Effect of Reynolds Number on Deposition in Fuels Flowing Over Heated Surfaces

Abstract

An increasing demand is being put on the fuel as a heat sink in modern aircraft. In the end, the fuel flows through the atomizer, which is both the hottest part in the thermal history of the fuel and the most critical for resisting deposition. Most studies have concentrated on the chemistry of deposition and in recent years there have been modeling efforts. Deposition is really the end product of a coupling between heat transfer to the fuel, chemical reactions to form insoluble gums, followed by the transport of these gums to the surface to form deposits. There is conflicting evidence and theory in the literature concerning the effect of turbulence on deposition, i.e., whether deposition increases or decreases with increasing Reynolds number. This paper demonstrates, through a heat transfer analysis, that the effect of the Reynolds number depends upon the boundary/initial conditions. If the flow is heated from the surface, deposition decreases with increasing Reynolds number; however, for isothermal flows, i.e., preheated, deposition can increase with the Reynolds number.