Semester

Summer

Date of Graduation

2007

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Donald Gray.

Abstract

Thermal management is considered one of the most challenging problems in practical and industrial applications such as space and satellite research. Among the most widely used techniques are spray and jet cooling. However it was found that spray cooling is the most efficient and complex technique. It was not possible to simulate the spray cooling in detail; this was due to a formation of a liquid layer above the heater surface. The interaction between the spray droplets and the liquid layer was studied in the present work indirectly by assuming a pre-existing liquid layer moving in the horizontal direction and modeling the flux of liquid spray as mass and momentum source terms in the continuity and momentum equations respectively for the layer flow. However, the energy equation was not altered because it was assumed that initially the spray and the surrounding are at the same temperature due to the small scale of the model and from the available experimental data. Even though this is not an exact representation of the interaction between the spray and the liquid layer, it gives a very good indication of how to improve the heat transfer.;The influence of adding source terms to the liquid layer on the heat transfer for a laminar flow moving parallel to a horizontal heated flat plate has been simulated. A commercial multiphysics code, CFD-ACE+, was used and verified for Heat, Flow and VOF modules. Three subroutines were written for the mass and momentum source terms, which run as part of the code. Many parameters were changed by using these subroutines, for example, the mass flow rate, the nozzle spacing, the velocity magnitude, the layer thickness and velocity. It was found that the momentum of the spray has a major effect on the heat transfer. The simulations results showed promising results due to adding the source terms on improving the heat transfer.

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