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

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

TEMPERATURE DISTRIBUTION IN A REALISTIC HUMAN HEAD DURING SELECTIVE AND WHOLE BODY COOLING AND DURING CIRCULATORY ARREST

ABSTRACT Using a realistic adult head and neck geometry and a thermal model, the transient temperature distribution is calculated during different cooling strategies and variations in cerebral blood flow. Given the importance of brain temperature in clinical therapy, temperature calculations using thermal models are necessary to optimize hypothermic therapies commonly employed for brain protection during surgery or in the treatment of brain injury. The calculations presented here show the effect of selective and whole body cooling strategies on the temperature gradients in the head; the time required to reach a stationary temperature distribution for the different cooling strategies; the importance of thermal stabilization when using deep hypothermic circulatory arrest, and the effect of selective head cooling in periods of lack of blood flow to control temperature gradients in the brain tissue produced by residual metabolic activity. Introduction The goal of this study is to use a thermal model that incorporates temperature dependent blood flow, metabolic activity and other important measurable physiological parameters to optimize and develop hypothermic therapies commonly used to achieve brain protection during conditions that affect cerebral blood flow, such as ischemia or traumatic brain injury. The use of biological thermal models to study hypothermic therapies is important because reduction of cerebral temperature is known to provid

Spiral microreformer assembly

A design for a microchannel steam microreformer has been developed to provide power in conjunction with a micro fuel cell for a portable, low-power device. The design is optimized for low pumping power and rapid operation as well as thermal efficiency, overall size, and complete generation of the available hydrogen. The design includes at least one microchannel having a grooved surface with a continuous groove oriented in a spiral configuration

Longitudinal electromagnetic levitator

An electromagnetic levitator is disclosed, comprising: a plurality of longitudinal sections formed from a conducting material and arranged around a longitudinal axis. The longitudinal sections are connected to a power source such that when the levitator is in operation, current flowing through adjacent longitudinal sections creates opposing magnetic fields. The levitator has first and second ends defining a levitation zone therebetween. When alternating current is passed through the conductors, a levitation tunnel is formed in the levitation zone, with the levitation tunnel having zero magnetic flux density along its center and non-zero magnetic flux density at all other points

Experimental Investigation Of Oscillation Controlled Thermal Transport In Water-Based Nanofluids

ASME Summer Heat Transfer Conference, JUL 10-14, 2016, Washington, DC, ASME, Heat Transfer DivThe oscillatory flows are often in order to augment heat transfer rates in various processes. It is also well known fact that nanofluids provide significant enhancement in heat transfer at certain conditions. In this research, heat transfer in an oscillatory pipe flow of both water and water-alumina nanofluid were studied experimentally under low frequency regime flow conditions. The aim of the conducted research is parametric experimental investigation of the convective heat transfer in the oscillatory pipe flow. Firstly, the nanofluids were prepared and thermophysical properties weare measured. The experimental apparatus consist of a capillary pipe bundle connecting two reservoirs which are placed at the top and bottom side of the capillary pipe bundle. Upper reservoir contains the hot fluid while lower reservoir and capillary pipe bundle filled with cold fluid. The oscillatory flow in the pipe bundle is driven by the periodic vibrations of a surface mounted on the bottom end of the cold reservoir. The effects of the maximum displacement amplitude of the vibrations and volumetric concentration of nanoparticles on heat transfer were evaluated based on the measured temperature and acceleration data. It is found that heat transfer rate increases with increasing vibration displacement in the fluid.The authors gratefully acknowledge the financial support for this work from The Scientific and Technological Research Council of Turkey (TUBITAK) under Grant # 113M211

Elements of heat transfer/ Bayazitoglu

xii, 439 hal.; 24 cm