, which contributes to the overall effectiveness of the apparatus concept. (C) 2014 Elsevier Ltd. All rights reserved.