Mechanical Engineering Commons^™

Numerical Modeling And Conjugate Heat Transfer Analysis Of Single U-Tube Vertical Borehole Heat Exchangers, Talha Khan

FIU Electronic Theses and Dissertations

The primary purpose of this thesis was to develop a design for improving the efficiency of the vertical type single u-tube borehole heat exchanger. A thorough literature review of the various existing analytical and numerical models of the borehole heat exchanger (BHEs) was performed and numerical modeling of the BHE was conducted to solve the conjugate heat transfer problem in the BHE in 3D using ANSYS Fluent 2019 R1. A comparison between the results obtained using various mesh sizes, types, different turbulence models showed the independence of the parameters on the numerical simulation results.

From the numerical simulation, it was …

Composite Gel Polymer Electrolytes For Extended Cyclability Of Lithium-Oxygen Batteries, Marcus Carlton Herndon

FIU Electronic Theses and Dissertations

In lithium-oxygen (Li-O₂) batteries, addressing challenges like electrode degradation, cell stability and electrolyte decomposition are key to creating more practical applications. Despite many attempts to minimize anode oxidation and cathode byproduct formation, the electrolyte remains the leading source for rapid capacity fading and poor cyclability in Li-O₂batteries. Understanding the loss of functionality in electrolytes, carbon nanotube (CNT) fillers and redox mediators (RM), during cycling within Li-O₂battery systems, could be the solution to prolonging battery lifetime. Determining the efficiency of these battery components and additives will push the medium towards lifelong, rechargeable and safe battery …

Mechanical Properties Of Permanent Foaming Fixatives For Deactivation & Decommissioning Activities, Tristan Maximilian Simoes-Ponce

FIU Electronic Theses and Dissertations

The Department of Energy is investigating fixative technologies that encapsulate and/or immobilize residual contamination in voids during deactivation and decommissioning (D&D). These technologies must have adequate mechanical and adhesion properties to withstand seismic activity that may occur. One solution is the implementation of polyurethane foams used as permanent foaming fixatives (PFF), specifically intumescent foams that contain expandable graphite, making them fire resistant when exposed to extreme heat conditions.

Tensile, compression, seismic, and tensile adhesion testing was done on six commercial-off-the-self polyurethane foams to determine if the expandable graphite and other filler intumescent technologies improve its mechanical limits. It was found …