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This article proposes a better alternative method to prepare CNT antifreeze nanofluid in EG/water by modifying the conventional method that requires long hours of sonication. Sonicating a sample for long hours is time and energy consuming and may deform the structure of CNT. In the modified method, the nanofluid preparation was carried out by dispersion of CNT in EG via sonication followed by adding water and again sonication. The study shows that nanofluid could be prepared in less sonication time of 1.5 h compared to the 5 h required in the conventional method. FTIR spectroscopy revealed that interaction of EG with CNT occurs via trans conformation resulting in greater stabilization and better interaction of nanofluid prepared by this method (85 days) as compared to nanofluid prepared by the conventional method (50 days). The nanofluid prepared by this method has better physical–chemical properties compared to nanofluid prepared by the conventional method. The nanofluid prepared by this method showed higher stability and better physical–chemical properties at a lower sonication time. Hence it is a more effective and cost efficient technique for preparing CNT (EG/water) nanofluid. [ABSTRACT FROM AUTHOR]

Experimental results for the transient heat transfer characteristics over a flat plate and over a plate with V-shaped ribs were compared to numerical results from a coupling environment applying FEM and CFD. In order to simulate transient effects in the cooling process of engine components during typical flight missions, the temperature and the velocity at the inlet of the channel were varied over time. The transient temperature distribution at the plate was measured using infrared thermography. Five different plate materials (perspex, PEEK, quartz, aluminum, and steel) were considered to investigate the influence of thermal conduction on the heat transfer between solid and fluid depending on the Biot number. The experimental results represent a reference database for a Python-based coupling environment applying CalculiX (FEM) and ANSYS CFX (CFD). The results were additionally compared to numerical results simulating the complete transient conjugated heat transfer with CFD. A good agreement between the numerical and the experimental results was achieved using different coupling sizes at different Biot numbers for the flat plate and the plate with V-shaped ribs. [ABSTRACT FROM AUTHOR]

This article proposes a better alternative method to prepare CNT antifreeze nanofluid in EG/water by modifying the conventional method that requires long hours of sonication. Sonicating a sample for long hours is time and energy consuming and may deform the structure of CNT. In the modified method, the nanofluid preparation was carried out by dispersion of CNT in EG via sonication followed by adding water and again sonication. The study shows that nanofluid could be prepared in less sonication time of 1.5 h compared to the 5 h required in the conventional method. FTIR spectroscopy revealed that interaction of EG with CNT occurs via trans conformation resulting in greater stabilization and better interaction of nanofluid prepared by this method (85 days) as compared to nanofluid prepared by the conventional method (50 days). The nanofluid prepared by this method has better physical–chemical properties compared to nanofluid prepared by the conventional method. The nanofluid prepared by this method showed higher stability and better physical–chemical properties at a lower sonication time. Hence it is a more effective and cost efficient technique for preparing CNT (EG/water) nanofluid.

In the last decade, growing awareness about CO2 emissions is supporting the authorities in a more sustainable society. The proposed solutions embrace different topics, such as renewable energy implementation, lower waste production, and carbon capture and storage technologies (CCS). The latter is based upon the best available knowledge about the thermophysical properties of CO2, which are not always satisfactory for its complete characterization. In this work, it is investigated the interaction of the CO2 in solid phase (dry-ice) with sandy soil, a phenomenon that can potentially occur following pipeline ruptures. An experimental setup and a numerical model have been developed to measure and validate the temperature profiles beneath the dry-ice bank at steady-state conditions. The model has been validated with the experimental data by defining a suitable range of the thermal conductivity at the solid phase (0.25–0.30 W m−1 K−1) that led to the best match (deviation of 7.81%). Finally, the overall heat transfer coefficient (85.56–86.35 W m−2 K−1) has been numerically calculated. [ABSTRACT FROM AUTHOR]

The semiconductor component of InGaN-based blue light-emitting diodes (LED) emits white light when combined with a yellow phosphor mixture. However, owing to the lattice dislocations and defect points in GaN, it exhibits a high thermal resistance, which leads to heat accumulation and an increase in temperature. This is problematic as overheating causes LED to produce dark spots and lines and reduces the luminous flux and optical power of high-power LED. In this study, we propose a variety of optimal structures for heat-transfer modules and apply the proposed architectures in the assembly of high-power LED. First, the high-power LED substrate was coated with a film of aluminum nitride. Then, copper fins were connected to the vacant spaces in the circuit boards to increase the surface area of the heat-transfer region. The Taguchi method was used to identify the optimal substrate thickness, fin arrangement, and fin depth for the effective heat dissipation in a 12 W high-power LED. A dielectric layer was grown on the surface of the aluminum nitride film to serve as a passivation layer to insulate the patient. The passivation layer reduces the physical damage caused by thermal stress, thereby improving the service life and characteristics of heattransfer modules. The proposed design not only yields a stable LED substrate (with low thermal stress) but also induces reliable heat transfer. [ABSTRACT FROM AUTHOR]

Experimental results for the transient heat transfer characteristics over a flat plate and over a plate with V-shaped ribs were compared to numerical results from a coupling environment applying FEM and CFD. In order to simulate transient effects in the cooling process of engine components during typical flight missions, the temperature and the velocity at the inlet of the channel were varied over time. The transient temperature distribution at the plate was measured using infrared thermography. Five different plate materials (perspex, PEEK, quartz, aluminum, and steel) were considered to investigate the influence of thermal conduction on the heat transfer between solid and fluid depending on the Biot number. The experimental results represent a reference database for a Python-based coupling environment applying CalculiX (FEM) and ANSYS CFX (CFD). The results were additionally compared to numerical results simulating the complete transient conjugated heat transfer with CFD. A good agreement between the numerical and the experimental results was achieved using different coupling sizes at different Biot numbers for the flat plate and the plate with V-shaped ribs.

As the parameters involved in the brake thermal efficiency of the engine cycles affect each other, the simultaneous investigation of the critical parameters, non-critical parameters, and the maximum temperature of the working fluid involved to optimize the brake thermal efficiency of the engine cycles is vital to implement the theoretical proposition into practical design perspectives. For this reason, a new method to compare the thermal efficiency of the engine cycles has been carried out with the simultaneous application of the optimal cycle design parameters (the geometric-compression ratio, expansion–compression​ ratio, and pressure ratio), the operating parameters (the heat-transfer loss, heat-release during combustion, friction loss, temperature-dependent specific heat ratio of the working fluid, and initial temperature of the working fluid), and the maximum temperature of the working fluid. The numerical examples show that the largest brake thermal efficiency is for the Dual-Miller cycle (46.32%) as compared to that for the classical-Otto (42.41%), classical-Diesel, classical-dual (40.22%), Otto-Miller (45.32%), Diesel-Miller (40.27%), Otto-Atkinson (42.31%), Diesel-Atkinson (32.19%), and dual-Atkinson (42.34%) cycles. When the heat-release during combustion and temperature-dependent specific heat ratio of the working fluid increased, the brake thermal efficiency of the Dual-Miller cycle rises and then begins to abate. As the heat-transfer coefficient, friction coefficient and initial temperature of the working fluid increased by about 20%, the brake thermal efficiency of the Dual-Miller cycle decreases by about 1.3%, 1.1%, and 3%, respectively. The numerical examples also show that the brake thermal efficiency of the Dual-Miller cycle first increases with increasing the maximum temperature of the working fluid, reaches its maximum value (43.01%) and then remains constant with further increases in the maximum temperature of the working fluid.

An experimental study on multi-nozzle spray cooling of a downward-facing heater surface has been carried out in the SPAYCOR facility at KTH, to provide data assessing the feasibility of spray cooling for in-vessel melt retention (IVR) in light water reactors. To help understand the characteristics and influential factors of the liquid film formed on the heater surface in spray, a numerical study on the dynamics of an isothermal liquid film on the heater surface has also been performed by adopting the OpenFOAM platform, and Eulerian and Lagrangian methods for liquid film and droplets, respectively. The present study is an extension of the previous modeling from hydrodynamics to thermal-hydraulics of the spray cooling problem, via adding heat flux of the heater and two convective heat transfer models between the heater wall and the liquid film. Moreover, droplets-film interaction model is modified. The SPAYCOR experiment is simulated by the numerical models, and the simulation results show a good agreement between the numerical and experimental data, in particular when the modified droplets-film interaction model is applied. After the validation of the numerical models against the SPAYCOR experiment, the numerical models are employed to investigate influential factors on heat transfer, such as mass flux, nozzle-to-surface distance, and nozzle matrix layout. The results indicate that heat transfer is enhanced by increasing mass flux and decreasing nozzle-to-surface distance, and the change of nozzle matrix from inline to staggered layout has little impact on heat removal capacity or temperature distribution of the multi-nozzle spray cooling. [ABSTRACT FROM AUTHOR]

Steady-case thermal analysis plays an important role in dimensioning thermal control systems for spacecrafts and aircrafts. Usually a trial and error approach is used based on engineering judgement and experience. When thermal models become complex or there are conflicting thermal requirements, however, it becomes harder for an engineer to gain insight as to which design decisions will lead to better results. Numerical optimization, on the other hand, could provide a more robust approach for the thermal design of complex spacecraft or aircraft models. In this paper, we suggest a gradient-based multidisciplinary optimization of thermal models where the coupled derivatives of the multidisciplinary system are obtained with the adjoint method. We show that in the case of steady-state thermal analysis, there is an analytic solution of a partial derivatives of implicit heat-transfer equation that can be used to derive total derivatives of the system. We present a practical application of this method by solving a small interplanetary spacecraft thermal optimization problem consisting of one objective, 15 design variables, and 10 constraints. We found that by using gradient-based optimization with exact derivatives, the best results can be achieved by exploring the design space at multiple initial starting points without major computational overhead.

In the last decade, growing awareness about CO2 emissions is supporting the authorities in a more sustainable society. The proposed solutions embrace different topics, such as renewable energy implementation, lower waste production, and carbon capture and storage technologies (CCS). The latter is based upon the best available knowledge about the thermophysical properties of CO2, which are not always satisfactory for its complete characterization. In this work, it is investigated the interaction of the CO2 in solid phase (dry-ice) with sandy soil, a phenomenon that can potentially occur following pipeline ruptures. An experimental setup and a numerical model have been developed to measure and validate the temperature profiles beneath the dry-ice bank at steady-state conditions. The model has been validated with the experimental data by defining a suitable range of the thermal conductivity at the solid phase (0.25–0.30 W m−1 K−1) that led to the best match (deviation of 7.81%). Finally, the overall heat transfer coefficient (85.56–86.35 W m−2 K−1) has been numerically calculated.

The minimum fluidization velocity (U mf), bubble size characteristics, and tube-to-bed heat transfer coefficient (h c) of ilmenite particles are investigated at pressures up to 2000 kPa. The U mf was found to decrease with pressure for d sv ≥ 236 μm and remain constant for d sv ≤ 109 μm. U mf was compared to various Wen and Yu type correlations (R e mf = C 1 2 + C 2 Ar − C 1) with the Saxena & Vogel (1977) constants resulting in the best fit (AARD = 10.5%) for d sv ≤ 109 μm and the Chitester et al. (1984) constants resulting in the best fit (AARD = 6.4%) for d sv ≥ 236 μm. Pressure marginally effected bubble size relative to gas velocity, with the data fitting the Mori & Wen (1975) correlation best (AARD = 26.4%). The tube-to-bed heat transfer coefficient experienced a maximum with increasing gas velocity and marginally increased with pressure. The Molerus et al. (1995) correlation matched the atmospheric heat transfer data. Unlabelled Image • Small and dense ilmenite ore particles were fluidized at elevated pressures. • Influence of pressure on minimum fluidization was dependent on particle size. • Influence of pressure on bubble size was minor relative to gas velocity. • Surface-to-bed heat transfer coefficient was not greatly affected by pressure. • Several correlations were tested to predict key design parameters. [ABSTRACT FROM AUTHOR]

An experimental investigation has been performed to study the film-cooling performance of the cylindrical holes embedded in the sine-wave-shaped-trench. The sine-wave-shaped-trench is obtained by changing the trailing edge of the transverse trench into sine-wave shape; the holes are located next to the peaks of the wave. The sine-wave-shaped-trench is expected to get a wider spread of the cooling jet in the spanwise direction. The film-cooling effectiveness, heat-transfer coefficient, and discharge coefficient of the sine-wave-shaped-trench hole configurations with different trench depths (0.75D, 1D) and wave peaks (1D, 2D) are measured by the transient thermal liquid measurement technique. The blowing ratio covers a range from 0.5 to 2.0. The transverse trench hole is investigated as a basis of the comparison. Thermal and hydrodynamic fields are investigated numerically using Reynolds-averaged Navier-Stokes (RANS) simulations with Realizable k-e turbulence model and enhanced wall treatment. Results show that broadening the wave peak of the sine-wave-shaped-trench improves the spanwise uniformity of the injection. There is a pair of anticounter-rotating vortices formed downstream of the sine-wave-trailing-edge. Increasing the trench depth shows positive effects on the heat-transfer coefficients ratio of the sine-wave-shaped-trench. The discharge coefficients of the sine-wave-shaped-trenches are higher than that of the transverse trench which means the sine-wave shape trench has a lower flow resistance. [ABSTRACT FROM AUTHOR]

Substation bus ampacity calculations perform a steady-state heat transfer analysis on a unit length of bus. In this analysis, the convective heat transfer coefficients for rectangular, universal angle bus (UAB), and integral web bus conductor (IWBC) have historically been calculated by applying flat plane correlations to the individual bus surfaces. The research presented here will show that the Nusselt correlations developed for the specific bus, similar to what is currently used for round bus, increases accuracy in bus ampacity predictions. Additionally, the correlations are easier to use and less likely to result in calculation error. This paper presents natural and forced convection correlations for rectangular, universal angle bus, and integral web bus. [ABSTRACT FROM AUTHOR]

Steady-case thermal analysis plays an important role in dimensioning thermal control systems for spacecrafts and aircrafts. Usually a trial and error approach is used based on engineering judgement and experience. When thermal models become complex or there are conflicting thermal requirements, however, it becomes harder for an engineer to gain insight as to which design decisions will lead to better results. Numerical optimization, on the other hand, could provide a more robust approach for the thermal design of complex spacecraft or aircraft models. In this paper, we suggest a gradientbased multidisciplinary optimization of thermal models where the coupled derivatives of the multidisciplinary system are obtained with the adjoint method. We show that in the case of steady-state thermal analysis, there is an analytic solution of a partial derivatives of implicit heat-transfer equation that can be used to derive total derivatives of the system. We present a practical application of this method by solving a small interplanetary spacecraft thermal optimization problem consisting of one objective, 15 design variables, and 10 constraints. We found that by using gradient-based optimization with exact derivatives, the best results can be achieved by exploring the design space at multiple initial starting points without major computational overhead. [ABSTRACT FROM AUTHOR]

• A model for NH 3 -SCR based on kinetics and computational fluid dynamics (CFD). • Model validation with SCR by monolithic Cu-ZSM-5. • Inhibition of effect of hydrocarbons in engine emission tests. A simple kinetic model for the standard NH 3 -SCR reaction by Cu-ZSM-5 catalysts has been developed by assuming three reaction steps: NH 3 adsorption (desorption), reactions of adsorbed NH 3 with O 2 (NH 3 oxidation) and NO (NH 3 -SCR). The model is based on Arrhenius parameters for NH 3 -SCR and NH 3 oxidation by a powder catalyst, combined with models for heat and mass transport and parameters of monolithic catalysts. The model is validated with the experimental results, not included in the estimation of the model, for NH 3 -SCR by monolithic catalysts with different parameters (catalyst loading and cell density). NOx removal from diesel exhaust, generated by engine bench, was also carried out by using monolithic Cu-ZSM-5 and Cu-AFX catalysts. The results suggest the poisoning effect of hydrocarbons in the exhaust emissions on NOx conversion is more significant for Cu-ZSM-5 than Cu-AFX. [ABSTRACT FROM AUTHOR]

Abstract Natural gas + water-in-diesel emulsion + AA systems with and without wax were used to investigate the influence of wax crystals and their heat- and mass-transfer effect on hydrate formation from macroscopic and microscopic aspect in a flow system. Hydrate nucleation and initial growth were found to be a partially occurred phenomenon. Wax was found to prolong the hydrate induction time through two significant effects: one was the macroscopic heat-transfer effect produced by wax deposition with insulating effect, and the other was the microscopic mass-transfer resistance originating from the wax crystals that were adsorbed at or adjacent to the oil-water interface. Hydrate induction time shortened and became less scattered with the increasing initial pressure. Based on the heat-transfer theory of a flow system and the hydrate nucleation theory, an improved model for hydrate induction time prediction was developed by coupling calculation of hydraulics and heat-transfer and by introducing mass-transfer effect of adsorption of wax crystals. The findings of this work are meaningful for providing essential information and supports for the ongoing deep-sea oil and gas production and the application of hydrate-management strategies in the presence of wax crystals in a flow system. [ABSTRACT FROM AUTHOR]

A new tyre model is developed that can predict the influence of both macroscopic and local flash temperature on tyre force generation. The model comprises two heat-transfer solvers. A macroscopic solver calculates the 3D temperature distribution across the tread and sidewall at a resolution of a few millimetres. A separate flash-temperature solver calculates the local hot-spot temperature distribution at the macro-asperity tyre-road contact interface at a resolution of micrometres. The two heat-transfer solvers are coupled with a structural model for the calculation of tyre forces and the sliding speed distribution along the contact patch. The sliding speed distribution feeds into the flash-temperature model and the local coefficient of friction is found as a function of sliding speed, flash temperature, normal pressure, road roughness and the complex modulus of rubber. The proposed tyre model is the first to include the effect of a changing macroscopic temperature distribution on the build-up of the local flash temperature, and to account for road-tread conduction at the macro-asperity contact interface. The model is applicable for identifying the friction envelope and optimum temperature range for tyres on roads with known roughness. This is important in motorsport where knowledge of grip offers a competitive advantage. [ABSTRACT FROM AUTHOR]

Energy crisis has set back the global progress on economic development, because the non-renewable energy sources are unsustainable, and renewable energy sources are not yet reliable. Therefore, improving the efficiency of energy usage becomes increasingly significant. Heat is the largest energy end-use in the world, taking good advantage of it is one of the most important subjects. Tubular heat exchangers are widely used in both civil and industrial processes, and the consumption of energy can be greatly reduced by improving the efficiency of heat transfer in pipes. Adding inserts into the pipes is a main way to enhance heat transfer. This paper mainly studies two new types of spiral spoilers, namely multi-channel spoilers and staggered spoilers, using numerical methods. The former divides the pipe into several channels, and the latter has deflecting angles at the end of every spiral period. Experiments were also conducted to verify the numerical results. Aiming at analyzing thermohydraulic characteristics of fluid flow in pipes inserted with two types of spoilers separately, the effects of channel number (N), deflecting angle (φ), pitch ratio (p'/D) were studied under different Reynolds numbers (Re). Evaluation parameters including Nusselt number (Nu), friction factor (f), heat deficit loss (e T), mechanical deficit loss (e p), exergy loss (E*) and performance evaluation criteria (PEC) were all considered as indices. Results show that flow channels and deflecting angles generate better mixed fluid, which is conducive to heat transfer enhancement at the expense of more irreversible loss. Multi-channel spoilers with a channel number N = 2 and pitch ratio p'/D = 1.5 maintain the best balance between energy loss and heat transfer. The heat transfer enhancement reaches the best performance in staggered spoilers with a deflecting angle φ = 15°, 45.07% irreversible loss can be reduced compared with φ = 120°. Staggered spoilers can enhance heat transfer better, compared with multi-channel spoilers, especially in laminar flow. • Two spiral spoilers increase the irreversible loss. • Heat deficit loss or mechanical deficit loss takes lead position. • Comprehensive index decreases with the increases of channel number. • Twist spoilers at end of each period enhance heat transfer greatly. [ABSTRACT FROM AUTHOR]

There are many emerging manufacturing processes whereby surface structures are processed by spatially laser patterning of an entire feature at a time, as opposed to rastering a small beam. It is important to ascertain and ideally control the induced thermal fields underneath the pattern. This paper develops a computational framework to rapidly evaluate the induced thermal fields due to application of a laser on the surface. The aggregate thermal fields are efficiently computed by superposing individual “beamlet” heat-kernel solutions, based on Green’s functions, to form complex surface patterns. The utility of the approach is that laser-process designers can efficiently compute the results of selecting various system parameters, such as spatially-variable laser intensity within a pattern. This allows one to rapidly compute system parameter studies needed in the manufacturing of new products. Included are:A computational framework to compute the time-transient thermal response from a spatio-temporally non-uniform laser beam in an arbitrary spatial pattern andAn analysis of how the results can be used to track the evolution of the thermal gradients and their correlation to thermal stresses. Three-dimensional examples are provided to illustrate the technique. The utility of the approach is that an analyst can efficiently ascertain a large number of laser-input scenarios without resorting to computationally-intensive numerical procedures, such the Finite Element Method. [ABSTRACT FROM AUTHOR]

Surface-roughness caused by the residue of an ablative Thermal Protection System (TPS) can alter the turbulence level and surface heating rates on a hypersonic re-entry capsule. Large-scale surface-roughness that could represent an ablated TPS, was introduced over the forebody of a 120 ° apex angle blunt cone, in order to test for its influence on surface heating rates in a hypersonic freestream of Mach 8.8. The surface heat transfer rates measured on smooth and roughened models under the same freestream conditions were compared. The hypersonic flow-fields of the smooth and rough-surfaced models were visualized to analyse the flow physics. Qualitative numerical simulations and pressure measurements were carried out to have an insight into the high-speed flow physics. Experimental observations under moderate Reynolds numbers indicated a delayed transition and an overall reduction of 17–46% in surface heating rates on the roughened model. [ABSTRACT FROM AUTHOR]

Atkinson cycle engines have become particularly popular because of high energy efficiency. A novel model considering heat-transfer, friction, and variable specific-heat has been established for an Atkinson cycle engine based on the finite-time thermodynamics. Different from the ones in previous investigations, the heat-transfer and friction losses are computed considering the effects of the cycle conditions, and the design and operation parameters. In this way, the study can have practical physical meanings and is closer to real conditions. The effects of mean piston speed, friction coefficient, cylinder bore, stroke length, stroke-to-bore ratio, equivalence ratio, and compression ratio on the energy losses and cycle performance have been investigated. The results show that there are the optimum values of compression and equivalence ratios making the cycle performance the best; the energy losses from friction, heat-transfer and exhaust process monotonously increase or decrease with respect to increasing the compression ratio. Increasing the friction loss, cylinder bore and stroke length has negative effects on the cycle performance. Increasing the mean piston speed has positive effect on the power output and the power density but less effect on the energy efficiency. The study results could provide significant guidance for designing a real Atkinson cycle engine and optimizing the performance. [ABSTRACT FROM AUTHOR]

The kinetic modeling of NH 3 -SCR with a Cu-ion-exchanged chabazite (Cu-CHA) catalyst in steady-state reactions was investigated by a combination of flow reactor experiments and kinetic modeling with an in-house computational code. Here H-CHA and Cu-CHA monolith cylindrical catalyst specimens were used to identify the reactions at both Brønsted (H+) acid sites and Cu sites. Based on the proposals in the literature for NH 3 -SCR mechanism, a scheme for SCR and side reactions incorporating 17 reactions is proposed, and some of the reactions were verified by the experimental results here for the adsorption/desorption of NH 3 , unsteady-state reactions of the adsorbed NH 3 with NO 2 over the Cu-CHA and H-CHA, and NH 3 oxidation over Cu-CHA. The Arrhenius parameters for Standard, Fast, and Slow SCR reactions, NH 3 oxidation, NO oxidation to NO 2 , NO 2 decomposition to NO, and NH 3 desorption were obtained by kinetic experiments. This report develops a quantitative simulation model for SCR and side reactions, and the model was validated by experimental data for adsorption/desorption of NH 3 and NO 2 , steady-state SCR reactions (Standard, Fast, and Slow SCR), and side reactions (NH 3 and NO oxidation). The simulation model developed in this study can predict the steady-state SCR data and adsorption/desorption of NH 3 and NO 2 under unsteady-state. [Display omitted] • Investigations of reactions over Brønsted and Lewis acid sites by Cu-CHA and H-CHA catalysts. • The identified 17 kinds of important reactions were suggested through experiments. • Ammonia nitrate (NH 4 NO 3) production in Fast and Slow SCR reactions. • The developments of a kinetic SCR model considering energy transport, mass transport, diffusion, and chemical reactions. [ABSTRACT FROM AUTHOR]

CaO sorbent is one of the most promising sorbents for CO 2 capture. However, the reactivity of CaO sorbent decreased rapidly with carbonation-calcination cycles. Steam activation is a feasible approach to improve the sorbent reactivity. In this study, the effects of steam on CaCO 3 calcination (CaO regeneration), CaO carbonation and CaO hydration were both investigated. Compared with pure CO 2 calcination atmosphere, introducing steam into calcination atmosphere enhanced CaCO 3 decomposition rate, which was because that (1) the partial pressure of CO 2 decreased; (2) the absorption of H 2 O by active site CaO* weakened the binding ability between CO 2 and CaO*; (3) the amount of heat-transfer between steam and CaCO 3 was higher. Lower decomposition temperature in steam/CO 2 calcination atmosphere resulted in lower sorbent sintering and higher sorbent reactivity. Besides, the carbonation reactivity of CaO sorbent was over doubled when steam was introduced into carbonation atmosphere, which was due to the formation of OH – . In CaO hydration reaction, sorbent particle pore structure was also developed by hydration treatment. The hydrated Ca(OH) 2 sorbent reactivity as well as cyclic reactivity of CaO sorbent was therefore enhanced. [ABSTRACT FROM AUTHOR]

Due to the ever wider use of composite materials within aerospace applications, fireproof tests get recently an increased attention. Numerical simulation is expected in the coming years to accompany engineers in their design work to increase the chance of success in the fireproof certification tests. The current research focuses on the numerical investigation of a premixed methane-air flame impinging normal to a flat composite panel. The effects of the exit burner geometry, of the Reynolds number (jet speed) and of the distance between the nozzle and the plate have been investigated. The accuracy and suitability of different turbulence models are discussed. The numerical results are validated with available experimental data. CFD calculations reproduce within 5% the so-called heat transfer efficiency where the realizable k-ε turbulence model demonstrates to be the best. The agreement to the experimental data is maximum (in the following order of importance): i) near the centre of the jet impingement, ii) for higher Reynolds number, iii) for higher distance between the panel and the flame. The Reynolds number increase conducts to an increase of the total heat transfer between the flame and the panel. This is related to the Nusselt number which presents higher value (over 20) in the regions for which the predictiveness of the calculation is found to be better. Efficient modeling parameters are found to reproduce an experimental flame that will serve later in fireproof test simulations. [ABSTRACT FROM AUTHOR]

Simulation models of welding processes allow us to predict influence of welding parameters on the temperature field during welding and by means of temperature field and the influence to the weld geometry and microstructure. This article presents a numerical, finite-difference based model of heat transfer during welding of thin sheets. Unfortunately, accuracy of the model depends on many parameters, which can not be accurately prescribed. In order to solve this problem, we have used simulated annealing optimization method in combination with presented numerical model. This way, we were able to determine uncertain values of heat source parameters, arc efficiency, emissivity, and enhanced conductivity. The calibration procedure was made using thermocouple measurements of temperatures during welding for P355GH steel. The obtained results were used as input for simulation run. The results of simulation showed that represented calibration procedure could significantly improve reliability of heat transfer model. [ABSTRACT FROM AUTHOR]