Fouling in crude preheat trains in petroleum refineries affect the heat recovery from product streams significantly. Clear understanding on the effects of various operating conditions on fouling is still lacking among the researchers and practitioners. In the present study, a three-dimensional CFD model of a heat exchanger tube has been developed to predict the rate of coke deposition and fouling resistance through species-transport framework, in which, petroleum, asphaltenes and non-asphaltenes are represented as lumped pseudo-components in the crude oil. Asphaltenes particles were introduced into the bulk of crude oil and considered to be the only reactant for coke formation. The coke deposition rate and fouling resistance are predicted by varying the flow velocity, wall shear stress and surface roughness. From the CFD simulations, it is observed that the fouling resistance reduces under wall shear stress and surface roughness conditions as compared to no-slip and smooth surfaces, respectively.

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A model-based stiction compensation algorithm has been developed based on the H. Zabiri et al. Mixed Integer Quadratic Programming (MIQP) model predictive controller (MPC) algorithm which uses optimization to compensate for backlash in actuators. MIQP-based MPC shows promising result for stiction compensation. However, the backlash compensation formulation alone can remove oscillation caused by stiction dead-band but fails to reduce the offset caused by stiction slip-jump. Several modifications are proposed to solve the offset issue. The MIQP optimization problem constrains were loosened to give more flexibility to the optimizer. Simulation studies were conducted using a 2x2 distillation column model. With loosened constraints, MIQP based MPC reduced the offset at the expense of introducing oscillation into the system.

Advancements in the computational techniques have led to the development of various numerical models and methods to predict the occurrence of crude oil fouling in heat exchangers. Computational fluid dynamics has been employed in the field of crude oil fouling research in the recent past, which led to the concept of investigating the effects of various operating conditions on deposit formations on heat transfer surfaces. Various processes associated with crude oil fouling, such as asphaltenes precipitation and chemical reactions, have been studied through CFD simulations. This chapter provides stateof-the-art review on various CFD approaches and describes the discrete-phase CFD modeling of crude oil fouling through asphaltenes deposition on heat transfer surfaces.

The present work investigates heat transfer through natural convection using a series of experiments and computational modeling using Computational Fluid Dynamics (CFD) simulations in a one-meter bundle pipe with three internal pipes. The exact complex geometry is modeled where the flow channel is reduced through a spiral groove attached to a rod inside the internal tubes which was challenging compared to the flow in circular pipes in previous studies. To support the computational modeling investigations, convective heat transfer analysis is also studied through experiments with water as the production and heating fluids. Further, simulations are carried out with water-crude oil and aqueous ethylene glycol-water as the heating mediums and production fluids, respectively. Based on the heat transfer rates estimated from experimental data and CFD simulation results for the respective tubes, a modification to an existing Nusselt number is proposed for the range of temperature and flow rates used in the experiments. The proposed model, Nu i = Pr i m Ra i n , was validated against experimental data and a good agreement with R 2 values of more than 0.94 was achieved.