Experimental and computational analysis of reduction in fouling by low energy surfaces

The goal of this work was to develop a computational model which estimates the amount and rate of fouling on the contact surfaces of heat transfer equipment under various operating conditions.;Fouling behavior on the test surfaces was analyzed experimentally and computationally for four different test conditions; two different milk flow rates, 3 g/s and 10 g/s, and two different inlet milk temperatures, 40°C and 60°C. Experimental results showed that there was up to 50% less deposit formation when the inlet milk temperature was 60°C compared to when it was 40°C. Results did not provide any definitive trend of deposit amount as a function of flow rate.;A relationship between the contact angle of a liquid on a solid surface that is a major indicator of fouling tendency of the surface, and fouling amount for the test surfaces was found based on experimental results. When the contact angle of the liquid on the solid surface is large, the wettability of the surface is less and thus the surface is less prone to fouling. In the case of AMC148 and CNT coated surfaces, which have relatively higher contact angles (145° and 180°, respectively) compared to the contact angle of the SS316 control surface (72°), the fouling amount was reduced approximately by 90%. Whereas, TeflonRTM based coated surfaces, Microlube/PTFE and TM117P (contact angles are 107° and 112°, respectively) did not reduce the fouling amount as much as AMC148 and CNT coated surfaces; that is only 20 to 70% depending on the operating conditions. The subpar performance of TeflonRTM based surfaces was attributed to insufficient improvement of the wettability of these surfaces.;The results of the computational model for each test case indicate that there is a good agreement with the measurements for control and TeflonRTM based coated surfaces; the average percent difference between the measured and calculated deposit amount for four test conditions was from 11.1% to 24.5%. In contrast, the average percent differences are the largest for the surfaces that are least prone to fouling (AMC148 and CNT, -57.1% and -68.2%, respectively). In other words, for the surfaces that have relatively higher contact angles the calculated and experimental fouling amount differ more. This is most likely due to the insufficiency of the semi-empirical correlation between the contact angle and deposit amount that was obtained by using limited number of test surfaces.;In this study, a computational model was proposed and validated to estimate the amount of foulants deposits that can be used to improve the thermal performance of the heat exchangers. The results of this study for bench scale tester show that the proposed computational model can be used to predict the fouling amount on any surface with known contact angle at different operating conditions with less experimental work. Furthermore, for the milk industry AMC148 coated surface is recommended for further investigation since it gave the most promising results in fouling mitigation. The same methodology can be extended to other industries where fouling is a major problem.;Keywords: Fouling, milk pasteurization, protein denaturation, beta lactoglobulin, plate heat exchanger, FLUENT, contact angle, wettability (Abstract shortened by UMI.)...