bluuebunny/crossref_metadata_2025 huggingface dataset:
A Material Model for Shortening-Dependent Stiffness of Tracheal Smooth Muscle
Authors: Sarma P. A. , Pidaparti R. M. , Meiss R. A.
Published: November 2021

The objectives of the present study are to develop a material model of a tracheal smooth muscle tissue from experimental data, and to simulate the mechanical response through a three-dimensional nonlinear finite element analysis. The developed material model and simulation models are validated against the experimental data. The results obtained indicate that the approach and the material model developed are useful for describing the length-dependent characteristics of tracheal smooth muscle tissue.
The Influence of Non-Newtonian Behavior on Mass Transfer in Separated Flows at High-Schmidt Numbers
Authors: Hammad Khaled J.
Published: November 2021

The present study examines the influence of non-Newtonian rheology on dilute species transport from laminar, separating and re-attaching flows to a confining adsorbing boundary under steady conditions. Wall-bounded separating and re-attaching flows are encountered in many biological applications such as those dealing with blood flows through arteries and prosthetic devices. The investigation is carried out in the axisymmetric sudden expansion geometry since it displays flow characteristics similar to those encountered in physiological flows. The fixed separation location and the always present flow reversal region immediately downstream of the expansion plane, even for creeping flows, makes it easier to relate changes in the flow structure to variations in a specific governing parameter. Particular uses of the sudden expansion geometry in modeling physiological flows are very well documented ([1], [2], [3] and [4]).
Modeling of Friction Induced Vibration due to Third-Body Effects
Authors: Xu David S. , Heshmat Hooshang
Published: November 2021

Friction induced vibration at contact interfaces is still a big challenging problem and not well understood how to affect the high cycle fatigue (HCF) failures in gas turbine engine and other machinery. Most researchers conducted on the subject of only two bodies in contact with the Coulomb’s friction law only. In this paper, the interface friction phenomena and induced vibration are investigated by means of the improved third-body composite interface micro-slip model which includes a variable friction coefficient and a flexible contact, represented as effective stiffness and equivalent viscous damping elements. The third-body considered herein is almost always present at contacting interfaces and is comprised of generated wear debris or a soft intermediate anti-fretting coating applied to the mating surfaces. This kind of third-body can be viewed as a thin factional damping material layer to provide shear energy dissipation in order to mitigate the destructive effects of high frequency vibrations in components with highly stressed contacts. A properly engineered third-body can also play the role of both a damping material and a lubricant to decrease wear rate.

For the study presented, a semi-empirical formula for the third-body powder properties was employed, depending on the experimental data and the non-linear regression approach. The experimental powder TiO2 data included density, shear strength, frictional coefficients, loss factor as a function of normal load, shear strain, speed and frequency. The results in this paper indicate that the third body semi-empirical equivalent stiffness / viscous damping representation of a flexible contact with variable friction coefficient does indeed have merit and does have influence on overall system response. It has been shown that the third body effects should be considered in the friction and damping induced vibration on the contact interfaces. Such a model may be used to assess designs and material coating approaches to counter fretting in highly stressed contacts as well as assessing the interaction of contact kinematics on HCF failures. Further experimental investigation of specified friction contact configuration of the components needs to be conducted in order to evaluate their friction characteristics and move this technology toward a practical engineering applications.
Simulation of Roll Grinding System Dynamics With Rotation Speed Control
Authors: Yuan LiHong , Järvenpää Veli-Matti , Keskinen Erno , Cotsaftis Michel
Published: November 2021

This paper is a discussion of a numerical simulation and a numerical stability study of the dynamics of a paper machine roll grinding process with an additional time delay effect, which is originated from a shape error trace on the surface of the roll under grinding. The simulation model presents the dynamic interaction between the roll and the grindstone during the process, the lateral deformations of the roll and the torsional rigid body vibration system of the roll and the grindstone with its drive. The normal and tangential forces of the grinding contact based on the wear theory and the driving torques of the roll and the grindstone with PD-controllers are considered. The mechanical model of the roll is described as a simply supported continuous beam element expressed in an eigenvector basis and in rotating coordinates. The time delay equation is based on the classical linear time delay theory with a constant delay. The numerical simulations conducted in time domain provide a view to observe the dynamic behavior and the stability of this grinding process and a tool for the design, analysis and verification of industrial roll grinding measurements in the future.
Nonlinear Dynamics Analysis of a Printed Wiring Board With Simple and Clamped Boundary Conditions
Authors: He Xiaoling
Published: November 2021

Dynamic response of a printed wiring board (PWB) is analyzed in nonlinear dynamics approach. Equations of motion for the simply supported PWB and the clamped PWB are obtained by the Galerkin’s method. A 2-layer plastic PWB made of isotropic laminates is studied for its boundary condition effect on the vibratory behavior in deflection and stresses. Failure due to plane stress interaction is estimated based on the composite failure criteria.

It is found that nonlinear resonance occurs almost periodically in both frequency and temporal domain. Load frequency and magnitude affect the deflection response under different boundary conditions. Resonance behavior is critical in PWB failure prediction based on the stress analysis. The analytical results can be extended to the nonlinear dynamics analysis of the thin laminated plate.
Analysis on an Oscillator With Delayed Feedback Near Double Hopf Bifurcations
Authors: Yu P. , Yuan Y.
Published: November 2021

This paper considers the effect of time delayed feedbacks in a nonlinear oscillator with external forcing. The particular attention is focused on the case where the corresponding linear system has two pairs of purely imaginary eigenvalues at a critical point, leading to double Hopf bifurcations. An analytical approach is used to find the explicit expressions for the critical values of the system parameters at which non-resonant or resonant Hopf bifurcations may occur. A fourth-order Ronge-Kutta numerical integration scheme is applied to obtain the dynamical solutions in the vicinity of the critical points. Both the cases with and without the external forcing are considered. It has been found the system exhibits very rich complex dynamics including periodic, quasi-periodic and chaotic motions. Moreover, a sensitivity analysis is carried out to show that chaotic motions are very sensitive to the time delay. This suggests that the time delay can be used: (1) to control bifurcations and chaos; and (2) to generate bifurcations and chaos.
Dynamics of a Nonlinear Mechanical Resonator in Micro-Electro-Mechanical Systems
Authors: Luo Albert C. J. , Wang F. Y.
Published: November 2021

Equilibrium, natural frequency and responses of a mechanical resonator with capacitors in a simplified micro-electro-mechanical system (MEMS) are determined. Under application of alternating current (AC) voltage, the resonant conditions for such a system are obtained. The chaotic motions in the vicinity of a specified resonant-separatrix are investigated analytically and numerically. For a given AC voltage amplitude, the AC frequency bands are obtained for chaotic motion in the specific resonant layers and resonant motions, and such chaotic motions can be sensed very easily by the output transducer in MEMS.
The Pressure Field Around a Vibrating Cylinder in a Fluid Annulus
Authors: Reynolds Robert R. , Cole Jack H. , Yuan Zhen
Published: November 2021

The influence of geometry on the pressure field within the confined, water-filled annulus between a central, vibrating cylinder and an outer, rigid enclosure is determined. A two dimensional model is constructed using the finite element (FE) method and parameters are identified to characterize the eccentricity of the nominal cylinder position, the size of the annulus relative to the inner cylinder and the degree to which the annulus is not circular (i.e. it is elliptic). The FE solution is verified using a closed form solution for the special case of a concentric cylinder and annulus. It is shown that the system acts as a force multiplier. Analyses of the asymmetrical geometries indicate that while the pressure field on the surface of the cylinder and enclosure can be highly asymmetric, the system is relatively insensitive to minor variations in annulus shape except when the vibrating cylinder is not centrally located within the fluid region or the annulus size itself is small.
4WID: A New Concept in Electrical Vehicles
Authors: Esmailzadeh E. , Goodarzi A. , Vossoughi G. R.
Published: November 2021

A comprehensive new dynamic model of a four-wheel independent drive electric vehicle has been developed and different types of the motor control laws were addressed. The first part of this study deals with the full description of the model scope in which the structure of the model including the sub-models has been fully developed. Subsequently, the sub-models including the tire sub-model, the body motion, and the motor dynamics were investigated, and the computer model of the vehicle has been simulated. Finally, the proposed motor control laws and the vehicle dynamic behavior of the vehicle were presented. Detailed analyses of the vehicle performance and comparison of the simulation results were also carried out.
Structural Sound Radiation on a Reflecting Plane by the Boundary Point Method
Authors: Cui Z. , Huang X. Q.
Published: November 2021

In this paper, the structural sound radiation from a reflecting plane is studied. The Green Function is used to develop a formula, which is implemented in applying the boundary point method to a semi-infinite region. A detailed description of this method is presented. Through the theory and numerical examples, it is shown that this method compared to other available ones is simple and efficient.
Development of a Driver Assistant System for Improving Passenger Ride Comfort of Automobiles
Authors: Wang Feng , Ma Ni , Inooka Hikaru
Published: November 2021

This paper describes the development of a driver assistant system for reducing passenger ride discomfort of automobiles. Based on results of psychophysical experiments of subjective ride discomfort evaluation, the ride discomfort caused by the velocity fluctuation of an automobile was investigated and a linear multiple regression model that evaluates the ride discomfort index (RDI) using longitudinal acceleration and jerk of the automobile as explanatory variables was proposed. A driver assistant system that evaluates the RDI and informs the driver of the RDI in real time using a microcomputer was developed. Experiments showed that with the help of the system, a driver can improve his/her driving skills and modify his/her driving behavior to reduce passenger ride discomfort and provide passenger-friendly maneuvers, thus verified the efficacy of the proposed driver assistant system.
The Integration of Reliability Techniques As an Aid to the Design Optimisation of an Earth Moving Machine
Authors: Arcidiacono G. , Delogu M.
Published: November 2021

The paper describes the design and structural optimisation of a mechanical system from the functional, safety, reliability and cost viewpoints, using a flexible, rapid approach which was developed from the integration of two methodologies: Axiomatic Design and FMEA. In particular, thanks to the information obtained from Axiomatic Design, FMEA is not carried out on the entire system but only on the components and subsystems which are more critical. This makes it possible to establish an order of priority for intervening on components or Design Parameters of a system which can be applied both prior to designing the system or in the diagnostic and validation phase of an already existing product. This approach has been validated by its application to the electro-hydraulic command of the working device of an Orenstein & Koppel (O&K) earth-moving machine.
Control Law for an Engine Starter Clutch in a Parallel Hybrid Electric Vehicle
Authors: Baraszu Robert C. , Cikanek Susan R.
Published: November 2021

This paper describes the control law for engaging and disengaging a dry clutch used for connecting an engine to a drivetrain in a Parallel Hybrid Electric Vehicle (PHEV). Brief descriptions of the component models and subsytem controllers are presented along with the powertrain’s dynamic equations. The engine clutch control is described in detail, including engagement and disengagement simulations. The hybrid drivetrain, (Figure 1), includes a conventional 2.01 spark-ignited, internal combustion engine and an dry clutch attached directly to an engine flywheel. The output of the dry clutch is connected to a starter/alternator (S/A) that starts the engine, charges and discharges a high-powered energy storage device and provides additional motive power. The powertrain is completed by a converterless automatic transmission connected to a differential and halfshafts that drive the front wheels. The engine clutch control strategy is presented together with simulations that demonstrate system performance.
Multiple Target Tracking in the Adaptive Cruise Control Environment Using Multiple Models and Probabilistic Data Association
Authors: Caveney Derek , Hedrick J. Karl
Published: November 2021

The multiple target tracking (MTT) performance of a new combination of the fuzzy interacting multiple model (FIMM) algorithm and the probabilistic data association filter (PDAF) is investigated. The ability of a set of these FIMMPDAFs to maintain the tracks of multiple targets in a cluttered adaptive cruise control (ACC) environment is compared to that of the likelihood approach, the IMMPDAF. The differences between the two methods are highlighted and simulation results for a typical highway driving scenario demonstrate the performance of each approach. These results show that both the IMMPDAF and FIMMPDAF strategies are capable of tracking multiple vehicles with low RMS position errors, while the FIMMPDAF appears to detect the initiation of a target maneuver more rapidly by adjusting model probabilities more quickly.
Effect of Multi-Modal Forcing on Thermal Transport in a Co-Axial Combustor Geometry
Authors: Chandra P. R. , Lau Chun L. , Acharya S.
Published: November 2021

This paper investigates open-loop control of the mixing between an inner stream and an outer stream in a coaxial combustor geometry. The inner and outer air streams enter the combustor geometry at different temperatures and mimic a gaseous fuel and combustion air stream respectively. Of specific interest in this study is the behavior of the coherent structures in the coaxial jet streams, and the manipulation of these coherent structures with controlled perturbation to enhance jet-spreading and scalar-mixing. The spectra of the unforced flow reveal the presence of a dominant coherent mode at 100 Hz (identified as the fundamental mode fo), as well as 150 Hz (3 fo/2) and 300 Hz (3 fo). Single-mode forcing of both the inner-jet and the outer-jet at 100 Hz, 150 Hz, 300 Hz, and 1 kHz is explored, and attention is focused on the spreading of the inner-jet shear layer and the outer-jet shear layer. It is observed that the 300 Hz mode shows the greatest enhancement in the spreading rate of the velocity shear-layer in the near field (x/D < 1), while downstream of x/D = 1, the 100 Hz appears to show the most significant effect. Scalar mixing is also significantly enhanced, with the 300 Hz forcing showing the largest enhancement. Dual-mode forcing is also investigated with 100 Hz inner-jet, 300 Hz outer-jet forcing and 300 Hz inner-jet, 100 Hz outer-jet forcing. The 100 Hz inner-jet, 300 Hz outer-jet forcing is shown to lead to greater enhancements in scalar mixing man all other cases considered.
Natural Convection on a Vertical Isoflux Plate With a Downstream Unheated Extension and a Parallel Shroud
Authors: Manca Oronzio , Musto Marilena , Naso Vincenzo
Published: November 2021

Air natural convection on a vertical isoflux plate with a downstream unheated extension and a facing parallel shroud has been experimentally investigated, for different values of the wall heat flux and of the geometrical parameters. In most configurations the adiabatic extension improves the thermal performance of the channel. For the larger values of the channel aspect ratio (Lh/b = 10) the system with a geometrically asymmetric chimney performs better than that with a geometrically symmetric chimney. Maximum wall temperatures and average Nusselt numbers are correlated to the thermal and geometrical process parameters, in the ranges Ra* B/b = 3.102 − 105 and L/Lh = 1.5–4.0.
Local Heat Transfer and Pressure Drop for Finned-Tube Heat Exchangers Using Oval Tubes and Vortex Generators
Authors: O’Brien James E. , Sohal Manohar S. , Wallstedt Philip C.
Published: November 2021

This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with an elliptical tube and one or two a delta-winglet pairs. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficients were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over a Reynolds number range based on duct height of 670–6300.

Pressure drop measurements have also been obtained for similar elliptical-tube and winglet geometries using a separate single-channel, multiple-tube-row pressure-drop apparatus. The pressure-drop apparatus includes four tube rows in a staggered array. Comparisons of heat transfer and pressure drop results for the elliptical tube versus a circular tube with and without winglets are provided.

Mean heat transfer results indicated that the addition of the single winglet pair to the oval-tube geometry yielded significant heat transfer enhancement, averaging 38% higher than the oval-tube, no-winglet case. The corresponding increase in friction factor associated with the addition of the single winglet pair to the oval-tube geometry was very modest, less than 10% at ReDh = 500 and less than 5% at ReDh = 5000.
High Speed Photographic Investigation of Liquid-Vapor Interface and Contact Line Movement During CHF and Transition Boiling
Authors: Kandlikar Satish G. , Steinke Mark E.
Published: November 2021

As the Critical Heat Flux (CHF) condition is approached, a thin layer of vapor begins to form between the heated surface and the liquid. The mechanisms leading to the formation of this interface are not clearly understood. The present investigation focuses on obtaining high-speed video images of the liquid-vapor interface and the solid-liquid-vapor contact line. The movement of the interface and the contact line is expected to provide information regarding conditions existing just prior to reaching the CHF.

The experimental setup consists of a droplet impinging on a heated surface in a controlled environment. Two high-speed cameras capable of capturing up to 8000 frames per second are employed to obtain two views of the droplet. The accompanying software is used to determine the velocity and other relevant information regarding the interface. The results are used to discuss the applicability of the CHF and transition boiling models available in literature.
Nanoscale Thermal, Electrical, and Thermoelectric Measurements Using Batch-Fabricated Scanning Probes
Authors: Miner Andrew C. , Li Deyu , Tan Kwong-Luck , Shi Li , Majumdar Arun
Published: November 2021

Recent interest in thermal, electrical and thermoelectric properties of thin films and nano-structures has driven the development of measurement tools. One promising technique integrates sensors into Atomic Force Microscope (AFM) probes to investigate thermal, electrical, and thermoelectric properties on nanometer scales. Our group has successfully developed such probes and used them to investigate thermionic coolers and the carbon nanotubes. In this paper, we will discuss the successes and deficiencies of these measurement methods, and present new nanoprobe designs, which address these deficiencies. The majority of AFM systems use laser reflectance to monitor the probe position. Current designs are adversely effected by the portion of absorbed laser energy in two ways: probe temperature rises and creates bending due to a bimaterial effect, and the variability of the laser input adds error to the sensor measurement. The finite thermal resistance between the probe and sample creates a temperature drop, contributing to experimental error. This work proposes refined microfabrication techniques to reduce the bi-material effects, alternative probe positioning schemes, and improved sensitivity of thermal measurement to significantly improve the reproducibility and accuracy of nanoscale property measurement.
Explicit Analytical Solutions of Natural Convective Heat Transfer in Saturated Porous Medium
Authors: Zhang Na , Cai Ruixian , Wang Wei
Published: November 2021

Analytical solutions have their own theoretical meaning; as benchmark solutions, they can also guide the computational methods. Therefore, six algebraically explicit analytical solutions are derived for the natural convective heat transfer nonlinear partial differential equation set to enrich the heat transfer theory and to promote the development of computational heat transfer.
Theoretical Thermal Conductivity of Soils at High Temperatures
Authors: Gori Fabio , Corasaniti Sandra
Published: November 2021

The prediction of the thermal conductivity of soils is important in several phenomena related to ground. Among the practical applications at high temperatures are geothermal energy extraction, enhanced oil recovery, radioactive waste storage, ground heat pump and heat exchanger, forest fires and related problems. Some experimental results are available in the literature at temperatures in the range 30°C – 90°C. The theoretical model of the present paper assumes the unit cell of the porous medium as composed of a cubic space with a cubic solid particle at the center. The thermal conductivity of the porous medium is evaluated with the assumption of parallel isotherms. The water in the porous medium is distributed around the solid particle according to the phenomena of adsorption and capillarity. The thermal conductivity of the gas present within the pores takes into account the thermal conductivity of the water-saturated vapor and dry air without enhanced vapor diffusion and with the assumption of a linear variation of the relative humidity from zero water content to the field capacity. The predicted results, compared to the experimental data of soils at high temperatures show that the agreement is very good at moderate temperatures (30–50°C) and fairly acceptable at 70°C. At high temperature (90 °C) the predictions are somewhat higher than the experiments but a better agreement could be obtained decreasing the thermal conductivity of the water-saturated vapor. In any case the trend of the theoretical predictions is in very good agreement to the experiments also at high temperatures.
A Continuum Model for the Liquid-to-Gas Phase Change and Growth in a Porous Medium at Constant Withdrawal Rates
Authors: Tsimpanogiannis Ioannis N. , Yortsos Yanis C.
Published: November 2021

We develop an effective continuum model to describe the heterogeneous nucleation and subsequent growth of a gas phase from a supersaturated, slightly compressible binary liquid in a porous medium, driven by solute diffusion. The evolution of the gas results from the withdrawal of the liquid at a constant rate. The model addresses two stages before the onset of bulk gas flow, nucleation and gas phase growth. We assume negligible gradients due to gravity or viscous forces, thus the critical gas saturation, which signals the onset of bulk gas flow, is only a function of the nucleation fraction. We show that the important quantities characterizing the process, such as the fraction of pores that host activated sites, the deviation from thermodynamic equilibrium, the maximum supersaturation in the system and the critical gas saturation depend crucially on the nucleation characteristics of the medium.
Experiments on Fluid Flow and Heat Transfer in a Packed Channel Between Two Parallel Grooved Plates
Authors: Du J. H. , Ma B. , Wu W. , Hu X. J. , Wang B. X.
Published: November 2021

Experiments on fluid flow and heat transfer in a glass bead packed channel between two parallel grooved plates were conducted. The effects of the grooves on the surface of the heated plate upon the flow resistance and heat transfer were investigated. The results indicated that the grooves on the plate surface change the contact condition of the packed beads to the wall and increase the wall effect of the packed channels. Its direct consequence is to lower the flow resistance. The film heat transfer coefficient on the wall may be increased or rebated. It is demonstrated that a proper combination of packed beads and grooves can lead to the optimum performance of heat transfer for a specific configuration.
Heat Transfer of Slug Air-Water Flow in a Slightly Upward Inclined Tube
Authors: Kim Jae-yong , Trimble Steve , Ghajar Afshin J.
Published: November 2021

This paper presents a preliminary study on the heat transfer in slug air-water flow in a slightly upward inclined tube, which is a widely appeared pattern in the inclined two-phase flow regime. Local heat transfer coefficients and flow parameters have been measured for slug air-water flow in a pipe [1.097 in (2.79 cm) I.D. and L/D = 100] at slightly upward inclination angles of 2° and 5°. The heat transfer data with slug air-water flow pattern were measured under a uniform wall heat flux boundary condition. The change on the heat transfer with inclination angle compared to the horizontal case is discussed in terms of the change in the overall heat transfer coefficient with respect to the superficial gas and liquid Reynolds numbers. For these data, the superficial Reynolds number ranged from about 3700 to 28000 for the water and from about 540 to 6500 for the air. The results indicate that there is an increase in the heat transfer with only slight increases in the inclination angle. However, the amount of increase is strongly dependent on the magnitudes of superficial liquid and gas Reynolds numbers.
Mechanisms of Subcooled Water Flow Boiling CHFS for Outlet Subcooling at a Flow Velocity With Pressures for Test Sections With Various Shapes
Authors: Sakurai Akira , Fukuda Katsuya
Published: November 2021

The mechanisms and the correlations for the subcooled water flow boiling CHF, qct,sub, for outlet subcooling at fixed flow velocities with the pressure as a parameter measured were investigated using the existing database measured for the test sections such as a vertical metal strip in the channel with a wide cross section, and the vertical tubes having the inside diameters ranging from 0.4 to 12 mm and the length-to-diameter ratio ranging from 2.4 and 96.6 with water flowing upward based on the unified subcooled pool and flow boiling CHF correlations previously presented: the unified CHF correlations based on the two different mechanisms due to the hydrodynamic instability (HI) and the heterogeneous spontaneous nucleation (HSN). The qct,sub versus outlet subcooling, ΔTsub,out, for the test tubes at a flow velocity with the pressure were clearly divided into four regions for the ΔTsub,out in general: namely, first, the qct,sub decrease down to minimum one for low ΔTsub,out (1st Region), secondly, the qct,sub increase up to maximum one for middle ΔTsub,out (2nd Region), thirdly, the qct,sub considerably decrease down to minimum one for transition ΔTsub,out (3rd Region), and finally, the qct,sub again increase monotonously for high ΔTsub,out (4th Region) with an increase in ΔTsub,out. The trend of the qct,sub versus the ΔTsub,out, in the third region for the transition ΔTsub,out became significant with a decrease in tube inside diameter though the trend of the qct,sub for the tubes having large inside diameters of 9 and 12 mm became insignificant. It was clarified that the qct,sub data for middle ΔTsub,out (2nd Region) and those for high ΔTsub,out (4th Region) for the test sections with various shapes of the metal strip and the tubes having the inside diameters ranging from 0.4 to 12 mm and length-to-diameter ratio ranging from 2.4 to 96.6 were well expressed by the unified subcooled water flow boiling CHF correlations derived based on the existing database.
Development of Pressurizer Transient Thermodynamics Analysis Code for Chashma Nuclear Power Plant
Authors: Mahmood Arshad , Jun Xu Ji
Published: November 2021

A computer program PRETTA “Pressurizer Transient Thermodynamics Analysis” has been developed for the prediction of pressurizer under transient conditions. It is based on the solution of the conservation laws of heat and mass applied to the three separate and non equilibrium thermodynamic regions. In the program all of the important thermal-hydraulics phenomena occurring in the pressurizer: stratification of the hot water and incoming cold water, bulk flashing and condensation, wall condensation, and interfacial heat and mass transfer have been considered. The bubble rising and rain-out models are developed to describe bulk flashing and condensation, respectively. To obtain the wall condensation rate, a one-dimensional heat conduction equation is solved by the pivoting method. The presented computer program will predict the pressure-time behavior of a PWR pressurizer during a variety of transients.

The results obtained from the proposed mathematical model are in good agreement with available data on the CHASHMA nuclear power plant’s pressurizer performance using RETRAN.
Simulating Analysis for Small Break LOCA Test Facilities by Applying the Volume Scaling With Reduced Pressure and Reduced Height
Authors: Moussavian S. K. , Salehi M. A.
Published: November 2021

In this paper first we briefly define the different scaling schemes and scaling logic in which we use these schemes to simulate the Small-Break Loss Of Coolant Accident (SB-LOCA) in test facilities. The simple loop of the test facility is considered and the mass, momentum and energy conservation equations are used for the derivation of the scaling model. The variations of mass flow rate, pressure drop and the void fraction in the loop as functions of the time scale or the inventories are obtained. Finally, the calculated results from the simulating schemes are compared with the experimental data previously obtained in an integral test facility.
A Study of Transient Heat Transfer in a Vertical Two-Phase Flow During Blowdown of a Pipeline
Authors: Bautista-Fragoso S. , Fairuzov Yuri V.
Published: November 2021

A numerical model of transient two-phase flow and conjugate heat transfer in a vertical pipeline is presented in the present paper. The drift-flux model is used to describe the fluid flow in the pipeline. The modeling of transient conjugate heat transfer is based on a mathematical formulation in which the pipe wall and the fluid are assumed to be in local thermal equilibrium. The effect of the thermal capacity of the pipe wall is taken into account by an additional term in the energy equation for the fluid flow. Such an approach allows significant simplifying the problem and reducing the computer running time. Numerical simulations of blowdown of a pipeline/riser system were performed. The effect of the pipe wall on the flow behavior was investigated.
Study on Enhancement of Critical Heat Flux by Supplying Liquid-Jets to Heating Surface: Mechanism on Enhancement of CHF and Measurement of Void Fraction Near Heating Surface
Authors: Ohtake Hiroyasu , Liu Kun , Koizumi Yasuo
Published: November 2021

The enhancement of a critical heat flux — CHF — in pool boiling was investigated by supplying liquid-jets to a heating surface, as a proposal of the high heat removal technology for the future industrial field. The mechanism on the enhancement of CHF was examined through measurement of void fraction near the heater by using a void probe and macrolayer model of CHF by Haramura-Katto.

Experiments were conducted using a copper block and saturated water for a pool condition at 0.1 MPa. One, two or three jet-nozzles were set away a certain distance from the test surface, 1 or 6 mm, for supplying liquid-jets to the heating surface. The effects of the distance, the diameter of jet-nozzles, 0.9, 0.5 or 1.5 mm, the liquid flow rate and the jet-velocity on the enhancement rate of the CHF were examined experimentally.

The CHF was enhanced by supplying three liquid-jets a factor of about three for 6 × 10−6 m3/s in the flow rate. The enhancement rate increased with the liquid flow rate and jet-velocity. The void fraction near the heating surface was a lower value by the supplying liquid-jets when the heat flux was similar to the normal CHF without the supplying liquid. These results suggests that the enhancement of the CHF is affected additionally by the quantity of supplied liquid to the macrolayer on the heating surface.
RBHT Steam Cooling and Droplet Injection Pre-Test Analysis Using COBRA-TF
Authors: Frepoli C. , Ireland A. J. , Hochreiter L. E. , Cheung F. B.
Published: November 2021

The droplet injection experiments to be performed in a 7 × 7 rod bundle heat transfer test facility are being simulated using an advanced thermal hydraulics computer code called COBRA-TF. A current version of the code, which provides a three-dimensional, two-fluid, three-field representation of the two-phase flow, is modified to facilitate the simulation of the droplet field produced by the injection system in the test facility. The liquid phase is split into a continuous liquid field and droplet field where a separate momentum and mass equation is solved for each field, with the effects of spacer grids being properly accounted for. Pre-test analyses using the modified COBRA-TF code have been conducted for different injection conditions. Results indicate that there are specific ranges of conditions that can be simulated within the facility constraints to provide for validation of the dispersed flow film boiling models. The numerical results also show important effects of the spacer grids on the local heat transfer in the dispersed flow film boiling regime.
Prediction of Heat Transfer Rate and Pressure Drop of a Humid Flue-Gas Flow Across a Tube Bank for Waste Heat Recovery
Authors: Jeong Dong Woon , Lee Sang Yong , Park Byung Kyu
Published: November 2021

A simulation program taking into account of the mass transfer effect was constructed to estimate the heat transfer rate and the pressure drop of a flow of humid flue gas across a tube bank. Higher heat transfer rate is expected when the flue gas temperature drops below the dew point because of the vapor condensation effect at the external surface of the tubes. The temperature variations of the flue gas and the cooling water and the pressure drop across the tube bank were compared with the experimental data reported previously. The predicted results for the temperature variations without any correction factor agree satisfactorily with the experimental data. As for the shell-side pressure drop, the single-phase friction factor for the tube-bank flow adopted. With this simulation program, the parametric studies have been conducted for various operating conditions, such as the velocities and temperatures of the vapor/gas mixture and the cooling water, the number of the tube-rows, and the conductivity of the wall material.
The Flow Regime of Oil-Gas-Water Three-Phase Flow in Pipes
Authors: Wang Yueshe , Zhou Fangde
Published: November 2021

The experiment for oil-gas-water flow pattern transition is carried out in a vertical tube 40mm I.D. and 6m long with a wide range of mixture velocity. Applying the concept of Weisman’s flow pattern transition zone to the investigation on oil-gas-water flow regime, every transition is quantified. The flow regime map, which includes transition zone mentioned above, is compatible with a lot of other pattern transitions. Meanwhile, according to this map the divergence of numerous transitions can be explained. So, that provides a reliable for reasonable understanding of the pattern transitions. Consequently, a method for regime recognition has been put forward with using simultaneously optical fiber probes and conductance probes. The availability of the method can be proved by the images of High Speed Motion Analyzer, which is from Kodak Company.
Flow Configure in Vertical 180 Degree Turning Duct
Authors: Yuanwei Lu , Fangde Zhou , Yueshe Wang , Huanqun Qian , Zhihua Hu
Published: November 2021

Bend is applied in many industries, which exert an influence on fluid and make the flow complicate. The second flow caused by the bend is strong enough that the flow behind it very long can be affected, so it is hard to make the flow in it steady. The long-term unsteady flow can make the pipe fatigue, so make the tube crack and leak. It is important to improve this situation.

In this paper a throttle is built in the exit of the bend to control the non-homogeneous flow inside the bend, which can overcome the disadvantage of bend in industrial application.

Through computed the flow field behind the bend by water, we can see that the throttle can improve the flow situation and make the flow steady behind it. Applying this method to the gas-liquid flow, the experimental result showed that the void fraction behind the bend is alike the fully developed flow. It means that the throttle can improve the two-phase flow situation in the invert U bend.

At last the gas-liquid flow pattern in-bend was studied by experiment and built the flow pattern map in the vertical parts of the invert U bend. It was found that the flow pattern in the vertical part of invert U bend is different from the fully developed gas-liquid flow in vertical tube. The throttle built in the bend make the unsteady region of two-phase flow being reduced.
Subcooled Boiling of Surfactant Solutions
Authors: Hetsroni G. , Gurevich M. , Mosyak A. , Rozenblit R. , Yarin L. P.
Published: November 2021

Boiling heat transfer from horizontal stainless steel tubes, submerged in subcooled surfactant solutions of various concentrations was studied experimentally. The kinetics of boiling (bubble nucleation, growth and departure) in pure water, fresh and degraded solutions was investigated by the high speed video recording in combination with Infrared Thermography. The specific features of boiling of surfactant solutions were revealed. It was found that the subcooled nucleate boiling of surfactant could not be described by a single curve in contrast to water. At given values of heat flux and bulk temperature the heat transfer coefficient does not depend significantly on the concentrations of the solution. A boiling hysteresis was found only for degraded solutions. This phenomenon may be related to formation of a surfactant monolayer, which results in damping of an interfacial motion.
Frost Growth in Regenerative Heat Exchangers: Part I — Problem Formulation and Method of Solution
Authors: Shang W. , Chen H. , Evitts R. W. , Besant R. W.
Published: November 2021

In this paper the problem of frost growth within the narrow flow passages of a regenerative rotary wheel is formulated. Frost growth is assumed to occur for the portion of the wheel subject to warm humid airflow. While the wheel is subject to cold dry airflow the frost is cooled but no frost grows. This cyclic frost growth and cooling process is continued with each wheel rotation. An analytical and numerical model is developed to simulate the frost growth over one to two hours while the wheel rotates at speeds from 5 to 35 rpm.
Frost Formation and its Density Behavior on Various Surfaces
Authors: Kim Cheolhwan , Shin Jongmin , Tikhonov Alexei V. , Ha Samchul , Choi Bongjun
Published: November 2021

An experimental study has been conducted to investigate the effects of surface energy on frost formation. Test samples with three different surfaces of which Dynamic Contact Angles (DCA) are 23, 55 and 88 degrees are installed in a wind tunnel and exposed to a humid airflow. The thickness and the mass of frost layer are measured and used to calculate frost density while frost formation is visualized simultaneously with their measurements. Results show that frost density increases as time increases at specific test conditions. The air Reynolds number, the airflow humidity and the cold plate temperature are maintained at 12,000, 0.0042 kg/kg and −20 degrees Celsius, respectively. The surface with a lower DCA shows a higher frost density for a two-hour test, but no differences in frost density have been found after two hours of frost generation. Empirical correlations for thickness, mass and density are proposed as the functions of test time and surface energy. Visualization of frost generation was in good agreements with test results.
Heat Transfer Characteristics in Melting of Granular Packed Bed Subject to Horizontal Forced Convection
Authors: Hao Y. L. , Tao Y.-X.
Published: November 2021

A series of experiments are conducted to investigate the characteristics of melting and heat transfer of a packed bed consisting of melting ice particles subject to horizontal forced convection. The packing pattern of ice particles in horizontally flowing water is recorded using a digital video camcorder and a digital camera at the water velocity of 0.01, 0.05, and 0.10 m/s, respectively, and supply water temperature of 4, 10, 20, and 30 °C, respectively. The mass of ice particles is measured at the desired time interval during the meting process. The volume of packed bed is obtained based on the digital images. The time variation of average melting rate per unit bed volume and average heat transfer coefficient is determined. Within the experimental conditions, the average melting rate per unit bed volume in the packed bed in horizontally flowing water increases during convective melting. The average heat transfer coefficient decreases during convective melting. The effects of water velocity and water temperature on the melting and heat transfer in the melting process are analyzed. The original experimental data and correlations for Nusselt number based on the present results are published.
Intermolecular and Surface Forces and Their Role in Nanoscale Liquid Transport and Phase Change
Authors: Weng Jian-Gang , Tien Chang-Lin , Majumdar Arun
Published: November 2021

When liquid molecules interact in a highly confined region, their bulk characteristics are often overshadowed by near-field intermolecular and surface forces. These include van der Waals, electrostatic, structural, and surface tension forces. This paper will present two examples of how thermodynamic models and Molecular Dynamic simulation can provide insight into nanoscale liquid transport and phase change: liquid film stability and the curvature effect on surface tension of droplets and bubbles. Both examples have major ramifications on problems such as nucleation, condensation, boiling, biological transport etc.
Thermal Modeling of Unlooped and Looped Pulsating Heat Pipes
Authors: Shafii M. B. , Faghri Amir , Zhang Yuwen
Published: November 2021

Analytical models for both unlooped and looped Pulsating Heat Pipes (PHPs) with multiple liquid slugs and vapor plugs are presented in this study. The governing equations are solved using an explicit finite difference scheme to predict the behavior of vapor plugs and liquid slugs. The results show that the effect of gravity on the performance of top heat mode unlooped PHP is insignificant. The effects of diameter, charge ratio, and heating wall temperature on the performance of looped and unlooped PHPs are also investigated. The results also show that heat transfer in both looped and unlooped PHPs is due mainly to the exchange of sensible heat.
Molecular Dynamics Simulation of Interfacial Tension of Ultra-Thin Liquid Films on a Solid Surface
Authors: Sinha Shashank , Freund Jonathan B. , Dhir Vijay K.
Published: November 2021

The effect of wall proximity on the interfacial tension of ultra-thin liquid films of Lennard-Jones (12,6) fluid has been studied using Molecular Dynamics Simulation. The wall’s presence can potentially affect drop-wise condensation and other phase change phenomena such as boiling. Initially the Lennard-Jones atoms are placed near a solid wall with FCC lattice structure in a doubly periodic box. Once equilibrated at a desired temperature, a thin liquid film forms on the solid wall. The surface tension of the liquid-vapor interface is computed statistically. When the film is thick (> 40 Å), surface tension at the liquid-vapor interface is found to be unaffected by the presence of the solid wall and matches bulk values reported for Argon. However for thinner films (< 15 Å), surface tension of the liquid-vapor interface deviates from the macroscopic value. This has been investigated for various temperatures ranging from the triple point to the critical point. As the film thins further (1–2 molecules thickness), the liquid-vapor interface resembles a solid-vapor interface. Surface tension of this solid-vapor interface is evaluated for a solid wall modeled both by an equivalent interacted potential and discrete atoms. The two cases are found to yield different results. The Equivalent potential for the wall gives lower surface tension and liquid density near the solid wall compared to the discrete atoms case.
Finite Element Interface-Tracking and Interface-Capturing Techniques for Flows With Moving Boundaries and Interfaces
Authors: Tezduyar Tayfun
Published: November 2021

We provide an overview of the interface-tracking and interface-capturing techniques we have developed in recent years for computation of flow problems with moving boundaries and interfaces, including two-fluid interfaces. The interface-tracking techniques are based on the Deforming-Spatial-Domain/Stabilized Space-Time formulation, where the mesh moves to track the interface. The interface-capturing techniques, which were developed for two-fluid flows, are based on the stabilized formulation, over non-moving meshes, of both the flow equations and the advection equation governing the time-evolution of an interface function marking the location of the interface. For interface-capturing techniques, to increase the accuracy in representing the interface, the Enhanced-Discretization Interface-Capturing Technique (EDICT) can be used to to accomplish that goal. We also provide and overview of some of the additional ideas developed to increase the scope and accuracy of these two classes of techniques.