Date of Award

4-2016

Document Type

Thesis - Open Access

Degree Name

Master of Science in Mechanical Engineering

Department

Mechanical Engineering

Committee Chair

Dr. Eduardo Divo

First Committee Member

Dr. Sandra Boetcher

Second Committee Member

Dr. Ilteris Demiirkrian

Abstract

This research project is about the use of an oscillatory flow mechanism to enhance heat transfer. The idea behind this is to induce oscillation of the end wall of one of two connected chambers of a heat exchanger which effectively will induce oscillation of the boundary layer within the connecting duct. The main idea of this thesis came from using species separation studies before 40 years ago in hyperventilation technology to help patients under anesthesia in hospitals. There are many applications for this research such as removing heat from chemical reactors, electrical devices and other enclosed environments such as submarines, underground facilities and so forth. Many parameters can be varied to maximize the convective heat transfer. These parameters include the amplitude and frequency of oscillation, as well as duct radius and length.

In this thesis, results from three-dimensional time-accurate studies carried out using computational fluid dynamics are presented. These results simulate the diffusion and convection of energy in air. The model consists of two chambers with inlets at two different temperatures, an oscillating piston wall on one of the chambers, and a connecting tube. Several cases are carried out reporting on heat transfer enhancement as a function of the tidal displacement to connecting tube diameter. Unlike previous studies which were undertaken using asymptotic analysis, the present models and results incorporate full entrance effects and 3D interactions. Results of this study will be useful as a guide for the design and miniaturization of an oscillating device for enhanced heat transfer in further research projects.

Simulations were performed to analyze the effect of oscillations on the heat transfer. A simulation was first carried out in steady-state to serve as the baseline for comparison with time-accurate oscillating results. The remaining simulations consist of altering the frequency and tidal displacement of the moving wall to analyze their effect on the heat transfer between the two chambers. The results suggest that the heat transfer is enhanced as a function of the frequency and tidal displacement of the moving wall and that there should be an optimal point. Results are presented in the form of contour and vector plots of the temperature and velocity fields as well as plots of the heat exchanger outlet temperatures as a function of frequency and displacement.

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