On the frame dependence of constitutive equations. I. Heat transfer through a rarefied gas between two rotating cylinders

1995 ◽  
Vol 7 (1) ◽  
pp. 57-72 ◽  
Author(s):  
F. M. Sharipov ◽  
G. M. Kremer
Keyword(s):  
Heat Transfer ◽  
Constitutive Equations ◽  
Rarefied Gas ◽  
Rotating Cylinders ◽  
Frame Dependence

Comparison of DSMC and CFD Models of Heat Transfer in a Rarefied Two-Dimensional Geometry

2018 ◽  
Author(s):  
Dilesh Maharjan ◽  
Mustafa Hadj-Nacer ◽  
Miles Greiner ◽  
Stefan K. Stefanov
Keyword(s):  
Heat Transfer ◽  
Rarefied Gas ◽  
Complex Geometry ◽  
Direct Simulation Monte Carlo ◽  
Accurate Method ◽  
Vacuum Drying ◽  
Helium Pressure ◽  
Two Dimensional ◽  
Dsmc Method ◽  
Cfd Simulations

During vacuum drying of used nuclear fuel (UNF) canisters, helium pressure is reduced to as low as 67 Pa to promote evaporation and removal of remaining water after draining process. At such low pressure, and considering the dimensions of the system, helium is mildly rarefied, which induces a thermal-resistance temperature-jump at gas–solid interfaces that contributes to the increase of cladding temperature. It is important to maintain the temperature of the cladding below roughly 400 °C to avoid radial hydride formation, which may cause cladding embrittlement during transportation and long-term storage. Direct Simulation Monte Carlo (DSMC) method is an accurate method to predict heat transfer and temperature under rarefied condition. However, it is not convenient for complex geometry like a UNF canister. Computational Fluid Dynamics (CFD) simulations are more convenient to apply but their accuracy for rarefied condition are not well established. This work seeks to validate the use of CFD simulations to model heat transfer through rarefied gas in simple two-dimensional geometry by comparing the results to the more accurate DSMC method. The geometry consists of a circular fuel rod centered inside a square cross-section enclosure filled with rarefied helium. The validated CFD model will be used later to accurately estimate the temperature of an UNF canister subjected to vacuum drying condition.

Rarefied-gas heat transfer in micro- and nanoscale Couette flows

2010 ◽  
Vol 81 (1) ◽  
Author(s):  
W. D. Zhou ◽  
B. Liu ◽  
S. K. Yu ◽  
W. Hua
Keyword(s):  
Heat Transfer ◽  
Rarefied Gas

Transient Three-Dimensional Heat Transfer Model of a Solar Thermochemical Reactor for H2O and CO2 Splitting via Nonstoichiometric Ceria Redox Cycling

2013 ◽  
Author(s):  
Justin Lapp ◽  
Wojciech Lipiński
Keyword(s):  
Heat Transfer ◽  
Heat Recovery ◽  
Fuel Efficiency ◽  
Three Dimensional ◽  
Reactor Design ◽  
Heat Transfer Model ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Rotating Cylinders ◽  
Solar Receiver

A transient heat transfer model is developed for a solar reactor prototype for H2O and CO2 splitting via two-step non-stoichiometric ceria cycling. Counter-rotating cylinders of reactive and inert materials cycling between high and low temperature zones permit continuous operation and heat recovery. To guide the reactor design a transient three-dimensional heat transfer model is developed based on transient energy conservation, accounting for conduction, convection, radiation, and chemical reactions. The model domain includes the rotating cylinders, a solar receiver cavity, and insulated reactor body. Radiative heat transfer is analyzed using a combination of the Monte Carlo method, Rosseland diffusion approximation, and the net radiation method. Quasi-steady state distributions of temperatures, heat fluxes, and the non-stoichiometric coefficient are reported. Ceria cycles between temperatures of 1708 K and 1376 K. A heat recovery effectiveness of 28% and solar-to-fuel efficiency of 5.2% are predicted for an unoptimized reactor design.

Extended Thermodynamic Approach for Non-Equilibrium Gas Flow

2013 ◽  
Vol 13 (5) ◽  
pp. 1330-1356 ◽  
Author(s):  
G. H. Tang ◽  
G. X. Zhai ◽  
W. Q. Tao ◽  
X. J. Gu ◽  
D. R. Emerson
Keyword(s):  
Heat Transfer ◽  
Equilibrium State ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Flow Characteristics ◽  
Bimodal Distribution ◽  
Thermodynamic Approach ◽  
Navier Stokes ◽  
Extended Thermodynamic ◽  
Non Equilibrium

AbstractGases in microfluidic structures or devices are often in a non-equilibrium state. The conventional thermodynamic models for fluids and heat transfer break down and the Navier-Stokes-Fourier equations are no longer accurate or valid. In this paper, the extended thermodynamic approach is employed to study the rarefied gas flow in microstructures, including the heat transfer between a parallel channel andpressure-driven Poiseuille flows through a parallel microchannel andcircular microtube. The gas flow characteristics are studied and it is shown that the heat transfer in the non-equilibrium state no longer obeys the Fourier gradient transport law. In addition, the bimodal distribution of streamwise and spanwise velocity and temperature through a long circular microtube is captured for the first time.

Heat transfer in a very rarefied gas

1980 ◽  
Vol 15 (1) ◽  
pp. 165-168 ◽  
Author(s):  
O. G. Fridlender
Keyword(s):  
Heat Transfer ◽  
Rarefied Gas

Modeling of Flow Characteristic and Heat Transfer for Micro Couette Flow

2001 ◽  
Author(s):  
Hong Xue ◽  
Ling Xie ◽  
S. K. Chou
Keyword(s):  
Heat Transfer ◽  
Couette Flow ◽  
Flow Characteristic ◽  
Rarefied Gas ◽  
Characteristic Length ◽  
Velocity Slip ◽  
Flow And Heat Transfer ◽  
Wide Range ◽  
Perturbation Velocity ◽  
Rarefaction Effects

Abstract Gaseous flow encountered in micro/nano electromechanical systems experiences change in Kn number across a wide range of flow regime due to variation in characteristic length in the system and significant compressibility of the rarefied gas. In this study, we attempt to develop a general, physics-based model to predict the flow and heat transfer in the slip and transition regimes. Such an extension is constructed on the fact that Chapman-Enskog’s approximation of the Boltzmann equation can be revised using a function of Kn number as a perturbation. Velocity slip and temperature jump at the solid boundaries are modified accordingly. Rarefaction effects on dynamic viscosity and thermal conductivity are considered. As a first step to evaluate the model, it is applied to the simplest shear-driven flow, micro Couette flow. Compared with the results of DSMC, satisfactory agreement has been achieved in a wide range of Kn and Ma numbers.

Augmentation of Pure Mixed Convection Heat Transfer in a Non-newtonian Power-law Fluid Filled Lid-driven Trapezoidal Cavity with Double Rotating Cylinders

2021 ◽  
Author(s):  
Hasib Ahmed Prince ◽  
Didarul Ahasan Redwan ◽  
Enamul Hasan Rozin ◽  
Sudipta Saha ◽  
Mohammad Arif Hasan Mamun
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Numerical Investigation ◽  
Power Law ◽  
Convection Heat Transfer ◽  
Cavity Surface ◽  
Rotating Cylinders ◽  
Power Law Fluid ◽  
Driven Cavity

Abstract In this study, a numerical investigation on mixed convection inside a trapezoidal cavity with a pair of rotating cylinders has been conducted. Three different power-law fluid indexes (n = 1.4, 1.0, and 0.6) have been considered to model different sets of non-Newtonian fluids. Four separate cases are considered dependent on the rotation orientation of the cylinders within the cavity. In the first two cases, the cylinders rotate in the same direction, i.e., both counter-clockwise (CCW), and both clockwise (CW), whereas, in the other two cases, cylinders rotate in opposite directions (CW-CCW and CCW-CW). Simulations have been carried out over a broad range of Reynolds number (from 0.5 to 500) and angular speeds (a dimensionless value from 0 to 10). The average Nusselt number values at the isothermal hot inclined cavity surface are determined to evaluate heat transfer performance in various circumstances. Streamlines and isotherm contours are also plotted for better understandings of the effects of different cases for various parameters on thermal and fluid flow fields. It is found that the Nusselt number varies non-linearly with different angular speeds of the cylinders. The combined effect of the mixing induced by cylinder rotation and viscosity characteristics of the fluid dictates the heat transfer in the system. Predictions from the numerical investigation provide insights onto the sets of key parametric configuration that have dominant influence on the thermal performance of lid driven cavity with double rotating cylinders.

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