Date of Award

12-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Dr. Richard S. Miller

Committee Member

Dr. John R. Wagner

Committee Member

Dr. Xiangchun (Schwann) Xuan

Abstract

Computational Fluid Dynamics (CFD) simulations are performed to investigate the heat loss at the gasket of a standard over/under domestic refrigerator. The study numerically simulates a unique experimental test cell with only the gasket region exposed to the ambient environment and other parts protected by insulation (see picture below). The test cell is cubic with an interior cavity having dimensions 2' x 2' x 2' within which a heating element is placed to create a specified temperature difference. A matching set of door and side panels exposes a 2' width of the gasket region to heat transfer with the surroundings. The primary objectives are to obtain the effective heat leakage in energy leakage per unit time, per unit length along the gasket, and per degree of temperature difference across the gasket (eg.W/m.K) and to be able to distinguish differences in heat leakages between different gaskets. To do so requires measuring the heat flux rate exiting the gasket region continuously along the surface normal to the gasket. However, only six experimental measurement locations were possible. Therefore, CFD was performed to provide 'shape profiles' which can be used to best fit the experimental data via a Least Mean Square Error approach. These then provide the continuous heat flux profiles which are then numerically integrated to obtain the desired heat leakage. The commercial ANSYS/Fluent CFD package is employed for the simulations which include both the inner air as well as conduction through all solid materials. A standard Boussinesq approximation is used in modeling the natural convection and air flow in the chamber of the test cell. The CFD shape profiles are shown to be in good agreement with the experimental data and to collapse well when non-dimensionalized. Additional simulations are also performed to test the relative impact on heat leakage from additional effects that are either not possible to include or control in the experiments. Simulations that include an electric fan in the chamber show that the heat transfer increases 22 % because of the addition of forced convection. The estimated heat loss at the gasket region increases 11 % when radiation is considered in the simulation with the Discrete Ordinate Method (DOM). The influence of the hot pipe in the freezer compartment is estimated by simulations under actual refrigerator conditions and the numerical results show that the heat loss at the gasket increases 18 % when the hot pipe is in operation.

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