Two- and four-way coupling of cohesive poly-disperse particulate foulants on a metal foam fibre immersed in quiescent fluid

The ubiquity and complexity of the unsteadiness of fouling and multiphase flows in various engineering systems signify the need to develop advanced numerical methods to study the underlying phenomena of two-phase particle-laden fluid flows in heat exchanger systems such as, compact electronics cooling (i.e. heat sinks) and HVAC&R systems. Fouling is omnipresent in many industries such as power generation, chemical, petroleum, among others. The mechanisms governing fouling coupled with multiphase foulant-laden fluid flow in porous heat exchangers, such as metal foams, are very complex and poorly understood. This investigation forms the basis for addressing the implications of fouling for a myriad of industrial processes. This study will discuss the development of a coupled finite volume method and discrete element method (FVM-DEM) numerical framework to investigate the mechanisms governing particulate fouling in an idealized metal foam heat exchanger. This study resolves four-way and two-way coupled interactions based on poly-disperse cohesive foulants in fluid-saturated foam. The significance stems from the inclusion of cohesiveness between particle-particle and particle-wall contacts which play a decisive role in the foulant aggregation process prevalent in particles with a diameter smaller than 50 μm. The present results show that the cohesive foulants exhibit strong tendency to aggregate with time and form chain-like projections. A rigid aggregate stack is formed which alters the fluid velocity of the fluid-filled foam. Quantitative analysis of the foulant count and time-averaged aggregate count is discussed. The presented results and the numerical framework could potentially be used to optimize heat exchanger designs by considering operating conditions and foam morphology (i.e. pore diameter, ligament thickness, porosity) that is most susceptible to particulate fouling.