The Parameters Identification Method of Radiation Heat Transfer for Nanoporous Materials

2013 ◽  
Vol 631-632 ◽  
pp. 341-347
Author(s):  
Ji Jun Yu ◽  
Fei Huang ◽  
Gui Qing Jiang
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Nanoporous Materials ◽  
Parameters Identification ◽  
Approximation Model ◽  
Identification Method ◽  
Flux Approximation ◽  
Flux Model ◽  
Identification Theory ◽  
Set Up

The two flux approximation model is usually used to calculate the heat transfer of radiation for porous materials. In this paper, the parameters identification method of the extinction coefficient and the albedo of scattering in the two flux model is set up by using the identification theory according to the data of the back temperature. The simulated process shows that the convergence rate is fast and the results by the parameters identification are very close to the origin values.

Experimental and numerical investigations on a high-density polyethylene (HDPE) blown film cooling with a new design of the counter-flow/radial jet air-ring

2021 ◽  
pp. 875608792110260
Author(s):  
ME Ismail ◽  
MM Awad ◽  
AM Hamed ◽  
MY Abdelaal ◽  
EB Zeidan
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Film Cooling ◽  
Radiation Heat Transfer ◽  
Absolute Error ◽  
Numerical Results ◽  
Upper Lip ◽  
Original Design ◽  
Blown Film ◽  
Set Up

This study experimentally and numerically investigates a typical HDPE blown film production process cooled via a single-lip air-ring. The processing observations are considered for the proposed subsequent modifications on the air-ring design and the location relative to the die to generate a radial jet, directly impinging on the bubble. Measurements are performed to collect the actual operating parameters to set up the numerical simulations. The radiation heat transfer and the polymer phase change are considered in the numerical simulations. The velocity profile at the air-ring upper-lip is measured via a five-hole Pitot tube to compare with the numerical results. The comparison between the measurements and the numerical results showed that the simulations with the STD [Formula: see text] turbulence model are more accurate with a minimum relative absolute error (RAE) of 1.6%. The numerical results indicate that the peak Heat Transfer Coefficient (HTC) at the impingement point for the modified design with radial jet and longer upper-lip is 29.1% higher than the original design at the same conditions. Besides, increasing the air-ring upper-lip height increased the averaged HTC, which is 13.4% higher than the original design.

Combined Conduction and Radiation Heat Transfer in Porous Materials Heated by Intense Solar Radiation

1985 ◽  
Vol 107 (1) ◽  
pp. 29-34 ◽  
Author(s):  
L. K. Matthews ◽  
R. Viskanta ◽  
F. P. Incropera
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Plane Layer ◽  
Single Scattering ◽  
Dominant Mode ◽  
Radiative Properties ◽  
Maximum Temperature ◽  
Transfer Model ◽  
Radiation Heat ◽  
Flux Approximation

An analysis is presented to predict the heat transfer characteristics of a plane layer of a semitransparent, high-temperature, porous material which is irradiated by an intense solar flux. A transient, combined conduction and radiation heat transfer model, which is based on a two-flux approximation for the radiation, is used to predict the temperature distribution and heat transfer in the material. Numerical results have been obtained using thermophysical and radiative properties of zirconia as a typical material. The results show that radiation is an important mode of heat transfer, even when the opacity of the material is large (τL > 100). Radiation is the dominant mode of heat transfer in the front third of the material and comparable to conduction toward the back. The semitransparency and high single scattering albedo of the zirconia combine to produce a maximum temperature in the interior of the material.

Radiation Heat Transfer Analysis of the Monolith-Type Solid Oxide Fuel Cell

2003 ◽  
Author(s):  
Sunil Murthy ◽  
Andrei Fedorov
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiation Effects ◽  
Radiation Transport ◽  
Radiation Heat Transfer ◽  
Heat Transfer Analysis ◽  
Radiation Heat ◽  
Modeling Framework ◽  
Flux Approximation ◽  
Ysz Electrolyte

In this study, a modeling framework for heat and mass transport is investigated for a unit cell of the monolith type SOFC, with emphasis on quantifying the radiation heat transfer effects. The Schuster-Schwartzchild two-flux approximation is used for treating thermal radiation transport in the optically thin YSZ electrolyte, and the Rosseland radiative thermal conductivity is used to account for radiation effects in the optically thick Ni-YSZ and LSM electrodes. The thermal radiation heat transfer is coupled to the overall energy conservation equations through the divergence of the local radiative flux. A commercially available CFD software was used as a platform for the global thermal-fluid modeling of the SOFC and the radiation models were implemented through the user-defined functions. Results from sample calculations show significant changes in the operating temperatures and parameters of the SOFC with the inclusion of radiation effects.

scholarly journals Efficiency of liquid flat-plate solar energy collector with solar tracking system

2015 ◽  
Vol 19 (5) ◽  
pp. 1673-1684 ◽  
Author(s):  
Marija Chekerovska ◽  
Risto Filkoski
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Tracking System ◽  
Radiation Heat Transfer ◽  
Solar Collectors ◽  
Cfd Modelling ◽  
Energy Capture ◽  
Operating Modes ◽  
Rotation System ◽  
Set Up

An extensive testing programme is performed on a solar collector experimental set-up, installed on a location in Shtip (Republic of Macedonia), latitude 41? 45? and longitude 22? 12?, in order to investigate the effect of the sun tracking system implementation on the collector efficiency. The set-up consists of two flat plate solar collectors, one with a fixed surface tilted at 30? towards the South, and the other one equipped with dual-axis rotation system. The study includes development of a 3-D mathematical model of the collectors system and a numerical simulation programme, based on the computational fluid dynamics (CFD) approach. The main aim of the mathematical modelling is to provide information on conduction, convection and radiation heat transfer, so as to simulate the heat transfer performances and the energy capture capabilities of the fixed and moving collectors in various operating modes. The feasibility of the proposed method was confirmed by experimental verification, showing significant increase of the daily energy capture by the moving collector, compared to the immobile collector unit. The comparative analysis demonstrates a good agreement between the experimental and numerically predicted results at different running conditions, which is a proof that the presented CFD modelling approach can be used for further investigations of different solar collectors configurations and flow schemes.

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