Modeling of Deposit Formation from "Waxy" Mixtures via Moving Boundary Formulation: Radial Heat Transfer under Static and Laminar Flow Conditions

A mathematical formulation, based on heat transfer considerations, is presented for solids deposition from “waxy” or paraffinic mixtures. The proposed unsteady-state model uses the moving boundary problem approach for investigating the deposit-layer growth in a circular pipe from binary eutectic mixtures of n-C16H34 and n-C28H58. The model equations were solved numerically to explore the deposition behavior and the growth of deposit layer with time in the radial direction under both static and laminar flow conditions. The deposit-layer growth was predicted to be dependent on the rate of heat transfer at the liquid-deposit interface as well as in the liquid and deposit regions. For cooling under static conditions, complete pipe gelling was predicted to be faster for relatively lower values of mixture temperature, pipe-wall temperature, concentration of C28 in the mixture, and pipe diameter. For cooling under laminar flow conditions, higher values of mixture temperature, pipe-wall temperature and/or heat transfer coefficient yielded a thinner deposit layer with a faster approach to thermal steady state.

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