Thermal ageing of proteinaceous fouling layers during the growth phase

Abstract

AbstractFouling in heat exchangers can complicate the characterisation and interpretation of thermal effects because of ageing phenomena that occur within the deposited fouling layer. The prevailing process temperatures between the liquid bulk and heat-transferring surfaces create a large thermal conductivity distribution according to the position of the layer within the deposit. During the growth phase, an interaction occurs between the fouling layer formation and ageing. Therefore, deposition and ageing should always be considered in combination to obtain a better understanding of fouling. This paper discusses an experimental method for determining temperature-dependent ageing, expressed as a change in thermal conductivity with time and along the cross section of the fouling layer. An experimental setup is presented that includes a newly developed flow channel and an experimental implementation of an ageing model. In the first experiments, proteinaceous fouling layers were generated from whey protein concentrate (WPC) with and without simulated milk ultrafiltrate (SMUF), applied for different durations to create different fouling layer thicknesses. The thermal conductivity increased more rapidly near the heat-transferring surface than for the entire fouling layer. These findings can be related to the temperatures within the sublayers.