Numerical investigation of the temporal evolution of particulate fouling in metal foams for air-cooled heat exchangers

Highlights: • A numerical method to investigate particulate fouling in metal foams is developed. • A Weaire-Phelan model is proposed as an alternative to a real metal foam model. • Fouling mechanisms vary depending on foulant properties and boundary conditions. • Foulant residence time and mathematical relations to assess fouling are proposed. - Abstract: Metal foams have gained popularity in the renewable energy industry due to their superior thermo-physical properties. In the present study, a coupled finite volume and discrete element numerical method is used to numerically investigate the mechanisms that govern particle-laden gas flows and particulate fouling in idealized metal foam air-cooled heat exchangers. This paper provides a systematic analysis of the foulant distribution and the pressure drop due to the metal foam structure and the presence of fouling. The idealized Weaire-Phelan metal foam geometry serves as a good approximation to a real metal foam geometry. The pressure drop and deposition fraction follows a linear relation for sandstone cases, whereas for the sawdust cases, the pressure drop is sensibly invariant with time although a noticeable increase in deposition fraction with time is realized. The foulant residence time in addition to the correlations between pressure drop, deposition fraction, and inlet velocity can be used to optimize metal foam heat exchanger designs. Optimum heat exchanger performance is achieved by keeping the same fiber thickness of 0.17 mm at a high porosity at 97.87%. An increase in fluid carrier velocity promotes particle transport by means of particle interception thereby reducing the deposition fraction irrespective of foam geometry.