Masters Theses

Date of Award

3-1985

Degree Type

Thesis

Degree Name

Master of Science

Major

Chemical Engineering

Major Professor

George C. Frazier

Committee Members

J. M. Holmes, F. Weber

Abstract

A simple steady state heat transfer model and computer code have been developed for designing tubular heaters for two-phase (gas-liquid) multicomponent mixtures. Principle assumptions on which the model is based include: approach to local equilibrium between the phases, both the gas and liquid phases are ideal, and the liquid phase is Newtonian. Ihe code utilizes correlations available from the literature for the two-phase pressure drop, the liquid holdup fraction, and the two-phase heat transfer coefficient. The assumption that the liquid is Newtonian can be readily relaxed as correlations become available for various classes of non-Newtonian fluids.

A tentative validation of the model and code has been made by comparing computed results for the air-water system with a limited amount of data found in the literature. Best agreement between computed and experimental results were obtained using the Johnson - Abou Sabe correlations for pressure drop and liquid holdup and by using a two-phase heat transfer coefficient as computed by the Davis - David correlation, but increased by 207o. Heat transfer coefficients in this range are still within the experimental data scatter.

For the air-water system, the calculated pressure drops agreed within 5.7% of the experimental values and the outlet mixture temperatures agreed within one degree Fahrenheit, except for one case, where the difference between calculation and experiment was 17.6°F.

Unfortunately, it is not possible to validate the model and code for two-phase multicomponent systems at this time because of the lack of experimental data. However, an illustrative example for such systems is provided for a gas-binary liquid system (heptane and decane), in order to demonstrate the use of the code and to show that iterative procedures converge properly for tight convergence criteria.

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