bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamic Analysis of a Molten Carbonate Fuel Cell System Using Waste Derived Fuel Gas
Authors: Desideri Umberto , Lunghi Piero , Ubertini Stefano 
Published: November 2021

Abstract
The increasing energy demand along with the growing concern for the environmental issues requires a significant research effort on the development of energy systems with high efficiency and low environmental impact. The use of waste derived fuel in fuel cell systems provides the benefits of high efficiency and very low polluting emissions as well as an effective way of waste disposal.
In the present work an investigation of the potential use of waste derived fuel gas in Molten Carbonate fuel cell systems has been performed. A detailed description of the simulation model developed by the authors with the Aspen Plus thermodynamic flow sheet code is presented. The basic configuration of the plant uses pure methane as fuel. An improved plant configuration has been proposed which allows an optimal exploitation of all the thermal streams giving as an output high electrical yield and heat at high temperature. The plant is then adapted to different gas blends as fuel: landfill gas and gas from the gasification of MSW (Municipal Solid Waste). The analysis is focused on the comparison between different fuel gases plants in terms of efficiency, feasibility and process requirements. Depending on the fuel characteristics, different solutions are applied to the plant in order to achieve optimal exploitation of the thermal streams. A general conclusion is that the use of low BTU gas results in an efficient and environmentally sound power generation but leads to a reduction of the plant net power output especially in the case of using gas derived from existing gasification plants. A consistent research activity is required to identify waste derived fuel processing systems that can yield gases which allow an optimal exploitation in fuel cell systems.
Stationary Electrical Power Generation From an Integrated Fuel Cell System With Thermal Energy Recovery
Authors: Dickman Anthony J. 
Published: November 2021

Abstract
The objective of this paper is to present an overview of design, operating and performance considerations for stationary electrical power generation utilizing a Proton Exchange Membrane (PEM) fuel cell stack integrated with a proprietary IdaTech hydrogen fuel processor. Additionally, electrical and combined (electrical plus thermal) efficiencies of integrated systems are presented.
Energy Efficient and Cool Storage Assisted Air-Conditioning System for Hospital Building
Authors: Maheshwari Gopal P. , Al-Murad Raba’a A. , Al-Hadban Yehya N. , Sebzali Mohammed J. 
Published: November 2021

Abstract
Air-conditioning (A/C) is an important sector for Kuwait. It is not only the single largest consumer of electricity, its yearly import accounts for well over 200 million US dollars. Energy conservation measures have been in practice in Kuwait since 1983 through a well defined code of practice enforced by the Ministry of Electricity and Water (MEW). Additional energy efficient products and techniques developed thereafter, however, have not been introduced as the electricity is highly subsidized and the MEW code has not been modified. Applications of some of the cost effective energy conservation measures and use of cool storage for peak power shaving have been carried out as a demonstration project in a two-story building, housing the Center for Speech and Audio Therapy having 3,180 m2 of air-conditioned space. As a first step, the building cooling load was re-estimated using an energy simulation computer program and proper design specifications. It was found to be 31.4% lower than the original estimated load of 161.3 tons of refrigeration (RT). Use of energy-efficient windows and cooling recovery units that were found to be cost-effective resulted in a final building load of 64.5 RT. Finally, ice storage was incorporated to meet 50% of the peak cooling load. This paper presents the complete design details including the impact of a building load simulation program and cost benefit analysis of important energy conservation measures. It also presents a design and operation scheme for a cool storage, assisted A/C system and its performance results collected during the summer of 1998.
Entropy Generation Maps of a Low-Specific Speed Radial Compressor Rotor
Authors: Iandoli Carmine Luca , Sciubba Enrico 
Published: November 2021

Abstract
The flow field in the rotor of a low-specific speed radial compressor is computed in a fully 3-D simulation and the irreversible entropy generation rates directly calculated from the local velocity- and temperature values. The code used for the simulation is a commercial CFD-finite volumes package, FLUENT™, augmented by an novel entropy generation routine adapted from the original formulation due to Bejan [1]. The model provides the designer with exact and detailed knowledge of the local values of the irreversibility production, allowing for a separate accounting of viscous- and thermal effects and thus resulting in a valuable tool for the search of design improvements. These local entropy generation rates can of course be integrated over the entire flow field to obtain the global irreversibility production, directly linked with the rotor efficiency: but more important is the possibility of obtaining an exact “mapping” of these local values in some particularly “critical” design areas (leading edge of the blade at the inlet, first portion of the channel on the pressure side, last portion of the channel on the suction side, rotor exit). By direct comparison of repeated simulations, the designer can then easily assess the relative performance of different blade arrangements and rotor configurations. In particular, it is possible to compute, via a direct application of the Gouy-Stodola lost work formula, the isentropic efficiency of the rotor.
The possibility is discussed of developing a “configuration optimisation procedure” based on the systematic, iterative and automatic application of this type of analysis.
Study of Lithium Polymer Interface to Enhance Efficiency and Safety in Lithium/Water Batteries
Authors: Cho Jeong-Ju , Urquidi-Macdonald M. 
Published: November 2021

Abstract
New gel electrolytes composed of silica powder and organic electrolytes for the application of lithium/seawater batteries were tested with a porous separator. The maximum current density was ∼25mA/cm2. The discharging current was decreased suddenly because of two reasons. One reason is that the porous separator became clogged with lithium hydroxide and the other is because of the deposition of lithiumsilicate on the lithium surface, which was confirmed using SEM, XPS and hydroxide ion flux measurements. The efficiency (5 ∼ 27%) of the lithium oxidation was also obtained by measuring the hydrogen volume. The efficiency is strongly dependent on the ambient temperature. The effect of additives and other gel systems was also investigated.
Three Dimensional Analysis of Transport and Reaction in Proton Exchange Membrane Fuel Cells
Authors: Um Sukkee , Wang C. Y. 
Published: November 2021

Abstract
A three-dimensional computational study based on the finite volume method is carried out for proton exchange membrane (PEM) fuel cells with a Nation 117 membrane and an interdigitated flow field on the cathode. Emphasis is placed on obtaining a fundamental understanding of fully three-dimensional flow in the air cathode and how it impacts the transport and electrochemical reaction processes. For the first time, fully three-dimensional results of the flow structure, species profiles and current distribution are presented for PEM fuel cells with the interdigitated flow field. The model results show that forced convection induced by the interdigitated flow field in the backing layer substantially improves mass transport of oxygen to, and water removal from, the reaction zone thus leading to a higher cell current density as compared to that of the serpentine flow field. The computations also indicate a need to account for water condensation and ensuing gas-liquid two-phase flow and transport in the porous cathode at high current densities. The present computer model can be used as a design or diagnostic tool for fuel cell cathodes with complex structural flow fields.
Molecular Tagging Fluorescence Velocimetry (MTFV) to Measure Meso- to Micro-Scale Thermal Flow Fields
Authors: Park J. S. , Kihm K. D. , Pratt D. M. 
Published: November 2021

Abstract
The development of a molecular tagging fluorescence velocimetry (MTFV) system is discussed and measurement results are presented for a meso-scale flow field of thermally driven capillary pore of 5-mm inner diameter that is tilted 5° from the horizon. The developed technique uses caged Dextran conjugates of caged fluorescene dyes of less than 10 nm in size for tracers. The frequency-tripled UV band (λ = 355 nm) of a pulsed Nd:YAG laser uncages the molecules by photo-cleaving that is decomposition of a caging chemical group and a fluorescence chemical group. Then a CW blue Argon-ion laser (λ = 488 nm) pumps the fluorescence of only those uncaged molecules, whose emmission band is centered at λ = 518 nm, and a sequential recording of the fluorescence images are digitally recorded and analyzed for Lagrangian velocity field mapping. The use of the technique allows detailed measurements of the thermally driven three-dimensional flow inside a heated capillary pore. The measurement shows that the meniscus surface flow is mainly driven by the thermocapillary stress field, occurring due to the surface temperature gradient, while the bulk flow inside the pore is driven largely by the natural convection buoyancy. The whole capillary flow is made by a combination of these two different flow effects. As to the heater position, above or below the interface, the three dimensional flow patterns are measured totally in the opposite way.
Optical Technique to Measure Transient Interface Temperature During Droplet Impingement on a Cooled Surface
Authors: Li Y. , Longtin J. P. 
Published: November 2021

Abstract
Liquid droplets impinging upon a solid surface are present in many diverse and important engineering and scientific applications. Examples include impingement cooling of surfaces, condensation phenomena in which liquid droplets fall and strike a surface, vigorous mixing of gas-liquid systems, and in manufacturing, e.g., pouring a liquid material onto a cooled surface or mold to form objects. The accurate measurement of the solid-liquid interface temperature of a liquid droplet impinging on a solid surface is extremely difficult to do using traditional, contact-based techniques, however. This work presents a laser-based technique that is capable of resolving the transient interface temperature change as a liquid droplet strikes a surface. The measurement records changes in reflected light from the liquid-solid interface, which is correlated to temperature change. In this work, the substrate is BK7 glass or quartz. The liquid falls from a height of several centimeters, while the laser beam is sent through the transparent solid material from the underside for the measurement. Results are presented for water and glycerin, with good agreement found between predicted and measured temperature histories. Additional features of the technique include extremely fast temporal resolution, which is limited only by the speed of the light-capturing electronics. A temporal resolution of 1 microsecond is readily obtainable with inexpensive electronics. Also, the use of a high-quality Gaussian laser beam from, e.g., a HeNe laser or a single-mode fiber can be focused to a spot size ranging from several millimeters to 10 microns in diameter at the liquid interface, thus providing a wide variety of spatial resolutions, including those in the microscale. Finally, an array of interrogation beams can be employed simultaneously to monitor the spatial temperature history of a droplet as it spreads and cools once striking the surface. Both present and future applications of the technique will be discussed in the talk.
Average Heat Transfer Coefficient Measurements in a Fuel Bundle: Method Development
Authors: Armfield Mary V. , Langford Heather M. , Beasley Donald E. , Conner Michael E. 
Published: November 2021

Abstract
Measurement of single-phase heat transfer rates in a laboratory-scale rod bundle can aid in the design of a full-scale nuclear fuel bundle. It is desirable to obtain heat transfer coefficient measurements as a function of axial position with a high degree of measurement confidence. To achieve this goal, a heated calorimeter is designed and instrumented to measure power input and temperature. Temperature measurement is accomplished using thermocouples embedded in the calorimeter material, and a cartridge heater inserted concentrically in the calorimeter material creates a constant heat flux. The present study examines the contributions of the design parameters and uncertainties in the measurements to the overall uncertainty in the heat transfer coefficient. A design stage uncertainty analysis allows prediction of the required uncertainty in temperature difference measurement to achieve a desired uncertainty in the heat transfer coefficient. The experimental design for differential temperature calibration and representative uncertainty results are presented. All significant contributions to the total uncertainty in heat transfer coefficient are described and quantified.
Characteristics of a Falling Liquid Film on the Outer Surface of a Vertical Pipe: Minimum Wetting Rates and Waves on the Film
Authors: Koizumi Yasuo , Ohtake Hiroyasu , Ikeda Shinichi 
Published: November 2021

Abstract
The minimum wetting rate (MWR) of an isothermal R-113 falling film on an outer surface of a vertical 25 mm OD pipe was examined. The fundamental characteristics of waves (the amplitude, frequency, velocity and wave length) on the falling film were also investigated in the range of the film Reynolds number Ref = 60 ∼ 600. The MWR was not obtained even at extremely small flow rate of 0.38 cc/min (Ref = 0.70). That flow rate was much smaller than the value expected for the smooth surface film although the surface observed was flat. It was pointed out that another factor such as the surface tension or the wettability might need to be included for the MWR expression. The mean film thickness was well represented by the Nusselt film thickness equation although the film surface was covered with many waves. In Ref ≤ 130, the waves were symmetrical and did not deform as the waves proceeded to downstream. When Ref ≥ 300, the waves were like roll waves and the amplitude grew as the waves traveled. The wave amplitude, frequency, velocity and length all showed similar variation tendency that each value changed the trend of variation for Ref across Ref ≅ 300. The waves behaved like theoretical small-perturbation waves in Ref ≤ ∼ 300 and the characteristics of the waves deviated from that when Ref &gt; 300.
Transient Bubble Formation on a Polysilicon Micro Resister
Authors: Tsai Jr-Hung , Lin Liwei 
Published: November 2021

Abstract
Transient bubble formation has been investigated on a polysilicon micro resister of 95μm long, 10μm wide, and 0.5μm thick. The polysilicon micro resister functions as both a heating source and a temperature transducer of thermal bubble nucleation process. At input current of 22 to 30 milliamps, a single spherical bubble is nucleated with a waiting period, when the heating wall temperature drops up to 8°C before a bubble nucleated, of about 1 to 2 seconds depending on the input current. Analytical models are developed to characterize the wall temperature behavior in this micro scale. Substrate warming is found effective to the wall temperature after 0.4 second of heating. Furthermore, evaporation is identified as the major contribution mechanism of the temperature drop before the bubble nucleation. An equivalent heat transfer coefficient is found in the order of 105 W/m2°C with the time constant of 1.25 to 2.5 seconds varying with input current.
Effect of Surface Roughness on Gaseous Flow Through Microchannels
Authors: Turner Stephen E. , Sun Hongwei , Faghri Mohammad , Gregory Otto J. 
Published: November 2021

Abstract
This paper presents an experimental investigation on nitrogen and helium flow through microchannels etched in silicon with hydraulic diameters between 10 and 40 microns, and Reynolds numbers ranging from 0.3 to 600. The objectives of this research are (1) to fabricate microchannels with uniform surface roughness and local pressure measurement; (2) to determine the friction factor within the locally fully developed region of the microchannel; and (3) to evaluate the effect of surface roughness on momentum transfer by comparison with smooth microchannels. The friction factor results are presented as the product of friction factor and Reynolds number plotted against Reynolds number. The following conclusions have been reached in the present investigation: (1) microchannels with uniform corrugated surfaces can be fabricated using standard photolithographic processes; and (2) surface features with low aspect ratios of height to width have little effect on the friction factor for laminar flow in microchannels.
Analysis and Characterization of Thermoelectric Microrefrigerators
Authors: Ju Y. Sungtaek 
Published: November 2021

Abstract
Advances in film growth techniques have sparked a renewed interest in thermoelectric (TE) devices. A previous study suggested that a drastic improvement in the figure of merit can be achieved for superlattices and quantum wells by exploiting phonon scattering/reflection at interfaces [1] or carrier pocket engineering [2]. Thin-film devices are also of great significance because of their capability to handle considerably higher heat flux than conventional bulk modules [3].
Microrefrigerators consist of a single or multiple thin-film thermoelement(s). The use of thin films introduces the full complexity of solid-solid interfaces into any complete discussion of these refrigerators. Many investigators noted that the electrical contact resistance has adverse effects on TE cooling. Less attention has been paid to thermal interface resistance and the boundary Seebeck effects. While previous studies [4] have indicated that the interface effects are related to each other via boundary forms of the Wiedemann-Franz-Lorenz law and the Kelvin-Onsager relation, the impact of their mutual interactions on thermoelectric cooling has remained relatively unexplored.
A Micro-Scale Membrane-Actuated Condenser/Evaporator for Enhanced Thermal Management
Authors: Francois Marianne M. , Shyy Wei , Chung Jacob N. 
Published: November 2021

Abstract
There is a strong need to improve our current capabilities in thermal management and electronic cooling. The present study investigates the feasibility of a micro-scale membrane-actuated dropwise condenser/evaporator. An actuated membrane is adopted as the droplet condensing and ejecting device. Droplets with appropriate dimensions and frequencies are formed and ejected for efficient cooling. The present system requires no mechanical moving parts, and hence is reliable. In addition, it needs little maintenance due to closed recirculation, exhibits favorable packaging scalability in view of the modular concept, and offers high energy transfer effectiveness. In this work, we outline the thermodynamic consideration based on a vapor-compression cycle to assess the performance of such a device. The coefficient of performance of the cycle is estimated for four different fluids: water, R12, R134a and FC-72. The system design parameters and operating performances are estimated for droplet sizes ranging from 10 to 500 micrometers. It is demonstrated that in this operating range, the gravity effect is small, making this device ideal for both earth-bound and spacecraft applications.
Anisotropic Thermal Conductivity of a Si/Ge Quantum Dot Superlattice
Authors: Borca-Tasciuc Theodorian , Liu Weili , Liu Jianlin , Wang Kang L. , Chen Gang 
Published: November 2021

Abstract
In this work, we present experimental results on the in-plane and cross-plane thermal conductivity characterization of a Si/Ge quantum-dots superlattice structure. The quantum-dots superlattice was grown by molecular-beam-epitaxy and self-organization. The anisotropic thermal conductivity measurements are performed by a differential two-wire 3ω method. The measured in-plane and cross-plane thermal conductivity values show a different temperature behavior. The results are compared and explained with heat transport models in superlattices.
Molecular Dynamics Simulation of Hydrogen Storage in Single-Walled Carbon Nanotubes
Authors: Maruyama Shigeo , Kimura Tatsuto 
Published: November 2021

Abstract
The hydrogen storage mechanism of SWNTs was studied through molecular dynamics simulations. Assuming the simple physical adsorption of hydrogen to the surface of SWNTs, potential forms between H2-H2 and C-H2 were both expressed by Lennard-Jones functions. Fixing the relative coordinates of carbon atoms to the center of mass of each SWNT, the center of mass motion was modeled with the van der Waals force between SWNTs. Hydrogen absorption in small bundles of (8,8), (10,10) and (12,12) SWNTs were tested. In order to realize the adsorption between SWNTs within reasonable simulation period, the van der Waals energy between tubes was once decreased and recovered. While the amount of hydrogen adsorption per unit carbon mass inside SWNTs increased with increasing diameter, adsorption between tubes was almost constant. Total amount of hydrogen adsorption for 77 K and 15 MPa system was predicted as 6.9, 7.7, and 8.1 wt % for (8,8), (10,10), and (12,12) bundles, respectively.
Film Cooling on a Flat Surface With a Single Row of Cylindrical Angled Holes: Effect of Discrete Tabs
Authors: Ekkad Srinath V. , Nasir Hasan , Acharya Sumanta 
Published: November 2021

Abstract
The effect of discrete delta-shaped tabs on the film cooling performance from a row of cylindrical holes is investigated. The holes are inclined at 35° along the streamwise direction. Three tab locations are investigated: (1) tabs placed along the upstream edge of the hole; (b) tab placed along the downstream edge of the hole; and (3) tabs placed along the lateral edges of the hole. Measurements were carried out in a low-speed wind tunnel using the transient liquid crystal technique. The mainstream velocity and free-stream turbulence intensity in the low speed wind tunnel are 8.5 m/s and 6% respectively and the Reynolds number based on hole diameter is 6375. Three blowing ratios of 0.56, 1.13, and 1.7 are tested. Results show that the tab placed upstream of the hole covering the 33% of the hole exit provides the highest film effectiveness compared to other tab locations studied. This is because the jet lift-off in the presence of the tabs is reduced and there is greater lateral spreading of the jet.