bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Temperature of Chemically Non-Reacting Internal Flows Using Tunable-Diode Laser Absorption Spectrometer
Authors: Akyuzlu K. M.
Published: August 2016

This study reports on the implementation of a non-intrusive measurement technique for the measurement of temperature in chemically non-reacting internal flows. The proposed technique is based on laser absorption spectroscopy. A low pressure, laboratory scale hybrid rocket motor simulator testbed was used to obtain a high temperature gas flow inside an electrically heated stainless steel pipe. The test section where the temperature measurements were made is located downstream of the heater and just before a convergent-divergent nozzle. This test section incorporates two viewing ports made of 1mm thick quartz plate to accommodate the laser beam of the Tunable Diode Laser Absorption Spectrometer (TDLAS) system. The TDLAS was originally designed to make measurement of temperature and velocity of hot gases inside the exhaust plume of a hybrid rocket motor. Consequently, the lasers were tuned to the absorption frequency of water vapor inside the combustion products.

For the present study, air was used as the working fluid. It was supplied from a compressed air cylinder which had low moisture concentrations. Therefore, the gas (air) flow had to be seeded with water vapor to obtain the necessary vapor concentrations for TDLAS measurements. This was accomplished by implementing a water vapor injector upstream of the heated section of the test apparatus. The superheated water vapor was supplied to the injector from an electrically heated, high pressure steam generator.

Temperature of the hot gas flow was also measured using flow-through thermocouples. Measurements were made and recorded during unsteady (startup and shutdown of the flow system) and steady state operation of the test apparatus. Experiments were repeated for different heat input rates and flow rates. Comparisons of the measurements indicate that TDLAS underestimate gas temperature by a constant value in the temperature ranges considered. A calibration (zeroing) of the TDLAS measurement improves the TDLAS readings. Based on this study, it is concluded that the TDLAS can be used to make real time temperature measurements of heated internal gas flows with reasonable accuracy.
Improved Non-Equilibrium Film Method for the Design of High-Temperature-Glide, Mini- and Microchannel Condensers
Authors: Fronk Brian M. , Garimella Srinivas
Published: August 2016

High-temperature-glide (i.e., large difference in dew and bubble point temperature) zeotropic mixtures such as ammonia/water have the potential to improve efficiency as new working fluids in advanced energy cycles for heating, cooling and power. Furthermore, the high heat capacity of ammonia/water mixtures makes them particularly attractive for use in compact mini- and microchannel devices. The non-isothermal condensation process of zeotropic mixtures leads to coupled heat and mass transfer resistances in each phase, which are not accounted for by single-component in-tube condensation modeling and correlation techniques. Previous attempts to design zeotropic condensers have relied on use of non-equilibrium film theory or mixture resistance correction factors. The film theory models have been developed with many simplifying assumptions including annular flow, negligible condensate and vapor sensible heat loads, and/or laminar condensate film, while the correction factor approaches do not directly consider mass transfer resistances. In the present study of high-temperature-glide mixtures in small channels, these assumptions are relaxed, and a new design method for mini- and microchannel zeotropic condensers is introduced. The approach is validated with experiments conducted for a range of tube diameters (0.98 < D < 2.16 mm), mass fluxes (50 < G < 200 kg m−2 s−1) and mass fractions of ammonia (0.80 < xbulk < 0.96). The results can be used in the development of compact, highly efficient heat and mass transfer devices.
A Computational Model for Performance Prediction of a Hybrid PV/T Module
Authors: Zevallos Francisco E. , Lin Cheng-Xian , Kiflemariam Robel
Published: August 2016

In this paper we investigate the performance of an integrated solar photovoltaic and thermal (PV/T) liquid (water) collector using a computational simulation program. A detailed time-dependent thermal model was formulated to calculate and correlate the thermal parameters in a standard PV/T collector, including solar cell temperature, back surface temperature, and outlet water temperature. Based on the energy balance of each component of the system, an analytical expression for the temperature of the PV module and the water was derived. In addition, an analytical expression for the instantaneous energy efficiency of the PV/T collector was also derived in terms of thermal, design and climatic parameters. Built on previously published model, a new computer simulation program was developed and validated. The thermal simulation results obtained are more precise than those previously reported in the literature.
A Multi-Objective Fire Safety and Sustainability Screening Tool for Specifying Insulation Materials
Authors: Roberts Bonnie C. , Webber Michael E. , Ezekoye Ofodike A.
Published: August 2016

Fire safety and sustainability goals in building design are frequently interdependent. Design elements chosen for their fire safety can have energy efficiency implications and vice versa. Furthermore, the environmental damage and carbon emissions from a single fire event can negate the utility of green features invested in the building. Therefore, while not obvious, fire safety and its impact on sustainability are inextricably linked. One of the decisions related to both sustainability and fire safety is the selection of thermal insulation materials. Insulating materials have always been an integral part of building design, serving as a key component in thermally controlling indoor environments. Modern designs and construction techniques often incorporate sustainability goals by seeking to minimize life cycle energy consumption and environmental impact. A well-insulated building reduces thermal load on the HVAC system, thus reducing energy consumption of the building. Therefore, a sustainably designed building is typically a heavily insulated building. In addition to thermal resistance characteristics, the choice of insulating material is often based on acoustic damping and cost. However, fire safety is generally overlooked as a factor for insulation material selection. Few treatments have considered how the competing objectives for sustainability and fire safety should be assessed when choosing insulation. This paper discusses a methodology for balancing these requirements by evaluating the aforementioned attributes of various insulating materials through implementation of a weighted mean. Each variable is normalized and then weighted according to the emphasis placed on each attribute, using experimental data for the relevant material property. Four weighting scenarios are presented, each emphasizing a different area of consideration: installed cost, fire safety, life-cycle assessment, and thermal. Materials considered are cellulose (newspaper), denim (cotton), fiberglass, stone wool, polyurethane, and polystyrene. Results of this analysis rank the materials in order of desirability and provide a method to reorder this ranking based on the priority assigned to each attribute. For the weighting scenarios presented herein, stone wool was consistently ranked as the best performer, while extruded polystyrene was typically the weakest. The intent is that this methodology would be informative for designers selecting materials and for planners contemplating revised building codes.
Temperature-Dependent Adsorption of Argon on Gold: A Molecular Dynamics Study
Authors: Easter Steven R. , Baker Christopher H. , Norris Pamela M.
Published: August 2016

When a gas and solid surface are brought into contact, some gas atoms may adsorb onto the surface, forming one or more denser layers. Adsorption has direct uses in many technologies, for instance filtration and pharmacology, and the prevalence of gas-solid interfaces means that it impacts many other technologies. However much is still unknown concerning the microscopic dynamics of adsorption. To investigate the effect of temperature on adsorption, molecular dynamics simulations were performed on an interface between solid gold and gaseous argon. The gas was placed in contact with the solid, allowing adsorption of gas atoms under a constant system temperature. The results of the simulations were analyzed to study the effect of temperature on the density of the adsorbed layer and its rate of formation. When brought into contact, the gas adsorbed to form one or more layers, the density of which was found to be strongly temperature-dependent. A monolayer was observed for temperatures above 150 K while below that value a secondary layer formed. Simulations above 450 K showed an exponential relationship between mean steady-state density and temperature of the form Deq = αeβT.
Influence of the Quench Process on Microstructure Evolution in a Landing Gear Steel
Authors: Chentouf Samir Mourad , Jahazi Mohammad , Fortin Rejean
Published: August 2016

The quench process of large size components is always problematic owing to non-uniform phase formation. In this context, the influence of cooling rate on phase transformation, for different cooling rates, in 300M steel is studied. A combination of high resolution dilatometry, optical microscopy, Vickers micro hardness measurements were employed to accurately determine the critical transformation temperature, and to identify microstructure constituents (bainite, martensite, and retained austenite).

A mixture of bainite, martensite and some retained austenite phases were observed to appear at cooling rate of 0.25°C/sec whereas for a cooling rate of 50°C/sec the microstructure is totally martensitic.
Knudsen Thermal Force Generation at the Microscale
Authors: Strongrich Andrew , Alexeenko Alina
Published: August 2016

The paper reports on the experimental studies targeting Knudsen forces on silicon microcantilevers. The devices were fabricated on a Silicon-On-Insulator wafer with one end anchored to the substrate. Measurements were performed through direct external heating of the underlying substrate. Device deflection was quantified using confocal microscopy, showing an increase in force magnitude for decreasing Knudsen number. Measurements were carried out at a constant substrate temperature with Knudsen number being controlled directly via ambient pressure.
Experimental and Computational Analysis of Film Cooling Hole Performance on a High Temperature Test Rig
Authors: Ramesh S. , Ekkad S. V. , Straub D. L. , Lawson S. A. , Alvin M. A.
Published: August 2016

Demand for more power from a gas turbine causes rotor inlet temperature to increase and in order to restrict the metal temperature in hot gas path components within a safe working limit, a better cooling system must be employed. This paper focuses on evaluating the performance of a film cooling hole in engine like conditions. Lab-scale experiments conducted prior to this study have established that tripod holes provide higher effectiveness compared to cylindrical and shaped holes while consuming only half the coolant. In spite of showing potential, it still has to yield superior cooling at engine like conditions. The high temperature test rig facility at NETL can raise the mainstream gas temperature as high as 1175 °C. Coolant temperature is adjusted to study film cooling performance at density ratio 2.8. This study presents results of baseline coupon testing. Metal coupons are made of Haynes230 alloy and are fabricated with cylindrical holes. Surface temperature is recorded using an IR thermographic camera which was calibrated using thermocouples, for different blowing ratios (0.5–2.0). Alongside experiment, a numerical model was also developed in an attempt to provide additional insight on the distribution of surface temperature and overall effectiveness downstream of cooling hole. It was observed that film cooling is effective at M=2.0 and 1.5 and this was associated with high inlet turbulence and swirling velocities disrupting the film cooling performance at lower blowing ratios. CFD predictions seemed to match better at M 1.0 but were found to deviate considerably at other blowing ratios.
Periodic Horizontal Heating of Enclosed Disconnected Solid Bodies Saturated With a Fluid
Authors: Mirehei S. M. , Franco A. T. , Junqueira S. L. M. , Lage J. L.
Published: August 2016

In the present study, the ensuing natural convection phenomenon inside a heated enclosure filled with disconnected, discrete solid blocks, and under time-periodic heating in the horizontal direction is investigated numerically. This configuration is akin to several practical engineering applications, such as in the food (baking) industry, metal parts (heat treating) industry, and containerization (storage and transportation) of discrete solid goods. Because of the relative large size of the solid bodies placed inside the enclosure, a porous medium approach is not appropriate in the present case. Hence, the solid and fluid constituents within the enclosure are viewed individually and modeled using continuum balance equations, with suitable compatibility conditions imposed at their interfaces. The periodic heating is simulated by imposing a sinusoidal time-function on the hot wall temperature, while maintaining the cold wall temperature constant. Results are presented in terms of surface-averaged (hot and cold) Nusselt numbers, time-varying energy capacity (equal to the thermal energy stored inside the enclosure), isotherms and streamlines, for Ra varying from 103 to 107, Pr = 1 and 36 uniformly distributed, conducting and disconnected solid square blocks. The results, focusing on the time-periodic regime, indicate the effect of varying Ra on the convection process. As Ra increases, the dynamic capacitor performance of the enclosure tends to be enhanced.
Experimental Study of Water Cooled Condenser Made of Three Dimensional and High Fin Density Integral-Finned Tubes
Authors: Ji Wen-Tao , Zhao Chuang-Yao , Dai Qi-Bin , Han Shu-Heng , Zhang Ding-Cai , He Ya-Ling , Tao Wen-Quan
Published: August 2016

The thermo-hydraulic performance of two shell and tube condensers was investigated with an experimental approach. The experiment is conducted in a water cooled centrifugal chiller test rig. The condensers are made of three-dimensional (3-D) and high fin density integral-finned (2-D) tubes. 2-D and 3-D tubes all have the diameter of 3/4 inch (19mm). The 2-D tube has external fin density of 56fpi (fins per inch), fin height 1.023mm and 48 internal ribs per circle. The 3-D enhanced tube has the external fin density of 45fpi, fin height of 0.981mm and 45 internal ribs per circle. The 3-D tube is widely used in the water cooled chillers. 2-D tube is a newly designed surface with enhanced external fin density. Condensing heat transfer coefficient of R134a outside single horizontal tube is firstly tested at saturate temperature of 40°C. At the internal water velocity of 2.2m/s, the overall heat transfer coefficients of 2-D tube is in the range of 10364.7 to 12420.9W/m2K, 4.2% ∼ 9.0% higher than 3-D tube. External condensing heat transfer coefficient is 16.3% ∼ 25.2% higher than 3-D tube. The condensers are manufactured with these two types of tubes. Both condensers have the same geometric parameters except the tubes and tube bundle space. The length of tube in the condenser is 4000mm. The tube bundles are arranged in a staggered mode. For the integral-fin tube condenser, the longitudinal tube pitch of tube arrays is 23mm in rows and the transverse is 20mm. At the same power input and cooling water inlet temperature of 32°C, the cooling power of 2-D tube condenser are respectively of 1755.4kW and 1769.4kW; 3-D tube condenser is 1727.5kW and 1770.5kW. The pressure drop increased about 11.2% ∼ 15.9% for the 2-D tube condenser compared with 3-D tube condenser. Generally, the two condensers have the same heat transfer performance, while the integral-fin tube condenser saves 15% of copper material consumption.
A Study on the Heat Transfer Characteristics in Busbars With Various Shape and Arrangement for the Industrial Switchgear
Authors: Cho Hyun Su , Park Sung Won
Published: August 2016

In this study, heat transfer analyses of copper bus bars which are installed in industrial switchgear have been conducted in order to obtain the heat transfer correlations for cooling design. The numerical analysis of temperature rise phenomena of copper busbars is carried out using a CFD (Computational Fluid Dynamics) code with various installation conditions under natural convection. The temperature rise test of copper busbars is conducted to provide useful database for verification of numerical analysis. Particularly various geometry and arrangement conditions such as number of parallel busbars and installation angels and gaps between the parallel busbars are considered in the numerical analysis to evaluate the cooling performance of busbars. From the comparisons between experimental and numerical results, it is found out that the obtained heat transfer correlations can predict temperature rise of busbars arranged in the switchgear.
Preliminary Numerical Study of Natural Convection in a Heterogeneous Horizontal Layer Heated From Below
Authors: Romano J. L. , Franco A. T. , Junqueira S. L. M. , Lage J. L.
Published: August 2016

In the present preliminary study the natural convection in a horizontal fluid layer heated isothermally from below and cooled from above, and having disconnected and conducting square solid blocks uniformly distributed in a square array within it, is numerically investigated. Nondimensional steady balance equations are presented, for a Newtonian fluid, with fluid and solid properties being considered constant and uniform. Among the nondimensional parameters ruling the phenomenon, the layer Rayleigh number is set as 105 and 106, the aspect ratio of the layer varies from 1 to 8, and the fluid Prandtl number and the solid-to-fluid thermal conductivity ratio are set as unity. The focus is on the effect of increasing the number of blocks in the layer, the blocks having progressively smaller size as to maintain the solid volume-fraction inside the layer constant and equal to 26% — this is equivalent to dispersing a fixed amount of solid material in smaller and large number of solid blocks within the layer. In general, the increase in the layer aspect ratio, with all other parameters kept constant, affects the results more as Ra increases — as expected because large Ra yields stronger convection effects. The increase in the number of blocks per unit of square cell in the layer affects the flow as to hinder convection; i.e., the finer the dispersion of solid material within the layer is (as the number of blocks increases) the weaker the resulting flow.
Experimental Study of the Local Response of a Low Swirl Flame to Acoustic Perturbation
Authors: Zhang Jianan , Ratner Albert
Published: August 2016

A low swirl burner is used to examine thermo-acoustic instability under different perturbation level. For a constant forcing frequency of 125 Hz, a low swirl flame with the velocity of 5 m/s is used to examine the effect of the driving pressure amplitude (0.045–0.649 % of atmospheric pressure) on the global and local flame response. Rayleigh Index is used in current research to show the local and global coupling level between the heat release and the pressure oscillation. The toroidal structures found in the Rayleigh Index map indicate that the coupling strength increases with the perturbation level and then stays stable. At the same time, the coupling location doesn’t change much with the forcing amplitude. In addition, the root mean square of the Rayleigh index (RRMS) exhibits a linear region and a nonlinear region when perturbation magnitude rises. Besides the global response, the local RRMS and locally-weighted RRMS are studied. The contributions of the positive and negative toroidal structures on the global RRMS are similar in current case. Locally phase-averaged OH-PLIF data are used to investigate the local heat release variation trend. Phase analysis shows that the local phase is not sensitive to the perturbation level, which induce that the Rayleigh Index is more dominated by the oscillation magnitude of the heat release.
Measurement of Thermal Conductivity of a Flexible Substrate
Authors: Vishwakarma Vivek , Jain Ankur
Published: August 2016

A number of past papers have described experimental techniques for measurement of thermal conductivity of substrates and thin films of technological interest. Nearly all substrates measured in the past are rigid. There is a lack of papers that report measurements on a flexible substrate such as thin plastic. The paper presents an experimental methodology to deposit a thin film microheater device on a plastic substrate. This device, comprising a microheater line and a temperature sensor line is used to measure the thermal conductivity of the plastic substrate using the transient thermal response of the plastic substrate to a heating current. An analytical model describing this thermal response is presented. Thermal conductivity of the plastic substrate is determined by comparison of experimental data with the analytical model. Results described in this paper may aid in development of an understanding of thermal transport in flexible substrates.
NOx Reduction in Partially Premixed Flames by Flue Gas Recirculation
Authors: Chudnovsky Yaroslav , Zelepouga Serguei , Saveliev Alexei , Wagner John , Gnatenko Vitaly
Published: August 2016

The authors are currently investigating new technical (both design and operation) approach, which is expected to enable the improvement of the performance of partially premixed type burners without jeopardizing the simplicity, cost, and reliability that this type of burners are well known for. The improvements include significant reduction of the NOx emission without substantial redesign of the combustion system. The results of the experimental investigation of burner operation and design improvements are to be presented and further discussed at the podium.
A Review on Nanofluid Heat Pipe
Authors: Shafahi Maryam , Anderson Kevin , Borna Ali , Lee Michael , Kim Alex , Subandi Syukrirashiduhakim , Khansari Parham
Published: August 2016

This paper reviews the improvement in the heat pipe’s performance using nanofluid as the working fluid. The use of nanofluid enhances heat transfer in the heat pipe due to its improved thermo-physical properties, such as a higher thermal conductivity. Nanofluids proved to be the innovative approach to a variety of applications, such as electronics, medical instruments, and heat exchangers. The influence of different nanoparticles on heat pipe’s performance has been studied. Utilizing nanofluid as the working fluid leads to a significant reduction in heat pipe thermal resistance, an increase in maximum heat transfer, and an improvement of heat pipe thermal performance.
Investigation on Moisture and Salt Transport in Heterogeneous Porous Media of Relics-Soil in Archaeology Museum
Authors: Luo X. L. , Gu Z. L. , Chai J. , Meng X. Z. , Lu Z. , Zhu B. X.
Published: August 2016

The unearthed relics in archaeology museum are usually being presented to the public as still partly connected to their primitive environment. Migration of moisture may cause the carbonate from the soil being deposited on the relic’s surface and some carbonates would react with the penetrating SO2 to form sulphates, which will change the relics’ primitive form and material properties. In this research, experiments were carried out to clarify the migration mechanism of water and salt in a soil-relic-atmosphere coupling environment. The research results show that there existing a one-way transport of moisture from the soil-relics to the air even though the relative humidity approximates to 100%. Meanwhile, the effects of soil properties, air temperature, relative humidity and salt concentration on the transports of moisture and salt are identified.
Investigation of Temperature Uniformity in an Open Cavity of Buoyancy Assisted Mixed Convection Heat Transfer With Multiple Discrete Inlet and Outlet Ports
Authors: Yang G. , Wu J. Y. , He Y. W. , Yan L.
Published: August 2016

Turbulent buoyancy assisted mixed convection heat transfer in an open cavity with multiple discrete inlet and outlet ports is investigated experimentally. The side walls of the rectangular cavity are symmetrically heated with constant and uniform temperature. The temperature distribution in the interior of the cavity is presented and discussed for the Reynolds numbers of 3919 ≤ Re ≤ 35405, the Grashof numbers of 1.56 × 107 ≤ Gr ≤ 3.45 × 107, the Prandtl number of Pr = 0.71 and for various quantities of inlet and outlet ports ranging from 1 × 1 to 5 × 5 with the same total opening area. Increasing Reynolds number and decreasing Grashof number can improve the temperature uniformity in the cavity. As the dispersion of the inlet ports increases, the maximum temperature gradient of the fluids in the cavity is decreased while the average temperature gradient is increased. The effect of inlet/outlet forms, Reynolds number and Grashof number on the Nusselt number is also investigated.
Atomistic-Continuum Hybrid Simulation of Heat Transfer Between Argon Flow and Copper Plates
Authors: Mao Yijin , Zhang Yuwen , Chen C. L.
Published: August 2016

A simulation work aiming to study heat transfer coefficient between argon fluid flow and copper plate is carried out based on atomistic-continuum hybrid method. Navier-Stokes equations for continuum domain are solved through the Pressure Implicit with Splitting of Operators (PISO) algorithm, and the atom evolution in molecular domain is solved through the Verlet algorithm. The solver is validated by solving Couette flow and heat conduction problems. With both momentum and energy coupling method applied, simulations on convection of argon flows between two parallel plates are performed. The top plate is kept as a constant velocity and has higher temperature, while the lower one, which is modeled with FCC copper lattices, is also fixed but has lower temperature. It is found that, heat transfer between argon fluid flow and copper plate in this situation is much higher than that at macroscopic when the flow is fully developed.
Investigation of Conjugate Heat Transfer in a Fin-and-Tube Heat Exchanger
Authors: Kadja M. , Mebrouk R.
Published: August 2016

A numerical study was achieved on a realistic fin-and-tube heat exchanger in order to investigate its heat transfer and friction characteristics. The computations assume a steady-state heat transfer and fluid flow. Nusselt number and friction factor characteristics of the heat exchanger are determined for various values of Reynolds numbers. Conjugate convection-conduction energy conservation equations in 3 dimensions have been solved along with mass and momentum conservation equations in order to determine these characteristics. Both laminar and turbulent flow regimes are considered. The effect of turbulence modeling was investigated using three different models (the one equation Spalart-Allmaras turbulence model, the standard k-ε model and the RSM model). The computations allowed the determination of the dynamic and thermal fields. Model validation was carried out by comparing the calculated friction factor f and Colburn j-factor to experimental results found in the literature. The plotted results showed a qualitatively good agreement between numerical results and experimental data.

The results obtained also showed that the simplest of the three turbulence models tested (i.e. Spalart-Allmaras) gives the closest values to the experimental data.
Scale Analysis and Experimental Results of a Solid/Liquid Phase-Change Thermal Energy Storage System
Authors: Siahpush Ali , O’Brien James , Crepeau John , Sabharwall Piyush
Published: August 2016

A detailed experimental study has been carried out to evaluate the heat transfer performance of a solid/liquid phase-change thermal energy storage system. The phase-change material (PCM) and metal foam are contained in a vertically oriented test cylinder that is cooled or heated at its outside boundary, resulting in radially inward melting, respectively. Detailed quantitative time-dependent volumetric temperature distributions and melt-front motion and shape data were obtained. As the PCM melts, the interface moves away from the surface of the heat source/sink, and a thermal resistance layer is built up, resulting in a reduced heat transfer rate and/or increased temperature difference between the system to be cooled (or heated) and the PCM. The phase-change medium was 99% pure eicosane, with a melting temperature of 36.5°C. Results have been generalized to apply to any low-Stefan number PCM.

A heat transfer scale analysis was used in order to help in interpretation of the data and development of heat transfer correlations. In the scale analysis, conduction heat transfer in the solid and natural convection heat transfer in liquid were considered. Comparison of experimental data with scale-analysis predictions of the solid-liquid interface position and temperature distribution was performed.
Modeling of Cavitation Bubble Motion in a Micro-Tube
Authors: Liu B. , Cai J. , Huai X. L. , Liu X.
Published: August 2016

The behaviors of cavitation bubble in a micro-tube are numerically investigated in the present work. The Navier-Stokes equations and volume of fluid (VOF) model are employed to track the liquid-gas interface during the growth and collapse of bubble. The results show a good agreement with experimental results in the literature, which proves the correctness and reliability of the model. Some important phenomena related to the confined bubble are observed in the study. For the bubble inside the micro-tube, liquid flows caused by the bubble motion are observed during the growth and collapse respectively. These unique flow patterns would have an important effect on heat transfer, which is totally different from the situation that a single bubble collapses near the solid wall in a semi-infinite space. On this basis, velocity vector field, pressure and temperature distributions on the wall are analyzed in details.
Higher Order Finite Elements for the Accurate Prediction of Temperature Gradients in Heat Conduction Problems
Authors: Aguirre-Rivas Donovan A. , Muci-Küchler Karim H.
Published: August 2016

When the Finite Element Method (FEM) is used to solve heat conduction problems in solids, the domain is typically discretized using elements that only include the nodal values of the temperature as Degrees of Freedom (DOFs). If the values of the spatial temperature gradients are needed, they are typically computed by differentiating the functional representation for the temperature inside the elements. Unfortunately, this differentiation process usually leads to less accurate results for the temperature gradients as compared to the temperature values.

For elliptic problems, like steady state heat conduction, with Neumann Boundary Conditions (BCs), recent research related to Adini’s element suggests that higher order elements that include spatial derivatives of the primary field variable as nodal DOFs are promising for obtaining accurate values for those quantities as well as providing a higher order of convergence than conventional elements.

In this paper, steady state and transient heat conduction problems which involve Dirichlet BCs or both Dirichlet and Neumann BCs are studied and a new auxiliary BC is proposed to increase the accuracy of the FE solution when Dirichlet BCs are present. Examples are used to illustrate that Adini’s elements converge faster and are more computationally economical than the conventional Lagrange linear elements and Serendipity quadratic elements when auxiliary BCs are used.
Evaluation of Cooling Water Storage for Liquid-Desiccant Air Conditioning System
Authors: Salimizad Danial , McNevin Chris , Harrison Stephen
Published: August 2016

Liquid-desiccant (LD) dehumidification technology has been used to extract moisture from humid air while attempting to consume less electricity than traditional air-conditioning methods. An evaporative cooling tower (ECT) was used as a cooling device to reject the latent heat gained by the system to regenerate the desiccant solution. The performance of an ECT was evaluated both experimentally and through TRNSYS simulations to investigate optimal operating conditions. The ECT often operated in humid conditions which resulted in reduced heat rejection rates and ineffective operation. To improve performance, cooling water storage (CWS) was investigated as a way to reduce ECT usage during periods of higher ambient humidity. To undertake this study, the complete LD system, incorporating CWS, was modelled in TRNSYS for a range of typical operating conditions. The results indicated that operation of the CWS system reduced the electrical power consumption and increased the electrical coefficient of performance (COPE) of the liquid desiccant air conditioning unit system by up to 16%. The total cooling rate improved by up to 6%. Smaller gains in COPT and solar fraction were also found in the simulation results.
Thermal Characterization of IM7/8552-1 Carbon-Epoxy Composites
Authors: Saad Messiha T. , Miller Sandi G. , Marunda Torrence
Published: August 2016

Thermal properties of composite materials such as, thermal conductivity, diffusivity, and specific heat are very important in engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells. Thermal conductivity is the property that determines the working temperature levels of the material; it plays a critical role in the performance of materials in high temperature applications, and it is an important parameter in problems involving heat transfer and thermal structures.

The objective of this paper is to develop a thermal properties data base for the carbon fiber-epoxy (IM7/8552-1) composite. The IM7 carbon fiber is a continuous, high performance, intermediate modulus, PAN based fiber. This fiber has been surface treated and can be sized to improve its interlaminar shear properties, handling characteristics, and structural properties. The 8552 is a high performance tough epoxy matrix for use in primary aerospace structures. It exhibits good impact resistance and damage tolerance for a wide range of applications. The IM7/8552-1 is an amine cured unidirectional prepreg. The manufacturer recommended cure cycle for this material was followed, which includes consolidation under vacuum and autoclave pressure. The composite has a service temperature up to 121°C (250°F).

The thermal properties of IM7/8552-1 carbon-epoxy have been investigated using experimental methods. The flash method was used to measure the thermal diffusivity of the composite. This method is based on the American Society for Testing and Materials standard, ASTM E1461. In addition, the Differential Scanning Calorimeter was used in accordance with the ASTM E1269 standard to measure the specific heat. The measured thermal diffusivity, specific heat, and density data were used to compute the thermal conductivity of the IM7/8552-1 carbon-epoxy composite.
A Network Model for the Thermal Conductivity of Pillared-Graphene Architectures
Authors: Shi Jingjing , Dong Yalin , Fisher Timothy , Ruan Xiulin
Published: August 2016

Carbon nanotubes and graphene are promising for thermal management applications due to their high thermal conductivities. However, their thermal properties are anisotropic and the radial or out-of-plane thermal conductivity is low. A graphene-CNT 3D structure has previously been proposed to overcome such limitation, and direct molecular dynamics simulations have been used to predict its thermal conductivity. In this work, by recognizing that the thermal resistance comes primarily from CNT-graphene junctions, we have proposed a simple network model of thermal transport in pillared graphene structures. Using non-equilibrium molecular dynamics, the resistance across an individual CNT-graphene junction is found to be around 6 × 10−11 m2 K/W, which is significantly lower than the typical values reported in literature for planar interfaces between dissimilar materials. The size-dependence of the CNT-graphene junction resistance is also explored in our work. The CNT pillar length between two graphene sheets is found to be an important parameter affecting the junction resistance, which decreases as the pillar length decreases. We explain this behavior by calculating the local phonon density of states near the junction. The junction resistance is then used in the network model to obtain the thermal conductivity, and the results agree well with the direct MD simulation data, demonstrating the effectiveness of our model.
A Review on Experimental and Numerical Investigations on Using Nanofluid in Volumetric Solar Energy Collectors
Authors: Mirmasoumi Siamak , Pourgol-Mohammad Mohammad
Published: August 2016

By a simple research in the scholarly articles, it can be realized that the tendency to using solar thermal energy has risen in the recent years due to its many reasonable advantages. In conventional solar thermal systems, HTFs (Heat Transfer Fluids) are pumped through the piping of a solar collector and after absorbing the solar radiant energy conveys it to water to make steam. No need to say that this method contains some losses via all methods of heat transfer. To solve this problem, researchers have shown that with direct steam generation, in which working fluid directly absorbs solar thermal and becomes vapor, solar power plants have the potential to be more productive. However, the aforesaid conventional HTFs don’t have efficient enough thermal properties and need to be improved. For this reason using nanofluid has become to some extent popular in heat transfer facilities like solar thermal collectors. In the present study, we are going to identify the advantages and disadvantages of using nanoparticles in direct solar absorption systems (DSASs). To achieve this, a general review on the experimental and numerical studies in this field is done. Additionally some of the most effective particles for such a special case, in which particles should have good radiative characteristics, are introduced. Finally, after discussion about the highlighted challenges of using nanofluids in DSASs, some helpful suggestions to overcome these problems will be presented.
Cavitation-induced damage of soft materials by focused ultrasound bursts: A fracture-based bubble dynamics model
Authors: Movahed Pooya , Kreider Wayne , Maxwell Adam D. , Hutchens Shelby B. , Freund Jonathan B.
Published: August 2016

A generalized Rayleigh–Plesset-type bubble dynamics model with a damage mechanism is developed for cavitation and damage of soft materials by focused ultrasound bursts. This study is linked to recent experimental observations in tissue-mimicking polyacrylamide and agar gel phantoms subjected to bursts of a kind being considered specifically for lithotripsy. These show bubble activation at multiple sites during the initial pulses. More cavities appear continuously through the course of the observations, similar to what is deduced in pig kidney tissues in shock-wave lithotripsy. Two different material models are used to represent the distinct properties of the two gel materials. The polyacrylamide gel is represented with a neo-Hookean elastic model and damaged based upon a maximum-strain criterion; the agar gel is represented with a strain-hardening Fung model and damaged according to the strain-energy-based Griffith's fracture criterion. Estimates based upon independently determined elasticity and viscosity of the two gel materials suggest that bubble confinement should be sufficient to prevent damage in the gels, and presumably injury in some tissues. Damage accumulation is therefore proposed to occur via a material fatigue, which is shown to be consistent with observed delays in widespread cavitation activity.
N
-Desmethylclozapine, Fluoxetine, and Salmeterol Inhibit Postentry Stages of the Dengue Virus Life Cycle
Authors: Medigeshi Guruprasad R. , Kumar Rinki , Dhamija Ekta , Agrawal Tanvi , Kar Meenakshi
Published: August 2016

Around 10,000 people die each year due to severe dengue disease, and two-thirds of the world population lives in a region where dengue disease is endemic. There has been remarkable progress in dengue virus vaccine development; however, there are no licensed antivirals for dengue disease, and none appear to be in clinical trials. We took the approach of repositioning approved drugs for anti-dengue virus activity by screening a library of pharmacologically active compounds. We identified
N
-desmethylclozapine, fluoxetine hydrochloride, and salmeterol xinafoate as dengue virus inhibitors based on reductions in the numbers of infected cells and viral titers. Dengue virus RNA levels were diminished in inhibitor-treated cells, and this effect was specific to dengue virus, as other flaviviruses, such as Japanese encephalitis virus and West Nile virus, or other RNA viruses, such as respiratory syncytial virus and rotavirus, were not affected by these inhibitors. All three inhibitors specifically inhibited dengue virus replication with 50% inhibitory concentrations (IC
50
s) in the high-nanomolar range. Estimation of negative-strand RNA intermediates and time-of-addition experiments indicated that inhibition was occurring at a postentry stage, most probably at the initiation of viral RNA replication. Finally, we show that inhibition is most likely due to the modulation of the endolysosomal pathway and induction of autophagy.
Association between Type A
blaZ
Gene Polymorphism and Cefazolin Inoculum Effect in Methicillin-Susceptible Staphylococcus aureus
Authors: Lee Sun Hee , Park Wan Beom , Lee Shinwon , Park Sohee , Kim Shin Woo , Lee Jong-Myung , Chang Hyun Ha , Kwon Ki Tae , Choe Pyoeng Gyun , Kim Nam Joong , Kim Hong Bin , Oh Myoung-Don
Published: August 2016

Some proportion of type A
blaZ
gene-positive methicillin-susceptible
Staphylococcus aureus
strains exhibit the cefazolin inoculum effect (CIE). The type A
blaZ
gene was divided into two groups by single nucleotide polymorphisms (SNPs) at Ser226Pro and Cys229Tyr. The median cefazolin MICs at a high inoculum concentration were 5.69 μg/ml for the Ser-Cys group and 40.32 μg/ml for the Pro-Tyr group (
P
= 0.01). The SNPs at codons 226 and 229 in the amino acid sequence encoded by the
blaZ
gene were closely associated with the CIE.
The Life Cycle Stages of Pneumocystis murina Have Opposing Effects on the Immune Response to This Opportunistic Fungal Pathogen
Authors: Evans Heather M. , Bryant Grady L. , Garvy Beth A.
Published: August 2016

The cell wall β-glucans ofPneumocystiscysts have been shown to stimulate immune responses in lung epithelial cells, dendritic cells, and alveolar macrophages. Little is known about how the trophic life forms, which do not have a fungal cell wall, interact with these innate immune cells. Here we report differences in the responses of both neonatal and adult mice to the trophic and cystic life cycle stages ofPneumocystis murina. The adult and neonatal immune responses to infection withPneumocystis murinatrophic forms were less robust than the responses to infection with a physiologically normal mixture of cysts and trophic forms. Cysts promoted the recruitment of nonresident innate immune cells and T and B cells into the lungs. Cysts, but not trophic forms, stimulated increased concentrations of the cytokine gamma interferon (IFN-γ) in the alveolar spaces and an increase in the percentage of CD4+T cells that produce IFN-γ.In vitro, bone marrow-derived dendritic cells (BMDCs) stimulated with cysts produced the proinflammatory cytokines interleukin 1β (IL-1β) and IL-6. In contrast, trophic forms suppressed antigen presentation to CD4+T cells, as well as the β-glucan-, lipoteichoic acid (LTA)-, and lipopolysaccharide (LPS)-induced production of interleukin 1β (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) by BMDCs. The negative effects of trophic forms were not due to ligation of mannose receptor. Our results indicate that optimal innate and adaptive immune responses toPneumocystisspecies are dependent on stimulation with the cyst life cycle stage. Conversely, trophic forms suppress β-glucan-induced proinflammatory responsesin vitro, suggesting that the trophic forms dampen cyst-induced inflammationin vivo.
Suppression of
fabB
Mutation by
fabF1
Is Mediated by Transcription Read-through in Shewanella oneidensis
Authors: Li Meng , Meng Qiu , Fu Huihui , Luo Qixia , Gao Haichun
Published: August 2016

As type II fatty acid synthesis is essential for the growth of
Escherichia coli
, its many components are regarded as potential targets for novel antibacterial drugs. Among them, β-ketoacyl-acyl carrier protein (ACP) synthase (KAS) FabB is the exclusive factor for elongation of the
cis
-3-decenoyl-ACP (
cis
-3-C
10
-ACP). In our previous study, we presented evidence to suggest that this may not be the case in
Shewanella oneidensis
, an emerging model gammaproteobacterium renowned for its respiratory versatility. Here, we identified FabF1, another KAS, as a functional replacement for FabB in
S. oneidensis
. In
fabB
+
or
desA
+
(encoding a desaturase) cells, which are capable of making unsaturated fatty acids (UFA), FabF1 is barely produced. However, UFA auxotroph mutants devoid of both
fabB
and
desA
genes can be spontaneously converted to suppressor strains, which no longer require exogenous UFAs for growth. Suppression is caused by a TGTTTT deletion in the region upstream of the
fabF1
gene, resulting in enhanced FabF1 production. We further demonstrated that the deletion leads to transcription read-through of the terminator for
acpP
, an acyl carrier protein gene immediately upstream of
fabF1
. There are multiple tandem repeats in the region covering the terminator, and the TGTTTT deletion, as well as others, compromises the terminator efficacy. In addition, FabF2 also shows an ability to complement the FabB loss, albeit substantially less effectively than FabF1.

IMPORTANCE
It has been firmly established that FabB for UFA synthesis via type II fatty acid synthesis in FabA-containing bacteria such as
E. coli
is essential. However,
S. oneidensis
appears to be an exception. In this bacterium, FabF1, when sufficiently expressed, is able to fully complement the FabB loss. Importantly, such a capability can be obtained by spontaneous mutations, which lead to transcription read-through. Therefore, our data, by identifying the functional overlap between FabB and FabFs, provide new insights into the current understanding of KAS and help reveal novel ways to block UFA synthesis for therapeutic purposes.