A Model for Hydrogen Thermal Conductivity and Viscosity Including the Critical Point

In order to conduct a thermal analysis of heat transfer to liquid hydrogen near the critical point, an accurate understanding of the thermal transport properties is required. A review of the available literature on hydrogen transport properties identified a lack of useful equations to predict the thermal conductivity and viscosity of liquid hydrogen. The tables published by the National Bureau of Standards were used to perform a series of curve fits to generate the needed correlation equations. These equations give the thermal conductivity and viscosity of hydrogen below 100 K. They agree with the published NBS tables, with less than a 1.5 percent error for temperatures below 100 K and pressures from the triple point to 1000 KPa. These equations also capture the divergence in the thermal conductivity at the critical poin

Spreading and Packing of Alumina Powder Using a Displacement-controlled Roller in SLFS

Selective laser flash sintering (SLFS) is a powder bed fusion process that enables direct additive manufacturing of ceramics. Similar to other powder bed fusion processes, the density of the ceramic powder bed impacts attainable density of the final part. Experiments were conducted using a spray-dried alumina powder that was spread and then packed using a displacementlimited roller. The spreadability of the powder was visually assessed. The microstructure of the resulting compacted powder was compared to a traditional method of pressing ceramic powder into a pellet using a die and hydraulic press. Packed regions were sintered to final density and compared in a scanning electron microscope to samples hydraulically pressed at known pressure to evaluate the efficacy of a roller-based packing process.Mechanical Engineerin

Complications and pitfalls of lumbar interlaminar and transforaminal epidural injections

Lumbar interlaminar and transforaminal epidural injections are used in the treatment of lumbar radicular pain and other lumbar spinal pain syndromes. Complications from these procedures arise from needle placement and the administration of medication. Potential risks include infection, hematoma, intravascular injection of medication, direct nerve trauma, subdural injection of medication, air embolism, disc entry, urinary retention, radiation exposure, and hypersensitivity reactions. The objective of this article is to review the complications of lumbar interlaminar and transforaminal epidural injections and discuss the potential pitfalls related to these procedures. We performed a comprehensive literature review through a Medline search for relevant case reports, clinical trials, and review articles. Complications from lumbar epidural injections are extremely rare. Most if not all complications can be avoided by careful technique with accurate needle placement, sterile precautions, and a thorough understanding of the relevant anatomy and contrast patterns on fluoroscopic imaging

Heat Transfer And Mass-transfer Analysis Of Bacon-type Hydrogen-oxygen Fuel Cells.

Ph.D.EnergyMechanical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/190662/2/7425142.pd

Methods For Automated Analysis Of Three-dimensional Dynamic Mechanical Systems With Application To Nonlinear Vehicle Dynamics.

PhDMechanical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/187478/2/7306785.pd

A NOTE ON MODELING OF NANO-SCALE THERMAL FLOW VIA THE LATTICE BOLTZMANN METHOD IMECE2012-89923

ABSTRACT Lattice Boltzmann (LB) method models have been demonstrated to provide an accurate representation of the flow characteristics in rarefied flows. Conditions in such flows are characterized by the Knudsen number (Kn), defined as the ratio between the gas molecular Mean Free Path (MFP, λ) and the device characteristic length (L). As the Knudsen number increases, the behavior of the flow near the walls is increasingly dominated by interactions between the gas molecules and the solid surface. Due to this, linear constitutive relations for shear stress and heat flux, which are assumed in the Navier-StokesFourier (NSF) system of equations, are not valid within the Knudsen Layer (KL). Various methods have been explored to extend the applicability of LB models to higher Knudsen number flows, including using higher order velocity sets, and using walldistance functions to capture the effect of the walls on the mean free path by incorporating such functions on the determination of the local relaxation parameters. In this study, a high order velocity model which contains a two-dimensional, thirteen velocity direction set (e.g., D2Q13), as shown in , derived by Arlemark et al The performance of the present LB model coupled with the implementation of the two wall-distance functions is tested using two classical flow cases. The first case considered is that of isothermal, shear-driven Couette flow between two parallel, horizontal plates separated by a distance H, moving in opposite directions at a speed of U 0 . The results obtained show that the effective MFP relationship based on the exponential function improves the results obtained with the high order LB model for both sheardriven and Fourier flows up to Kn~1. The results also show that the effective MFP relationship based on the Power Law distribution function greatly enhances the results obtained with the high order LB model for the two cases addressed, up to Kn~3. In conclusion, the resulting LB models represent an effective tool in modeling non-equilibrium gas flows expected within micro/nano-scale devices