A Heat and Mass Transfer Model for Paraffin Wax Deposition from Flowing Oil Onto a Cold Surface

A new transport model is proposed for paraffin wax deposition on a cold finger from flowing wax-containing oils. The model describes the movement of the deposit front into the oil and the aging of the deposit by diffusion and precipitation of soluble wax into the deposit. While the model describes deposition of a single wax component, it is readily extendable to multi-component waxes. The model solves the transient energy and mass balances simultaneously for a reversible first-order kinetic rate for precipitation and redissolution. For the first time, the effects of yield stress are taken into account using a critical solid wax concentration to withstand flow-induced stress at the deposit-fluid interface, C_pi. With this C_pi parameter, and heat and mass transfer coefficients to quantify the transport by advection, as well as a precipitation rate constant, the model can predict (1) the time evolution of the deposit thickness, (2) the spatial and temporal evolution of temperature and wax concentration in the deposit, and (3) the temporal evolution of spatially uniform temperature and wax concentration in the fluid. The model was validated using experiments involving a cylindrical cold finger, but it can be adapted to other geometries as well.