Conductive Heat Flux Research Articles

Heat and mass transfer analysis of non-Newtonian power-law nanofluid confined within annulus enclosure using Darcy-Brinkman-Forchheimer model

Non-Newtonian fluids are encountered in many engineering applications, such as the petroleum industry and lubrication. In this investigation, the Magnetohydrodynamic (MHD) and convective boundary (heater) are assumed to analyze the heat transport phenomena of non-Newtonian type Carboxy-Methyl-Cellulose (CMC)/Aluminum oxide (Al2O3) hybrid nanofluid in an annulus enclosure. A porous medium saturates the enclosure under the privileges of Darcy-Brinkman law. Galerkin Finite Element Method (GFEM) is employed for numerical findings. Power-law type non-Newtonian-nanofluid is investigated for different volume fractions (φ) in an aqueous solution of CMC. The flow and the thermal behavior of the nanofluid are investigated for dissimilar values of Rayleigh (Ra), Hartman (Ha), and Darcy (Da) numbers and power-law index (n). The average Nusselt (Nuavg) and Bejan (Beavg) numbers were evaluated for the nanofluid flow. The results indicate that the present composition of nanofluid enhances the heat transfer inside the enclosure. This effect can be further improved by increasing Ra and Da numbers or decreasing the power-law index or magnetic forces. The Da number and power-law index are excellent control parameters for entropy generation. Overall, these results offer a good lead into the design and optimization of thermal performance within an annulus enclosure inundated by a Darcy medium. On the other hand, the outcomes also indicate that, at Ra = 1000, owing to the limited drive of fluid flow inside the cavity, the conduction heat flux is predominant, and the upsurge of the parameter n hasn't a significant effect on Nuavg variations. At the highest Ra, increasing n, and Ha, reduced Nuavg by 50% and 40%, respectively. While increasing, Da improved Nuavg by 245%.

Electrical resistivity of the Fe–Si–S ternary system: implications for timing of thermal convection shutdown in the lunar core

The composition of the lunar core has been suggested to be Fe-rich with varying amounts of lighter elements, such as Si and S. Presence of Si and S affects electrical and thermal transport properties and thus influences core thermal processes and evolution. Paleomagnetic observations constrain a high intensity magnetic field that ceases shortly after formation of the moon (~ 3.5–4.2 Ga year ago), and thermal convection in the core may contribute to generation of this field. In this study, the electrical resistivity of Fe-14 wt% Si-3 wt% S was measured in both solid and molten states at pressures up to 5 GPa and thermal conductivity was calculated via the Wiedemann–Franz Law from the electrical measurements. The results were used to estimate the adiabatic conductive heat flux of a molten Fe-14 wt% Si-3 wt% S lunar core and compared to a Fe-2-17 wt% Si lunar core, which showed that thermal convection of either core composition shuts down within the duration of the high intensity magnetic field: (1) 3.17–3.72 Ga year ago for a Fe-14 wt% Si-3 wt% S core; and (ii) 3.38–3.86 Ga years ago for a Fe-2-17 wt% Si core. Results favouring compatibility of these core compositions with paleomagnetic observations are strongly dependent on the temperature of the core-mantle boundary and time-dependent mantle-side heat flux.

Development and assessment of five-component wall boiling heat flux partitioning model

A mechanistic framework of wall boiling model with the total heat flux partitioned into five components, i.e. solid quenching, sliding-induced transient conduction, lift-off induced transient conduction, evaporation and single-phase convection, is developed and implemented into the unsteady two-fluid solver in the OpenFOAM. As important sub-models, bubble departure diameter, lift-off diameter and sliding length are calculated based on force balance analysis. A two-phase wall function is employed to account for the effect of nucleated bubbles on the near-wall turbulence. The developed model framework is assessed with the DEBORA experiment with the R12 as work fluid at the pressure of 1.46 MPa and 2.62MPa. The assessment indicates that the two-phase wall function improves prediction of liquid and vapor velocity profile and that the void fraction, the liquid and wall temperature can be well predicted. Under the condition of lower pressure and higher surface heat flux, bubble grows faster, which increases bubble departure and lift-off diameter. Higher liquid mass flux increases quasi-steady drag force and shear lift force, which consequently reduces the bubble departure and lift-off diameter. Due to large nucleation site spacing, relatively large sliding length appears in the lower-pressure cases. Nucleation awaiting time dominates the bubble departure frequency which increases steeply when the near-wall liquid approaches saturated. Comparing with the RPI model, the current model predicts relatively small evaporation heat flux. The predicted solid quenching and transient conduction heat flux induced by bubble lift-off are less significant in all the cases. The calibrated algebraic bubble size model can be adequate in the simulation of subcooled boiling at high pressure condition.

Temporal instability of confined three-dimensional liquid jet with heat and mass transfer under longitudinal acoustic oscillations

The temporal instability of a confined viscous liquid jet surrounded by high-speed co-flowing viscous gas phase is studied in this work. The effect of the longitudinal acoustic oscillations, which is regarded as gas axial velocity oscillations, is also considered. The heat and mass transfer is characterized by the ratio between conduction heat flux and the evaporation heat flux; then, an explicit dispersion relation equation is obtained. The results suggest that more than one unstable region appears because of the gas velocity oscillations, including Kelvin–Helmholtz (K–H) instability and parametric instability regions. Increasing the forcing frequency enhances the K–H instability, while it has a stabilizing effect on the parametric instability. In addition, the liquid jet tends to be more unstable in non-axisymmetric modes when the gas rotating strength is strong. Although the gas viscosity has a destabilizing effect on the gas–liquid interface, the destabilizing effect is weak due to the low viscosity of the gas phase. According to the linear instability theory, the dominant wavenumber will locate in the most unstable region. Moreover, the parametric instability in non-axisymmetric modes may be observable when the Weber number is large.

Enhanced 2D finite element model and its application in laser cutting of carbon fiber reinforced plastic composites.

A tailored 2D finite element model (FEM) is proposed to describe the temperature distribution and stress distribution by the UV nanosecond pulsed laser cutting of carbon fiber reinforced plastic (CFRP) composites. This model coupled thermodynamic and thermal stress and considers the heat conduction, thermal stress, and heat flux effects during the UV laser cutting of CFRP composites. In this study, the main mechanism of UV laser cutting of CFRP is elucidated, such as pressure gradient, plasma, and vaporization effects. The temperature field and stress field in a single pulse period are successfully simulated based on these theoretical models. We believe that this research will supply a theoretical reference for the UV laser cutting of CFRP composites and pave the way for applications in the aerospace industry in the future.

Radiative Coefficients and Their Influence on In-Depth Heating of Porous Ablators

High entry speeds and exotic planetary gases can result in significant radiative heat loads on space capsules. The mechanism behind the transport of radiative signatures is fundamentally different from the conductive mode of energy transport, and penetration of radiative signatures depends on the radiative coefficients of the thermal protection system (TPS) material that protects the space capsule. The radiative coefficients of carbon-based and silica-based fibrous materials have been computed as functions of wavelength using the photon path length Monte Carlo method by explicitly accounting for the microstructure of the material. Significant variations in the radiative coefficients are observed at wavelengths that are relevant to shock-layer emissions. Although carbon-based fibrous materials exhibit higher absorption coefficients in comparison to silica-based systems, the absorption coefficients of carbon-based material drop by two orders of magnitude in the range of 100–200 nm. The radiative coefficients of carbon-based fibrous material are seen to be dominated by scattering and absorption with minimal transmission. However, the transmission coefficients for the silica system dominated the radiative coefficients in the range of 100–1000 nm, which corresponds to most shock-layer emissions. The radiative coefficients are used to solve the radiative transfer equation using the P-1 approximation to obtain the in-depth radiative heat flux. The total energy equation for decomposing porous TPS materials is solved with the radiative heat flux from the P-1 approximation and the conductive heat flux using the Fourier law. It is observed that peak temperatures inside the material are higher when radiative transport is explicitly accounted for through the P-1 approximation. Small variations in the absorption coefficient of the silica-based materials also affected the in-depth temperature profiles. Additionally, a broader temperature distribution is obtained inside the material with a low absorption coefficient, and the charring density profiles are influenced by the radiative heat flux. This study demonstrates that it is important to include radiative transport in material response solvers, and radiative coefficients must be accurately computed by accounting for the microstructure of the material.

Snow redistribution onto young sea ice: Observations and implications for climate models

Vertical heat conduction through young ice is a major source of wintertime sea ice growth in the Arctic. However, field observations indicate that young ice preferentially accumulates wind-blown snow, resulting in greater snow thickness on young ice than would be expected from precipitation alone, and hence greater snow thickness on young ice than climate models represent. As snow has a low thermal conductivity, this additional snow thickness due to redistribution will reduce the actual heat conduction. We present new observations from the Multidisciplinary drifting Observatory for the Study of Arctic Climate Expedition which show that young ice rapidly accumulates a snow thickness of 2.5–8 cm, when wind-blown snow is available from the nearby mature ice. By applying a simple redistribution scheme and heat flux model to simulated conditions from the Community Earth System Model 2.0, we suggest that neglecting this snow redistribution onto young ice could result in the potential overestimation of conductive heat flux—and hence ice growth rates—by 3–8% on average in the Arctic in the winter in the absence of climate feedbacks. The impacts of snow redistribution are highest in the springtime and in coastal regions.

The Significance of Convection in Supraglacial Debris Revealed Through Novel Analysis of Thermistor Profiles

AbstractMelt from debris‐covered glaciers represents a regionally important freshwater source, especially in high‐relief settings as found in central Asia, Alaska, and South America. Sub‐debris melt is traditionally predicted from surface energy balance models that determine heat conduction through the supraglacial debris layer. Convection is rarely addressed, despite the porous nature of debris. Here we provide the first constraints on convection in supraglacial debris, through the development of a novel method to calculate individual conductive and nonconductive heat flux components from debris temperature profile data. This method was applied to data from Kennicott Glacier, Alaska, spanning two weeks in the summer of 2011 and two months in the summer of 2020. Both heat flux components exhibit diurnal cycles, the amplitude of which is coupled to atmospheric conditions. Mean diurnal nonconductive heat flux peaks at up to 43% the value of conductive heat flux, indicating that failure to account for it may lead to an incorrect representation of melt rates and their drivers. We interpret this heat flux to be dominated by latent heat as debris moisture content changes on a diurnal cycle. A sharp afternoon drop‐off in nonconductive heat flux is observed at shallow depths as debris dries. We expect these processes to be relevant for other debris‐covered glaciers. Debris properties such as porosity and tortuosity may play a large role in modulating it. Based on the present analysis, we recommend further study of convection in supraglacial debris for glaciers across the globe with different debris properties.

Computational study on the flame and extinction behavior of a high enthalpy air slab

A solid fuel ramjet has been recognized as a viable contender for atmospheric supersonic flight due to its performance and simple construction. However, the static temperature increases due to shock compression at the inlet that results in high temperature air entering the combustor. As such, the goal of this study is to analyze how the kinetics and flame sustainment properties are altered with this higher enthalpy air exposure. To examine these effects, a slab burner is modeled with gaseous using OpenFOAM© software. The reaction processes are modeled using complete University of California San Diego chemical-kinetic mechanism for burning in a hydrogen–air environment. Temperatures in the air intake range from 300 to 1000 K in 100 K increments, with the hydrogen fuel temperature kept at 300 K. In examining the conductive and convective heat flux data at the fuel surface, two distinct temperature regimes appeared for each respective heat flux mechanism. The results showed a large drop in conductive heat flux seen only between inlet temperatures of 300 and 500 K. Conversely, convective heat flux saw an increase in heat flux as a fully turbulent flow was approached for temperatures between 600 and 1000 K. In analyzing the Damköhler numbers of involved reactions, it was found that higher temperatures activated an endothermic chain branching reaction, which contributed significantly to the OH radical pool. This activation prevented a large drop in conductive heat flux for high inlet air temperatures. The results showed the impact of inlet temperatures on reaction pathways, which allows improved flame holding at higher air velocities.

Numerical Prediction of the Heat Transfer in Air Gap of Different Garment Models

Abstract This study aims to investigate the characteristics of heat transfer and its mechanism for styling a design garment differently, and to improve thermal comfort caused by clothing styling design, a computational fluid dynamics (CFD) approach has been used to perform numerical investigations of fluid flow and heat transfer across a clothing air gap. Relationships between the heat transfer from the body to clothing (computed by heat transfer equations) and the air gap were examined by body heat loss of different styles of garments. Also, the clothing temperature distribution of different garments was obtained and compared. Computed results reveal that the air gap can play a central role in the heat transfer from the body to the surface of different style garments. When the air gap is small enough, namely about 5 mm in the chest and bust of the X-type of clothing, the conductive heat flux can transfer through the air gap and reach the cloth surface easily, which will bring about the increase of temperature on the clothing surface. The decreasing air gap distance from 50 mm (O-type) to 10 mm (X-type) increases the convective heat flux by up to 25% on the waist. However, the airspeed will increase to greater numbers while the air gap decreases to narrow channels, and it will bring about fierce forced convection heat flux. So the heat transfer must be considered in the process of garment design, and the air gap should be kept at a suitable level. These findings can be used to improve the clothing’s thermal comfort or optimize the cloth structure.

Comparative Analysis of Machine Learning and Numerical Modeling for Combined Heat Transfer in Polymethylmethacrylate.

This study has compared different methods to predict the simultaneous effects of conductive and radiative heat transfer in a polymethylmethacrylate (PMMA) sample. PMMA is a type of polymer utilized in various sensors and actuator devices. One-dimensional combined heat transfer is considered in numerical analysis. Computer implementation was obtained for the numerical solution of the governing equation with the implicit finite difference method in the case of discretization. Kirchhoff transformation was used to obtain data from a non-linear equation of conductive heat transfer by considering monochromatic radiation intensity and temperature conditions applied to the PMMA sample boundaries. For the deep neural network (DNN) method, the novel long short-term memory (LSTM) method was introduced to find accurate results in the least processing time compared to the numerical method. A recent study derived the combined heat transfer and temperature profiles for the PMMA sample. Furthermore, the transient temperature profile was validated by another study. A comparison proves the perfect agreement. It shows the temperature gradient in the primary positions, which provides a spectral amount of conductive heat transfer from the PMMA sample. It is more straightforward when they are compared with the novel DNN method. Results demonstrate that this artificial intelligence method is accurate and fast in predicting problems. By analyzing the results from the numerical solution, it can be understood that the conductive and radiative heat flux are similar in the case of gradient behavior, but the amount is also twice as high approximately. Hence, total heat flux has a constant value in an approximated steady-state condition. In addition to analyzing their composition, the receiver operating characteristic (ROC) curve and confusion matrix were implemented to evaluate the algorithm’s performance.

Numerical prediction of slug flow boiling heat transfer in the core-catcher cooling channel for severe accident mitigation in nuclear power plant

This paper presents the steps followed to implement and validate a hybrid multiphase flow model in the open-source code, OpenFOAM. The modeling approach couples the interface capturing model with the dispersed flow model. The resulting multiphase model can be used to predict the slug flow boiling regime. The flow regime in question occurs during the external cooling of a core-catcher and in-vessel retention (IVR) which are severe accident mitigation strategies. A distinctive key feature of this multiphase-type flow is the co-existence of large-scale slug vapor bubbles with both dispersed vapor bubbles and the carrying liquid phase. The slug vapor bubbles are generated from the coalescence of the smaller dispersed bubbles. Also, due to the tilted orientation of the core-catcher and reactor vessel lower head (for the IVR option), these large-scale bubbles remain in the vicinity of the heated surface, while being transported by the flow. This is due to the buoyancy force acting upward in these two design configurations. The latter phenomenon engenders the fact that a liquid film is occupying a thin layer separating the large bubbles from the heated surface. Under such flow conditions, the existing wall boiling model, commonly known as the (Rensselaer Polytechnic Institute) RPI model, has been demonstrated to be inadequate for the determination of the boiling heat transfer characteristics. Therefore, an extended near-wall boiling model accounting for the conduction heat flux across the liquid film (trapped underneath the slug bubbles) is formulated and implemented in this study. Using this enhanced model, the simulation of a slug flow boiling on a downward-facing heated surface produces a better prediction of the wall superheat than the original model. In addition, the morphologies of the vapor slug coexisting with dispersed bubbles are adequately captured and compared fairly well with experimental visualizations. This new multiphase model is then used to simulate a prototypical core-catcher cooling channel. Once again, a fair representation of the wall heat transfer is predicted in good agreement with measurements. Finally, it has been also successfully proven that under subcooled nucleate flow boiling conditions, the present model can reproduce the RPI model predictions.

Influences of changing sea ice and snow thicknesses on simulated Arctic winter heat fluxes

Abstract. In the high-latitude Arctic, wintertime sea ice and snow insulate the relatively warmer ocean from the colder atmosphere. While the climate warms, wintertime Arctic surface heat fluxes remain dominated by the insulating effects of snow and sea ice covering the ocean until the sea ice thins enough or sea ice concentrations decrease enough to allow for direct ocean–atmosphere heat fluxes. The Community Earth System Model version 1 Large Ensemble (CESM1-LE) simulates increases in wintertime conductive heat fluxes in the ice-covered Arctic Ocean by ∼ 7–11 W m−2 by the mid-21st century, thereby driving an increased warming of the atmosphere. These increased fluxes are due to both thinning sea ice and decreasing snow on sea ice. The simulations analyzed here use a sub-grid-scale ice thickness distribution. Surface heat flux estimates calculated using grid-cell mean values of sea ice thicknesses underestimate mean heat fluxes by ∼16 %–35 % and overestimate changes in conductive heat fluxes by up to ∼36 % in the wintertime Arctic basin even when sea ice concentrations remain above 95 %. These results highlight how wintertime conductive heat fluxes will increase in a warming world even during times when sea ice concentrations remain high and that snow and the distribution of snow significantly impact large-scale calculations of wintertime surface heat budgets in the Arctic.

Dissipation of energy and higher-order fluctuations of the largest fragment charge in projectile fragmentation

Abstract The higher-order fluctuations of the largest fragment charge were found to exhibit the signatures of a second-order phase transition in experimental data and simulations of the statistical multifragmentation model recently (Pietrzak et al 2020 Phys. Lett. B 809 135763). This work is devoted to study the dissipation of energy and higher-order fluctuations of the largest fragment charge in projectile fragmentation. The isospin-dependent quantum molecular dynamics (IQMD) model is used to study the non-equilibrium thermalization and fragmentation. The statistical code GEMINI is applied to simulate the second decay of the pre-fragments. To reveal how the incident energy dissipates into the excitation energy of the projectile-like system, the time evolution of the density, collective velocity, and random kinetic energy are displayed. It is found that the competition between the heat conduction and heat flux affects the excitation energy of the projectile-like system, which is the key variable in the fragmenting process. Displaying the mean multiplicity of the intermediate mass fragments and the higher-order fluctuations of the largest fragment charge, it is found that the decay mechanism of the projectile-like system transfers from the multi-fragmentation at mid-peripheral collision into the nucleon-evaporation at peripheral collision. The pseudo-critical point of this transition can be indicated by the zero of third order fluctuation together with the minimum of fourth order fluctuation. The calculations of the pseudo-critical point by the IQMD + GEMINI model agree with that extracted from the experimental data. Finally, the influences of the pseudo-critical point by the second decay, the mass number of the colliding system, and the incident energy are studied.

An experimental study of the summer and winter thermal performance of an opaque ventilated facade in cold zone of China

As a promising envelope technology for energy saving, opaque ventilated facades (OVFs) have spread to various climates and regions. Nevertheless, few reports have been published on their application in a typical continental climate zone with hot summers and cold winters, especially in China. Within the framework of a Chinese nationally funded project, comparative experiments were conducted on two full-scale test rigs to assess the thermal and energy performance of an OVF in cold zone of China. By comparing the conductive heat flux across the internal wall, the facade design features, including joint opening ratio, external cladding color, air vents openness and cavity width, showed substantial impacts on the thermal behaviors of the OVFs. It was highlighted that the surface solar radiation control features most affected the summer performance, while those restricting the cavity ventilation dominated winter. By integrating the optimal solutions for each design feature, the summer- and winter-optimal OVF configurations were proposed, bringing 11.4% and 6.5% energy use reductions compared to a conventional monolithic facade, respectively. Moreover, the daytime energy-saving effects of the OVFs were proved more significant, meaning that they were more suitable for daytime use buildings. However, considering the highly differed structures for these optimal OVFs, an integrated configuration was further qualitatively proposed through a normalized analysis of all tested facades, aiming for the optimal annual performance with minimal construction and operation complexities. These results provide general guidelines for designing performance-optimized OVFs while demonstrating a climatically representative sample from cold zone of China.

Simulation of CZTSSe kesterite thin film photovoltaics with TiO2 or CdS/ZnO: Comparing the electrical and thermal properties

The optical, electrical and thermal properties of two Cu2ZnSn4SxSe4−x (CZTSSe) based thin film solar cells with TiO2 and CdS/ZnO electron transport layer (ETL) were investigated through 2D and 3D mapping simulations. The simulations compared the optical photogeneration rates, current-voltage characteristics of the two cells, Shockley-Read-Hall (SRH) recombination rate and the electric-field distribution at the interface of CZTSSe and ETL materials by solving the coupled drift-diffusion, Poisson, and rate equations. The maximum non-radiative SRH recombination is 2.5 × 1028 1/m3s at CSSs/TiO2 interface which is half of it at CZTSSe/CdS/ZnO interface (5 × 1028 1/m3. s). This is because of the electric-field spike at the CdS/ZnO/ITO interface which enhances the electron passivation at this interface and in turn improves the open-circuit voltage of the CZTSSe/CdS/ZnO based solar cell to 0.55 V. The heat generation in the two cells was also simulated by solving the heat equation coupled with electrical and optical wave equations. SRH recombination heat is higher in CZTSSe/CdS/ZnO cell (1010 W/m3) compared to cell with CZTSSe/TiO2 (0.4 × 1010 W/m3) due to less average heat conductivity of CdS/ZnO. The conductive heat flux is higher at the junction of CZTSSe/TiO2 (5 × 105 W/m2) which is over 10 times more than the heat conduction flux at the junction of CZTSSe/CdS/ZnO (2 × 104 W/m2). The practical outcome of this simulation is that although CdS/ZnO is a better ETL material for electrical characteristics of the cell, the thermal stability of the cell is better with TiO2 layer. This might be a guiding outcome for practical realization of CZTSSe solar cell structures with high thermal stability.

The sensitivity of parameterization schemes in thermodynamic modeling of the landfast sea ice in Prydz Bay, East Antarctica

Abstract Based on the measurements conducted over the landfast sea ice in Prydz Bay, East Antarctica during the sea-ice growth season in 2016, various parameterization schemes in the high-resolution thermodynamic snow/ice model HIGHTSI are evaluated. The parameterization scheme of turbulent fluxes produces the largest errors compared with the parameterization schemes for other surface heat fluxes. However, the sea-ice thickness simulation is most sensitive to the differences in upward longwave radiation at the surface. In addition, the sea-ice thickness simulation during the growth season is highly sensitive to the oceanic heat flux, and a new oceanic heat flux parameterization scheme based on the bulk method is proposed. The new parameterization scheme is tested in a second year, and it significantly improves the model performance relative to the standard configuration when compared against observations. Finally, the seasonal variation in the heat budget and its influence on the sea-ice thickness variation are analyzed. The net shortwave radiation, sensible heat flux and conductive heat flux (the net longwave radiation and latent heat flux) are found to be the surface heat sources (heat sinks) during the growth season. The larger conductive heat flux and the smaller oceanic heat flux can intensify the growth of sea ice.

Enhancing anisotropy of thermal conductivity based on tandem acoustic Bragg reflectors

Thermal metamaterials have emerged as one of the latest research topics in applied science due to breakthrough advantages in modifying conductive heat flux. An acoustic Bragg reflector (ABR), composed of alternating arrays of two materials with contrasting acoustic impedances, is anticipated to coherently manipulate the transport properties of thermally important phonon branches by attaining interface roughness close to the monoatomic scale. However, there is a lack of research on how a narrow portion of the phononic band of a particular ABR can be extended to cover the entire thermal spectrum. Here, we report a modeling study of thermal transport using ABR, representatively based on GaAs/AlAs, GaN/AlN, or HfO2/SiO2 superlattices. Our calculations show that the anisotropy of thermal conductivity in HfO2/SiO2 can be significantly improved by tandemizing four different ABR layers, thus approaching the theoretically anticipated values based on monolayered materials. This work demonstrates how the tandem ABR can expand forbidden phononic bands beyond that occupied by a single ABR and proposes a practical strategy for realizing spectrally functionalized thermal properties from compound semiconductor materials that can be directly integrated into the existing device fabrication processes.

Numerical Prediction of Convective Heat Flux on the Flight Deck of Naval Vessel Subjected to a High-Speed Jet Flame from VTOL Aircraft

This study examines the heat flux and convective heat transfer generated when a vertical take-off and landing (VTOL) aircraft takes off and lands on the flight deck of a naval vessel. A procedure for analyzing the convective heat transfer imposed on the deck by the high-temperature and high-velocity impingement of a VTOL jet is described. For the analysis, the jet velocity and the deck arrival temperature were calculated by applying computational fluid dynamics (CFD), assuming that the heat flow is an impingement jet. The relationships between the diameter of the jet, the speed of impingement, and the exhaust temperature of VTOL are introduced to assess the inlet condition. Heat flow was analyzed using CFD techniques, and Reynolds-averaged Navier–Stokes (RANS) and k-ε models were applied to model the turbulent motion. A procedure for evaluating the convection coefficient and convective heat flux from the calculated local velocity and temperature is presented. Simultaneously, a method for compensating the convection coefficient considering the singular velocity at the stagnation point is proposed. Furthermore, the accuracy was verified by comparing the convective heat flux and deck temperature predicted using CFD with the existing experimental studies. Finally, by applying finite element analysis (FEA) based on the thermal-structural interaction, the magnitude of thermal deformation due to conductive temperature and heat flux was presented as a design application of the flight deck.

The influence of magnetic and gravitational fields in a non-ideal dusty gas with heat conduction and radiation heat flux

The influence of magnetic and gravitational fields in a non-ideal dusty gas with heat conduction and radiation heat flux