scholarly journals Experimental Measurements of Thermal Accommodation Coefficients for Microscale Gas-Phase Heat Transfer

2007 ◽  
Author(s):  
Wayne Trott ◽  
Daniel Rader ◽  
Jaime Castaneda ◽  
John Torczynski ◽  
Michael Gallis
Keyword(s):  
Heat Transfer ◽  
Gas Phase ◽  
Experimental Measurements ◽  
Thermal Accommodation ◽  
Accommodation Coefficients

Noncontinuum Gas-Phase Heat Transfer From a Heated Microbeam to the Adjacent Substrate

2005 ◽  
Author(s):  
M. A. Gallis ◽  
J. R. Torczynski ◽  
D. J. Rader ◽  
B. L. Bainbridge
Keyword(s):  
Heat Transfer ◽  
Gas Phase ◽  
Computational Methods ◽  
Direct Simulation Monte Carlo ◽  
Navier Stokes ◽  
Temperature Jumps ◽  
Thermal Actuation ◽  
Accommodation Coefficients ◽  
Low Pressures ◽  
Good Agreement

Noncontinuum gas-phase heat transfer in two microscale geometries is investigated using two computational methods. The motivation is microscale thermal actuation produced by heating-induced expansion of a near-substrate microbeam in air. The first geometry involves a 1-μm microgap filled with gas and bounded by parallel solid slabs. The second geometry involves a heated I-shaped microbeam 2 μm from the adjacent substrate, with gas in between. Two computational methods are applied. The Navier-Stokes slip-jump (NSSJ) method uses continuum heat transfer in the gas, with temperature jumps at boundaries to treat noncontinuum effects. The Direct Simulation Monte Carlo (DSMC) method uses computational molecules to simulate noncontinuum gas behavior accurately. For the microgap, the heat-flux values from both methods are in good agreement for all pressures and accommodation coefficients. For the microbeam, there is comparably good agreement except for cases with low pressures and near-unity accommodation coefficients. The causes of this discrepancy are discussed.

Numerical modeling of the influence of bubbles on flow and heat transfer in the descending gas-liquid flow in a pipe

2012 ◽  
Vol 9 (1) ◽  
pp. 131-135
Author(s):  
M.A. Pakhomov
Keyword(s):  
Heat Transfer ◽  
Gas Phase ◽  
Liquid Flow ◽  
Bubble Diameter ◽  
Gas Content ◽  
Two Phase ◽  
Eulerian Description ◽  
Flow And Heat Transfer ◽  
Gas Liquid Flow ◽  
The Mathematical Model

The paper presents the results of modeling the dynamics of flow, friction and heat transfer in a descending gas-liquid flow in the pipe. The mathematical model is based on the use of the Eulerian description for both phases. The effect of a change in the degree of dispersion of the gas phase at the input, flow rate, initial liquid temperature and its friction and heat transfer rate in a two-phase flow. Addition of the gas phase causes an increase in heat transfer and friction on the wall, and these effects become more noticeable with increasing gas content and bubble diameter.

An Experimental Study of Free Corrective Heat Transfer in a Parallelogrammic Enclosure

1983 ◽  
Vol 105 (3) ◽  
pp. 433-439 ◽  
Author(s):  
N. Seki ◽  
S. Fukusako ◽  
A. Yamaguchi
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Nusselt Number ◽  
Correlation Equation ◽  
Transformer Oil ◽  
Experimental Measurements ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Prandtl Numbers ◽  
Rayleigh Numbers

Experimental measurements are presented for free convective heat transfer across a parallelogrammic enclosure with the various tilt angles of parallel upper and lower walls insulated. The experiments covered a range of Rayleigh numbers between 3.4 × 104 and 8.6 × 107, and Prandtl numbers between 0.70 and 480. Those also covered the tilt angles of the parallel insulated walls with respect to the horizontal, φ, of 0, ±25, ±45, ±60, and ±70 deg under an aspect ratio of H/W = 1.44. The fluids used were air, transformer oil, and water. It was found that the heat transfer coefficients for φ = −70 deg were decreased to be about 1/18 times those for φ = 0 deg. Experimental results are given as plots of the Nusselt number versus the Rayleigh number. A correlation equation is given for the Nusselt number, Nu, as a function of φ, Pr, and Ra.

An experimental assembly for precise measurement of thermal accommodation coefficients

2011 ◽  
Vol 82 (3) ◽  
pp. 035120 ◽  
Author(s):  
Wayne M. Trott ◽  
Jaime N. Castañeda ◽  
John R. Torczynski ◽  
Michael A. Gallis ◽  
Daniel J. Rader
Keyword(s):  
Precise Measurement ◽  
Thermal Accommodation ◽  
Experimental Assembly ◽  
Accommodation Coefficients

Experimental and Numerical Investigation of a Large Cylindrical Oil-Fired Combustor

1983 ◽  
Author(s):  
F. M. ElMahallawy ◽  
E. E. Khalil ◽  
O. Abdel Aal
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Gas Phase ◽  
Combustion Model ◽  
Steam Boiler ◽  
Discrete Ordinate ◽  
Radiation Model ◽  
Droplet Motion ◽  
Transfer Rates ◽  
Lagrangian Equations

The present work presents measurements of velocity, temperature and heat transfer rates carried out on a segmented water-cooled cylindrical oil-fired flame tube typical of a 0.56 kg/s packaged fire-tube steam boiler. A prediction procedure, that solves the conservation equations of the various entities, was successfully used to produce computed velocities, temperatures and heat flux distributions. A two-equation turbulence model, a combustion model and a discrete ordinate radiation model were used to approximate the various characteristics of the flow. The combustion model solved the Eulerian equations of the gas phase, and the Lagrangian equations of the droplet motion, heating, evaporation and combustion.

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