Simulation Of Coupled Heat Transfer Research Articles

Coupling Conduction, Convection and Radiative Transfer in a Single Path-Space: Application to Infrared Rendering

In the past decades, Monte Carlo methods have shown their ability to solve PDEs, independently of the dimensionality of the integration domain and for different use-cases (e.g. light transport, geometry processing, physics simulation). Specifically, the path-space formulation of transport equations is a key ingredient to define tractable and scalable solvers, and we observe nowadays a strong interest in the definition of simulation systems based on Monte Carlo algorithms. We also observe that, when simulating combined physics (e.g. thermal rendering from a heat transfer simulation), there is a lack of coupled Monte Carlo algorithms allowing to solve all the physics at once, in the same path space, rather than combining several independent MC estimators, a combination that would make the global solver critically sensitive to the complexity of each simulation space. This brings to our proposal: a coupled, single path-space, Monte Carlo algorithm for efficient multi-physics problems solving. In this work, we combine our understanding and knowledge of Physics and Computer Graphics to demonstrate how to formulate and arrange different simulation spaces into a single path space. We define a tractable formalism for coupled heat transfer simulation using Monte Carlo, and we leverage the path-space construction to interactively compute multiple simulations with different conditions in the same scene, in terms of boundary conditions and observation time. We validate our proposal in the context of infrared rendering with different thermal simulation scenarios: e.g., room temperature simulation, visualization of heat paths within materials (detection of thermal bridges), heat diffusion capacity of thermal exchanger. We expect that our theoretical framework will foster collaboration and multidisciplinary studies. The perspectives this framework opens are detailed and we suggest a research agenda towards the resolution of coupled PDEs at the interface of Physics and Computer Graphics.

A multi-time scales semi-decoupled CHT (Coupled Heat Transfer) model and its application on piston transient heat transfer simulation

Transient CHT simulations between in-cylinder combustion and chamber components are difficult to achieve due to time scale issues. In this study, a multi-time scales semi-decoupled CHT model is proposed and verified by mature CFD (Computational Fluid Dynamics) tools (e.g., Openfoam, Star CCM+, and Fluent) in a simple structure. Then, the established model is used to simulate the transient CHT process between the in-cylinder combustion and the piston. The calculated results are compared with the experimental results of the piston hardness plug. The 1D (one Dimensional) analysis demonstrates that the amplitude of the solid temperature fluctuation reaches an equilibrium state almost at the beginning of the calculation. The comparative results show that the calculation speed of the multi-time scales semi-decoupled CHT model is increased by about 15 to 20 times. The accuracy of the calculated results of the four methods is highly consistent (the difference is less than 0.4 °C). In the coupled heat transfer simulation of the piston and in-cylinder combustion, only four in-cylinder cycles are calculated to achieve the convergence of piston temperature. The hardness plug test value on the piston's top surface is higher than the peak value of the temperature wave.

A broadband metamaterial absorber with flexible low infrared radiation

In this paper, based on split resonant ring (SRR) and NaCl solution (NS), a conformal and low thermal infrared radiation (LTIR) broadband metamaterial absorber (MA) with double SRRs and NS resonant cavity is proposed. Through simulation and measurement, it is proved that the proposed absorber has electromagnetic (EM) wave absorptivity of more than 90% under different polarization angles and different conformal conditions at 9.58–24.42 GHz. By introducing microfluidic channels, coupled electromagnetic thermal and coupled heat transfer simulations demonstrate that the design MA can maintain the thermal stability and LTIR characteristics under different power EM waves irradiation with low flow velocity (0.05 m s−1). Based on its good absorption performance and LTIR performance, it can be predicted that the proposed MA will have great application value in non-planar surface EM wave stealth and infrared stealth.

The "teapot in a city": A paradigm shift in urban climate modeling.

Urban areas are a high-stake target of climate change mitigation and adaptation measures. To understand, predict, and improve the energy performance of cities, the scientific community develops numerical models that describe how they interact with the atmosphere through heat and moisture exchanges at all scales. In this review, we present recent advances that are at the origin of last decade’s revolution in computer graphics, and recent breakthroughs in statistical physics that extend well-established path-integral formulations to nonlinear coupled models. We argue that this rare conjunction of scientific advances in mathematics, physics, computer, and engineering sciences opens promising avenues for urban climate modeling and illustrate this with coupled heat transfer simulations in complex urban geometries under complex atmospheric conditions. We highlight the potential of these approaches beyond urban climate modeling for the necessary appropriation of the issues at the heart of the energy transition by societies.

Unsteady Coupled Heat Transfer Simulation of Unsteady numerical simulation of slot flow in anti-heating tile

An unsteady coupled heat transfer solver is developed in the study. The coupled solver, solving the partial differential equations for fluid flow and thermal conduction in the solid, is employed to predict the unsteady heat and transfer in the anti-heating tile. The influence of gap depth on the fluid flow and solid thermal conduction is studied. The results show that the flow field distribution between the different gap depths is similar, otherwise reducing the gap depth is conducive to reducing the thermal load in the bottom plate.

Coupled heat transfer simulations for evaluation of thermal performance during hydrogen absorption in cylindrical uranium-based hydride beds

In this work, we established a three-dimensional coupled heat transfer model to evaluate the heat transfer during the hydrogenation reaction process in a uranium-based hydride bed. We constructed numerical simulations combined with the proposed model using Fluent to systematically investigate the influence of structure configurations, cooling media, and material thermal–physical properties on the thermal performance. Importantly, because the coolant temperature and the bed wall continuously changed during the hydrogen recovery process, the solid–liquid interface temperature had to be considered for an efficient thermal design of the bed wall cooling system. Accordingly, a coupling iteration algorithm was developed to improve the temperature prediction accuracy. In addition, we systematically investigated the effects of layer thickness, thermal conductivity, and cooling systems on the heat transfer behavior. The results demonstrated that reducing the hydride layer thickness, mixing the metal hydride bed with high-conductivity materials, increasing the cooling agent flow velocity, and using a cooling agent with a lower temperature were more beneficial in improving the thermal performance of the metal hydride bed. In addition, thinning the hydride layer and enhancing the hydride material thermal conductivity were found to decrease the peak temperature. Furthermore, the heat transfer efficiencies of hydride materials, bed structures, and cooling systems should be well matched to obtain optimal operating parameters. The results highlighted the applicability of the proposed model and the coupled heat transfer method to effectively characterize the temperature patterns of uranium-based hydride beds during hydrogen absorption.

Aero-thermal-elastic Coupled Simulations of An Air-cooled Turbine with an FDM solver

The aero-thermal-elastic coupled simulations of an air-cooled turbine vane were carried out by a developed coupled solver, HIT3D, employing the finite difference method. The pressure on the vane surface and the temperature in the solid vane were obtained by the coupled heat transfer simulation, then the single-way aero-elastic and thermal-elastic analysis on the turbine vane were performed. It shows that the predicted profile temperature employing the transition model agrees well with the measured one, the blade deformation caused by aerodynamic force is negligible, and that the greater thermal deformation and thermal stress locate at the blade leading edge pressure side and at the blade trailing edge, as the result of the strong temperature gradient and the constraint at the vane endwalls.

Perspectives for 700 °C ultra-supercritical power generation: Thermal safety of high-temperature heating surfaces

The advanced 700 °C ultra-supercritical (A-USC) power generation is the most important developing direction of power generation due to the highest efficiency and great potential for energy conservation. The heating surfaces will be more sensitive to metal temperature due to the narrow safety temperature allowance at higher steam parameter. The tube wall temperature is depended on heat transfer characteristics between flue gas and working fluid in tube. However, the tube wall temperature was usually calculated with decoupled method for predicting the energy flux between flue gas and working fluid. The accuracy of tube wall temperature by using this method is sufficient for 600 °C USC boiler design based on huge experience data of power plants. While for A-USC boiler, the accuracy of that was not sufficient due to the more sensitive of tube wall temperature on boiler safety operating. To address those issues, some perspectives are given: some experimental apparatus which combined combustion and heat transfer surfaces at 700 °C level of working fluid is needed to conduct heat transfer characteristics; the coupled heat transfer simulation method is essential for A-USC boiler design and operating; long-term testing verification of candidate surfaces is imperative for commercialization of A-USC technology.

Coupled Heat Transfer Simulation of the Spiral Water Wall in a Double Reheat Ultra-supercritical Boiler

This paper presented a coupled heat transfer model combining the combustion in the furnace and the ultra-supercritical (USC) heat transfer in the water wall tubes. The thermal analysis of the spiral water wall in a 1000 MW double reheat USC boiler was conducted by the coupled heat transfer simulations. The simulation results show that there are two peak heat flux regions on each wall of spiral water wall, where the primary combustion zone and burnt-out zone locate respectively. In the full load condition, the maximal heat flux of the primary combustion zone is close to 500 kW/m2, which is higher than that in the conventional single reheat USC boilers. The heat flux along the furnace width presents a parabolic shape that the values in the furnace center are much higher than that in the corner regions. The distribution of water wall temperature has a perfect accordance with the heat flux distribution of the parabolic shape curves, which can illustrate the distribution of water wall temperature is mainly determined by heat flux on the water wall. The maximal water wall temperature occurs at the middle width of furnace wall and approaches 530°C, which can be allowed by the metal material of water wall tube 12Cr1MoVG. In the primary combustion zone, the wall temperatures in half load are almost close to the values in 75% load condition, caused by the heat transfer deterioration of the subcritical pressure fluid under the high heat flux condition. The simulation results in this study are beneficial to the better design and operational optimization for the double reheat USC boilers.

Coupled Heat Transfer Simulation of a Low-Pressure Turbine Vane

A coupled heat transfer (CHT) solver was established. The solver couples the N-S equations with the heat conduction equation using the finite volume method. The developed CHT solver was verified by Mark II 5411 case. The numerical results agree well with experimental data, proving the accuracy of the developed CHT code. The solver was applied to the coupled heat transfer simulations of an air-cooled turbine with a single cooling channel. Adiabatic results and CHT results were compared. Different turbulence and transition models were employed. The result shows that the developed code is of great use in engineering simulations, and in order to predict thermal loads on turbine vane accurately, transition needs to be considered.

Numerical Simulation of Coupled Heat Transfer, Stress, and Electromagnetic Properties in an SMES Magnet

This paper describes the analysis procedure and FEM model considering the parallel effects of stress and thermal problem coupled with the electromagnetic field problem of a 10 MJ Superconducting Magnetic Energy Storage (SMES) magnet. Since the coupled processes in most analyses are very simplified or even not considered, the general aim of this paper was to create, solve, and validate a numerical model of the coupled stress and thermal phenomena that occur within an SMES magnet. A finite element model has been developed to solve the coupling of the magnetic field, stress, and thermal problems. Temperature and stress distribution of the SMES magnet in two operating conditions are simulated, taking into account the eddy current, ac loss, and heat conduction. This provides useful insight for optimized coil design and condition assessment of SMES.

Coupled Heat Transfer Simulations of Air-Cooled Turbines with an Algebraic Transition Model

The investigation was to study the effect of laminar-turbulent transition on predicting thermal load of vane. The Abu-Ghannam and Shaw (AGS) algebraic transition model was applied in the coupled solver, HIT3D. Then the solver was employed to carry out coupled heat transfer simulations, and the test case was 5411 run of NASA0-MARKⅡ vane, a high-pressure turbine vane. The results shown that AGS model was able to predict the transition process in the boundary layer near the vane, and that the simulation with such model leads to thermal load agreeing well the measured one. Then the developed solver was applied to predict a low-pressure vane, and the results shown that CHT simulation with full turbulence model would predict higher thermal load than that with transition model.

Coupled Heat Transfer Simulations of Air-Cooled Turbines with an Algebraic Transition Model

The investigation was to study the effect of laminar-turbulent transition on predicting thermal load of vane. The Abu-Ghannam and Shaw (AGS) algebraic transition model was applied in the coupled solver, HIT3D. Then the solver was employed to carry out coupled heat transfer simulations, and the test case was 5411 run of NASA0-MARKⅡ vane, a high-pressure turbine vane. The results shown that AGS model was able to predict the transition process in the boundary layer near the vane, and that the simulation with such model leads to thermal load agreeing well the measured one. Then the developed solver was applied to predict a low-pressure vane, and the results shown that CHT simulation with full turbulence model would predict higher thermal load than that with transition model.

Coupled Flow-Thermal-Structural Analysis of Hypersonic Aerodynamically Heated Cylindrical Leading Edge

:A new flow-thermal-structural coupling approach based on coupled heat transfer simulation is applied to the analysis of a hypersonic aerodynamically heated leading edge. The three-dimensional unsteady flow-thermal-structural coupling is studied for Mach Number 6.47 flow over a cylinder for which the flow behavior and aero-thermal loads are calibrated by experimental data, and the numerical results of surface pressure, cold-wall heating-rate, hot-wall heating-rate and temperature distributions are all well consistent with experimental data. Interactions between the flow, structural heat transfer and deformation as well as the requirement of grid resolution for k – ε – R turbulence model are also studied.

Coupled Heat Transfer Simulation of a High-pressure Turbine Nozzle Guide Vane

The investigation is intended to verify a coupled solver developed for turbines to illustrate how transition exerts effects on the predicted thermal loads. The solver couples the N-S solver named HIT-3D, with a thermal conduction module using the finite difference method. Three operating conditions of the NASA-MarkII vane are selected to be the cases for tests. The models used in the simulations include Baldwin-Lomax (B-L) algebraic model, q-ωlow-Re model and B-L & Abu-Ghannam and Shaw (AGS) model. The predicted profile pressure distributions obtained in all the simulations agree well with the measured ones. The predicted profile temperatures acquired with different models in the turbulent zones and those with the B-L & AGS model in the laminar and transition zones accord with the measured ones. Therefore, in order to accurately predict the thermal loads on the turbine vane, it is necessary to take transition into account in the simulations.