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A hybrid nanofluid (HYNF) is an excellent working medium for improved heat transfer performance. To investigate the convective heat transfer performance of an HYNF of various particle mixing ratios (MR), at first samples of MgO-SiO2/water HYNF are prepared by varying the MR of MgO to SiO2 as 0:100, 40:60, 50:50, 60:40, and 100:0 at 0.05 mass % of concentration; then convective heat transfer characteristics are determined experimentally by exposing different mass flows of HYNF from 0.03–0.27 kg/s to a constant heat flux of 5630 W/m2. The results describe that the variation in MR strongly influences the Nusselt number (Nu) of HYNF. The maximum Nu, which is 1.94 times (~ 94.50%) higher than the same with base fluid, is obtained at MR of 60:40 and the mass flow rate of 0.13 kg/s. The variation of MR does not affect the friction factor of HYNF and it is nearly comparable to that of the base fluid. Further, a new concept has been proposed to determine the thermo-economic feasibility of HYNF in heat transfer applications. It was recommended to maintain the MR at 60:40 and 0.13 kg/s mass flow rate for optimum thermo-economic performance. [ABSTRACT FROM AUTHOR]

Proper thermal management is crucial to improving the reliability of aerostatic thrust bearing with high air supply pressures. Due to the obvious temperature diffenence in the flow channel clearance, a remarkable conjugate heat transfer phenomenon exists between the gas film and solid discs. Moreover, the changes in temperature and pressure in the clearance cause apparent variations in thermal properties, which inversely effect the heat transfer characteristics of the gas film. In this study, a 3D aerostatic thrust bearing with high supply air pressure is modelled. To investigate the influence of changes in pressure and temperature in clearance on thermal properties, numerical computations are performed to solve the 3D compressible forced convection conjugate heat transfer. Based on the preceding analysis, an effective correction method of air thermal properties is proposed. The effects of thermal properties correction on 3D conjugate heat transfer of gas film are discussed, and it is demonstrated that thermal properties correction at the temperature plays an important role in the conjugate heat transfer analysis of aerostatic thrust bearing with high air supply pressures. [ABSTRACT FROM AUTHOR]

The anisotropic structure of wood will lead to a macroscopic anisotropic property in both mechanical strength and heat transfer. Previous experimental studies of wood materials were mainly focused on the mechanical property while their anisotropic thermal property in different environments is not sufficient. In this research, the anisotropic thermal performance of spruce wood is studied at different temperature, humidity, and mechanical load. The one-dimensional steady-state method and the transient plane source method are adopted to conduct the test. The thermal conductivity in both radial and longitudinal directions of spruce wood at temperature ranging from 25 °C to 422 °C, relative humidity ranging from 30 to 90 % RH, and mechanical load ranging from 0 to 20 MPa are obtained. The accuracy of the TPS method is validated using the 1D steady-state method. Both methods can be utilized to gauge the anisotropic thermal conductivity of spruce wood. Due to the unidirectional distribution of fiber, spruce wood has a longitudinal thermal conductivity that is roughly three times greater than its radial thermal conductivity. Among environmental conditions of temperature, humidity, and mechanical load, the thermal conductivity of spruce wood is varied with temperature more significantly, which is followed by humidity and mechanical load. The measurement uncertainty is also discussed. [ABSTRACT FROM AUTHOR]

Inverse heat transfer problems are used to study the thermophysical properties of promising highly porous cellular materials. The article presents the results of thermal tests on samples of these materials with different structures determined by the diameter of the cells. The thermophysical characteristics of the samples were obtained, which can be used to construct and verify mathematical models of heat transfer in highly porous cellular materials. [ABSTRACT FROM AUTHOR]

In this study, the experimental and numerical effects of using waste glass as aggregates of asphalt pavement are evaluated. The main reason for using this waste material as aggregates of hot mix asphalt (HMA) is to alleviate an environmental problem associated with asphalt pavements called urban heat islands. This phenomenon can increase the temperature in urban areas compared to their suburbs. Regarding the experimental part, two different HMA mixtures containing 100% limestone aggregates (HMAL) and 100% glass aggregates (HMAG) are made in this study. An experimental setup is used to simulate the solar radiations on top of HMA specimens. As a result, thermal parameters, including thermal conductivity, thermal diffusivity, and specific heat capacity, are measured and calculated using the heat transfer equations and the heat transfer test. These results are then used to develop finite element models for two different pavement structures with different asphalt concrete layers (one of them with HMAL and the other with HMAG). Furthermore, the air temperature data, extracted by TRNSYS software for Bechar city in Algeria, are used for modeling. The surface temperature, first and second temperatures in the asphalt pavement are obtained. The results revealed that using this waste aggregate increased the surface temperature during the day, which can make it susceptible to rutting. However, it reduced the surface temperature at night. More importantly, the HMAL absorbs 34% and released 47% more heat than HMAG during days and nights. Hence, the HMAG performance can mitigate the UHI effects. Moreover, using this waste material as aggregates in HMA can introduce a recycling method with low costs. [ABSTRACT FROM AUTHOR]

High-performance thermal insulations (HPI) have outstanding thermal properties minimizing heat transfer for a particular application. The term "high performance" is a relative assessment: whether an insulating property for a material or material system, i.e. the thermal conductivity or thermal transmittance, is significantly lower than for conventional insulating materials or systems depends on the use case and the associated conditions. Fields of applications for thermal insulations include energy, construction, industry and transport sector, as well as space and aviation industries. The total effective thermal conductivity of evacuated HPI depends on the contributions of the heat transfer via the solid skeleton of the porous insulation material and radiative heat exchange. At a given operating temperature, the effective thermal conductivity results in a minimum that depends on the density and the infrared-optically extinction properties of the insulation material. Examples for HPI with outstanding low thermal conductivity values are presented and compared with the theoretical predictions based on a percolation model for the solid thermal conductivity of the skeleton and on a diffusion model for the radiative heat transfer. [ABSTRACT FROM AUTHOR]

This paper develops an FEA modeling protocol for simulating ultra-high-performance concrete-filled double-skin tubes (CFDST) for heat transfer analysis purposes. The research presented in this paper refines the existing FE methodologies for circular, rectangular, elliptical, hexagonal, and octagonal CFDST members under fire conditions. Various modeling parameters, such as thermal properties of different materials and the thermal contact conductance at the interaction surfaces, are incorporated and controlled via an automatic algorithm for proficient modeling. It is found that the available models for calculating the thermal contact conductance at the interfaces between metal tubes and the concrete cores have a strong dependence on the cross-sectional shape. Thus, a refined model of the thermal conductance for the hexagonal and octagonal CFDST columns is proposed. Extensive experimental results (212 fire tests) are assembled from the literature to verify the proposed FE methodology. Good agreements with test results are demonstrated when predicting the temperature fields within the considered CFDST cross-sections. Consequently, extensive results from the proposed algorithm can provide an initial basis for parametric studies and for forthcoming nonlinear stress analysis simulations of CFDST columns under fire, which are primary goals in future studies. Finally, complying with the existing design codes, a new simplified analytical model based on the finite difference (FD) method is presented for predicting the temperature developments through CFDST columns. [ABSTRACT FROM AUTHOR]

This research focuses on the thermal performance of masonry walls overlayed with textile reinforced concrete (TRC) sandwich panels subjected to different climatic zones. Three types of TRC sandwich panels are explored by integrating expanded polystyrene, gypsum and calcium silicate board as core material. The TRC sandwich panels are integrated as outer layers of clay brick masonry wall panels to reduce the amount of heat transfer. Numerical simulation has been carried out using transient heat transfer analysis to determine the performance of various systems under a realistic daily temperature variation in a hot humid and warm humid climatic zone. Thermal response of TRC sandwich panel integrated masonry is validated against the requirements of a design code accepted thermal performance. From the investigations, the most feasible TRC sandwich panel solution that can be integrated for a specific climatic zone is arrived, which leads to reduced heat transfer and it is also ensured the solution satisfies codal requirements. The acceptance of proposed thermally efficient TRC sandwich panel integration with masonry would lead to environmentally friendly and sustainable alternative to achieve thermal comfort inside buildings. [ABSTRACT FROM AUTHOR]

Underground nuclear explosions generate non-isothermal two-phase flow, heat and mass transfer, and tracer transport through fractured porous media. The governing equations of these coupled phenomena on the Darcy scale are presented and the corresponding numerical code is briefly described. Two configurations are considered. In the first one, the damaged zone generated by the explosion is replaced by equivalent macroscopic boundary conditions at the bottom of the medium. Vapor condensation at distance from this zone plays a crucial role and slows down the tracer transport to the ground surface, while the presence of hot liquid water and of hot rubble particles in it accelerates it. In the second configuration, the damaged zone itself is treated as a porous medium with specific properties and is integrated in the simulation domain. Several regions can be distinguished with different properties, such as the chimney, the cavity, the solidified magma, the fractured porous medium, and the intact porous medium. Phase change, heat transfer and tracer transport can be detailed in these regions and at the boundaries between them. Among the most important conclusions, the role of phase change, of the thermal properties and therefore of the temperature, is pointed out. [ABSTRACT FROM AUTHOR]

A study was made of a thermal interface based on a two-dimensional allotropic modification of carbon (graphene), presented in the form of a powder, for cooling integrated circuits. Such physical properties of the thermal interface as thermal conductivity, heat capacity, thermal diffusivity, and density are determined by the empirical method. The process of heat transfer in the most efficient thermal interface sample during the operation of integrated circuits in the ANSYS engineering analysis system is presented. The prospects of using pressed graphene powder as a thermal interface in order to eliminate the use of a binder are described. The paper also makes a comparison with the most effective type of thermal interfaces currently in use. [ABSTRACT FROM AUTHOR]

MXene, a recently created nanomaterial, offers significant potential for thermal, electrical, and a variety of other uses. MXene was utilized to generate heat transfer nanofluids with improved thermophysical properties for thermal applications and to establish the optimal parameters for achieving the best thermal performance. In this study, a palm oil/MXene nanofluid was used as the heat transfer fluid in a circular pipe to evaluate its thermal impact at different Reynolds numbers and applied heat fluxes at a range of introduced MXene nanoparticles' concentrations. Thermal conductivity and viscosity were shown to be linked to temperature and nanoparticle concentrations ranging from 0.01 to 0.1 mass%. The influence of concerted MXene nanoparticles (0.01 to 0.1 mass%) on the behavior of the PO/MXene nanofluid was studied using CFD simulations at various flow Reynolds numbers (2,500–5,000) and wall heat fluxes (40,000–90,000 W.m−2). The results indicate that increasing the nanoparticle concentration resulted in higher heat transfer coefficients and lower Nusselt numbers. MXene nanoparticles were more efficient at lowering the wall temperature and increasing the pace of cooling when applied at larger heat fluxes and lower Re numbers. The results reported in this article indicate that MXene nanomaterials have a strong potential for overcoming the low heat transfer difficulties encountered in heat exchange systems. [ABSTRACT FROM AUTHOR]

In this research, two alternative approaches to fractional derivatives, namely Caputo–Fabrizio (CF) and Atangana–Baleanu (AB) fractional operators, are used to propose a generalized model of thermoelastic heat transfer of a rigid cylinder with thermal characteristics. The proposed model can be constructed by combining the DPL model with phase delays and the two temperature theories. It will be taken into account that the solid cylinder has variable physical properties. It was also assumed that the surface of the cylinder is penetrated by a continuous magnetic field and is regularly exposed to thermal loading from a continuous heat source. The numerical solutions of the studied physical fields in the AB and CF fractional derivative cases were derived using the Laplace transform method and are compared visually and tabularly and discussed in detail. [ABSTRACT FROM AUTHOR]

Carbonate sands (CS) have the potential to be utilized as construction materials, and their porous particles may bring unique thermal properties, which is critical for the thermal design of geosystems; however, this area of research is highly understudied. The present work provides a new contribution in this field by investigating the thermal conductivity (λ) of five uniform fractions of CS from the South China Sea, with emphasis on the influence of particle size and relative density of the sand. The impact of the size of particles on the index void ratios and thermal conductivity of the samples was profoundly different from that of silica sands. Contrary to silica sands, the extreme void ratio (emax, emin), which is critical for calculation of relative density, of the CS increased as the mean grain size increased. The maximum thermal conductivity of each fraction was negatively correlated with the particle size, and the thermal conductivity of the finer fractions exhibited higher sensitivity to the packing density. Literature models were found to be ineffective in predicting the thermal conductivity of the CS given the unique thermal energy transferring mechanisms of the porous particles. Two thermal conductivity models, stemming from semi-analytical and empirical approaches, were proposed in the light of providing useful guidance for the thermal designs that include CS. [ABSTRACT FROM AUTHOR]

Traditional ice and snow removal methods damage roads. In this paper, the thermal performance and a heat transfer model of conductive ethylene propylene diene monomer rubber composites in pavement were studied. The thermal performance was determined by snow melting tests. An active snow melting model was established and compared with the test results. The temperature field and energy distribution of the conductive rubber composite, upper asphalt layer, and lower asphalt layer were determined. The results show that the conductive rubber composite can be used to melt snow at a low voltage. Active snowmelt pavement can melt 10 mm of snow in 58 min at − 5 °C. For the same mass of snow and ice, snow melts faster than ice. Draining the melted water can shorten the snow melting time. However, capillary action weakens the drainage effect. In addition, the test results verify the accuracy of the numerical simulation. The energy absorbed by the structures was determined by the finite element model. The energy utilization rate for snow was determined to be 24.27%. This study determines the thermal properties of conductive rubber composites in pavement. A new active snow melting method and a finite element model are proposed. Furthermore, the model is convenient for energy analysis and engineering optimization. [ABSTRACT FROM AUTHOR]

In recent years, with the adaptation of nanotechnological engineering applications to complex systems, the use of nanofluids with better thermo-physical properties compared to conventional fluids has become widespread. In addition, studies on the preparation techniques of nanofluids, improving their thermal properties and evaluating their thermal performance are increasing. This study presents a review about preparation, evaluating and enhancement of the stability and thermal properties of nanofluids. Furthermore, the recent advances about the thermo-hydraulic, thermodynamic and thermo-economic performances of nanofluids in different types of thermal systems are summarized as well. The stability of nanofluid is a significant factor affecting its applicability. Various techniques have been used in the literature to enhance the stability of nanofluids such as surfactant addition, ultrasonic mixing and pH control. By using nanofluids, the desired thermo-physical properties can be obtained in order to improve the heat transfer property in the system. Some researchers recommend to hybrid nanofluids because of the hybrid effect of two or more particle types they contain. The reviewed literature also indicates that the use of nanofluids instead of conventional working fluids is an effective way to increase the thermo-hydraulic performance of thermal systems. In addition, according to the literature review, minimum entropy generation is an effective way to increase the energy efficiency and improve thermodynamic performance of the thermal system and the use of nanofluids provide a significant reduction in entropy production. [ABSTRACT FROM AUTHOR]

In order to predict the evolution of the vulcanization process of cork-rubber slabs, a numerical approach was developed combining heat transfer by conduction and kinetics models. A one-dimensional model was applied to predict the evolution of temperature and degree of cure at different stages of the vulcanization of a cork-rubber composite. Also, due to the degradation verified by the compound, an existent reversion model was added to the problem. Based on rheometer data, cure and reversion parameters were determined. Experimental data were used to determine the thermal properties of the compound, assuming a constant value or according to its degree of cure and temperature. The results obtained by simulation showed a good correspondence with experimental results, even when assuming constant thermal properties. The application of the proposed methodology provides information about the optimum process parameters for each thickness slab, without compromising the homogeneity and characteristics of the final product, which can be a valuable tool during the development and product stages of cork-rubber composites. [ABSTRACT FROM AUTHOR]

Heat transfer enhancement by suspending nano-sized particles in a liquid, called nanofluid, has attracted considerable attention over the past few decades. The underlying mechanisms are an area of active research. The present study focused on the inhomogeneous and non-isotropic aspects of the thermophysical properties of nanofluids. A non-equilibrium molecular dynamics simulation was conducted, such that the temperature gradient was applied directly to the simulation domain where various particles were located, and local and directional characteristics of the heat transfer were investigated. The ordered structure in the liquid region next to the liquid-solid atomic interface played a critical negative role in altering the thermal properties that could not be predicted through the simple composite model of Maxwell. The formed liquid structure was sensitive to the surroundings, and the size, shape, and multi-particle arrangement affected the performance accordingly. Two nano-particles oscillating in the temperature-gradient direction were significantly effective in enhancing heat transfer. [ABSTRACT FROM AUTHOR]

The motorized spindle will produce a lot of heat at high speed, thereby making the physical structures deformed and changing the bearing performances. However, the interaction between thermal and mechanical characteristics has not been deeply studied. This paper aimed to consider the coupling of interference fit, centrifugal effect, and thermal effect in these components to build a comprehensive and optimized spindle model. Firstly, the displacements related to contact angles under the thermo-mechanical coupling effect were analyzed, and the oil film factor was added to the bearing static model to be studied together with centrifugal force and gyroscopic moment of the ball. Next, based on thermal network method, a quasi-3D model of cooling water pipe was established by considering its structural characteristics. Meanwhile, for the discussion of the number of balls and their thermal resistances, the heat transfer between the bearing ring and the ball was investigated and improved. Lastly, the influences of thermal characteristics on bearings parameters and spindle temperature rise were investigated under different speed, cooling water, and oil-air variables, which provide a reference for regulating and controlling motorized spindle. [ABSTRACT FROM AUTHOR]

Hole shrinkage is a common phenomenon in drilling difficult-to-cut materials like Ti6Al4V due to their poor thermal properties and high elasticity, which can lead to increase in tool wear and decrease in surface integrity. In this study, an in-depth analysis of hole shrinkage mechanism is carried out through a hybrid modelling approach for both dry and cryogenic cutting conditions. The plastic deformation induced by chip formation and tool-workpiece interaction is treated as equivalent thermomechanical loads, and heat convection conditions are described along tool path in order to perform details in heat transfer process for both cases. Quantitative analysis is presented through numerical simulation and experimental data of temperature and deformation along hole contour to analyze deformation components in order to reveal the hole shrinkage mechanism. Additional interactions between cutting tool and workpiece material are induced by recovery of elastoplastic deformation, and plastic portion is a more devastating factor in tool wear and surface damage induced by hole shrinkage. This study presents an in-depth and fundamental understanding of the hole shrinkage mechanism through a hybrid modelling approach, which can characterize heat transfer process during machining for both dry and cryogenic conditions, and simulation of this fully coupled thermomechanical cutting process with supply of coolants was rarely reported in previous research. The results show that plastic deformation induced hole shrinkage can enhance the interaction between workpiece material and cutting tool, and cryogenic assistance presents a good performance in restricting this kind of phenomenon. The related results could be used to optimize strategies of eliminating hole shrinkage with cryogenic assistance in industrial applications. [ABSTRACT FROM AUTHOR]

Knowledge about the thermal properties of human teeth is imperative for accurate understanding of heat transfer in dentistry. Despite the presence of specific heat in thermal conduction and heat transfer equations, and requiring this parameter for calculation of conductivity based on diffusivity, adequate attention has not been paid to experimental assessment of specific heat of the human enamel and dentin. Specific heat can be a temperature-dependent property. Thus, this study aimed to assess the specific heat of the human enamel, sound dentin, and carious dentin at 20 °C to 70 °C temperature (which is the realizable temperature range in dental procedures) using the differential scanning calorimetry (DSC). The results showed that the specific heat of the enamel, sound dentin and carious dentin increased with temperature rise. The specific heat of the enamel, sound dentin and carious dentin at 20 °C to 70 °C ranged from 709 J·kg−1·K−1 to 921 J·kg−1·K−1, 880 J·kg−1·K−1 to 1139 J·kg−1·K−1 and 951 J·kg−1·K−1 to 1311 J·kg−1·K−1, respectively. [ABSTRACT FROM AUTHOR]

The present analysis describes the effect of dissipative heat energy transfer in Ethylene–Glycol (EG) based on conducting nanofluid over a heated semi-infinite vertical plate past through a porous medium. Uniform magnetic field, heat source/sink, and the effect of particle concentration also have been discussed by incorporating in the energy and solutal transfer equations, respectively. In addition to that, the thermal properties of the nanofluid are affected by the thermal slip boundary condition since; the temperature slip is favorable for the reduction in the heat transfer. Assuming self-similar transformations, the governing PDEs are transformed into non-linear coupled ODEs. These transformed equations are solved by using semi-analytical techniques such as Adomian Decomposition Method (ADM). The characteristics of different parameters on the flow phenomena are obtained and presented via graphs. The numerical values of the thermophysical properties of both the nanoparticles and the base fluid are shown in the table. Validation of the present work is obtained by comparing our result with the earlier established result and it is found that both the results are coinciding with each other. However, the main quantified results are the following: due to heavy density of the Cu nanoparticles, increasing volume fraction in ethylene–glycol base fluid resists the fluid motion and the inclusion of dissipative heat energy is favorable to enhance the nanofluid temperature. [ABSTRACT FROM AUTHOR]

Improved heat transfer efficiency with considering economic analysis in heating systems is an interesting topic for researchers and scientists in recent years. This research investigates the heat transfer rate (HTR) and flow of non-Newtonian water-Carboxyl methyl cellulose (CMC) based Al2O3 nanofluid in a helical heat exchanger equipped with common and novel turbulators using two-phase model. The requirements for dimensions and cost reduction and also energy saving in thermal systems are the main goal of this study. According to gained results usage of corrugated channel in helical heat exchanger has a considerable influence on thermal and hydraulic performance evaluation criteria (THPEC) index of helical heat exchanger and can improve the THPEC index. Thus, Re = 5000 is obtained as an optimum value, in which the maximum THPEC value is achieved. As it is found in this paper, in case of using novel heat exchanger instead of the basic smooth system, the thermal properties (by considering Nusselt number) increases about 210%, the hydraulic performance (friction factor) reduces about 28%, performance evaluation criteria index increases about 57% and the material consumption (in case of similar THPEC) decreases about 31%. In another word, with considering economic analysis for the basic and novel system which has same efficiencies, the novel one has lower length and consequently 31% lower material. [ABSTRACT FROM AUTHOR]

In present work, semiconducting iron (III) oxide (Fe2O3) nanoparticles have been synthesized by sol–gel method. X-ray diffraction (XRD), UV–Visible (UV–Vis) absorption spectroscopy and transmission electron microscopy (TEM) have been used for the characterization of the synthesized nanoparticles. Two-step technique was used to formulate stable ethylene glycol (EG) based Fe2O3 nanofluids at room temperature. Thermal conductivity of nanofluids has been measured using hot disc thermal constants analyzer. Significant enhancement in the thermal conductivity is noted at very low nanoparticle loading (up to 1 wt%). Ultrasonic velocity and ultrasonic attenuation in the prepared nanofluids were investigated using an ultrasonic interferometer and acoustic particle sizer (APS-100), respectively. APS-100 was also used for the analysis of particle size distribution (PSD) of Fe2O3 nanoparticles in the prepared nanofluids. The PSD result of APS-100 has been found in good agreement with that of TEM. The characteristics behaviour of Fe2O3 nanofluid has been illustrated based on its ultrasonic and thermal properties. Our investigations advocate that Fe2O3 nanofluids have potential application for effective heat transfer management in various cooling industries. [ABSTRACT FROM AUTHOR]

Establishing and optimizing a distributed parameter thermal path model for transformer windings is an important means to analyze the hot-spot temperature of the windings; furthermore, in the process of improving the thermal path model of transformers and improving the accuracy of their models, the thermal characteristics of the insulation paper are extremely important. A microscopic thermal contact resistance model was established for the contact interface of insulation paper and copper, according to the microscopic morphology parameters of copper and insulation paper observed by atomic force microscopy, the thermal contact resistance under different temperatures was calculated. A dual heat flow test platform was built to test the heat transfer behavior of four different thickness insulation papers under four temperatures, and the thermal contact resistance and thermal bulk resistance with temperature were analyzed. The results show that as the temperature increases, the thermal resistance of the insulation paper becomes larger and the thermal conductivity decreases. The average error between the experimental and theoretical values of the thermal contact resistance under four temperature points in the study is 6.6%. The results provide a data support for establishing and optimizing transformer heat generation and heat transfer models. [ABSTRACT FROM AUTHOR]

Marquetry method is important in the culture of the Italian community as can be witnessed from the large quantity of artworks that have been realized in this way. The monitoring of the integrity of such pieces poses a great challenge given the need for a reliable and nondestructive technique able to detect surface and subsurface defects. In this work, two ancient marquetry samples containing natural defects were inspected thanks to active thermography by using time-tested, safe, and resilient advanced signal processing algorithms (i.e., principal component thermography, correlation contrast, pulsed phase Fourier transform amplitude and phase, cold image subtraction contrast, and polynomial fitting). The latter have been applied to provide a 2D map of the defects. Anyway, in the cultural heritage field, one of the main interests of restorers is the volume of the subsurface defects for structural analyses. The emphasis in this study is placed on the use of dynamic thermal tomography (DTT) as an advanced technique of active thermal nondestructive testing. The main concepts of DTT are illustrated in the manuscript, while a special technique for defect thermal characterization has been used during the second analysis to validate tomographic results. Finally, the position of the main defects retrieved by means of the established techniques applied during the first analysis has been confirmed by DTT. [ABSTRACT FROM AUTHOR]

This paper is concerned with the measurement of thermal properties and in-cavity pressures in cold chamber high-pressure die casting. The influence of in-cavity pressure on the casting porosity, heat flux, and heat transfer coefficient has been investigated during die casting of an A380 alloy. The die was instrumented with heat transfer and pressure sensors to measure these values directly. Direct measurement of the in-cavity pressure was found to be more reliable than the metal pressure calculated from pressure measurements in the hydraulic system. Variations on the intensification pressure directly affect the in-cavity pressure. Changing the intensification pressure between 17 MPa and 90 MPa had little effect on the heat flux and heat transfer which likely reach saturation at a lower pressure during the rapid filling stages. Increases in intensification pressure reduced the level of porosity within the castings, being most effective up to a value of 67.4 MPa. [ABSTRACT FROM AUTHOR]

In this work, the convection heat transfer and pressure drop of the turbulent flow for a non-Newtonian fluid containing nanoporous graphene were investigated in baffled heated annulus tube by considering the inner tube under constant heat flux. The solution of 0.2 mass% carboxymethyl cellulose (CMC) in DI water was used as the base non-Newtonian fluid. The rheological properties of the nanofluid (0.2 mass% nanoporous graphene, 0.2 mass% CMC and DI water) were measured through an experimental setup. By measuring the thermophysical and rheological properties at several temperatures, the temperature-dependent equations were calculated by a least square approximation method. By using the extracted equations and adding the nanoporous graphene to the base fluid in the annulus, the thermal performance was numerically investigated. Furthermore, the effects of the geometry and perforated baffles number at the various Reynolds numbers were studied. According to the results, the nanoporous graphene had a significant effect on the average Nusselt number and pressure drop which were increased by up to 32 and 75%, respectively, compared to the base fluid. It was also predicted that in the annular tubes possessing three and seven baffles with four holes (Re = 4000 and H = 4 mm), applying nanoporous graphene can improve the efficiency of the system up to 11.9%. [ABSTRACT FROM AUTHOR]

In this article, thermal analysis of radial moving fins of hyperbolic and rectangular profiles is performed. A time-dependent nonlinear differential equation modeling heat transfer in a radial moving fin is considered. The thermal conductivity and heat transfer coefficient are modeled as linear and power-law functions of temperature, respectively. The analytical solutions are generated using the differential transform method which is an analytical solution technique that can be applied to various types of differential equations. The accuracy of the analytical solutions is validated by benchmarking against the numerical solutions obtained by applying the inbuilt numerical solver in Maple (pdsolve). A good agreement is observed between the analytical and numerical solutions. The effects of embedding parameters on the dimensionless temperature and heat transfer rate are analyzed. The results show that the fin rapidly dissipates heat to the surrounding fluid with an increase in the speed of the moving fin, that is, an increase in the values of the Peclet number. The results also show that the heat transfer through a rectangular fin is more efficient when compared to a fin of hyperbolic profile. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the variation of physiological responses and mortality of day-old chicks subjected to different thermal conditions and exposure times during simulated transport. For this purpose, day-old chicks (n = 900) were used and subjected to simulated conditions of transport in a climate chamber. The experimental design was a completely randomized block design, with the structure of the treatments in a 3 × 3 factorial scheme (thermal ranges and time intervals) and each level of containers considered a block. The physiological variables used in this trial were body weight, respiratory rate, cloacal temperature, average surface temperature, and gene expression of heat shock protein (HSP70). Regarding body weight, a small variation was observed between treatments (P > 0.05). The animals subjected to the heat treatment exhibited respiratory rates above 100 movements per minute (P < 0.05), average cloacal temperatures above 44.7 °C, surface temperatures above the comfort zone (greater than 39.6 °C; P < 0.05), and increased gene expression of HSP70 (P < 0.001), especially after 3 initial hours of exposure. In addition, the heat treatment lead to increased mortality of the animals (over 6%). Also in the cold treatment, despite the absence of mortality, the animals showed hypothermia from 3 h of exposure, based on the results of the average surface (28 °C) and cloacal temperatures (39.6 °C; P < 0.05). In this way, the results imply that the effects of thermal stress caused by heat as well as by cold in a simulated transport condition are increased when traveling for more than 3 h, indicating a trend of rising mortality after long-term transportation of day-old chickens. [ABSTRACT FROM AUTHOR]

Molten-salt-based nanofluids and ionic-liquid-based nanofluids are developed for thermal storage and heat transfer at relatively high temperatures, in the past few years. Preparation and stabilization techniques are briefly introduced firstly, and then, thermal properties, e.g., specific heat, thermal conductivity and viscosity, are summarized and discussed in detail. The properties are not only affected by the characteristics of nanomaterials and base fluids, but also affected by the synthesis method, such as the sonication intensity and duration. Some of the thermophysical property data are still incomplete, especially the thermal conductivity of molten-salt-based nanofluids, and properties of ionic-liquid-based nanofluids at high temperatures. While several literature works show that the Krieger–Dougherty model can well predict the viscosity, no general models for thermal conductivity and specific heat have been developed yet for both types of nanofluids. [ABSTRACT FROM AUTHOR]

The procedure of numerical identification of thermophysical properties of concrete during its hardening is presented. Heat of cement hydration, thermal conductivity and specific heat are determined for purpose of modelling temperature evolution in massive concrete elements. The developed method is based on point temperature measurements in a cylindrical mould and the numerical solution of the inverse heat transfer problem by means of direct search optimization algorithm. The determined thermal characteristics of concrete are not constant and depend on the maturity of concrete. The procedure was verified on set of concrete mixes designed with Portland cement CEM I 42.5R and Portland-slag cement CEM II/B-S 32.5 N. Calcareous fly ash was also used for partial replacement of cement in the mixtures. The obtained results have been compared with experimentally measured temperature in concrete and a fair agreement has been found. [ABSTRACT FROM AUTHOR]

Low-melting-point alloy has the characteristics of high thermal conductivity, low solidus temperature and the wide range of use temperature, which is a potential heat transfer medium. The microstructure and thermal properties of Sn–Bi–Pb–Zn alloys as heat transfer and storage material were investigated in this paper. The phase compositions, microstructure and thermal properties were investigated by X-ray diffusion (XRD), electron probe microanalysis (EPMA) and differential scanning calorimeter (DSC) analysis, respectively. The results show that the phases of Sn–Bi–Zn and Sn–Pb–Zn alloys are mainly eutectic formed by solid solution, while the formation of Pb7Bi3 intermetallic compounds decreases the melting point of Sn–Bi–Pb and Bi–Pb–Zn. The thermal properties of the zinc-containing alloys are better than that of Sn–Bi–Pb, but the weight of the zinc-containing alloys significantly reduces above 900 °C. As the density, specific heat capacity and thermal diffusivity change with temperature and physical state, the thermal conductivity of the alloys first decreases and then increases. These results demonstrate the feasibility of using low-melting alloys as the heat transfer and storage material. [ABSTRACT FROM AUTHOR]

A wide range of speculation regarding lithospheric thermal thickness in a region calls for quantifying the uncertainties associated with model parameters. In this paper, we present an attempt to decipher it by solving the differential equations governing the heat transfer through the lithosphere. Adequately quantifying the temperature field is very important, since it is highly dependent on the controlling thermal parameters. Thermal conductivity is modeled as a random parameter with a known mean value and correlation structure. We compute the temperatures in the crust and lithospheric mantle, along with their error bounds, using an analytical solution to the steady-state heat equation and the Adomian method of decomposition. We apply these solutions in the Archean Dharwar craton, which is divided into western Dharwar craton (WDC) and eastern Dharwar craton (EDC). We obtain a Moho temperature estimate of 304 ± 58 °C in WDC, whilst in EDC it is 375 ± 74 °C for a 20% coefficient of variability in thermal conductivity. The range of lithospheric thickness obtained for WDC is 150-280 km, and 110-160 km for the EDC. These values are in agreement with other geophysical and geological findings in the region. The thermal lithosphere obtained from this study is based on the mantle solidus and the surface wave seismological studies considering radial anisotropy reveal that the lithosphere is characterized by higher shear wave velocities, and decrease at the lithosphere-asthenosphere boundary. Average shear velocity model for two different cratonic blocks (EDC and WDC) is used to show the LAB thickness for the eastern and western Dharwar craton. The two independent studies show a correlation in the lithospheric thickness. [ABSTRACT FROM AUTHOR]

Hybrid nanofluid can be considered as a new generation of nanofluids. Despite the success of the researchers in the field of hybrid nanofluids, no acceptable model has been proposed yet that can accurately predict the thermal conductivity of these nanofluids. The nanofluids, containing carbon nanotubes, are not excluded. This research to provide a model based on previous models to predict the thermal conductivity of hybrid nanofluids containing carbon nanotubes. For this reason, the thermal conductivity of MWCNT-MgO/water-EG nanofluids was experimentally measured. The experimental data were in seven solid volume fractions from 0.015 to 0.96%, in which the tests have been done at the temperature range 30-50 °C. A modified conventional model (as a proposed correlation in present study) can produce better results in forecasting the experimental data. The predicted data error by modified Jang-Choi model as proposed correlation was less than 3%. In addition, the price-performance analysis of the thermal conductivity data shows that hybrid nanofluids are better than single particle nanofluids. [ABSTRACT FROM AUTHOR]

The tendency of the polymers to melt and drip when they are exposed to external heat source play a very important role in the ignition and the spread of fire. Numerical simulation is a promising methodology for predicting this behaviour. In this paper, a computational procedure that aims at analyzing the combustion, melting and flame spread of polymer is presented. The method models the polymer using a Lagrangian framework adopting the particle finite element method framework while the surrounding air is solved on a fixed Eulerian mesh. This approach allows to treat naturally the polymer shape deformations and to solve the thermo-mechanical problem in a staggered fashion. The problems are coupled using an embedded Dirichlet-Neumann scheme. A simple combustion model and a radiation modeling strategy are included in the air domain. With this strategy the burning of a polypropylene specimen under UL-94 vertical test conditions is simulated. Input parameters for the modelling (density, specific heat, conductivity and viscosity) and results for the validation of the numerical model has been obtained from different literature sources and by IMDEA burning a specimen of dimensions of 148×13×3.2mm3. Temperature measurements in the polymer have been recorder by means of three thermocouples exceeding the 1000 K. Simultaneously a digital camera was used to record the burning process. In addition, thermal decomposition of the material (Arrhenius coefficient A=7.14×1016min-1 and activation energy E=240.67kJ/mol) as and changes in viscosity (μ) as a function of temperature were obtained. Finally, a good agreement between the experimental and the numerical can be seen in terms of shape of the polymer as well as in the temperature evolution inside the polymer. [ABSTRACT FROM AUTHOR]

In this paper, an enriched FEM technique is employed for thermo-mechanical contact problem based on the extended finite element method. A fully coupled thermo-mechanical contact formulation is presented in the framework of X-FEM technique that takes into account the deformable continuum mechanics and the transient heat transfer analysis. The Coulomb frictional law is applied for the mechanical contact problem and a pressure dependent thermal contact model is employed through an explicit formulation in the weak form of X-FEM method. The equilibrium equations are discretized by the Newmark time splitting method and the final set of non-linear equations are solved based on the Newton-Raphson method using a staggered algorithm. Finally, in order to illustrate the capability of the proposed computational model several numerical examples are solved and the results are compared with those reported in literature. [ABSTRACT FROM AUTHOR]

Three main types of cryothermal vacuum units for testing spacecraft products at liquid-helium temperature are considered. Methods for heat removal from test objects depending on their geometric and thermophysical properties are presented. The designs of the different thermal vacuum chambers are discussed considering the thermophysical processes occurring in them. The operating efficiency of the thermal vacuum chambers and their advantages and disadvantages are estimated based on an analysis of heat-transfer processes. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cell (SOFC) systems can be fueled by natural gas when the reforming reaction is conducted in a stack. Due to its maturity and safety, indirect internal reforming is usually used. A strong endothermic methane/steam reforming process needs a large amount of heat, and it is convenient to provide thermal energy by burning the remainders of fuel from a cell. In this work, the mathematical model of afterburner-powered methane/steam reformer is proposed. To analyze the effect of a fuel composition on SOFC performance, the zero-dimensional model of a fuel cell connected with a reformer is formulated. It is shown that the highest efficiency of a solid oxide fuel cell is achieved when the steam-to-methane ratio at the reforming reactor inlet is high. [ABSTRACT FROM AUTHOR]

Nowadays, the thermal insulation both of existing and new buildings is one of the most important actions for reducing the energy loss of buildings and to reduce the emission of green house gases. In the European Union, buildings account for about 20-40% of the total final energy consumption. Examination of the thermal properties (e.g., effective thermal conductivity) of building materials and structures are very important both for the manufacturers and for the consumers. Several possibilities are available for measuring this parameter of materials. The mainly used thermal insulating materials are the plastic foamy and mineral wool materials; moreover, the nanotechnological insulators (e.g., aerogel, hollow nanospheres) are requiring spaces for themselves also. One promising them for the future is the silica aerogel-based slabs. Aerogels are nanoporous lightweight materials that were discovered more than 70 years ago. Nowadays, their applications are truly widespread. Firstly, in this article thermal transmittance measurements of wall structures will be presented with calibrated chamber method. These measurements were accomplished through an inbuilt plaster/brick/plaster wall construction individually. After that, it was covered with a 0.013-m-thick aerogel layer at first in a cold and then in the warm side. Comparison of the heat fluxes, insulation capabilities and effective thermal conductivities measured by the above-mentioned method will be presented. The change in the retardation time and in the surface temperatures will be also discussed. Secondly, in order to investigate the conductive effect, thermal conductivity measurements with Holometrix lambda 2000 apparatus were accomplished too. [ABSTRACT FROM AUTHOR]

The propositions of the development of reactor systems using UF6 as the nuclear fuel were put forward in USSR and USA already in the fifties of the last century, while from the beginning of the seventies the UF6-based reactors have become considered as the power sources for spaceborne nuclear power plants (NPP). The application of UF6 circulating in the closed NPP contourmakes it possible to realize the potential advantages of the flow-through design due to the gaseous fuel mobility compared with the existing NPPs with solid cores. At different plant designs, reactor arrangements, and special flow organization in fuel elements the power range from hundreds of kilowatts to tens megawatts can be realized. The areas of application of power plants with circulating UF6 can, in particular, include the spaceborne NPPs of wide power range for electric and plasma rocket engines used in the manned flight to Mars, the reactor-laser with direct pumping of gaseous laser mixtures with nuclear fission products, and the on-ground nuclear electric power plants of new generation with high performance with respect to the fuel cycle and safety. On the basis of an analysis of the results of investigations performed in USSR and USA to the end of the nineties of the last century and presented in this overview it can be concluded that from the standpoint of the physics of working processes and constructional materials resistant in the UF6 environment, there are no insurmountable obstacles for developing the NPPs with circulating UF6. The list of problems, whose solution can favor the further development of this line of research, if it would be implemented, is formulated. In Section 1 the fuel element designs are described and the techniques of flow organization in them are experimentally validated. In Section 2 the computational and experimental support of the programs is presented. It includes the calculations of the fluid dynamics and heat and mass transfer, the thermal and transport properties of uranium hexafluoride, the special properties of uranium hexafluoride as a working body, and the uranium hexafluoride effect on the constructionalmaterials. In Section 3 the projects of spaceborne power plants of closed and open type on a wide power range are reviewed. In Section 4 one of the promising lines in the field of the nuclear energy use, namely, the reactor-laser development, is presented. Section 5 overviews the on-ground plants, where, apart from the electric power plants, of interest are transport power plants, high-temperature engineering systems, in particular, for hydrogen production, the plants for producing high neutron fluxes, and some others. Section 6 presents considerations concerning the realization of rig reactor experiments with uranium hexafluoride circulating in the reactor core, whose criticity is fully ensured by the gaseous UF6. These experiments could be the final stage in corroborating the power source of the new type both under space and on-ground conditions. Section 7 contains an analysis of the available publications on the state of the art of investigations in the United States, which allows one to suppose that in USA a vast program of studies on the use of nuclear reactors with circulating UF6 in the space and on-ground energetics is being systematically performed. In Section 8 some problems which need to be solved in developing the power plants with circulating uranium hexafluoride are listed; they require a vast amount of scientific research. The work on the determination of the design of the power plants with circulating UF6 and hydrodynamic processes occurring in them were conducted in the Keldysh Research Center (before 1976 the Institute of Thermal Processes) under the supervision of A.A. Pavel'ev, who was the author of many ideas in the field of hydrodynamic stability and turbulence realized in experimental setups and computationmethods. In memory of his invaluable contribution into this line of research the authors dedicate to him this overview. [ABSTRACT FROM AUTHOR]

Fast estimation of thermal transmittance based on temperature measurements is uncertain, and the obtained results can be burdened with a large error. Nevertheless, such attempts should be undertaken merely due to the fact that a precise measurement by means of heat flux measurements is not always possible in field conditions (resentment of the residents during the measurements carried out inside their living quarters), and the calculation methods do not allow for the nonlinearity of thermal insulation, heat bridges or other fragments of building envelope of diversified thermal conductivity. The present paper offers the estimation of thermal transmittance and internal surface resistance with the use of temperature measurements (in particular with the use of thermovision). The proposed method has been verified through tests carried out on a laboratory test stand built in the open space, subjected to the influence of real meteorological conditions. The present elaboration involves the estimation of thermal transmittance by means of temperature measurements. Basing on the mentioned estimation, the authors present correction coefficients which have impact on the estimation accuracy. Furthermore, in the final part of the paper, various types of disturbance were allowed for using perturbation numbers, and the introduced by the authors “credibility area of thermal transmittance estimation” was determined. [ABSTRACT FROM AUTHOR]

Rigid polyurethane foam (PUF) is one of the outstanding insulation materials and has been widely used in freezers and cryogenic facilities. Among the various blowing agents used in the manufacturing PUF, water-blown PUF is attracting much attention as environmentally friendly PUF as prominent replacements for the environmentally hazardous CFCs and HCFCs due to their significant ozone depletion potential. We investigated the effective thermal conductivity of PUF blown with different amounts of water, on the basis of the heat transfer mechanisms in terms of thermal conduction of solids and gases and the thermal conductivity of radiation in the cells. A predictive model for the effective thermal conductivity of PUFs with different densities is presented. The predictive model was validated by comparing the predicted values with the experimentally measured ones. The result showed that the effective thermal conductivity increased from 0.023 to 0.027 W m−1 K−1 as the PUF density increased from 48 to 120 kg m−3: increased by 158% from 0.0034 to 0.0089 W m−1 K−1 for the thermal conductivity of solid PUF and decreased by 50% from 0.0037 to 0.0018 for the thermal conductivity of radiation. [ABSTRACT FROM AUTHOR]

An experimental and numerical investigation was conducted to characterize the influence of the cellulosic substrate used to assess the ignition propensity (IP) of cigarettes. Such an IP test is currently prescribed by the ISO 12863 standard and its results typically show poor repeatability. It is believed that such a low reproducibility is mainly due to the variability of the cigarette itself but it is unclear as to what extent the substrate also influences the variability of the test results. Therefore, the objective of this investigation was to analyze the potential influence of the substrate by first characterizing the thermodynamic behavior experimentally and then constructing a numerical model that can quantify the relative influence of the distinct parameters. A suite of experimental methods that included TGA, DSC, infrared measurements and laser triangulation among others was used to measure the thermophysical properties of the substrate. These properties were then used to build a CFD model that simulated the smoldering combustion experienced by the substrate during the IP test. After validating the model against contactless temperature measurements, a parametric study consisting of 363 IP simulations was performed, which served to quantify the relative importance of 13 thermophysical parameters when varying in ranges of about 5%-50%. The results indicated that the heat capacity, pyrolysis activation energy, and air gap thickness are the most influencing aspects of the substrate because they influence the heat absorbed by the substrate about 7%, 26% and 33%, respectively. The latter parameter was found to significantly vary with each test and its influence was comparable to that of some major properties of the cigarette such as the cigarette’s temperature and burning rate. It is therefore postulated that the variability of the substrate itself plays an important role on the poor repeatability of the test and it may comprise its reliability. [ABSTRACT FROM AUTHOR]

Nanofluids are advanced heat transfer fluids that exhibit thermal properties superior than that of the conventional fluids such as water, oil etc. This paper reports the experimental study on convective heat transfer characteristics of water based titanium dioxide nanofluids in fully developed flow through a uniformly heated pipe heat exchanger fitted with modified butterfly inserts. Nanofluids are prepared by dispersing TiO2 nanoparticles of average particle size 29 nm in deionized water. The heat transfer experiments are performed in laminar regime using nanofluids prepared with 0.1% and 0.3% volume fractions of TiO2 nanoparticles. The thermal performance characteristics of conventional butterfly inserts and modified butterfly inserts are also compared using TiO2 nanofluid. The inserts with different pitches 6 cm, 9 cm and 12 cm are tested to determine the effect of pitch distance of inserts in the heat transfer and friction. The experimental results showed that the modification made in the butterfly inserts were able to produce higher heat transfer than conventional butterfly inserts. [ABSTRACT FROM AUTHOR]

In this article a new methodology is introduced to create a ladder-type analytical thermal model for microscale channel based heatsink structures. The presented model is applicable to determine the local heat transfer(s) and the temperature distribution along the channel depending on the channel geometries, the thermal properties of the fluid and the wall temperature(s). The channel is divided into several segments and for each segment a T-equivalent circuit is created. The ladder-type thermal model obtained by applying the T-equivalent subcircuit as a building block can be used as a compact model of microscale channel structures. This model was implemented in a conventional thermal field solver (CTFS) simulation tool to augment the capability of simulating the thermal impact of integrated heat sink structures even with radial channel pattern. The implementation steps and the results are compared to the analytically calculated, CFD modelled and measured values. This augmented CTFS engine gives the opportunity to investigate the operation of system-on-package devices by electro/logi-thermal simulation. [ABSTRACT FROM AUTHOR]

We present the results of studying the effect of technological synthesis regimes of a solar furnace using the method of a partial metal reduction of one of the oxides on the phase formation of cermet composite materials of the TiO2–CuO system. It has been established that the phase composition of the synthesized cermet composite materials depends on the carbon concentration, melting temperature and cooling rate. The dependence of the spectral-optical properties of selectively absorbing coatings on the production technology and properties of synthesized composite materials has been presented. It has been found that the coatings fabricated by melting in air with overheating at a melt cooling rate of about 105–106°C/s have the highest values of the integral absorption coefficient, αs = 91.0–94.5%. [ABSTRACT FROM AUTHOR]

The method, procedure, and results of the investigation of a high-speed air plasma flow effect on the structure of an ultrahigh-temperature coating made for a composite silicon carbide material are considered. The coating is based on hafnium diboride, silicon carbide, and oxides of hafnium, yttrium, and zirconium. The effect of a high-speed plasma flow on the samples was studied in a VAT-104 wind tunnel (Central Aerohydrodynamic Institute); this facility enables simulation of the conditions of high-velocity flight in the upper atmosphere. During the tests, the main parameters of the plasma flow were recorded, and the temperature distribution of the sample was measured. The weight loss of the samples was determined. Using the results of numerical parametric simulation of flow past and heat transfer of the samples, the catalytic activity of the coating was determined. After testing in a high-enthalpy flow, X-ray diffraction analysis and X-ray phase analysis of the samples were performed, and their surface microstructure was analyzed. [ABSTRACT FROM AUTHOR]

We have employed noise thermometry for investigations of thermal relaxation between the electrons and the substrate in nanowires patterned from 40-nm-thick titanium film on top of silicon wafers covered by a native oxide. By controlling the electronic temperature $$T_\mathrm{e}$$ by Joule heating at the base temperature of a dilution refrigerator, we probe the electron-phonon coupling and the thermal boundary resistance at temperatures $$T_\mathrm{e}= 0.5$$ -3 K. Using a regular $$T^5$$ -dependent electron-phonon coupling of clean metals and a $$T^4$$ -dependent interfacial heat flow, we deduce a small contribution for the direct energy transfer from the titanium electrons to the substrate phonons due to inelastic electron-boundary scattering. [ABSTRACT FROM AUTHOR]

This research focuses on the Cattaneo-Christov theory of heat and mass flux for a three-dimensional Maxwell liquid towards a moving surface. An incompressible laminar flow with variable thermal conductivity is considered. The flow generation is due to the bidirectional stretching of sheet. The combined phenomenon of heat and mass transport is accounted. The Cattaneo-Christov model of heat and mass diffusion is used to develop the expressions of energy and mass species. The first-order chemical reaction term in the mass species equation is considered. The boundary layer assumptions lead to the governing mathematical model. The homotopic simulation is adopted to visualize the results of the dimensionless flow equations. The graphs of velocities, temperature, and concentration show the effects of different arising parameters. A numerical benchmark is presented to visualize the convergent values of the computed results. The results show that the concentration and temperature fields are decayed for the Cattaneo-Christov theory of heat and mass diffusion. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on ac losses of superconducting bulk with the help of finite element software of Comsol Multiphysics. The calculation ac loss result was compared with that from analytical formulas for type-II superconducting slab and cylinder. Three different geometries of the columnar bulk are analyzed, which are bulk with no core, bulk with a central columnar air core, and bulk with a central columnar iron core. The core is parallel to the c-axis of bulk. The temperature dependence of the ac loss is presented, and the thermal behavior of the bulk is analyzed by associating ac loss with heat transfer characteristic through the external surface of the bulk sample. [ABSTRACT FROM AUTHOR]