bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrodynamics and Thermodynamics of Newtonian Stars
Authors: Kwak Ho-Young , Jun Jung-Hwan 
Published: November 2021

Abstract
We investigated spherically symmetric solution for nonrelativistic cosmological fluid equations and thermodynamic equation of state for Newtonian stars. It was shown that the assumption of a polytropic state equation, P 0 = κ ρ 0 γ , at the center of the star only suffices to integrate the equations explicitly. Our exact solution yields many fruitful results such as stellar stability, spherical oscillation and collapses of stars. Pressure, temperature, and density profiles inside stars were obtained. Central densities, pressures and temperatures of the Newtonian stars such as Sun, Jupiter and Saturn were also calculated. Analytical results show that stars with γ ≤ 4/3 are unstable so that they are collapsing or they may expand forever. On the other hand, stars with γ &gt; 4/3 are stables so that they could undergo spherical oscillation. The upper bound value of white dwarf mass obtained turns out to be close to the Chandrasekhar limit. Motion of the Universe was also discussed within the framework of Newtonian mechanics.
Exergy Analysis of Integration Between Air Separation Process and IGCC
Authors: Liu Zelong , Jin Hongguang , Lin Rumou 
Published: November 2021

Abstract
Integrated Gasification Combined Cycle (IGCC) is considered as one of the advanced clean coal power technologies. Here, we have investigated an IGCC with air separation unit (ASU) on the basis of exergy analysis, and clarified the distribution of exergy destruction in sub-systems including air separation unit, coal gasifier, coal gas clean-up unit, air compressor, combustor of gas turbine, gas turbine, heat recovery steam generation and steam turbine. Particularly, we have focused on the interaction between the ASU and the gas turbine (GT). The results obtained disclosed the significant role of the integration between air separation unit and air compressor in the GT, and the effect of nitrogen injection to the combustor on IGCC overall performance. The study also points out that larger exergy destruction take place in the processes of gasification, combustion in GT, and air separation, and so does the change of exergy destruction distribution with the air integration degree and the nitrogen injection ratio. We have demonstrated the potential for improving the IGCC system. This investigation will be valuable for the synthesis of next-generation IGCC.
Evaporative Gas Turbine Cycle: A Description of a Pilot Plant and Operating Experience
Authors: Lindquist Torbjörn O. , Rosén Per M. , Torisson Tord 
Published: November 2021

Abstract
In recent years the interest for new advanced thermodynamical gas turbine cycles has increased. One of the new designs is the evaporative gas turbine cycle. A lot of effort worldwide has been put into predicting the possible efficiency, pollutants, and dynamic behaviour of the evaporative gas turbine cycle, but all results so far have been affected by uncertain assumptions. Until now this cycle has not been demonstrated in a pilot plant. The purpose of this work has been to identify the potential of this cycle, by erecting a pilot plant at the Lund Institute of Technology. The project was financed on a 50/50 basis from the Swedish National Energy Administration and the industrial partners.
Three different thermodynamical cycles have been tested in the pilot plant: the simple, the recuperative, and the evaporative cycle. The final pilot plant roughly consists of a 600 kW gas turbine, a hydraulic brake, a recuperator, a humidification tower, an economiser, and a flue gas condenser. All layout and functional analysis were made within the project. The pilot plant is, however, optimized neither for best efficiency nor for best emissions, due to the choice of standard components out of economical reasons. It has only been built for demonstration purpose.
Maximum simplicity, flexibility and safety have been the main emphasis in the design of the EvGT cycle. The flow mismatch that occurs between the compressor and the expander in evaporative cycles makes it hard to use a standard gas turbine unit. To be able to use a standard unit, an air bleed off system has been introduced. The water circuit can, at any time, be connected or disconnected from the humidification tower, thereby creating a possibility of controlling when humidification takes place or not by means of a water bypass past the humidification tower. Two starting sequences have been developed, one with the humidification process fully integrated from the beginning and one without. It has been shown that it is possible to reach full power output from the evaporative gas turbine cycle almost as fast as for the simple cycle. It has also been shown that the process is very stable when operated at various loads and during load transients. Furthermore, it is possible to start the power plant quickly from a remote place.
Computational Heat Transfer Analysis of a Furnace Using the WSGG Model
Authors: Omori Toshiaki , Yamaguchi Shunichi , Fusegi Toru 
Published: November 2021

Abstract
Accurate radiative heat transfer analysis is challenging due to the strongly spectral-dependent absorption coefficient and the requirement for satisfying both the summation and reciprocity laws in thermodynamics. In the paper, nongray radiation is treated by way of a computationally efficient Weighted Sum of Gray Gases (WSGG) model without much sacrificing prediction accuracy. In the present model, three gray gas components are used, one of which simulates the radiative window. The thermodynamic laws are simultaneously treated using a Monte Carlo method subject to a symmetrization procedure. As a test problem, radiative heat transfer in an industrial model furnace is solved to demonstrate effects of gray/nongray radiation and the grid size for CFD and radiation calculations.
Transient Radiative Transfer in Anisotropically Scattering Media Using Monotonicity-Preserving Schemes
Authors: Sakami M. , Mitra K. , Hsu P.-F. 
Published: November 2021

Abstract
This research work deals with the analysis of transient radiative transfer in one-dimensional scattering medium. The time-dependant discrete ordinates method was used with an upwind monotonic scheme: the piecewise parabolic scheme. This scheme was chosen over a total variation diminishing version of the Lax-Wendroff scheme. These schemes were originally developed to solve Eulerian advection problem in hydrodynamics. The capability of these schemes to handle sharp discontinuity in a propagating electromagnetic wave front was compared. The accuracy and the efficiency of the discrete ordinates method associated with the piecewise parabolic advection scheme were studied. Comparisons with Monte Carlo and integral formulation methods show the accuracy and the efficiency of this proposed method. Parametric study for optically thin and thick medium, different albedos and phase functions is then made in the unsteady state zone.
The pH Distribution During CO2 Dissolving Into Water Under Mid-Depth Sea Condition
Authors: Someya Satoshi , Nishio Masahiro , Chen Baixin , Okamoto Koji , Uchida Tsutomu 
Published: November 2021

Abstract
Sequestration of liquid CO2 into the intermediate depth ocean has been considered as a means to reduce atmospheric concentration of this greenhouse gas and mitigate global warming. A number of CO2 droplets are released and diluted into the intermediate ocean. The behavior of CO2 dissolution is very important in order to control the concentration of CO2 and to keep the environmental impact minimum.
Under conditions in the intermediate ocean, that is, high pressure and low temperature, the CO2 clathrate hydrate film was formed on the CO2 droplet surface. The hydrate film has been considered to decrease the dissolution rate and the CO2 concentration near the droplet surface.
The authors applied a LIF technique with a new kind of the dye as a pH indicator. The new dye in the CO2 dissolved water emitted intense fluorescence dependent on its pH. The visualized images showed the two dimensional distribution of the pH, i.e., CO2 concentration, around the CO2 droplet with or without the hydrate film.
A Mixed Environment for Effective Heat Transfer Learning
Authors: Braga Washington 
Published: November 2021

Abstract
This paper discusses aspects related to the undergraduate teaching of Heat Transfer in an environment using both Internet and classroom. The use of such an environment can be focused on the learning process of each student, using the classroom as formal check point for group work, sharing experiences and questioning, while the Internet is used for private follow-up, study and self evaluation. The paper describes the experience of one term using such an environment and several using Internet only as a tool for the learning process. The advantages already observed are reported, as well as the major difficulties still noticed. Internet is used continually throughout the course. Available material consists of quizzes, solved exercises, tutorials, spreadsheets, applets and others that the student may use through the Net or through a CD-Rom. Interaction between students and teacher is done mostly using an e-groups conference. Teamwork is strongly recommended, but challenging questions or exercises are expected to be solved exclusively on an individual basis. This paper supports the idea that the skill and attitude towards learning are most important to an effective life long learning.
Integrated Undergraduate, Graduate, and Professional Student (Distance Learning) Education in Thermal Systems Design
Authors: Garimella Srinivas 
Published: November 2021

Abstract
This paper describes an educational program in practical thermal systems design that encompasses design project-oriented teaching of undergraduate, graduate and off-campus professional students, industry-university collaboration, and community outreach. The program uses an integrated approach that treats thermodynamics, fluid mechanics, and heat transfer as parts of one interconnected area, in which solutions to real-life design problems can be obtained only when all these aspects are considered simultaneously. Cooperation between students at various stages of their educational and professional careers is fostered to maximize the synergy that results from combining insights gained in industry and those developed in structured classroom instruction.
The program consists of a comprehensive portfolio of Thermal Systems Design Instruction Initiatives. An interactive design laboratory format is used for cooperative execution of open-ended mini-projects spanning two-to-three weeks, and a semester-long project. The use of virtual project groups through the web removes geographical barriers. Computer programs for the solution of projects are placed on-line to create a design library for use by students in future semesters as case studies. An Energy-Efficient Environmentally-Safe Design Studio is planned where projects on environmental responsibility, and energy efficiency can be conducted for the local community. Annual design studio conferences will be held to foster K-12 and community involvement, and to demonstrate sustainable technologies. Collaboration with local thermal systems related organizations such as the Iowa Energy Center is also being pursued, which will provide inherent mechanisms for technology transfer from course-related projects to industry and the community.
Convective Heat Transfer in Micro and Nano Channels: Nusselt Number Beyond Slip Flow
Authors: Hadjiconstantinou Nicolas G. 
Published: November 2021

Abstract
We present calculations of the constant-wall-heat-flux Nusselt number for fully developed transition flow in two-dimensional microchannels. The Nusselt number cannot be obtained by a continuum analysis since the continuum description breaks down in the transition regime. We have used a molecular simulation technique known as the direct simulation Monte Carlo (DSMC). DSMC is a stochastic simulation technique previously shown to capture the hydrodynamic behavior of hard sphere gases. A wide range of Knudsen numbers is investigated: a channel height range of approximately 50 is analyzed starting from the micrometer scale that corresponds to slip flow. The channels have a length/height ratio of 20 to ensure fully developed flow, and care was taken to ensure that the Brinkman number is always small. The Nusselt number is found to decrease with increasing rarefaction (Knudsen number). The effects of thermal creep are discussed.
Mixed Convection Adjacent to 3-D Backward-Facing Step
Authors: Li A. , Armaly B. F. 
Published: November 2021

Abstract
Results from three-dimensional numerical simulation of laminar, buoyancy assisting, mixed convection airflow adjacent to a backward-facing step in a vertical rectangular duct are presented. The Reynolds number, and duct geometry were kept constant at Re = 200, AR = 8, ER = 2, and S = 1 cm. Heat flux at the wall downstream from the step was kept uniform, but its magnitude was varied to cover a Grashof number (Gr) range between 0.0 to 4000. All the other walls in the duct were kept at adiabatic condition. The flow, upstream of the step, is treated as fully developed and isothermal. The relatively small aspect ratio of the channel is selected specifically to focus on the developments of the three-dimensional mixed convection flow in the separated and reattached flow regions downstream from the step. The presented results focus on the effects of increasing the buoyancy force, by increasing the uniform wall heat flux, on the three-dimensional flow and heat transfer characteristics. The flow and thermal fields are symmetric about the duct’s centerline. Vortex generated near the sidewall, is the major contributor to the three dimensional behavior in the flow domain, and that feature increases as the Grashof number increases. Increasing the Grashof number results in an increase in the Nusselt number, the size of the secondary recirculating flow region, the size of the sidewall vortex, and the spanwise flow from the sidewall toward the center of the channel. On the other hand, the size of the primary reattachment region decreases with increasing the Grashof number. That region lifts away and partially detaches from the downstream wall at high Grashof number flow. The maximum Nusselt number occurs near the sidewalls and not at the center of the channel. The effects of the buoyancy force on the distributions of the three-velocity components, temperature, reattachment region, friction coefficient, and Nusselt number are presented, and compared with 2-D results.
Radiation Effects on Natural Convection Between Horizontal Walls With Heated Upper Plate
Authors: Guidotti Giuseppe , Manca Oronzio , Nardini Sergio , Morrone Biagio 
Published: November 2021

Abstract
Radiation heat transfer affects natural convection of air inside an open ended cavity with a heated horizontal upper plate and an unheated lower parallel plate. The influence is mainly due to radiative heating of the lower plate, and plane fluid layer secondary motion could arise. In this paper an experimental study is carried out to describe and to detect the influence of radiation on air flow and on heat transfer coefficient by means of wall temperature profiles, smoke visualization, and air temperature measurements. The analysis is obtained for an emissivity of the horizontal plates equal to 0.8, for distances between the plates of 20.0, 32.3, and 40.0 mm. By means of flow visualization and local air temperature measurements in the cavity as a function of time, remarkable secondary motion in the cavity is observed when qΩ is equal to 120 W/m2. Measurement of the air temperature in the cavity also shows that radiation causes and damps secondary motion at the same time. Profiles of the mean value of the air temperature as a function of the x and y coordinates confirm both the main flow path inside the cavity and radiation effects on convective heat transfer. Finally, correlations related to average Nusselt number are proposed for natural convection as well as for heat transfer as a whole, that is convection along with radiation.
Motion of Liquid Drops on an Inclined Solid Surface
Authors: Kim H.-Y. , Lee H. J. , Kang B. H. 
Published: November 2021

Abstract
The shape and motion of sliding drops on an inclined plane have been studied experimentally. In the experiments, various volumes of water, ink, ethylene glycol, and glycerin drops are placed on solid surfaces and the substrate is tilted to record the motion of the drops. A scaling law is provided to predict the steady-state velocity of the drop. It is shown that Poiseulle flow analysis cannot describe the steady-state motion of a drop. Instead, much stronger dissipation arising near the contact line is shown to play a major role in determining the speed of the drop. The scaling analysis agrees with experimental results using highly viscous liquid drops of ethylene glycol and glycerin. On the other hand, relatively inviscid drops of water and ink more slowly before abruptly accelerating to a high speed. This suggests that there exist two jumps in the dynamic state of those drops, one corresponding to initiation of movement and the other to a subsequent transition to a steady motion.
An Investigation of Microscale Explosive Vaporization of Water on an Ultrathin PT-Wire
Authors: Glod S. , Poulikakos D. , Zhao Z. , Yadigaroglu G. 
Published: November 2021

Abstract
The present study investigates at the microscale level the explosive vaporization of water close to its superheat limit. In the course of the research, it was possible to obtain simultaneously unique results of visualization, temperature and pressure of the vapor microregion, thus accomplishing a marked step forward in understanding the complex behavior of explosive vapor nucleation growth and subsequent collapse, despite the very small time and length scales of the phenomena of interest. To this end, a short (1 mm in length) and ultrathin (10 μm in diameter) Pt-wire is very rapidly heated by imposing a short and intense current pulse. Deionized and degassed water in contact with the wire is, as a consequence, also rapidly heated during the time of application of the current (in the range of 6 to 50 μs) and vaporizes explosively.
For the visualization of the very short boiling process, a strobe microscopy technique was developed and employed. The dynamic interaction between the exploding vapor microlayer and the surrounding liquid can be quantified and further characterized by measuring the acoustic pressure wave in the liquid during the boiling process. A fast pressure transducer allows us to capture the acoustic emission from the expanding vapor volume. From these data, the pressure inside the growing vapor layer and the mechanical energy released from its rapid expansion can be estimated.
An important result of the present experiments is the determination of the vapor nucleation temperature. The method for measuring the maximum superheat temperature of the water involves measuring the change in resistance of the Pt-wire during a heating pulse and relating the change in resistance to the change in temperature. The slope of the temperature curve changes shape when the fluid in contact with the wire changes phase, because when the vapor phase covers the wire, it reduces the rate of heat transfer to the fluid. This produces an inflection point in the temperature curve. A curve-fitting method was developed, which enabled us to define the vapor transition point and thus to determine the temperature of the heater surface, when explosive boiling is initiated. In the present study we were able to operate with the shortest heating pulses (&lt;4.5 μs) for an electrically heated body reported (to the best of our knowledge) and thus apply more electric power to the Pt-wire. The shorter the heating pulse, the more unlikely it is that nucleate boiling is promoted by gases trapped on the surface of the wire. It was shown that with a shorter pulse and higher power, the maximum attained superheat temperature increases. To the best of our knowledge, the superheat temperatures obtained for water (∼305 °C) in this study are higher than those reported in previous experiments in the open literature.
Heat Transfer for Gaseous Flow in Microtubes With Viscous Heating
Authors: Tunc Gokturk , Bayazitoglu Yildiz 
Published: November 2021

Abstract
Convective heat transfer for steady state, laminar, hydrodynamically developed flow in microtubes with a boundary condition of constant temperature is solved by the integral transform technique. Temperature jump condition at the wall and viscous heating within the medium are included. For a given Brinkman number, at specified axial lengths, the viscous effects are presented for the developing range, reaching the fully developed Nusselt number. In previous studies without temperature jump condition at the wall, a 22% increase in the Nusselt number was found for Knudsen numbers ∈ [0,0.12]. In this work we have found that for the same range of Knudsen numbers, the Nusselt number decreases by 35.6%. In addition, as we increase the Prandtl number the temperature jump effect diminishes.
Thermal Conductivity of Nanochanneled Alumina
Authors: Kumar A. R. , Achimov D.-A. , Zeng T. , Chen G. 
Published: November 2021

Abstract
We present an experimental study on the thermal conductivity of anodized alumina with regular nanochannels. Thermal conductivity values in both directions parallel and perpendicular to the nanochannel axis are measured at room temperature using the 3ω technique. An anisotropic heat conduction model is developed to analyze the experimental data.
Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls
Authors: Singh M. , Panigrahi P. K. , Biswas G. 
Published: November 2021

Abstract
A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.