bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tracing the total molecular gas in galaxies: [CII] and the CO-dark gas
Authors: Madden S. C. , Cormier D. , Hony S. , Lebouteiller V. , Abel N. , Galametz M. , De Looze I. , Chevance M. , Polles F. L. , Lee M.-Y. , Galliano F. , Lambert-Huyghe A. , Hu D. , Ramambason L. 
Published: September 2020

Context.Molecular gas is a necessary fuel for star formation. The CO (1−0) transition is often used to deduce the total molecular hydrogen but is challenging to detect in low-metallicity galaxies in spite of the star formation taking place. In contrast, the [C II]λ158 μm is relatively bright, highlighting a potentially important reservoir of H2that is not traced by CO (1−0) but is residing in the C+-emitting regions.Aims.Here we aim to explore a method to quantify the total H2mass (MH2) in galaxies and to decipher what parameters control the CO-dark reservoir.Methods.We present Cloudy grids of density, radiation field, and metallicity in terms of observed quantities, such as [O I], [C I], CO (1−0), [C II],LTIR, and the totalMH2. We provide recipes based on these models to derive totalMH2mass estimates from observations. We apply the models to theHerschelDwarf Galaxy Survey, extracting the totalMH2for each galaxy, and compare this to the H2determined from the observed CO (1−0) line. This allows us to quantify the reservoir of H2that is CO-dark and traced by the [C II]λ158 μm.Results.We demonstrate that while the H2traced by CO (1−0) can be negligible, the [C II]λ158 μm can trace the total H2. We find 70 to 100% of the total H2mass is not traced by CO (1−0) in the dwarf galaxies, but is well-traced by [C II]λ158 μm. The CO-dark gas mass fraction correlates with the observedL[C II]/LCO(1−0)ratio. A conversion factor for [C II]λ158 μm to total H2and a new CO-to-total-MH2conversion factor as a function of metallicity are presented.Conclusions.While low-metallicity galaxies may have a feeble molecular reservoir as surmised from CO observations, the presence of an important reservoir of molecular gas that is not detected by CO can exist. We suggest a general recipe to quantify the total mass of H2in galaxies, taking into account the CO and [C II] observations. Accounting for this CO-dark H2gas, we find that the star-forming dwarf galaxies now fall on the Schmidt–Kennicutt relation. Their star-forming efficiency is rather normal because the reservoir from which they form stars is now more massive when introducing the [C II] measures of the total H2compared to the small amount of H2in the CO-emitting region.
Recent advances in the catalytic cyclopropanation of unsaturated compounds with diazomethane
Authors: Menchikov Leonid G. , Shulishov Evgeny V. , Tomilov Yury V. 
Published: September 2020

The main achievements and development trends of the past 10–15 years related to the catalytic cyclopropanation of unsaturated compounds with diazomethane are integrated and analyzed. The attention is focused on the most efficient catalysts based on palladium compounds. Data on the effects of substrate structure and nature of catalyst components on the regio- and stereoselectivity of these reactions are systematized. Characteristic features of safe methods for diazomethane generation are considered, including the use of membrane technologies and continuous-flow andin situpreparation methods, which have prospects for industrial application.The bibliography includes 281 references.
The finger flexors occlusion threshold in sport‐climbers: an exploratory study on its indirect approximation
Authors: Bergua Pedro , Montero‐Marin Jesús , Gomez‐Bruton Alejandro , Casajús José A. 
Published: September 2020

AbstractBlood flow partially determines specific climbing endurance (SCE) as it mediates oxygen bio‐availability in the finger flexors. Blood flow is related to occlusion threshold (OT), which is defined as the contraction intensity at which intramuscular pressure exceeds perfusion blood pressure resulting in the cessation of local blood flow. The OT is represented as an inflection point on a force‐time graph when isometric force is registered and applied through maximal and continuous tests. Endurance time (ET) to exhaustion is influenced by the relative isometric applied force and is different for each climber. The aim of this study was to explore whether an approximation of the finger flexoŕs OT in sport climbers through records of ET to exhaustion at different isometric relative intensities was possible. We measured maximum finger hang ETs at 6 intensities ranging from 85% to 35% maximal force in 34 sport climbers of advanced and elite level. The values obtained were analysed by two different methods in an attempt to determine a change in the shape of the curve in the intensity‐ET relationship graphs that approximated the OT for each climber. The results suggest that the finger flexoŕs OT could be different among climbers, regardless of their strength and ability level. The presented methods do not accurately reflect the OT, but could indicate the intensity at which blood flow is restored in the active muscles. This is the first study to indirectly approximate the finger flexors OT in sport‐climbers, a parameter that could be essential to assess SCE.
Enabling Compact Thermal Systems through Insights on Microscale Coupled Heat and Mass Transfer Phenomena
Authors: Garimella S 
Published: September 2020

Abstract
Heat transfer in microscale geometries offers the advantage of high heat transfer coefficients and large surface area-to-volume ratios, and therefore, the potential to develop compact heat and mass transfer devices and systems. This paper provides an overview of a variety of applications ranging from tens of Watts to Megawatts of heat transfer rates that can benefit from these insights into coupled heat and mass transfer. Practical challenges and innovations in implementing microscale heat exchangers are briefly discussed. This is followed by examples that include wearable cooling systems, thermally driven heat pumps, cooling of aircraft carriers, carbon capture and methane gas cleaning using microscale hollow fibers, and the incorporation of microchannel heat exchangers into electrochemical storage systems and nuclear reactor cores.
Thermal Performance Investigation by Infrared Analysis of Mini Pulsating Heat Pipe
Authors: Bonfiglio C , Bozzoli F , Cattani L , Iwata N , Rainieri S. , Vocale P 
Published: September 2020

Abstract
A promising solution in the field of passive two-phase heat transfer devices is represented by Pulsating Heat Pipes (PHPs). They are undoubtedly appealing due to the high heat transfer capability, efficient thermal control, adaptability and low cost. In the last years they are raising concern for space applications that are characterised by extreme environmental conditions, strictly constrains in terms of compactness, reliability and the need to dissipate efficiently heat in microgravity conditions. In this study, the thermal performance of oscillating heat pipes that consists of extra-thin metallic pipes are investigated: the adoption of metallic pipes with an inner diameter less than 0.4 mm permits to couple flexibility and compactness with high heat transfer performance. HFC-134a is used as working fluid. Many authors have investigated the pulsating behaviour of this type of heat transfer devices only considering the average temperature of the evaporator and condenser. In this work, to deeply investigate the oscillating behaviour of the proposed PHP, it is adopted an approach based on the study of the local temperature distributions on the wall of the PHP, acquired with a high-speed and high-resolution infrared camera. The local analysis of the temperature trends is of fundamental importance in the understanding of the complex phenomena that govern the pulsating field.
Experimental investigation of two-side heat transfer in spacer-filled channels
Authors: Ciofalo M , Cacciatore F , Di Liberto M , Tamburini A 
Published: September 2020

Abstract
In Membrane Distillation (MD), spacers support the membranes and promote mixing, thus reducing temperature polarization. Their efficient design requires a knowledge of the distribution of the local heat transfer coefficient h and of its dependence on Reynolds number, spacer geometry and flow-spacer relative orientation. In previous work, we applied Thermochromic Liquid Crystals (TLC) and digital image processing to the measurement of h distributions for different spacer configurations; data were used to validate CFD simulations and select turbulence models. For constructive reasons, the test section allowed only one-side heat transfer, while in most MD configurations (e.g. spiral-wound modules) heat transfer occurs from both sides of the feed water channels. Analytical and numerical solutions show that changing from one-side to two-side heat transfer deeply affects h values. This motivated the design and construction of an improved test section in which a hot channel is sandwiched between two cold channels, and twin cameras and lighting equipment allow the simultaneous acquisition of TLC images on both walls. This paper describes this new test section and the experimental technique, discusses measurement uncertainty, and presents preliminary results.
Numerical prediction of dropwise condensation performances on hybrid hydrophobic-hydrophilic surfaces
Authors: Croce Giulio , Suzzi Nicola , D’Agaro Paola 
Published: September 2020

Abstract
The use of hybrid surfaces, alternating hydrophobic and hydrophilic (or less-hydrophobic) areas, has been recently proposed as a valuable tool for dropwise condensation performances enhancement. The hydrophilic region, in particular, is designed in order to promote the removal of the droplet from the hydrophobic region, reducing their average size and thus increasing the heat transfer performance. Here, dropwise condensation on heterogeneous surfaces composed by a texture of alternating hydrophobic and hydrophilic (or less-hydrophobic) vertical strips is numerically investigated through a Lagrangian-based phenomenological model, originally developed to study droplet evolution in the framework of in-flight icing phenomenon. The effects of droplet nucleation, growth, coalescence and motion are implemented. The model is extended to the case of curved surface. In order to properly assess the hybrid surface, however, a better knowledge of the interaction between the droplet and the film is required. Thus, additional numerical simulations are carried out using an in-house Eulerian full solver of the liquid film layer, in order to understand the migration mechanism of a drop between two different wettability regions. This will give useful information for a proper implementation of the effect of hydrophilic strips in the phenomenological Lagrangian model. A parametric analysis allows to find the optimal geometric configuration of the hybrid pattern, leading to maximum heat transfer performance, for a given set of wettability properties, nucleation density and condensation rate per unit area. Comparison with experimental data from the available literature ensures the capability of the current Lagrangian model to properly catch the physics behind dropwise condensation process on both planar and curved hybrid surfaces. The uncertainty of the estimate of some model input parameter and their influence on the computed solution are be also discussed.
Flow boiling heat transfer characteristics of R245fa refrigerant in a plate heat exchanger
Authors: Ghorbani Tari Z 
Published: September 2020

Abstract
Plate heat exchangers (PHEs) are used extensively in industrial applications and, owing to their compactness, and higher thermal efficiency, they are keys component of organic Rankine cycle (ORC) application. This study presents the experimental heat transfer characteristics during flow boiling of R245fa refrigerant with a commercial working fluid used in ORCs; inside brazed plate heat exchanger with chevron angle of 65 degree. The flow boiling heat transfer characteristics were measured with varying saturation temperatures, mass flux and heat flux, which range from 55.5 °C-61.8 °C, 15.5-17.4 kg m−2 s−1, and 6400-10120 W m−2, respectively. The experimental results showed that flow boiling heat transfer coefficient is dependent upon the heat flux and mass flux. The results showed that the heat transfer coefficient increases with the increase of heat flux, and then starts to decrease due to local dry out. However, at low mass flux, locally triggering dry out was more prominent than that high mass flux. The heat transfer coefficient showed to be sensitive to the change in the saturation temperature. Moreover, flow boiling heat transfer coefficient showed a linear relationship with mass flux of the refrigerant.
Simulations of paraffine melting inside metal foams at different gravity levels with preliminary experimental validation
Authors: Iasiello M , Mameli M , Filippeschi S , Bianco N 
Published: September 2020

Abstract
In this work, the results of a numerical code based on the porous media Local Thermal Non-Equilibrium (LTNE) and the apparent heat capacity methods, are compared with experiments aiming at a preliminary validation. The test cell consists in a 50 mm aluminum foam cube filled with a paraffin wax, heated and cooled on the same face. The heat flux is measured by two miniaturized sensors, while the temperature is measured in three different locations along the cube edge. Finally, one side is equipped with a Zinc Selenide window which is transparent to the long wave InfraRed. This system allows to track the paraffin melting front evolution together with the temporal trend of the whole temperature distribution simplifying the comparison with the numerical outputs at different time steps.
The numerical model is then set with the same boundary conditions (heat flux) to predict the experimental temperature fields, considering both conduction in the solid domain and natural convection in the liquid domain. The preliminary validation shows that the numerical results match the experimental data with good agreement. Results are also presented for different gravity levels. This study can be a starting point for all those applications where gravity has a major role.
Influencing factors on flow boiling of carbon dioxide in enhanced tubes and comparison with correlations
Authors: Mastrullo R , Mauro A W , Thome J R , Vanoli G P , Viscito L 
Published: September 2020

AbstractCarbon dioxide two-phase flow characteristics are different from those of conventional refrigerants, due to the CO2particular thermodynamic and transport properties obtained by working at high reduced pressures. Moreover, the use of peculiar heat transfer surfaces such as grooves and internal fins are often preferred to enhance the boiling heat transfer performance. This paper collects CO2flow boiling heat transfer coefficient data from different independent databases available in scientific literature, regarding both smooth and enhanced geometries and a wide range of operative conditions, that are typical of refrigeration systems and heat pumps. The database for enhanced tubes covers internal diameters from 0.8 to 8.92 mm, saturation temperatures from -30 to +20 °C, imposed heat fluxes from 1.67 to 60 kW/m2and mass velocities from 75 to 800 kg/m2s, collecting more than 800 points. Heat transfer data for smooth and enhanced surfaces under the same conditions are collected, in order to measure the enhancement and to correlate it to the geometry augmentation. The assessment of quoted prediction methods explicitly developed for carbon dioxide is finally carried out, with a proposal for a correction factor.
Average Friction Factors of Choked Gas Flow in Microtubes
Authors: Kang D , Hong C , Rehman D , Morini G L , Asako Y , Faghri M 
Published: September 2020

Abstract
A micro-tube passage is a basic and important element in the design of micro heat exchangers and for this reason during the last decade a series of investigations have been made with the aim to clarify the main scaling effects playing an important role in microtubes. In this paper, a combined analysis of numerically and experimentally obtained average friction factors in microtubes under the situation of under-expanded (choked) gas flow is presented. The working fluid (nitrogen) passes through the microtube and discharges into the atmosphere under an increasing inlet pressure. Experiments and numerical computations are performed for microtubes with 249 and 528.9 mm in diameter, by varying the aspect ratio (i.e. length/diameter) from 100 to 200. The numerical methodology to solve the governing equations is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. In order to capture the under-expansion characteristics of the flow during choking, the computational domain is extended in the downstream region beyond the microtube outlet. Both experimental and numerical results were obtained for a wide range of Mach number and Reynolds number. In the previous study, it was demonstrated how the outlet Mach number can be expressed as a function of the tube diameter under choked conditions. In this paper, a data reduction procedure for the estimation of the average friction factor between the inlet and the outlet of the microtube is proposed for choked flows in which the outlet gas temperature and pressure are obtained by using the outlet Mach number calculated numerically as a function of the microtube diameter. It is demonstrated how this data reduction method allows an accurate calculation of the average friction factors in microtubes by using a limited number of parameters which are easy to measure. The results obtained in this way are in good agreement with the numerical predictions as well as with the most common empirical correlations.
Influence of moisture content, temperature and absorbed solar radiation on the thermal performance of a spruce XLAM wall in the Italian climates
Authors: Danovska M , Pernigotto G , Baratieri M , Baggio P , Gasparella A 
Published: September 2020

Abstract
In building simulation codes, conduction transfer functions or finite difference methods are generally implemented to model the heat transmitted through the opaque components. Thermal conductivity is conventionally assumed constantly equal to its nominal value, even if it depends on both temperature and moisture content, especially for porous building materials, like timber. Therefore, the adoption of constant nominal values can bring inaccuracies on the calculated heat flux, affecting the predicted building energy performance. In this research, the magnitude of such inaccuracies is quantified for a spruce cross-lam (i.e. XLAM) wall, by comparing hourly specific heat fluxes calculated with variable thermal conductivity and those with nominal one. To achieve such a goal, a MATLAB® 1D heat and mass transfer model was developed according to the finite difference method. Material’s thermal conductivity was characterised as a function of moisture content and temperature. Finally, the developed model was calibrated and validated against experimental data collected in the Building Physics Laboratory of the Free University of Bozen-Bolzano. Annual simulations were run considering 110 Italian climates and different orientations and inclinations of the wall. Constant internal boundary conditions and hourly variable external conditions were adopted; in particular, external solicitations were expressed through the sol-air temperature definition.
Thermal Efficiency of a Concentrating Solar Collector Under High-Vacuum
Authors: De Maio D , Alessandro C D’ , De Luca D , Musto M , Di Gennaro E , Rotondo G , Russo R 
Published: September 2020

Abstract
A new frontier in solar thermal panel technology can be a high vacuum collector, thick enough to be equipped with solar concentrators based on non-imaging optics, such as the Compound Parabolic Concentrators (CPC). The high vacuum technology guarantees higher operating temperatures thanks to the enhanced thermal insulation, which leads to pay particular attention to the absorber radiative emission. In this paper, by means of numerical simulations, we compare the efficiency of a flat selective solar absorber under high vacuum to the efficiency of a CPC under high-vacuum collector.
Modelling of Natural Convective Heating of a Standard Wet Brick for Oven Energy Consumption Tests
Authors: Lucchi M. , Suzzi N. , Lorenzini M. 
Published: September 2020

Abstract
The environmental impact of buildings is directly influenced by low-efficiency appliances like electric ovens. Their energy class is estimated through a test prescribed by the EN 60350 European standard, where a wet clay brick is heated under set conditions and the energy consumption is measured; throughout the test, particular attention is devoted to the control of air temperature. In this work, a transient model of the oven suitable for control design was realized including the heat and mass transfer within the brick. A lumped-parameter approach was used to ensure good predictive properties and low computational cost. The dynamics of the cavity air and the Pt500, which is used in normal operation to maintain the desired set point, was also included in the model. Model parameters were determined through an optimization procedure based on the experimental data collected during energy consumption tests with the oven in natural convective heating mode. The model was then validated. Good results were obtained in the prediction of both temperature and heating time.
Experimental and modelling evaluation of possible solutions for compact design of producer-gas heat exchangers
Authors: Morselli N , Puglia M , Mason J , Parenti M , Ottani F , Tartarini P 
Published: September 2020

Abstract
An experimental and numerical campaign was carried out to investigate the performances of tubes in shell heat exchanger applied to cool down the producer gas of a small-scale commercial wood biomass gasifier built by All Power Labs. Producer gas is contaminated with soot and tars that condensate under 300 °C, for this reason the heat exchanger was designed in order to have an in-situ cleaning mechanism. The heat exchanger was tested both with standard plain tubes and with a set of metal twisted tapes (TT) with the aim of enhancing the heat transfer between producer gas and water. Temperatures and mass flows analyses shown a maximum increase of thermal power output and overall heat transfer coefficient respectively of 19% and 76% when TT are applied to the standard plain tubes in shell heat exchanger. Numerical simulations shown a consistency in the trends giving an average discrepancy with experimental results of the 12%.