An Experimental Examination of the Validity of the Commonly Used Methods of Radiant Heat Transfer Analysis

1968 ◽  
Vol 90 (4) ◽  
pp. 429-436 ◽  
Author(s):  
J. R. Schornhorst ◽  
R. Viskanta
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Stainless Steel ◽  
Radiant Heat ◽  
The Body ◽  
Heat Transfer Analysis ◽  
Radiant Heat Transfer ◽  
Local Irradiation ◽  
Experimental Examination ◽  
Predicted Values

In this work the validity and accuracy of the commonly used methods of radiant heat transfer prediction were checked experimentally. The local irradiation was measured for five different materials in two simple configurations. The materials tested were sand-blasted stainless steel, electropolished stainless steel, rough electroplated gold, smooth electroplated gold, and PV100 white paint. Measurements were made over the temperature range from 50 deg F to 850 deg F for each of four sets of geometric parameters. The predicted values of local incident fluxes using the diffuse, specular, and diffuse-specular models were compared with experimental data. The data agree with the diffuse model within the accuracy of the measurements for all the surfaces tested. Additional conclusions, recommendations, and procedures, which should be followed for more realistic radiant heat transfer calculations, are given in the body of the paper.

Design and Testing of a Rig to Investigate Buoyancy-Induced Heat Transfer in Aero-Engine Compressor Rotors

2020 ◽  
Author(s):  
Dario Luberti ◽  
Marios Patinios ◽  
Richard Jackson ◽  
Hui Tang ◽  
Oliver J Pountney ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Radial Distribution ◽  
Radiant Heat ◽  
Tip Clearance ◽  
Heat Transfer Analysis ◽  
Radiant Heat Transfer ◽  
Rotating Disc ◽  
Central Cavity ◽  
Engine Operation ◽  
Aero Engine

Abstract The change in compressor blade-tip clearance across the flight cycle depends on the expansion of the rotor, which in turn depends on the temperature and stress in the discs. The radial distribution of temperature is directly coupled to the buoyancy-driven flow and heat transfer in the rotating disc cavities. This paper describes a new test rig specifically designed to investigate this conjugate phenomenon. The rig test section includes four rotating discs enclosing three cavities. Two discs in the central cavity are instrumented with thermocouples to provide the radial distribution of temperature; the two outer cavities are thermally insulated to create appropriate boundary conditions for the heat transfer analysis. An axial throughflow of air is supplied between a stationary shaft and the bore of the discs. The temperature of the throughflow air is measured by thermocouples in rakes upstream and downstream of the central cavity. For a cold throughflow, the outer shroud of the central cavity is heated. Two independently-controlled radiant heaters allow differential shroud temperatures for the upstream and downstream discs, as found in aero-engine compressors. Alternatively, the throughflow can be heated above the shroud temperature to simulate the transient conditions during engine operation where stratified flow can occur inside the cavity. The rig is designed to operate in conditions where both convective and radiative heat transfer dominate; all internal surfaces of the cavity are painted matt black to allow the accurate calculation of the radiant heat transfer.

Experiment and Analysis of Directional Effects on Radiant Heat Transfer

1972 ◽  
Vol 94 (4) ◽  
pp. 459-466 ◽  
Author(s):  
J. S. Toor ◽  
R. Viskanta
Keyword(s):  
Experimental Data ◽  
Radiant Heat ◽  
Radiant Heat Transfer ◽  
Local Irradiation ◽  
Constant Property ◽  
Directional Characteristics ◽  
Parallel Surfaces ◽  
Property Model ◽  
Finite Extent ◽  
Specular Component

Validity of the commonly used simplified models for predicting local and overall radiant heat interchange among real surfaces is critically examined. The spectral local irradiation was measured at wavelengths of 3.08 and 4.51 μ in a configuration consisting of three plane parallel surfaces of finite extent. The test surfaces were gold with mechanical roughness and temperature varying from 0.02 to 7.1 μ and 77 to 760 deg K respectively. Comparisons between experimental data and predictions for six different models ranging from the simple diffuse to the most detailed diffuse-plus-specular-directional-property model with specular component calculated according to Beckmann are presented. It is shown that the calculation of the overall irradiation using appropriate constant-property models agrees well with the experimental data to within combined experimental and analytical uncertainty. In general it is concluded that for accurate prediction of local irradiation the directional characteristics of the surfaces must be considered.

Radiant Heat Transfer From Isothermal Dispersions With Isotropic Scattering

1967 ◽  
Vol 89 (4) ◽  
pp. 300-308 ◽  
Author(s):  
R. H. Edwards ◽  
R. P. Bobco
Keyword(s):  
Heat Transfer ◽  
Approximate Solutions ◽  
Radiant Heat ◽  
Second Order ◽  
Isotropic Scattering ◽  
Radiant Heat Transfer ◽  
Approximate Methods ◽  
First Order ◽  
Order Solution ◽  
Radiant Transfer

Two approximate methods are presented for making radiant heat-transfer computations from gray, isothermal dispersions which absorb, emit, and scatter isotropically. The integrodifferential equation of radiant transfer is solved using moment techniques to obtain a first-order solution. A second-order solution is found by iteration. The approximate solutions are compared to exact solutions found in the literature of astrophysics for the case of a plane-parallel geometry. The exact and approximate solutions are both expressed in terms of directional and hemispherical emissivities at a boundary. The comparison for a slab, which is neither optically thin nor thick (τ = 1), indicates that the second-order solution is accurate to within 10 percent for both directional and hemispherical properties. These results suggest that relatively simple techniques may be used to make design computations for more complex geometries and boundary conditions.

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