Heat In Conjunction Research Articles

A high temperature engine materials test facility.

Gas turbine engines subject materials to extreme conditions. Their high temperature materials and co-developed coatings must survive combustion gas temperatures currently approaching 1800 °C, large thermal gradients, severe thermal shock, and static and fatigue inducing applied stresses, all the while operating in highly reactive, high-pressure, high-speed combustion gas flows containing significant partial pressures of water vapor, oxygen, and other reactive species for many tens of thousands of hours. We describe the design and development of a test facility for the study of materials under individual and combinations of test parameters similar to those experienced within legacy and future engines. A hydraulic load frame capable of applying static or cyclic tension-compression stresses up to 400 MPa to flat-dog bone-shaped test specimens is integrated within an environmental test chamber capable of sustaining gas pressures from 0.1 to 1.2 MPa (1-12 atm). An adjustable0.1-2 kW power CO2 laser whose 10.6 µm wavelength radiation is strongly absorbed by ceramic coating materials is used to heat sample surfaces to temperatures of 1800 °C and above, while rear surface air jet cooling establishes through-thickness thermal gradients. Rapid laser heating in conjunction with transiently applied front and/or rear-side air cooling is used to create hot or cold thermal shock effects. This is accompanied by the impingement of a high pressure (up to 1.3 MPa) reactive gas jet upon the sample with speeds up to 300m/s by preheating dry air, mixing it with steam to the desired humidity, heating to 850 °C, and then expanding it through a converging nozzle. Thermal imaging pyrometers measure specimen front and back surface temperature fields, while environmental test chamber view ports permit digital image correlation and strain mapping.

Influence of microwave irradiation and water-based cooling on the fracturing behavior and failure mode transition of CSTBD granite

Utilizing microwave heating in conjunction with water-based cooling technology can effectively reduce the fracture toughness of hard rocks. However, the fracturing characteristics and failure modes of hard rocks following microwave heating and water-based cooling remain undisclosed. Granite, being one of the most common types of hard rocks, was selected for this study, employing Cracked Straight Through Brazilian Disc (CSTBD) specimens for laboratory testing. CSTBD specimens with various crack angles (0, 30, 60, and 90°) underwent treatment with varying microwave durations (30, 60, 180, 300, and 420 s). Subsequently, Brazilian splitting tests were conducted on the damaged specimens. To simulate the entire process of microwave heating and mechanical testing of CSTBD specimens, we developed a coupled Finite Element Method – Distinct Lattice Spring Model (FEM-DLSM) approach. The results indicate that microwave heating with water-based cooling significantly influences the fracture toughness of CSTBD granite. Mode-I fracture toughness decreases with microwave heating temperature at a low crack angle (pure tensile failure and tensile–shear mixed failure) and increases at a high crack angle (compressive–shear failure and compressive failure). Mode II fracture toughness decreases with microwave heating temperature at any crack angle. Microwave heating with water-based cooling causes a decrease in the transition angles from tensile–shear failure to compressive–shear failure and from compressive–shear failure to compressive failure. Thermally induced microcracks in the rock specimen are responsible for changes in fracture toughness and failure mode transitions. After microwave heating and water-based cooling, numerous microcracks are induced in the rock interior. While macroscopic cracks predominantly control failure, growing microcracks, by weakening the rock matrix, shift the initiation position of the failure crack from the tip of the macroscopic crack to other positions, following the principle of the weakest failure path.

Integrating Solar Heaters with Building Energy Systems : A Simulation Study

This paper looks at the topic of high-tech solar water heating systems being incorporated into existing building energy infrastructure. Hybrid systems that use solar water heating in conjunction with other renewable energy sources are also discussed, as are technical developments in collector designs, the use of cutting-edge control and monitoring systems, and the like. Reduced carbon emissions and optimized resource utilization are only two of the environmental advantages highlighted in the report. It also emphasizes the need of precise system sizing and regional life cycle assessments (LCAs) in achieving maximum energy efficiency. The paper highlights knowledge gaps in the areas of performance analysis, localized environmental impact studies, integration difficulties, and economic assessments. By filling up these spaces, it hopes to promote more eco-friendly and economical construction methods. Sustainable construction, energy savings, less of an influence on the environment, and new innovations in solar water heating are some of the terms that come to mind.

Nondestructive thermographic detection of internal defects using pixel-pattern based laser excitation and photothermal super resolution reconstruction

In this work, we present a novel approach to photothermal super resolution based thermographic resolution of internal defects using two-dimensional pixel pattern-based active photothermal laser heating in conjunction with subsequent numerical reconstruction to achieve a high-resolution reconstruction of internal defect structures. With the proposed adoption of pixelated patterns generated using laser coupled high-power DLP projector technology the complexity for achieving true two-dimensional super resolution can be dramatically reduced taking a crucial step forward towards widespread practical viability. Furthermore, based on the latest developments in high-power DLP projectors, we present their first application for structured pulsed thermographic inspection of macroscopic metal samples. In addition, a forward solution to the underlying inverse problem is proposed along with an appropriate heuristic to find the regularization parameters necessary for the numerical inversion in a laboratory setting. This allows the generation of synthetic measurement data, opening the door for the application of machine learning based methods for future improvements towards full automation of the method. Finally, the proposed method is experimentally validated and shown to outperform several established conventional thermographic testing techniques while conservatively improving the required measurement times by a factor of 8 compared to currently available photothermal super resolution techniques.

First-passage time theory of activated rate chemical processes in electronic molecular junctions.

Confined nanoscale spaces, electric fields, and tunneling currents make the molecular electronic junction an experimental device for the discovery of new out-of-equilibrium chemical reactions. Reaction-rate theory for current-activated chemical reactions is developed by combining the Keldysh nonequilibrium Green's function treatment of electrons, Fokker-Planck description of the reaction coordinate, and Kramers first-passage time calculations. The nonequilibrium Green's functions (NEGF) provide an adiabatic potential as well as a diffusion coefficient and temperature with local dependence on the reaction coordinate. Van Kampen's Fokker-Planck equation, which describes a Brownian particle moving in an external potential in an inhomogeneous medium with a position-dependent friction and diffusion coefficient, is used to obtain an analytic expression for the first-passage time. The theory is applied to several transport scenarios: a molecular junction with a single reaction coordinate dependent molecular orbital and a model diatomic molecular junction. We demonstrate the natural emergence of Landauer's blowtorch effect as a result of the interplay between the configuration dependent viscosity and diffusion coefficients. The resultant localized heating in conjunction with the bond-deformation due to current-induced forces is shown to be the determining factors when considering chemical reaction rates, each of which results from highly tunable parameters within the system.

EPR hyperthermia of S. cerevisiae using superparamagnetic Fe3O4 nanoparticles

Presently we communicate a newly developed method of resonant radiofrequency heating, applicable in hyperthermal therapy. This method uses electron paramagnetic resonance (EPR) to transform the electromagnetic field energy into heat. We report the growth dynamics of the S. cerevisiae yeast cells exposed to EPR heating with superparamagnetic magnetite (Fe3O4) nanoparticles, with only 4% of yeast cells surviving hyperthermia. Given that EPR functions independently of type of the biologic species exposed, and produces spatially localized heating in conjunction with MRI hardware, it may be used in hyperthermal therapy of cancer and other diseases.

Rapid One-Pot Microwave Synthesis of Mixed-Linker Hybrid Zeolitic-Imidazolate Framework Membranes for Tunable Gas Separations

The relatively slow and complex fabrication processes of polycrystalline metal-organic framework (MOF) membranes often times restrict their way to commercialization, despite their potential for molecular separation applications. Herein, we report a rapid one-pot microwave synthesis of mixed-linker hybrid zeolitic-imidazolate framework (ZIF) membranes consisting of 2-methylimidazolate (ZIF-8 linker) and benzimidazolate (ZIF-7 linker) linkers, termed ZIF-7-8 membranes. The fast-volumetric microwave heating in conjunction with a unique counter diffusion of metal and linker solutions enabled unprecedented rapid synthesis of well-intergrown ZIF-7-8 membranes in ∼90 s, the fastest MOF membrane preparation up to date. Furthermore, we were able to tune the molecular sieving properties of the ZIF-7-8 membranes by varying the benzimidazole-to-2-methylimidazole (bIm-to-mIm) linker ratio in the hybrid frameworks. The tuning of their molecular sieving properties led to the systematic change in the permeance and selectivity of various small gases. The unprecedented rapid synthesis of well-intergrown ZIF-7-8 membranes with tunable molecular sieving properties is an important step forward for the commercial gas separation applications of ZIF membranes.

Development of a new urban heat island modeling tool: Kent Vale case study

Urban heat island is intensified by anthropogenic activities and heat in conjunction with the built-up urban area, which absorbs more solar radiation during daytime and releases more heat during nighttime than rural areas. Air cooling systems in Singapore, as one of the anthropogenic heat sources, reject heat into the vicinity and consequently affect urban microclimate. In this paper, a new urban heat island modeling tool is developed to simulate stack effect of split type air-conditioners on high rise buildings and solar radiation induced thermal environment. By coupling the Computational Fluid Dynamics (CFD) program with the solar radiation model and perform parallel computing of conjugate heat transfer, the tool ensures both accuracy and efficiency in simulating air temperature and air relative humidity. The annual cycle of sun pathway in Singapore is well simulated and by decreasing the absorptivity or increasing the reflectivity and thermal conductivity of the buildings, the thermal environment around buildings could be improved.

Supercritical CO2 Rankine cycles for waste heat recovery from gas turbine

A supercritical carbon dioxide (S-CO2) Rankine cycle for waste heat recovery (WHR) from a gas turbine can achieve high efficiency despite its simplicity and compactness in comparison to a steam/water cycle. With respect to WHR, it is very important to maximize the net output power by incorporating the utilization efficiency of the waste heat in conjunction with the cycle thermal efficiency. A simple S-CO2 Rankine cycle used for a high-temperature source cannot fully utilize the waste heat because the working fluid is preheated by the recuperator to a high temperature to achieve a high cycle efficiency. To recover the remaining waste heat from a simple cycle, a cascade cycle with a low-temperature (LT) loop can be added to the high-temperature (HT) loop, or a split cycle—in which the flow after the pump is split and preheated by the recuperator and LT heater separately, before the HT heater can be used. This study presents a comparison of three cycles in terms of energy and exergy analyses of their systems. The results show that a split cycle can produce the highest power of the threes systems considered over a wide range of operating conditions. The reasons for this are explained in detail.

Eddy Current Pulsed Thermography with Different Excitation Configurations for Metallic Material and Defect Characterization

This paper reviews recent developments of eddy current pulsed thermography (ECPT) for material characterization and nondestructive evaluation (NDE). Due to the fact that line-coil-based ECPT, with the limitation of non-uniform heating and a restricted view, is not suitable for complex geometry structures evaluation, Helmholtz coils and ferrite-yoke-based excitation configurations of ECPT are proposed and compared. Simulations and experiments of new ECPT configurations considering the multi-physical-phenomenon of hysteresis losses, stray losses, and eddy current heating in conjunction with uniform induction magnetic field have been conducted and implemented for ferromagnetic and non-ferromagnetic materials. These configurations of ECPT for metallic material and defect characterization are discussed and compared with conventional line-coil configuration. The results indicate that the proposed ECPT excitation configurations can be applied for different shapes of samples such as turbine blade edges and rail tracks.

Diurnal and semi-diurnal tidal structures due to O2, O3 and H2O heating

Today with increased availability of data of middle atmospheric winds and temperature, modelling of middle atmospheric tides has acquired greater importance. The theory of atmospheric tides has two main parts: (i) Investigation of the sources of periodic excitation, and (ii) calculation of the atmospheric response to the excitation. Other than stratospheric ozone and tropospheric water vapour absorption, the thermal energy available from the absorption in Schumann–Runge (SR) continuum leading to photo-dissociation of O2 is important energy source for tides in the lower thermosphere. PHODIS radiative transfer model is capable of providing tidal forcing due to combined effect of solar and chemical heating in the wavelength region 116 to 850 nm. In this paper, we present an atmospheric tidal model based on classical tidal theory and the prime objective is to obtain the tidal structure due to conventional ozone and water vapour heating in conjunction with the O2 absorption. Mean wind and dissipation mechanisms are not considered. The present tidal model reveals that the diurnal amplitude peaks in mid to low latitudes, whereas semidiurnal component is stronger at higher latitudes. The semidiurnal tide is about an order of magnitude weaker than the diurnal tide. Also, semidiurnal wave has longer vertical wavelength than diurnal tide. The results of present model are qualitatively in good agreement with the other tidal models, which utilize more sophisticated parameterization. Thus, the salient features of the tidal structure are obtained using basic computations without considering the effects of background winds and dissipation processes. Further refinements to the model can serve as an inexpensive substitute to the presently available tidal models.

Microwave-assisted synthesis of Pt-WC/TiO2 in ionic liquid and its application for methanol oxidation

Tungsten carbide/titanium oxide (WC/titanium dioxide (TiO2)) particles are prepared by microwave-assisted heating in conjunction with ionic liquid and the subsequent reduction–carbonization. The platinum particles are loaded on the WC/TiO2 to prepare Pt-WC/TiO2. The electrocatalytic performances of the Pt-WC/TiO2 toward methanol oxidation are evaluated by cyclic voltammetry, chronoamperometry, and the CO stripping tests. It is found that electrocatalytic activity of Pt-WC/TiO2 is enhanced by adding ionic liquid (IL) during sample preparation. The results indicate that better performance toward methanol oxidation and higher tolerance to CO are achieved with an optimal addition of 1.5 ml 1-methyl-imidazoliumtetr-afluoroborate for preparing Pt-WC/TiO2. To investigate the function of IL, the phase structure and morphology of samples at different stages during preparation are examined by X-ray diffraction and transmission electron microscopy. Ionic liquid is found to act as not only a good solvent offering the excellent microwave absorption, but also a structure-directing agent to control the morphology and structure of sample, which affect the activity of the final catalysts.

Winters, Summers, and Destructive Leadership Cultures in Rich Regions

Van de Vliert’s (2009) climato-economic theory of culture proposes that the impact of climatic demands on culture is influenced by wealth resources. In rich regions, much cold and heat in conjunction with relatively little wealth ( undermatching) and little cold and heat in conjunction with relatively much wealth ( overmatching) both are thought to produce less destructive leadership cultures than do approximations of just enough wealth to successfully cope with thermal climate ( optimal matching). Avoiding confounding influences of numerous cross-national differences, we tested this tenet using employee survey data gathered in a sample of 191 Norwegian municipalities. Destructive leadership culture is less prevalent in less wealthy regions with more demanding winters and more demanding summers ( undermatching) and in more wealthy regions with milder winters and milder summers ( overmatching) than in more or less wealthy regions with either more demanding winters and milder summers or more demanding summers and milder winters ( optimal matching). Disconfirmative tests could not obscure or destroy these findings.

ChemInform Abstract: Microwave Heating in Conjunction with UV Irradiation: A Tool for the Oxidation of 1,4‐Dihydropyridines to Pyridines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Continuous measurements of near surface aerosols in the south-western European (Portugal) region in 2006–2008

Abstract. Scattering and absorption coefficients near the ground were measured in Évora, Portugal, in the period of 2006 to 2008. The average scattering coefficient, at the wavelength of 550 nm, for the whole period of measurements was found to be 40.3 Mm−1 and the absorption coefficient, at the wavelength of 670 nm, 8.6 Mm−1. These values are comparable to those measured in rural or background locations and reflect the small size of the city and relatively low magnitude of anthropogenic production at the site. A marked seasonal variation was found for the absorption coefficient, with a significant increase from 5.8 Mm−1, in summer, to 13.4 Mm−1, in winter. Regarding black carbon mass concentrations, this twofold increase, from 0.9 to 2.0 μgm−3, is mainly attributed to the wood combustion used for heating in conjunction with lower boundary layer mixing heights. The average scattering coefficient presented a more complex behaviour, although with a tendency for higher values in winter and lower values in spring.

Use of a silicon carbide multi-well plate in conjunction with microwave heating for rapid ligand synthesis, formation of palladium complexes, and catalyst screening in a Suzuki coupling

The preparation of a library of bis-imidazolium salts and corresponding palladium complexes is reported. These complexes are screened as catalysts in the Suzuki reaction between 4-bromoanisole and phenylboronic acid. Each step is performed in parallel using a 24-position silicon carbide plate and microwave heating. The plate allows for use of standard glass vials as reaction vessels. The ease and speed of operation show the potential for microwave heating in conjunction with the silicon carbide plate as a tool for catalyst screening.

Microwave Heating in Conjunction with UV Irradiation: a Tool for the Oxidation of 1,4-Dihydropyridines to Pyridines

Microwave heating is used for the preparation of 1,4-dihydropyridines and then, in conjunction with UV irradiation, is used for the efficient oxidation of the 1,4-dihydropyridines to pyridines. The oxidation reactions are performed in a sealed vessel using oxygen as the oxidant and an electrodeless discharge lamp as the irradiation source.

Microwave-Promoted Desulfurization of Heavy and Sulfur-Containing Crude Oil

We have probed the effect of microwave irradiation on desulfurization of crude oil and dibenzothiophene. A range of catalysts have been screened. We find that it is possible to perform hydrodesulfurization reactions using microwave heating in conjunction with iron powder as a catalyst. The effect of hydrogen pressure, reaction temperature, reaction time, and catalyst source have been studied. The effectiveness of catalyst- and hydrogen-free desulfurization has been probed briefly. Approaches included microwave-promoted cracking, high-temperature water chemistry, and the use of metal hydrides but, with the conditions screened in this study, these proved not to be effective. We believe that our results here build on work in the scientific and patent literature suggesting that microwave irradiation can be a useful tool for effecting desulfurization chemistry.

Recent progress in the impact of the Tibetan Plateau on climate in China

Studies of the impacts of the Tibetan Plateau (TP) on climate in China in the last four years are reviewed. It is reported that temperature and precipitation over the TP have increased during recent decades. From satellite data analysis, it is demonstrated that most of the precipitation over the TP is from deep convection clouds. Moreover, the huge TP mechanical forcing and extraordinary elevated thermal forcing impose remarkable impacts upon local circulation and global climate. In winter and spring, stream flow is deflected by a large obstacle and appears as an asymmetric dipole, making East Asia much colder than mid Asia in winter and forming persistent rainfall in late winter and early spring over South China. In late spring, TP heating contributes to the establishment and intensification of the South Asian high and the abrupt seasonal transition of the surrounding circulations. In summer, TP heating in conjunction with the TP air pump cause the deviating stream field to resemble a cyclonic spiral, converging towards and rising over the TP. Therefore, the prominent Asian monsoon climate over East Asia and the dry climate over mid Asia in summer are forced by both TP local forcing and Eurasian continental forcing.

Advances in organic synthesis using polymer-supported reagents and scavengers under microwave irradiation

Microwave-assisted and polymer-supported organic syntheses have emerged independently as versatile tools for rapid generation of organic molecules. Chemists are increasingly looking for a combination of both techniques for efficient organic synthesis. This review covers the recent literature on organic synthesis using microwave heating in conjunction with polymer-supported reagents and scavengers.