Fouling is a major problem in the operation of heat exchangers, resulting in increased capital, operational, and maintenance costs. Shell-and-tube heat exchangers are traditionally designed using fixed values of fouling resistances, ignoring that fouling rates depend on the exchanger geometry, rendering different fouling resistances for the same thermal service. This article discusses the use of fouling rate models in the design of shell-and-tube heat exchangers. We link a heat exchanger design algorithm to a dynamic simulation of the fouling rate. The proposed procedure is explored for the design of heat exchangers where fouling occurs in the tube side due to crude oil flow. Four examples illustrate how the utilization of the fouling rate model alters the solution of the design problem, including aspects related to a "no fouling" condition in the design, the impact of the duration of the operational campaign in the results, and how the uncertainty in the fouling prediction can be handled.

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In the scenario of offshore rigs angular indifference, modularity, and compactness strongly influence selection of technology for natural gas purification. Gas−liquid contactors have such attributes and perform gas absorption without the concerns of packing columns like weight, flooding, gravitational alignment, and water saturation. This paper proposes a model for gas−liquid hollow fiber contactors using aqueous alkanolamines for CO 2 removal from high pressure natural gas. The model assumes high-pressure compressible flows of both permeate and retentate with full thermodynamics via equations of state. Permeate is approached as a reactive vapor−liquid equilibrium flow of solvent with CO 2 /CH 4 from membrane fluxes. Phase change and reactive heat effects are modeled via mass, energy, and momentum balances written for permeate/retentate as a differential-algebraic system for dependent variables temperature, pressure, and component flows. Profiles are obtained via numerical spatial integration with algebraic resolution imbedded, accounting for permeate reactive vapor−liquid equilibrium with only the molecular species incorporated into a Chemical Theory framework.

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