An experimentally validated heat and mass transfer model for wax deposition from flowing oil onto a cold surface

Abstract

A transport model is proposed for wax deposition onto a cold finger from flowing wax-containing oils. The model solves transient energy and mass balances simultaneously for a reversible first-order kinetic rate for precipitation of pseudo-singlecomponent wax, and the effects of yield stress using a critical solid wax concentration to withstand flow-induced stress at the deposit-fluid interface. The model can predict the time evolution of the deposit thickness, and the spatial and temporal evolution of temperature and wax concentration as validated using cold finger experiments. It was found that for high wax content oils, deposit thickness growth is dominated by heat transfer. For low wax content oils that are unable to gel, the thickness growth is slow and accompanied by occasional sloughing. Regardless of the mechanism controlling the growth, mass transfer cannot be neglected as wax diffusion into the deposit continues to take place after the deposit has stopped growing.

Role of a Nanocomposite Pour Point Depressant on Wax Deposition in Different Flow Patterns from the Perspective of Crystallization Kinetics

“…These observations were consistent with previous studies showing that chemical agents and flow regulation served to arrest the formation of wax deposits in field operations. 27 , 28 Further analyses of deposition characteristics based on crystallization kinetics are given in the next section.…”

Bioinspired Hybrid Nanostructures for Wax Inhibition Coatings with Superhydrophilicity

“…The simulation experiment of wax deposition in the pipeline was carried out with a self-designed apparatus based on the cold-finger method, which had been described by previous researchers. , There are two key controlling factors in the wax deposition process. One is the temperature gradient, which is the main cause of wax deposition and formed by external hot water kept at a constant temperature and the internal cold-finger tube with cooling water.…”

Robust Wax Deposition Modeling Incorporating Non-Newtonian Characteristics

“…On the other hand, the deposit growth rate would be mass transfer driven when the concentration of solid required for gelation to take place is much higher than the concentration in the existing oil, such as in situations where the oil has low solid wax content or the flow shear stress is relatively high, both of which are typical in field cases. 5,6 The objective of this work was to assess and compare the predictive performances of the non-Newtonian approach and the conventional diffusion approach to modeling wax deposition. For conciseness, we will interchangeably call the conventional diffusion method as the Newtonian approach.…”

“…1−4 Mahir et al describe the process as the gelation of oil due to the ability of the local fluid to resist flow due to the presence of wax crystals which confers it a yield stress. 5,6 Under the socalled heat transfer-controlled growth, the deposit formed has the same composition as the oil due to the process being akin to freezing.…”

“…Thermal drive deposition is a scenario where the deposit growth rate is governed primarily by the rate of heat transfer. Mehrotra et al consider the process as a moving boundary problem involving the liquid–solid phase transformation. − Mahir et al describe the process as the gelation of oil due to the ability of the local fluid to resist flow due to the presence of wax crystals which confers it a yield stress. , Under the so-called heat transfer-controlled growth, the deposit formed has the same composition as the oil due to the process being akin to freezing.…”