C. Dreiser

Kinetics and Quantity of Crystallization Fouling on Polymer Surfaces: Impact of Surface Characteristics and Process Conditions

Kinetics and quantity of crystallization fouling on different polymeric surfaces are studied for the model salts of calcium sulfate and calcium carbonate and compared with those on stainless steel. The promising low scaling affinity of the polymers is attributed to their different surface properties compared to stainless steel. The crystallization kinetics and quantity are also affected by the degree of supersaturation due to higher local temperatures and concentrations. The results can be utilized in thermal desalination plants.

Polymer Film Heat Exchangers

Polymeric heat exchangers have an enormous application potential when corrosive media are involved. The disadvantage is the low heat conductivity of polymeric materials. However, this can be compensated when using thin films (thickness smaller 0.1 mm) supported by a spacer grid. The latter acts as turbulizer and stabilizes falling films and hinders breakup and formation of rivulets. The paper analyzes mechanical and chemical stability and limits in usage as well as scaling and fouling propensity. In contrast to stainless steel, the polymers have good wetting characteristics after pre-treatment (corona or plasma treatment) and a self-cleaning nature due to the flexibility of the polymeric films. Mineral deposits and biofilms can be easily removed rippling the film and the rigid fouling layer falls apart. Correlations for heat transfer and CaCO3 scaling are given for this with a spacer grid-supported polymeric thin-film heat exchanger having a similar structure as a plate heat exchanger.