This paper reports a study into the fouling of heat exchangers caused by large particles. This type of fouling is a major problem in the agricultural and off highway environments. The fouling mechanism caused by large particles has been found to be fundamentally different to that caused by small particles. An experimental rig has been developed, in which the velocity, temperature and humidity of the air approaching the heat exchanger can be controlled. The mass flow rate of the particles added to the air flow can be varied in order to achieve concentrations similar to those encountered in the field. Some of the findings of this work appear to directly contradict the perceptions within the industry. For example, the received wisdom has always been that flat fin heat exchangers fouled less than the more modern herringbone fin types. The results from experimental testing have shown that instead of being better, the flat fin heat exchanger fouls twice as fast as the equivalent herringbone fin heat exchanger. Propensity of various heat exchanger design geometries to foul have been quantified and empirically correlated, and a number of descriptive parameters defined. An empirical correlation for heat exchanger fouling due to large particles with surface geometry (related to fin geometry and fin density) has been developed.
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