Date of Award

2018

Document Type

Open Access Thesis

Department

Chemical Engineering

Sub-Department

College of Engineering and Computing

First Advisor

James A. Ritter

Abstract

This work evaluates the role of different design variables on the effective thermal conduction of a structured adsorbent bed for its possible application in a temperature swing adsorption (TSA) process. The structured adsorbent bed is represented by eight parallel layers of intercalated smooth and corrugated foils of a metal support coated with 13X zeolite resulting in the formation of parallel triangular channels. The variables investigated include the thickness of the adsorbent coating, thickness of the metal, nature of contacts between smooth and corrugated foils, type of metal, presence and magnitude of an air gap between the foils, difference in alignment of the metal foil, difference in the coating methodology and effect of different void gases.

The effective thermal conductivity evaluated in this work was that obtained by modelling the heat transfer through the bed in the direction perpendicular to the foils and at steady state. This two-dimensional model representing the cross section of the bed was developed in COMSOL Multiphysics. The specific heat power at one end of the bed was defined and fixed at 500 W/m2 while the temperature of the other end was fixed at 293.15 K. The sides of the structured bed were thermally insulated. The pressure of the void gas within the channels was fixed at 1 atm, with the gas density freely adjusting with temperature and according to the ideal gas law. Depending on the design parameters the width of the bed cross section varied between 1.247 and 1.827 cm while the depth of the bed cross section was identical in all cases and equal to 0.32 cm.

The results showed that the effective thermal conductivity in the direction perpendicular to the foils is significantly impacted by the conductivity of the metal, if the foils were in direct contact either via imbedding or via direct metal to metal point contacts. Under this condition, the thermal conductivity depended strongly on the conductivity of metal, and weakly on the conductivity of gas medium and all other design properties. For these metal foils in air, the thermal conductivities varied between 0.561 and 0.629 W/m/K, when the metal was stainless steel, whereas for aluminum, a value of 6.66 W/m/K was obtained. In contrast, when the foils were separated either by air gaps or by a 13X coating, the effective thermal conductivity was significantly reduced, and it depended strongly on the conductivity of the gas medium and weakly on the metal conductivity and all other design properties. For example, in air and whether the metal was stainless steel 304 or aluminum, the thermal conductivities were always around 0.090 and 0.125 W/m/K.

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