Doctoral Defense - Aiman Aween

About the Event

The Department of Mechanical Engineering

Michigan State University

Ph.D. Dissertation Defense

Tuesday, April 22, 2025 at 2:00 PM EDT

Virtual via Zoom 

Contact Department or Advisor for Zoom Information

ABSTRACT

A FUNDAMENTAL STUDY ON THE THERMOMECHANICAL BEHAVIOR OF ELASTIC SPHERES CHARGED WITH A TWO-PHASE FLUID

By: Aiman Aween

Advisor: Dr. James Klausner

Several studies have examined the elasticity of expanding spheres containing either gas only or liquid only. Several other studies have examined encapsulated phase change materials for energy storage with the focus on solid-solid and solid-liquid phase change. It appears that the coupling of thermodynamics and elasticity of elastic spheres charged with a two-phase fluid has yet to be addressed in the open literature.

This Ph.D. dissertation considers the thermodynamic and non-linear elasticity modeling and experimental validation of an encapsulated two-phase fluid within an expanding and contracting sphere. Thermodynamics are related to the spherical membrane elasticity through a volume equation that predicts the sphere’s volume based on the temperature of the vapor within the sphere and the pressure of the surrounding ambient environment. Two experimental methods have been followed; the first considers transient thermodynamic states while the sphere undergoes expansion and contraction, while the other considers only equilibrium states. The first method visually records the sphere expansion during the evacuation of the air in the vacuum chamber within which the sphere is suspended. In the second method, the sphere is submerged in water and the pressure of the environment (vacuum chamber) is brought down to a constant value using a vacuum pump and a solenoid valve.

The spheres are fabricated in the laboratory using a silicone rubber blend called “Dragon Skin Very Fast.” Two sphere sizes were investigated, 50mm and 70mm in diameter. The spheres have been successfully modeled for equilibrium and transient conditions. The conditions include temperature, pressure, and fill level. The temperature ranged from room temperature to 18C while the pressure ranged from 1atm to 400 pascals. Three fill-levels were considered, 25%, 50% and 75%, and the fluid used was pure ethanol. Experimental results agree relatively well with theory using the Gent-Gent elasticity model, which was modified to account for a linear stress-stretch relationship at a low magnitude of stretch.

This work builds the foundation upon which further studies can be conducted to explore the utility of the expanding sphere in thermal energy storage and thermal management.

Persons with disabilities have the right to request and receive reasonable accommodation. Please call the Department of Mechanical Engineering at 355-5131 at least one day prior to the seminar; requests received after this date will be met when possible.