Experimental validation of indirect conduction theory and effect of particle roughness on wall‐to‐particle heat transfer

Abstract

Abstract Conduction between a flat wall and solid particles is important to heat transfer in various industrial unit operations. Predicting heat transfer in such systems requires theories for the two relevant modes of heat transfer: conduction through the particle‐wall contact area (direct conduction), and conduction through the interstitial fluid surrounding the particles in the near‐wall region (indirect conduction). While the former mechanism is well understood, experimental exploration of the latter is lacking. Here, experimental heat transfer coefficients for packed‐beds of glass and steel particles are compared to computational fluid dynamics–discrete element method simulations, which include an existing theory for indirect conduction. Reasonable agreement is found when the particle Biot number (Bi) is much less than unity (steel), but significant differences occur for Bi ~ 1 (glass). Additionally, the surface morphology of the glass particles is modified to experimentally elucidate the effects of roughness on particle‐wall heat transfer.