bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow Boiling of Deionized Water in Ultrahigh-Aspect-Ratio Microchannel Heat Sink
Authors: Cui Peilin , Liu Zhenyu 
Published: July 2021

Abstract
Microchannel heat sinks have attracted much attention due to its superiority of removing high heat flux with a very small size, which recently have been applied in the electronic cooling. The flow boiling of deionized water in the ultrahigh-aspect-ratio copper microchannels was experimentally investigated in this work. The heat sink consists of 20 rectangular straight microchannels (5000μm × 200μm) with the hydraulic diameter of 385 μm and the aspect ratio of 25. The experiment was conducted with the heat flux range of 39.7–1368 kW/m2 and the mass flow range of 21.3–41.6 kg/(m2·s) (the inlet temperature of 30°C). The flow patterns in the ultrahigh-aspect-ratio microchannels were captured using the visualization technique and four flow regimes (bubbly flow, slug flow, churn flow and annual flow) were clearly observed. The nucleate boiling sites increase significantly in the depth direction on the large-area side wall at bubbly flow. An obvious delay for flow patterns transformation in the upper regions compared with the lower region of microchannel was found. The bubble sliding was observed with a large sliding distance compared to the conventional low-aspect-ratio microchannels, which leads to an enhanced the heat transfer. It shows that the higher effective heat flux and the lower pressure drop were achieved in ultrahighaspect-ratio microchannel due to its special flow patterns in the channel and large surface area in the limited volume.
Influence of Flue Gas Turbulence Intensity on the Heat and Mass Transfer and Pressure Drop Inside a TMC Based Heat Exchanger
Authors: Al-rifai Saja , Lin Cheng-Xian 
Published: July 2021

Abstract
In this study, a numerical analysis of turbulent flow heat and mass transfer in the cross-flow transport membrane condenser (TMC) based heat exchange was carried out. The heat exchanger under investigation was designed to recover both sensible and latent heat due to transport of heat and mass through a nanoporous ceramic membrane in the bundle of tubes of the heat exchanger. The shear stress transport SST k-ω turbulence model was used to model the turbulent flow of the flue gas mixture. The condensation rate of the water vapor from the flue gas were calculated using a mixed condensation model. The mixed model was based on the capillary condensation and wall condensation in the membrane tube. The numerical study was focused on the investigation of the impact of the turbulence intensity of the flue gas at various inlet conditions, such as Reynolds numbers and temperatures, on the heat and mass transfer and pressure drop characteristics. The numerical results were validated against the experimental results reported in the literature. Different tube diameters were used in the simulation, with the Reynolds number varied from 3000 to 10000. The results showed that an increase in turbulence intensity led to a significant increase in the turbulent kinetic energy, condensation rate, average convective Nusselt number and change on the pressure drop in the heat exchanger. The effects of inlet flow Reynolds number and tube diameter on the heat and mass transfer were also presented and discussed.
Numerical Analysis on the Leading Edge Film Cooling of Bifurcation Holes for Gas Turbine Blade
Authors: Tang Zhonghao , Xie Gongnan , Li Honglin , Gao Wenjing , Tan Chunlong , Li Lei 
Published: July 2021

Abstract
Film cooling performance of the cylindrical film holes and the bifurcated film holes on the leading edge model of the turbine blade are investigated in this paper. The suitability of different turbulence models to predict local and average film cooling effectiveness is validated by comparing with available experimental results. Three rows of holes are arranged in a semi-cylindrical model to simulate the leading edge of the turbine blade. Four different film cooling structures (including a cylindrical film holes and other three different bifurcated film holes) and four different blowing ratios are studied in detail. The results show that the film jets lift off gradually in the leading edge area as the blowing ratio increases. And the trajectory of the film jets gradually deviate from the mainstream direction to the spanwise direction. The cylindrical film holes and vertical bifurcated film holes have better film cooling effectiveness at low blowing ratio while the other two transverse bifurcated film holes have better film cooling effectiveness at high blowing ratio. And the film cooling effectiveness of the transverse bifurcated film holes increase with the increasing the blowing ratio. Additionally, the advantage of transverse bifurcated holes in film cooling effectiveness is more obvious in the downstream region relative to the cylindrical holes. The Area-Average film cooling effectiveness of transverse bifurcated film holes is 38% higher than that of cylindrical holes when blowing ratio is 2.
High-Throughput Screening of Aperiodic Superlattice for Minimum Thermal Conductivity Based on Atomistic Simulation-Informed Effective Medium Theory and Genetic Algorithm
Authors: Lin Shangchao , Liu Yixuan , Cai Zhuangli 
Published: July 2021

Abstract
Superlattices with suppressed thermal conductivity are of great significance in the field of thermoelectricity and can improve the thermoelectric conversion efficiency of materials. Due to Anderson localization of coherent phonons, aperiodic superlattices have lower thermal conductivity than their periodic counterparts. At present, the thermal conductivity of superlattices is mostly predicted through ab initio or molecular dynamics simulations, which is computationally expensive and limits the size of the system. Meanwhile, there are many layered structural combinations for aperiodic superlattices, making it difficult to efficiently screen through all the combinations to search structures with the minimum thermal conductivity. In this work, based on a modified series thermal resistance model (STRM), a new effective medium theory (EMT) is established to predict the thermal conductivity of periodic and aperiodic superlattices. An adjacency factor near the maximum-resistance layers and a correction function, respectively, are introduced to account for the phonon coherence effect and the degree of randomization in the layer thickness. Combined with the genetic algorithm, EMT enables high-throughput screening of millions of aperiodic superlattice structures. This work demonstrates that the thermal conductivities of aperiodic superlattices at a wide range of system size can be constantly reduced to 1.4∼1.8 W/(m·K), which occurs at averaged periodic thicknesses in a stable range of 2.0∼2.5 nm.
The Use of Variational Bayes Compared to Markov Chain Monte Carlo in The Estimation of Thermal Properties
Authors: Emery Ashley F. 
Published: July 2021

Abstract
Estimating the parameters that describe a thermal problem using Bayes statistics requires the specification of appropriate prior probabilities. That is p(P|D) = p(D|P)p(P)/p(D) where P = parameters, D = data and p(P) is the prior probability. For thermal problems this requires prior probabilities for density, specific heat, thermal conductivities, surface convective coefficients, radiative properties, and local heat release, Q. For many problems it is common to choose Gaussian probabilities to represent the errors. If the standard deviation is large, then the predictions can lead to negative values — a result that is not possible except for Q. Variational Bayes (VB) is an alternative to Markov Chain Monte Carlo (MCMC) and assumes that complex distributions p(a,b) can be replaced by factorization, p(a,b) = p(a)p(b), the mean field theory of physics. Overall Variational Bayes is particularly important for posterior probabilities, p(a|D), that have multiple maxima distributions.
Visualization of Heat Transfer Characteristics of 1EHT and Smooth Surface Tubes
Authors: Santos Humberto , Alves Ailson , Kukulka David , Smith Rick , Li Wei 
Published: July 2021

Abstract
High efficiency heat transfer tubes play a major role in industrial applications due to its benefits in recovering more energy, smaller footprint and lower operational costs. Given the importance of enhanced heat transfer tubes, an experimental investigation was carried out to compare the performance of the Vipertex 1EHT tube with an equivalent smooth tube using Particle Image Velocimetry (PIV). For the experimental setup a Dantec Dynamics PIV system was considered, and both tubes used had an outer diameter of 19.05 mm and inner diameter of 17.09 mm. Heat transfer experiments were conducted at 100% of the heater power capacity, i.e. 750 W, and observations were made in terms of boiling visualization, particle velocity vector field, and seeding particle velocity. The results obtained from the visualization showed higher density of bubble formation on the surface of 1EHT tube compared to the smooth tube, as well as a more frequent formation of bubbles. Moreover, the high-speed camera films recorded for comparison between smooth and enhanced tubes, showed that the dimples provided nucleation sites. Additionally, the average particle velocity for the 1EHT tube was 0.300 m.s−1 and for the smooth tube it was only 0.230 m.s−1, as a result of the higher heat transfer of the enhanced tube. These results suggest that the 1EHT tube performs better in boiling heat transfer application, which can be attributed to the enhanced heat transfer area produced by the series of dimples/protrusions and petals distributed over its surface.
The Simulation of Water Transports in Proton Exchange Membrane Fuel Cell Based on Lattice Boltzmann Method
Authors: Zhou Shikun , Zhang Yingchun , Xie Gongnan 
Published: July 2021

Abstract
The proton exchange membrane fuel cell (PEMFC) has many advantages, such as low operating temperature, fast reaction, and high energy density, etc. It is a very potential energy source. During battery operation, PEMFC will produce a large amount of water in the catalyst layer where the reaction occurs. The catalyst layer and gas diffusion layer (GDL) inside the battery are made of porous media. The water produced during the reaction will be discharged through these porous media structures, but the narrow gaps of the porous media structures will complicate the process. For example, too much water will flood the internal structure of the battery, making liquid water unable to drain smoothly. The above process may cause the reaction rate of the battery to decrease or even stop. Studying and understanding the water transportation process inside PEMFC is of great help in solving the above problems. Lattice Boltzmann method (LBM) is a promising numerical method for simulating the flows in porous media. Compared with the traditional CFD method, the lattice Boltzmann method (LBM) can deal with the pore structure of fine-scale better. In this paper, the lattice Boltzmann method (LBM) is employed to simulate the flow in the PEMFC. In order to reconstruct the porous media structure in PEMFC, the numerical reconstruction technique is used to generate porous media structures with different porosity. By simulating the flow of water in porous media, the transport laws of water in different porosity rates can be obtained. It provides a reference for improving the operating efficiency of proton exchange membrane fuel cells.
Numerical Investigation of Photovoltaics Cooling Using Wicking Channels
Authors: Poudel Sajag , Ranjan Durgesh , Zou An , Maroo Shalabh C. 
Published: July 2021

Abstract
The performance of a photovoltaics (PV) panel is dependent on its surface temperature. Cooling the PV panel can substantially enhance its efficiency and thus the output power. Thermal management with spray cooling in porous nanochannels device offers a high heat flux removal capability due to thin-film evaporation occurring at micro/nano scale menisci. By integrating the nanochannels device on the back face of the PV panel, it is possible to dissipate heat from the PV panel so that it operates within a desired range of temperature values. In the present work, we utilize the results of spray cooling on such nanochannels device and perform the numerical investigation of PV panel cooling and enhancement in power output. A range of solar irradiation 500–900 W/cm2 is considered and the transient state transport equation for energy balance is solved numerically for 6 cases. With the applied thermal management using nanochannels device, the power output of PV panel is enhanced by ∼27% for the maximum solar irradiation of 900 W/cm2.
A Study of Wall Temperature Jump Using UGKS Simulation With Diffuse-Specular Maxwell-Type Boundary
Authors: Dai Lianfu , Wu Huiying 
Published: July 2021

Abstract
As the Maxwell-type boundary treatment can automatically capture temperature jump on boundary, it is widely used in gas flow simulation like Lattice Boltzmann method and Direct simulation Monte Carlo method. In present study, diffuse-specular Maxwell-type boundary with a diffusive fraction (a), which decides the mechanism of interaction between gas molecules and boundary, is realized in UGKS simulation. This diffuse-specular boundary can recover diffuse Maxwell boundary when a = 1.0, which proves the reliability of present boundary treatment. The influence of diffusive fraction on wall temperature jump under Knudsen number ranging from 0.001 to 1.0 is tested. The test cases are steady and unsteady state conditions of heat conduction and Couette flow between two infinite plates setting at specified temperatures. It is found that: 1) for cases of Knudsen number ranging from 0.01 to 1.0, owing to the loss of influence from equilibrium part on evolution of boundary gas distribution, the relative temperature jump increases when diffusive fraction varies from 1.0 to 0.25, this phenomenon is especially obvious on extreme point part in unsteady state cases; 2) for cases of Knudsen number equaling to 0.001, diffusive fraction has no significance influence on temperature jump as the temperature jump is less noticeable for such condition. Present study will help the further researches of heat transfer in rarefied gas.
A Simplified Numerical Approach to Characterize the Thermal Response of a Moving Bed Solar Reactor
Authors: Al Sahlani Assaad , Randhir Kelvin , Ozalp Nesrin , Klausner James 
Published: July 2021

Abstract
Concentrated solar thermochemical storage in the form of a zero-emission fuel is a promising option to produce long-duration energy storage. The production of solar fuel can occur within a cylindrical cavity chemical reactor that captures concentrated solar radiation from a solar field. A heat transfer model of a tubular plug-flow reactor is presented. Experimental data from a fixed bed tubular reactor are used for model comparison. The system consists of an externally heated tube with counter-current flowing gas and moving solid particles as the heated media. The proposed model simulates the dynamic behavior of temperature profiles of the tube wall, gas, and particles under various gas flow rates and residence times. The heat transfer between gas-wall, solid particle-wall, gas-solid particle, are numerically studied. The model is compared with experiments using a 4 kW furnace with a 150 mm heating zone surrounding a horizontal alumina tube (reactor) with 50.8 mm OD and a thickness of 3.175 mm. Solid fixed particles of magnesium manganese oxide (MgMn2O4) with the size of 1 mm are packed within the length of 250 mm at the center of the tube length. Simulation results are assessed with respect to fixed bed experimental data for four different gas flow rates, namely 5, 10, 15, 20 standard liters per minute of air, and furnace temperatures in the range of 200 to 1200 °C. The simulation results showed good agreement with maximum steady state error that is less than 6% of those obtained from the experiments among all runs. The proposed model can be implemented as a low-order physical model for the control of temperature inside plug-flow reactors for thermochemical energy storage (TCES) applications.
Effect of Variation of Pin-fin Height on Jet Impingement Heat Transfer on a Rotating Surface
Authors: Bhansali Pratik S. , Ekkad Srinath V. 
Published: July 2021

Abstract
Heat transfer over rotating surfaces is of particular interest in rotating machinery such as gas turbine engines. The rotation of the gas turbine disc creates a radially outward flow on the disc surface, which may lead to ingress of hot gases into the narrow cavity between the disc and the stator. Impingement of cooling jet is an effective way of cooling the disc and countering the ingress of the hot gases. Present study focusses on investigating the effect of introducing pin-fins over the rotating disc on the heat transfer. The jet Reynolds number has been varied from 5000 to 18000, and the rotating Reynolds number has been varied from 5487 to 12803 for an aluminum disc of thickness 6.35mm and diameter 10.16 cm, over which square pins have been arranged in an inline fashion. Steady state temperature measurements have been taken using thermocouples embedded in the disc close to the target surface, and area average Nusselt number has been calculated. The effects of varying the height of the pin-fins, distance between nozzle and the disc surface and the inclination of the impinging jet with the axis of rotation have also been studied. The results have been compared with those for a smooth aluminum disc of equal dimensions and without any pin-fins. The average Nusselt number is significantly enhanced by the presence of pin fins. In the impingement dominant regime, where the effect of disc rotation is minimal for a smooth disc, the heat transfer increases with rotational speed in case of pin fins. The effect of inclination angle of the impinging jet is insignificant in the range explored in this paper (0° to 20°).
Effect of Protuberances in the Heat Transfer Enhancement in Mini-Channels
Authors: Cruz Diaz Ariel , Carbajal Gerardo 
Published: July 2021

Abstract
This study presents the effects of adding an array of protrusions in a microchannel for heat transfer enhancement. The presence of mini-channels increases the overall heat transfer area and boosts the mixing development near the solid-fluid interaction; therefore, it can remove more heat than conventional mini-channels without protuberances. A numerical study proved that protuberances in a mini-channel increase the heat transfer performance by disturbing the relative fluid motion near the solid wall. The numerical simulation was performed with three different protuberances arrays: aligned, staggered, and angular. Each array consists of a thin flat plate with a hemispherical shape; the working fluid and the solid materials were water and copper. The study also includes the effect of different Reynolds numbers: 1,000, 1,500, and 2,000. Three heat inputs were applied in the numerical simulation; these were 1W, 3W, and 5W. The study was compared with a simple microchannel with non-protuberances to analyze the microchannel performance regarding heat removal and pressure drop. For heat transfer performance, the best array was the staggering array with a maximum heat removal increase of 5.26 percent. In terms of pressure drop performance, the best array was the aligned array, with a maximum increase of 34.73 percent.
Real Time Rainfall Monitoring for Pipeline Geohazards
Authors: Ferris Gerry , Grover Patrick , Zahradka Aron 
Published: July 2021

Abstract
Oil and gas pipelines are subjected to multiple types of geohazards which cause pipeline failures (loss of containment); two of the most common types occur at watercourse crossings and at landslides.
At watercourse crossings, the most common geohazard which causes pipeline failures is flooding during which excessive scour may result in the exposure of the buried pipeline and if the exposure results in a free spanning pipeline, then this may fail due to fatigue caused by cyclic loading from vortex-induced vibration. Fortunately the free span length and water velocity combinations that lead to failure can be defined and can be used to identify the flood discharge that should be monitored for in order to trigger actions to manage the hazard and avoid failure. Most watercourse crossings in a pipeline network are on ungauged watercourses and necessitate the use of a proxy gauged watercourse. The “proxy” gauged watercourse is used to infer whether flooding is occurring on the ungauged crossing, and the owner can take appropriate actions. Often the proxy gauged watercourse is too far away or the watercourse may not be representative of the crossing of concern (e.g. large difference in the drainage areas). Real-time rainfall data can be used in conjunction with streamflow monitoring to determine when extreme precipitation has occurred within the ungauged watercourses catchment which may result in flooding.
Where pipelines cross landslide prone areas, large scale movements can be initiated, or slow on-going movement rates increased when extreme rainfall occurs. The definition of the extreme rainfall event for slope sites is the key component of providing a suitable warning of potentially dangerous conditions; shallow slides can be caused by short term events from sub-hourly to 3 day duration precipitation events whereas large deep seated (creeping) landslides can be driven by annual and intra-annual rainfall amounts. Monitoring of real time rainfall can be used to determine when extreme rainfall occurs at a landslide site.
The density of in-situ weather stations collecting real-time rainfall data prevents the application along remote sections of pipeline routes and within large sections of Canada. Gridded real time rainfall from quantitative precipitation estimations which integrate a multiple data sources including in-situ, numerical weather prediction, satellite and weather radar, can be used to overcome this problem and provide warnings when pre-determined rainfall thresholds are exceeded on a site-specific basis.