bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the Thermal Behaviour of Thin Phase Change Material Packages as a Solution to Temperature Control in Electronics
Authors: Sponagle Benjamin , Maranda Simon , Groulx Dominic
Published: October 2017

This paper presents an experimental and numerical investigation of the thermal behavior of thin phase change material (PCM) packages as a solution to thermal management in portable electronic devices. The thin packages are made of encapsulated PCM in aluminized laminated film. The experimental setup is designed to include the most fundamental aspects of a portable electronic system while also being simple enough to be easily simulated using the finite element method; it is rectangular in nature. Two different types of PCM are used for the experimental work; the commercially available PT-37 and n-eicosane. It was determined that the use of a thin PCM thermal energy storage package significantly improved the temperature behavior of the experimental setup, by reducing the rate of temperature increase at the heater and the back cover. The time needed to reach a critical cover temperature of 45°C was increased by 12 to 18% while the time for the heater temperature to reach 70°C was increased by up to 66%. Numerical simulations of the system were in good agreement with the experimental data.
Effect of Materials on the Heat Transfer to Supercritical Pressure Fluids
Authors: Lei Xianliang , Kong Xiangfei , Zhang Qian , Zhang Weiqiang , Li Huixiong
Published: October 2017

Supercritical pressure fluids are widely used in many advanced single-phase thermosiphons as a working medium due to its high convective heat transfer efficiency and simpler design. However, the heat transfer in the pseudocritical region is very complex due to its steep variation of thermophysical properties and effect by the operating parameters. Under supercritical pressures, special heat transfer phenomenon can be observed in the heated tubes, three totally different heat transfer regimes present. As a result of the similarity between subcritical boiling phenomena and the deteriorated heat transfer behavior at supercritical pressure, scholars observed that heater with different materials but the same operating conditions, different types of free convection would be appeared by investigating the boiling-like phenomenon of carbon dioxide, which seems that boiling-like phenomena are specific to heater materials.

The aim of this present study is to investigate the effects of thermophysical and chemical properties of heater materials upon heat transfer to supercritical water. In the present paper, two circular pipes with differential usual materials (AISI 321 and Inconel 600) are experimentally investigated by the electrically heating methods. The difference between AISI 321 and Inconel 600 in both enhanced and deteriorated heat transfer regimes are discussed respectively, then the heat transfer discrepancy caused by the materials analyzed. The results show that the heat transfer of supercritical pressure fluids dependent not only on the variation of the operating/boundary conditions but also on the materials of heating surface.
Reducing Crossflow Effects in Arrays of Impinging Jets
Authors: Arens Nicholas R. , Morem Mitchell P. , Doom Jeffrey , Michna Gregory J.
Published: October 2017

With increasing heat fluxes in microelectronics, thermal management of these devices will soon no longer be attainable through current methods. One thermal management technology that could be integrated into the design of microelectronics is jet impingement cooling. Past research has primarily focused on evenly spaced, equal-sized, circular or slot jets perpendicular to the surface. A significant problem associated with this technology, especially as the surface to be cooled increases in size, is crossflow. This is the interaction of the transverse flow from the spent inner jet fluid with the jets closer to the outer edge of the surface. In an attempt to attenuate the crossflow effects, the heat transfer performance of jet arrays with non-uniform jet diameter and jet spacing were investigated. The testing apparatus housed a 3D-printed jet array nozzle that could be easily exchanged to accommodate many tests. The use of advanced manufacturing techniques allows for array geometries that may have previously been difficult to create. The impingement surface was a circular, polished, oxygen-free copper surface with a diameter of 25.4 mm. Heat transfer rates nearing 400 W could be delivered to the surface, for a heat flux of more than 75 W/cm2. The working fluid was single phase water, and the heat transfer rate was measured for each jet array over a range of flow rates. Experimental data was compared to simulation data obtained through CFD analysis. CFD modeling was used to predict the most promising geometries, which were then validated through experiment. Out of the nozzles tested, it was determined that the nozzle with larger diameters toward the edge of the surface attained the highest heat transfer rate of h = 38,822 W/m2-K. The nozzle with closer jet spacing at the outside of the array was found to have the highest experimental Nusselt number with NuD = 88.8. It was determined that angled confining walls do not have a definitive association with improved heat transfer. The simulation data was found to predict the heat transfer performance of the various geometries with an average percent difference in heat transfer coefficient of 11%.
Condensation of Different Refrigerants on the Outside Surface of Smooth Cylindrical Tubes
Authors: Chen Tailian
Published: October 2017

The Nusselt model of condensation provides the fundamental theory in predicting the heat transfer during the condensation process. Widely verified, its significance lies in the fact that it has been used as the baseline in evaluating the heat transfer enhancement of the condensation and often used as the basis of validating the test rig for multiphase heat transfer. The aim of this work is to re-examine the correlation for condensation on smooth cylindrical tubes. The heat transfer coefficients during condensation of four different refrigerants R123, R245fa, R134a, and R22 on the outside surface of a smooth cylindrical tube were individually measured at large degrees of subcooling, up to 25 K. The experiments were conducted at a fixed saturation temperature of 36.1 °C. Measurements showed that, for each refrigerant, the condensation heat transfer coefficient decreases with increasing degree of subcooling. At a given degree of subcooling, a higher-pressure refrigerant corresponds to a higher condensation heat transfer coefficient, with the exception that the condensation heat transfer coefficients of R134a and R245fa are nearly the same in spite of much higher pressure of the former. The predictions from the Nusselt theory for condensation heat transfer over cylinder tubes match very well with the measurements, where the predictions are 3–9% lower than the measurements for all refrigerants within the range of degree of subcooling considered in this work. A modified constant in the Nusselt number provides more accurate prediction of condensation on smooth cylindrical tubes.
The Design, Analysis, and Fabrication of an Additively Manufactured Twisted Tube Heat Exchanger
Authors: Bernardin John D. , Ferguson Kyle , Sattler David , Kim Seung-Jun
Published: October 2017

The rapid development of Additive Manufacturing (AM) technologies has provided engineers with new methods to design and fabricate complex mechanisms. AM offers unique methods to allow for integration and simplification of components, reduced manufacturing time, fabrication of complex-shaped objects, improvements upon existing designs, and extending the creative design space which engineers rely on for ingenuity.

For many applications, heat exchanger performance can be improved by reducing its size, increasing the overall heat transfer coefficient and surface area, and making more efficient use of the mechanical structure for heat exchange. Traditional manufacturing often limits or prohibits many of these enhancements due to increased manufacturing and assembly costs. This study explored using AM to design and fabricate a compact twisted tube stainless steel shell and tube heat exchanger that would improve upon all of the features just mentioned.

This paper discusses the design of the heat exchanger and the AM technique used to fabricate a prototype. The manuscript will show via CFD analyses, how the heat transfer area of the unit was improved 18% and the overall heat transfer coefficient as increased by 40% over a traditional round tube heat exchanger with an identical footprint. Further, the study will show how AM was leveraged to combine five manufacturing steps into one to fabricate a prototype, fully functional twisted tube heat exchanger.
Advanced Thermal Measures of Vascular Reactivity
Authors: Akhtar M. Wasy
Published: October 2017

New measures of Digital Thermal Monitoring (DTM), a low cost non-invasive tool to assess vascular health, are developed. Original measures of thermal vascular reactivity tend to be dependent upon the initial vascular state (such as temperature before occlusion).

The objective of this study is to identify new measures that will provide a single independent predictor of vascular health. Full three dimensional simulations were carried out to simulate transient finger tip temperature response during brachial occlusion and reperfusion. These numerical results were validated with patient data and then used to simulate a variety of test cases and discern relationships between the thermal measure and the surge in flow rate (reactive hyperemia).

Defining the zero-reactivity response as the response to a step change in flow rate from near zero back to the original steady state value before occlusion, a reference signal is constructed which accounts for the finger size, thermo-physical properties, external environment and the start temperature (initial vascular state). This reference is used to normalize the temperature reactivity, forming a new measure called adjusted temperature reactivity that is a function of reactive hyperemia only. It is independent of the initial vascular state and external environment, leading to a more robust and reliable measure of vascular health.
Molecular Dynamics Study on Thermal Resistance Between Amorphous Silica Nanoparticles
Authors: Meng Fanhe , Liu Jin , Richards Robert F.
Published: October 2017

Nanoparticle-based materials have demonstrated extremely low thermal conductivities, a property that has made them attractive candidates in a variety of macroscale and microscale applications. Understanding the thermal transport between nanoparticles is necessary for the further development of these materials. Molecular dynamics simulation is an effective method to investigate thermal transport on these scales because no assumption about phonon transmission at the nanoparticle interface, nor prior knowledge of thermal transport of the system is necessary. In this work, the total thermal resistance between adjacent amorphous silica nanoparticles is calculated using non-equilibrium molecular dynamics simulations (NEMD). Numerical results show that interparticle resistance depends strongly on the forces between particles, in particular the presence or absence of chemical bonds between nanoparticles. In addition, the effect of interfacial force strength on thermal resistance increases as nanoparticle diameter decreases. Numerical results are compared to interparticle resistances determined from the predictions of the analytical constriction resistance model. The simulation results are shown to be in good agreement the constriction resistance theory depending on the choice of surface energy.
Simulation of Single Bubble Growth in a Planar Microchannel With Temperature Recovery Model
Authors: Luo Yang , Zhang Jingzhi , Li Wei , Zhang Zhengjiang , Du Jincai , Liu Fu
Published: October 2017

In the study numerical simulations are performed to investigate the saturated fluid flow through a two dimensional microchannel (1000μm×200μm, with a superheated bottom wall) by building a comprehensive physical method and updating the standard solver in the OpenFOAM software package. On basis of previous numerical study, most of the numerical methods for the micro-scale flow boiling emphasizes the mass transfer and interfacial heat exchange. Simultaneously, geometric reconstruction technology for liquid-vapor interface is widely used, which evidently captures the interfacial boundary characteristic accurately but costs lots of computational resources. In the present study, the temperature recovery model is adopted to maintain the liquid-vapor interface temperature, and an interface-cell searching algorithm is added into the model, while the geometric interface reconstruction technology is abandoned. For the validation of the new codes developed in OpenFOAM, 1-d Stefan Problem and the experimental results of Mukherjee are both utilized to compare with our simulation results. The growth process of a single bubble in the laminar flow regime is studied in order to explore the underlying mechanism of flow boiling in microchannels. The qualitative investigation for effects of wall superheat, Reynolds number, contact angle and surface tension on heat transfer are comprehensively discussed. In general, heat flux of the bottom wall increases because of the motion of liquid-vapor interface. Wall superheat determines the rate of bubble growth on the heated wall, which is roughly proportional to wall heat flux due to the Fourier’s Law. The distribution of velocity and temperature fields in the channel refresh progressively with increasing inflow Reynolds number, which speeds up the evolution of interface position and augments the wall heat flux significantly. Furthermore, the area of thin liquid film between the wall and the bubble is enlarged by reducing the contact angle, thus augmenting the wall heat flux by several times compared with the single phase microchannel flow. However, surface tension and gravitational acceleration are found to be negligible in the present study.
Temperature Effects on Optical Resonances in Single-Mode Circular Ring and Squircular Resonators
Authors: Panindre Prabodh , Kumar Sunil
Published: October 2017

Optical dielectric microresonators have been extensively studied due to their potential applications in optical sensing and measurements, and as optical interconnects. Although sensitive to temperature variations, the effect on temperature on their performance is often overlooked. In the present study the sensitivity of resonance to temperature arising from thermal expansion or contraction based change in physical path length, and minute changes in dielectric material and surrounding refractive indices is examined. The multiphysics finite element approach used in this study combines the heat transfer in solids with solid mechanics to understand the micro-level deformation of optical resonator due to thermal heating. This is coupled with electromagnetic frequency domain analysis of Maxwell’s equations with temperature dependent refractive indices to quantify the change in resonant frequency. It is found that the temperature induced change in refractive index of the resonator material primarily drives the change in resonant frequency.
Experimental Study on Heat Flux Effect on Evaporation in Two Dimple-Grooved Tubes
Authors: Chen Jingxiang , Li Junye , Hong Xiaoqiang , Li Wei , Zhu Hua , Kukulka D. J. , Sun Zhijian , Zhang Zhengjiang
Published: October 2017

An experimental study on local flow boiling heat transfer performance in two longitudinal dimple-grooved tubes and an equivalent smooth tube was performed. All three test cooper tubes have the same inner diameter of 11.5 mm; the working fluid is the near-azeotropic mixture, R410A; and all test runs are conducted in a 2 m long horizontal tube-in-tube heat exchanger. Constant evaporation temperature at 10 °C was maintained when heat flux ranging from 32 kW/m2 to 37 kW/m2 and refrigerant quality varied from inlet 0.1 to outlet 0.9 at mass flux 150 kg/(m2 s). The local heat transfer coefficients were obtained for all test conditions using refrigerant R410A. The test results for evaporation were presented compared to the equivalent smooth tube. Wall temperature and local and average heat flux is measured; heat flux effect and surface superheat effect is discussed on the tube side evaporation. The enhanced heat transfer area of two longitudinal dimple-grooved tubes are 1.02 and 1.03, respectively.
Comparison of R410A Condensation Heat Transfer Performance on Three Horizontal Tubes
Authors: Chen Xu , Hong Xiaoqiang , Li Wei , Kukulka David J.
Published: October 2017

An experimental investigation of R410A condensation outside a horizontal smooth tube, a herringbone tube and a newly developed enhanced surface EHT tube has been conducted. The herringbone tube has a fin root diameter of 11.43 mm, a helical angle of 21.3 °, 48 fins with a fin height of 0.262 mm and an apex angle of 36 °, the EHT tube has an outer diameter of 11.5 mm with special structure, while the smooth tube has an outer diameter of 11.43 mm. Experiments were taken at a constant saturation temperature of 45 °C, a constant inlet vapor quality of 0.8 and a constant outlet vapor quality of 0.1; mass flux ranging from 5 kg/(m2.s) to 250 kg/(m2.s). Those tubes have different heat transfer performance at different mass flux. The EHT tube has the least heat transfer coefficient than the other two tubes at a low mass flux, while at a high mass flux, the enhanced tubes have a better heat transfer performance than the smooth tube. Heat transfer performance combined with pressure drop measurements reveal that the herringbone tube generally has a better heat transfer performance than the EHT tube, pointing out the herringbone is a wise choice for shell side condensation instead of the EHT tube. Characteristic analysis is made to account for various phenomena in this series of experiments.
Experimental Investigation of Flow Boiling Inside Three Three-Dimensional Surface Enhanced Heat Transfer Tubes
Authors: Tang Weiyu , Zhang Zhengjiang , Du Jincai , Li Wei , Han Jincheng , Liu Zhichun , Zhu Yanyan , He Yan , Wang Zepeng , Ma Lianxiang
Published: October 2017

An Experimental investigation was conducted to compare the evaporation characteristics of R410A inside three newly developed horizontal enhanced heat transfer (EHT) tubes with the same OD12.70mm and ID11.50mm, and the result of them are compared with that of a plain tube. The inner enhanced surface of 1EHT tube consists of dimples/protrusions and petal arrays, while that of 2EHT-1 tube and 2EHT-2 tube is composed by longitudinal grooves and dimples of different depths. The mass velocities are in the range of 70kg/m2s-200kg/m2 s with a nominal saturation temperature fixed at 279K and the vapor quality in the test section varies from 0.2∼0.9. As the mass flux increases, both the heat transfer coefficient and pressure penalty increase accordingly. The heat transfer coefficient of EHT tubes can achieve 1.14–1.53 times higher than that of the smooth tube while the pressure gradients is 1.43–1.83 times larger than that of smooth tubes. Besides, the enhancement ratios of all the enhanced surface tubes are larger than their respective surface area ratio, and the enhancement ratio comparisons of heat transfer coefficient are made to obtain the enhancing mechanism. The results show that the EHT tubes appear higher performance at low mass fluxes. In all, the EHT1 tube has the best heat transfer performance at low mass velocity, which can be attributed to its special enhanced inner surface, resulting in the increase of nucleation sites, flow separation and turbulent fluctuations. The other two 2EHT tubes can enhance the evaporation greatly with small respective surface ratios as well as relatively little pressure drop penalty, and them shows outstanding performance especially at high mass velocity.
Heat Transfer Correlations for Condensation in Three-Dimensional Surface Enhanced Heat Transfer Tubes
Authors: Tang Weiyu , Li Wei , Chen Jingxiang , Zhu Hua , Liu Zhichun , Du Jincai , Sun Zhijian , Kukulka David
Published: October 2017

Experimental condensation heat transfer data from our previous studies were collected to find a suitable heat transfer correlation for three-dimensional surface enhanced heat transfer tubes. Dimples/protrusions and petal arrays make up the enhanced surface of the 1EHT tube, while longitudinal grooves and dimples constitute that of the other two 2EHT tubes. Working fluids investigated includes three refrigerants R22, R32, R410A and three enhanced tubes have a same nominal inner diameter of 12.7mm. Due to the unique and complex surface structure of three EHT tubes, a constant is proposed and utilized for each EHT tube to estimate the impact of enhanced surfaces on interfacial turbulence, boundary layer disruption, flow separation and secondary flow generation. In addition, the Cavallini correlation modified with the constant can predict almost all the data points within a ±5% error band, which can be a good example for how to predetermine the heat transfer coefficient of three-dimensional enhanced tubes with a unique surface.
Experimental Investigation of Spray Cooling Heat Transfer on Circular Grooved Surface
Authors: Salman Azzam S. , Khan Jamil A.
Published: October 2017

An experimental study was conducted in a closed loop spray cooling system working with deionized water as a cooling medium, to investigate the effects of surface modification on the spray cooling heat transfer enhancement in the single-phase region. Plain copper surface with diameter 1.5 cm and an enhanced surface with circular grooves were tested under different operating conditions. The volumetric flow rate of the coolant ranged from 115 mL/min to 177 mL/min., and the water inlet temperature was kept between 21–23 °C. Also, the distances between the nozzle and the target surface were varied at 8, 10, and 12 mm respectively. The results show that the distance between the nozzle and the target surface did not have a significant effect on the heat transfer performance for the low flow rates, while it has a slight effect on high flow rates for both surfaces. Also, increasing the liquid volumetric flow rate increases the amount of heat removed, and the heat transfer coefficient for both surfaces. Moreover, the maximum enhancement ratios achieved were 23.4% and 31% with volumetric flow rates of 153 mL/min, and 177 mL/min respectively.
Inexpensive Numerical Method for Heat Transfer Computations Using Excel
Authors: Abdelmessih Amanie N.
Published: October 2017

Most thermal engineers will model and analyze thermal engineering cases, using any of the numerous thermal analysis software, available in the market. These commercial software need years of continuous use to be fully mastered. Large companies can afford to acquire expensive software available in the market and train their engineers; but small companies do not have the financial means to acquire such expensive software. Thus for modeling and analysis, small companies or private practice need a different alternative. Excel is one of the programs that come with Microsoft Office suite of software, which is installed on any purchased computer. Most users of Microsoft office are proficient in using Word, and can use Excel as a spread sheet to speed up calculations. Technical personnel can easily use the charting capability of Excel, but very few engineers can use Excel for intensive Numerical Analysis. Engineers should be able to use the available inexpensive Excel software to perform numerical analysis at their work place.

In this article three Heat Transfer Numerical cases using Microsoft Excel are discussed in detail. the first case is two dimensional steady state heat transfer with different isothermal boundary conditions. The second shows other boundary conditions: uniform heat flux, adiabatic, and convection. The third case is transient conditions. The results from the three cases are compared with results from Patran Thermal software.
Investigation of Heat Transfer Phenomena in Blast Furnace Tuyere/Blowpipe Region
Authors: Liu Xiang , Tang Guangwu , Okosun Tyamo , Silaen Armin K. , Street Stuart J. , Zhou Chenn Q.
Published: October 2017

The blast furnace (BF) is a crucial stage in the iron-steel making process. Pulverized coal injection (PCI) and natural gas (NG) have been utilized in blast furnaces as a substitute fuel source for reducing coke rate. Due to introduction of injected fuels into a blast furnace, the combustion and heat transfer in the tuyere/blowpipe region affects the tuyere/blowpipe structure. A comprehensive computational fluid dynamics (CFD) model including PCI/NG combustion, multi-mode heat transfer for the blowpipe/tuyere region of a blast furnace at AK Steel Dearborn Works has been developed, considering detailed material properties in the blowpipe region. The model has been validated by comparing the blowpipe skin temperature profile with thermographic images under typical operating conditions. Based on the developed CFD model, the detailed PCI/NG co-injection combustion has been investigated and the thermal effect on the tuyere tip has been revealed.
Analogy Between Transient Heat Conduction and Dissolution of Solid Particles in Liquids Based on the Shrinking Core Model
Authors: Ma Qin
Published: October 2017

In this study, the analogy between transient heat conduction and mass transfer is applied to investigate the dissolution behavior of solid particles in liquids, particularly, for the transport phenomenon associated with the controlled drug release process. Mathematical modeling is established assuming the shrinking core is solely caused by the diffusion mechanism. The transport governing equations for the dissolution process of controlled drug release are compared with the transient heat conduction differential equations. Analogous quantities, certain analytical solutions and numerical solutions for complex geometry are obtained to demonstrate the dissolution behavior of this specific type of solid particles in liquids based on the proposed shrinking core model. It is found that the shape of the drug capsule plays an important role for effective and timely release of drug content after intake. Among the three shapes investigated herein, sphere, cube and cuboid, we conclude that the drug concentration in a cuboid shaped drug head depletes the quickest whereas the spherical shaped head dissolves the slowest.
Performance Evaluation of Multi-Stage Shell and Tube Transport Membrane Condenser Heat Exchangers for Low Grade Waste Heat and Water Recovery
Authors: Soleimanikutanaei Soheil , Lin Cheng-Xian , Wang Dexin
Published: October 2017

In this work for the first time the performance of multi-stage shell and tube Transport Membrane Condenser (TMC) based heat exchangers are evaluated numerically. The present heat exchanger is design to work under high pressure and temperature condition for both heat and water recovery in Oxy-Combustion processes. TMC heat exchangers use the nano-porous and ceramic membrane technology to extract the water vapor and latent heat of condensation from the flue-gas. The most important application of TMC heat exchangers is in the power plants which the water vapor in the presence of other non-condensable gases (i.e. CO2, O2 and N2) exist. Effect of the different arrangement of the multi-stage shell and tube TMC heat exchangers, number of branches and number of heat exchangers in each branch on the heat transfer and water recovery have been studied numerically. A single phase multi-component model is used to assess the capability of single stage TMC heat exchangers in terms of waste heat and water recovery at various inlet conditions. Numerical simulation has been performed using ANSYS-FLUENT software and the condensation rate model has been implemented applying User Define Function. Finally, an optimum configuration for the TMC heat exchanger unit has been proposed and the results of numerical simulations are depicted in terms of temperature and water vapor mass fraction contours.
Experimental Validation of Numerical Predictions for the Transient Performance of a Simple Latent Heat Storage Unit (LHSU) Utilizing Phase Change Material (PCM) and 3-D Printing
Authors: Kumar Navin , Banerjee Debjyoti
Published: October 2017

Experimental validation was performed in this study to verify the efficacy of numerical models for predicting the location of solid-liquid interface in an axi-symmetric configuration during both melting and solidification in a Latent Heat Storage Unit (LHSU). Development of analytical solutions for predicting the location of the solid-liquid interface is often intractable in LHSU due to non-linear temperature distribution in the Phase Change Material (PCM). This is further complicated by the moving boundary problem with free convection within the liquid phase of the PCM. Analytical solutions available in the contemporary literature are based on simplified transient heat conduction models and often fail to reliably predict the charging and discharging time constants for LHSU with complex configurations. This study is designed with the goal of developing more sophisticated numerical models for the estimation of transient thermal performance of an LHSU with a simple configuration involving a shell and tube heat exchanger (HX).

The LHSU utilized in this study is realized by integrating various types of Phase Change Materials (PCM) contained in the shell side of a HX. The LHSU is charged or discharged by pumping hot or cold fluids in the tube side of the HX (i.e., by pumping water at a fixed inlet temperature from a commercial chiller apparatus). This study enabled the characterization of the transient response of a LHSU subjected to conduction and forced convection heat transfer. The PCM used in this material was paraffin wax (PURETEMP 29). The HX in the LHSU consisted of a single pass straight tube (½ inch copper pipe) mounted within a single shell configuration. The shell was fabricated from plastic material using additive manufacturing (i.e., “3D Printing”). The temperature variation during melting and solidification of the PCM were measured at different radial and axial locations within the cylindrical shell that was mounted vertically. Temperature measurements were performed at different mass flowrate ranging from 0.004 Kg/sec to 0.007 Kg/sec for the same fluid temperature. The water bath temperatures were maintained at a constant temperature of 40°C for melting and 15°C for solidification. The experiment results show that the transient response of the LHSU for charging and discharging (i.e., time required for melting and solidification of the PCM) vary significantly. Comparison of the experimental data with analytical results (involving quasi-stationary models for phase change) demonstrate that natural convection is the dominant mode during the melting process, while conduction is the dominant mode during the solidification process.
Large Eddy Simulation of Heat Transfer Over In-Line Flat-Tube Array in Laminar and Turbulent Flows
Authors: Taghizadeh Salar , Acharya Sumanta , Ling Kong , Kanani Yousef , Ge Xuan
Published: October 2017

This study presents a transient three-dimensional numerical study on fluid flow and heat transfer of flat-tube array using large eddy simulation (LES) covering both laminar and turbulent flow regimes. The simulations were performed in a rectangular region containing only one tube with periodic conditions specified on all boundaries. A staggered flat-plate array was first studied, and an existing solution was used for validation purpose. The numerical models were then applied to an in-line array composed of flat tubes with an aspect ratio of 0.25 and fixed tube spacings. By varying the in-flow velocity, the tube array was studied over a wide range of Reynolds number (600–12000). Temperature, velocity, and turbulent kinetic energy distributions as well as the interactions between them are presented and analyzed. Furthermore, the local heat transfer rate was analyzed along the various parts of the tube (leading edge, flat-top and wake or trailing-edge regions). Heat transfer correlation for each region of the tube and the entire tube array is proposed.
Thermal Conductivity Measurement of In0.10Ga0.90As0.96N0.04 Thin Film
Authors: Jan Antony , Cheaito Ramez , Goodson Kenneth E. , Clemens Bruce M.
Published: October 2017

Dilute indium gallium arsenide nitrides (InxGa1-xAs1-yNy) are valuable in photonic applications as long wavelength emitters and for pairing with silica optical fibers for low attenuation optical fiber communications. The reliable operation of these devices is tied to a precise temperature control and the knowledge of the thermal properties of their components. However, the thermal conductivity of bulk or thin film InGaAsN of any composition are, to the best of our knowledge, not available in literature. In response, we use time-domain thermoreflectance (TDTR) to measure the thermal conductivity of a 78 nm In0.10Ga0.90As0.96N0.04 film grown by metalorganic chemical vapor deposition (MOCVD) on GaAs substrate. The thermal conductivity of In0.10Ga0.90As0.96N0.04 is found to be 6 +/− 0.5 Wm−1K−1, a factor of two lower than that of bulk In0.10Ga0.90As. To our knowledge this is the first reported thermal conductivity measurement on InGaAsN. We also present an analytical model for predicting the thermal conductivity of InGaAsN for any composition. Using this model, we find that the reduction in thermal conductivity can be attributed to the scattering of phonons by nitrogen impurities and boundary scattering of long mean free path phonons from the film thickness.
Improved Melting and Solidification in Thermal Energy Storage Through Topology Optimization of Highly Conductive Fins
Authors: Pizzolato Alberto , Sciacovelli Adriano , Verda Vittorio
Published: October 2017

Thermal energy storage units based on phase change materials (PCMs) need a fine design of highly conductive fins to improve the average heat transfer rate. In this paper, we seek the optimal distribution of a highly conductive material embedded in a PCM through a density-based topology optimization method. The phase change problem is solved through an enthalpy-porosity model, which accounts for natural convection in the fluid. Results show fundamental differences in the optimized layout between the solidification and the melting case. Fins optimized for solidification show a quasi-periodic pattern along the angular direction. On the other hand, fins optimized for melting elongate mostly in the bottom part of the unit leaving only two short baffles at the top. In both cases, the optimized structures show non-intuitive details which could not be obtained neglecting fluid flow. These additional features reduce the solidification and melting time by 11 % and 27 % respectively compared to a structure optimized for diffusion.
Preliminary Forensic Engineering Study on the Fukushima Accident
Authors: Saji Genn
Published: October 2017

Even after 6 years since the accident, the exact accident progression for each unit and location of core debris has not been clarified. Currently efforts are directed towards robotic inspection with remote cameras, as well as dose and temperature measurements of the environment inside of the Primary Containment Vessels (PCV). In spite of their effort, the observed environmental data do not support the existence of a large radiation heat sources attributable to the molten core at the bottom of the Primary Containments.

Under this situation the author has conducted a forensic engineering study (i.e., different fields of science work together to collect and integrate independent evidences) to clarify the most likely accident scenarios of the Fukushima Daiichi accident. Through this study the author found that the environmental contamination and public exposure could have been substantially mitigated should the following vulnerabilities have been removed before the accident:

(1) The threat of hydrogen generation through “radiation-induced electrolysis”.

(2) Potential threat of “internal hydrogen explosion” in the suppression pools. The atmosphere on top of the suppression pool water (cover gas) should have been nitrogen.

(3) Potential threat of “internal hydrogen explosion” in pipes which had occurred in the case of the Hamaoka Unit 1 accident.

(4) The leak rate of PCV should have been testable at its design pressure. Intrinsic safety factor of the containment flanges against effluent leakage should have been rated as a 3 for functional integrity of the PCV.

(5) Spread of hydrogen gas from vent lines through duct networks connected to SGTS. The hardened vent line should be independent and provided with filters for Dry Well venting. No rupture disks should have been installed in the vent lines.
A Method Evaluating Fire Hazard of Multiple-Layer Cable Tray and its Validation
Authors: Huang Xianjia , Bi Kun , Xiao Jun , Peng Lan , Zhu He , Zheng Zihui
Published: October 2017

Multi-layer cable tray fire has special burning characteristics that the cable flame spreads horizontally along cable tray and propagates vertically from bottom layer to upper layer at the same time. With respect of accuracy and speed of calculation, simulation of multi-layer cable tray fire remains a challenge for fire models. In this paper, a method is proposed to simulate multi-layer cable tray fire. By developing a more accurate fire source description, this method can provide accurate simulation for multi-layer cable tray fire rapidly.

In this method, Firstly, the heat release rate of each burning cable tray is evaluated by FLASH-CAT model. Based on the results from FLASH-CAT, a more accurate fire source definition for multiple lay cable tray is developed for zone model. Taking account of each burning cable tray considered as one fire source point, zone model is applied to predict the fire dynamics process. In order to validate this method, four-layer cable tray fire experiments and replicated experiments were carried out in a confined compartment. The histories of mass loss rate of cable tray and temperatures at the middle of compartment were recorded during the cable fire. From the replicated experimental results of total mass loss rate, it is concluded that the four-layer cable tray fire experiment has good repetition in this scenario. Vertical temperature profile shows that the fire circumstance generated by multiple-layer cable tray burning can be divided into upper hot layer and lower cool layer, which conforms to the basic assumption of zone model. As a consequence, the zone model can be applied to simulating multiple-layer cable tray fire.

By comparing the experimental total heat release rate with predictions, it is found that characteristics of multiple-layer cable tray fire are well captured. On account of good prediction on overall heat release rate for multi-layer cable tray fire, predicted heat release rate for each burning cable layer by FLASH-CAT model is believed to be reliable. Then, each burning cable layer is set as one fire source and the heat release rate of each burning cable layer is input into zone model, respectively. The comparisons between simulations and experimental data show that the predicted upper layer temperature and lower layer temperature agree well with experimental data. As a result, it can be concluded that this method provides reliable prediction for multiple-layer cable tray fire rapidly.
Review of the Content Analysis of Physics School Books Coming From Different European Countries on Radioactivity and Nuclear Energy
Authors: Baumont Genevieve , Perko Tanja , Zakrzewska Grażyna , Kralj Metka , Diaconu Daniela , Železnik Nadja
Published: October 2017

The EAGLE project was a Euratom FP7 which helped to identify and disseminate good practices in information and communication processes related to ionizing radiation.

For this purpose, the consortium reviewed national and international data, tools and methods as well as institutional work in order to identify education, information and communication needs.

Generally in high school the first concepts on radioactivity and ionizing radiation (IR) are introduced mainly in the subjects of physics or physical chemistry.

There are a number of concepts in relation with IR and nuclear topics, and different ways to teach them: theoretical, mathematical, historical or practical. The question also rose, to what extend the various topics related to ionizing radiation (health, environment, history) are dealt with.

As already mentioned, all these questions let to the idea to compare the content dealing with radioactivity and nuclear topics in different physics school books and more specifically schoolbooks for high school students (in the age 17 to 18). The method was as follows:

- For the review the different partners of EAGLE have sent the schoolbooks used for the target group, or scanned documents.

- Spanish schoolbooks and English schoolbooks were purchased to extend the review to other EU countries.

- IRSN works in partnership with a high school based in the French town Vichy.

- Each book was analyzed in detail to list with precision the content. A matrix helped to compare them.

The paper presents the comparison of the contents of these books and their analysis. Some recommendations coming from the Eagle project will be discussed.
Application of Joint Boring Technique in Solving RCL Wall Thickness Problem
Authors: Zhu Huadong
Published: October 2017

Nuclear Power Project RCL (reactor coolant loop) is one of the most critical nuclear safety class 1 equipment in PWR nuclear power plant. Filled with borated water, the RCL is a closed loop and serves as pressure boundary incorporating the reactor pressure vessel, steam generator and reactor coolant pump. Since in-service inspection is required for welds of the RCL, the two sides of the welds shall be bored to meet UT (Ultrasonic Testing) inspection requirements. The design standard states that “if the weld is subject to service inspection, the length of the counterbore shall be 2Tmin (Tmin = minimum of wall thickness) for pipe and Tmin for components and fittings. Therefore, the minimal wall thickness of the boring area inside the RCL shall also meet design requirements. Examination of the RCLs delivered to the nuclear power project sites showed that the wall thickness of some parts of the RCL exceed tolerance in varying degrees (the wall thickness is too thin). The RCL borings need to be analyzed to mitigate the negative impact of insufficient wall thickness, maintain RCL wall thickness to the largest extent and meet design requirements. Under the condition of the jobsite data are idealized, this study analyzes the boring plans for the cold leg of loop B at the reactor vessel side for this nuclear power plant Unit 1 NI (Nuclear Island) and discusses the three methods of boring, namely, general boring, taper boring and eccentric boring. It finds that a combination of taper boring and eccentric boring is the optimal plan. This joint boring technique can help achieve the minimal boring wall thickness, reduce the grinding quantity and maintain the required wall thickness, thus resolving the out-of-tolerance issue. In addition, it meets the design requirements, the wall thickness and in-service inspection requirements. Supervision agency approved the application of the joint boring technique to the RCL for the projects. The RCL installation has proved to be a success.
Application Differences of In-Service Inspection Regulations Between RSE-M2010 and ASME Section XI in China PWRs
Authors: Cheng Yang , Xueliang Zhang , Peng Xia , Qingyue Zeng , Tian Li
Published: October 2017

RSE-M 2010 and ASME Section XI are the widely used and most detailed PWR in-service inspection regulations applied in China PWRs which are separately belong to French AFCEN and American ASME regulations, and come from the different nuclear industry practices of their countries. In 1987, the French M310 type reactor was imported to China and therewith the RSE-M in-service inspection regulation was introduced, beginning to be widely used in China PWRs since that time. Meanwhile, Chinese nuclear power institutes began to independently develop its own PWR reactor named Qinshan Phase I Nuclear Power Plant, and then ASME Section XI in-service inspection regulation was used which was also beginning to be widely used in some Chinese PWRs. With the nuclear power technology development and innovation, such regulations are continually updated and perfected. Thus, there are many differences during application in Chinese specific PWRs. This paper has performed quite deeply application difference analysis between the two regulations based on several aspects, such as upstream laws cited, component classification, inspection requirement, NDE, qualification, pressure test and the Safety Authority review requirements for licensing. Some preliminary thinking has been presented during applying these two regulations and some technical suggestions have been also provided to perfect the regulations in the hope to provide better reference during application on the third generation PWRs (including HPR1000) in China.
A Novel Method for Solving Reactor Physics Diffusion and Transport Equation
Authors: Wenjun Hu , Yonggang Cao
Published: October 2017

The computational software based on the numerical technology are widely being utilized in the nuclear design, where the numerical method has been always being a topic attracting abundant concern. Combining the feature of reactor physics equation and non-structure mesh technology, a novel method appropriate for structure/non-structure mesh calculation is proposed. The paper illustrates the implementation of the method taking the diffusion and 1st order discrete ordinate transport equation as an example, by demonstrating the discretization of region, the discretization of equation and the implementation of boundary conditions.
Unprotected Overpower Transient Analysis of a Million Kilowatt Traveling Wave Reactor Core
Authors: Qiao Pengrui , Zhang Jian , Lin Chao
Published: October 2017

Traveling wave reactor (TWR) is an innovation concept nuclear reactor, through the once-through deep burning, the proliferation of fuel can be achieved and the utilization rate of Uranium can be increased. TWR has the characteristics of long lifetime, deep burn up and nuclear nonproliferation, because of its physical character, which makes it to be an attractive innovation concept fast reactor. The China institute of atomic energy (CIAE) has designed a million kilowatt TWR core based on a breeding and burn principle, which has considered the current technological level of sodium cooled fast reactor. In this paper, based on the TWR core design scheme, considered the design of fuel assembly, neutronics and thermal-hydraulic, analyzed the unprotected overpower transient (UTOP) accident in the TWR core with the SAS4A code, through which research about the transient safety characteristics of a million kilowatt travelling wave reactor core has been done. Analysis shows that the peak temperature of fuel, cladding and coolant in the TWR core have a certain margin from the safety limits through the negative feedback of itself in the UTOP accident, the core of the million kilowatt TWR demonstrates a good safety performance.