scholarly journals Gas-Solid Heat Transfer Computation from Particle-Resolved Direct Numerical Simulations

Fluids ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 15
Author(s):  
Mohamed-Amine Chadil ◽  
Stéphane Vincent ◽  
Jean-Luc Estivalèzes
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Penalty Method ◽  
Accurate Estimate ◽  
Second Order ◽  
High Order ◽  
Direct Numerical Simulations ◽  
Transfer Coefficients ◽  
Carrier Fluid ◽  
Heat Transfer Coefficients

Particle-Resolved simulations (PR-DNS) have been conducted using a second order implicit Viscous Penalty Method (VPM) to study the heat transfer between a set of particles and an incompressible carrier fluid. A Lagrange extrapolation coupled to a Taylor interpolation of a high order is utilized to the accurate estimate of heat transfer coefficients on an isolated sphere, a fixed Faced-Centered Cubic array of spheres, and a random pack of spheres. The simulated heat transfer coefficients are compared with success to various existing Nusselt laws of the literature.

Numerical Modeling of Film Condensation in Horizontal Mini- and Macrocircular Tubes

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Jun-De Li
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Numerical Differentiation ◽  
Vapor Condensation ◽  
High Order ◽  
Film Condensation ◽  
Thickness Variation ◽  
Condenser Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

A partial differential–integral equation has been derived to connect vapor condensation and the development of condensate film thickness in both the tangential and axial directions in a horizontal circular condenser tube. A high-order explicit numerical scheme is used to solve the strongly nonlinear equation. A simple strategy is applied to avoid possible large errors from high-order numerical differentiation when the condensate becomes stratified. A set of empirical friction factor and Nusselt number correlations covering both laminar and turbulent film condensation have been incorporated to realistically predict film thickness variation and concurrently allow for the predictions of local heat transfer coefficients. The predicted heat-transfer coefficients of film condensation for refrigerant R134a and water vapor in horizontal circular mini- and macrotubes, respectively, have been compared with the results from experiments and the results from the simulations of film condensation using computational fluid dynamics (CFD), and very good agreements have been found. Some of the predicted film condensations are well into the strong stratification regime, and the results show that, in general, the condensate is close to annular near the inlet of the condenser tube and becomes gradually stratified as the condensate travels further away from the inlet for all the simulated conditions. The results also show that the condensate in the minitubes becomes stratified much earlier than that in the macrotubes.

Heat Transfer Measurements and Numerical Simulations in the Cooling of a Circular Cylinder by a Slot Jet of Air

2003 ◽  
Author(s):  
F. Gori ◽  
I. Petracci
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Numerical Simulations ◽  
Convective Heat Transfer ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Commercial Code ◽  
Convective Heat Transfer Coefficients

The present paper reports heat transfer measurements on a circular cylinder, electrically heated, and cooled by a slot jet of air. The diameter of the cylinder is equal to the slot height. Temperature measurements in five positions along the circumference of the circular cylinder, allow the evaluation of the convective heat transfer coefficients or Nusselt numbers at several Reynolds numbers. The Nusselt numbers are compared with the corresponding results in uniform flow around a circular cylinder. The experiments have been performed at several distances from the slot jet exit and different Reynolds numbers. Numerical simulations have been carried out with a commercial code.

scholarly journals Simulations of Hot-Gas Flow in Internally Cooled Cascade of Turbine Vanes

2019 ◽  
Vol 26 (2) ◽  
pp. 151-158
Author(s):  
Janusz Sznajder
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Simulations ◽  
Gas Flow ◽  
Turbulence Models ◽  
Turbulence Energy ◽  
Transfer Coefficients ◽  
Cooling Channels ◽  
Heat Transfer Coefficients ◽  
Outlet Flow

Abstract An experiment in cooling of gas turbine nozzle guide vanes was modelled numerically with a conjugate viscous-flow and solid-material heat conduction solver. The nozzle vanes were arranged in a cascade and operated in high-pressure, hot-temperature conditions, typical for first turbine stage in a flow of controlled-intensity, artificially-generated turbulence. The vane cooling was internal, accomplished by 10 channels in each vane with cooling-air flow. Numerical simulations of the experiment were conducted applying two turbulence models of the k-omega family: k-omega-SST and Transition SST implemented in the ANSYS Fluent solver. Boundary conditions for the simulations were set based on conditions of experiment: total pressures and total temperature on inlet to cascade, static pressure on the outlet of the cascade and heat flux on the surface of cooling channels. The values of heat flux on the surface of cooling channels were evaluated based on Nusselt numbers obtained from experiment and varied in time until steady-state conditions were obtained. Two test cases, one with subcritical outlet flow, and another one, with supercritical outlet flow were simulated. The result of experiment – distributions of pressure, surface temperature, and heat transfer coefficients on the vane external surface were compared to results of numerical simulations. Sensitivity of the vane surface temperatures and heat transfer coefficients to turbulence models and to boundary-condition values of parameters of turbulence models: turbulence energy and specific dissipation of turbulence energy was also studied.

scholarly journals Fundamental Evaluation of Thermal Switch Based on Ionic Wind

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2963 ◽  
Author(s):  
Keiichiro Yoshida
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Waste Heat ◽  
Copper Plate ◽  
Ionic Wind ◽  
Transfer Coefficients ◽  
Heat Management ◽  
Heat Transfer Coefficients ◽  
Thermal Switch ◽  
Basic Characteristics

A significant amount of thermal energy (mainly under 200 °C) is wasted in the world. To utilize the waste heat, efficient heat management and thermal switching is required. The basic characteristics of a thermal switch that controls the flow of heat by switching on/off the ionic wind is discussed in this study. The study was conducted through experiments and numerical simulations. A heater made of aluminum block maintained at 100 °C was used as a heat source, and the rate of heat flow to a copper plate placed over it was measured. Ionic wind was induced by corona discharge with a needle placed on the heater. The ratio of heat transfer coefficients was obtained in the range of 3–4, with an energy efficiency of around 10. The heat flux at this condition was approximately 400 W/m2. The numerical simulations indicate that the heat transfer is enhanced by ionic winds, and the results were found to corroborate well with the experimental ones.

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