Combined Radiation—Convection for a Real Gas

1977 ◽  
Vol 99 (1) ◽  
pp. 60-65 ◽  
Author(s):  
N. K. Nakra ◽  
T. F. Smith
Keyword(s):  
Circular Tube ◽  
Tube Wall ◽  
Gas Absorption ◽  
Radiative Properties ◽  
Tube Length ◽  
Weighted Sum ◽  
Gas Temperature ◽  
Zone Method ◽  
Real Gas ◽  
Method Of Solution

A study of interaction of radiative transfer with convective transfer is presented for slug flow of an absorbing-emitting gas in a circular tube with an isothermal black wall. The zone method of solution is utilized to evaluate axial gas temperature and wall heat flux distributions using recently developed direct exchange areas for arbitrary zone width to radius ratio. Gas radiative properties are evaluated from the weighted sum of gray gases model with weighting factors and gray gas absorption coefficients applicable for an equimolal mixture of carbon dioxide and water vapor. Results are presented for several values of the governing parameters which are the Boltzmann and Stanton numbers, inlet gas and tube wall temperatures, as well as tube length to diameter ratio. Effects of cooling and heating of the gas are examined.

scholarly journals Extension of Weighted Sum of Gray Gas Data to Mathematical Simulation of Radiative Heat Transfer in a Boiler with Gas-Soot Media

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Samira Gharehkhani ◽  
Ali Nouri-Borujerdi ◽  
Salim Newaz Kazi ◽  
Hooman Yarmand
Keyword(s):  
Heat Transfer ◽  
Absorption Coefficient ◽  
Radiative Heat ◽  
Measured Data ◽  
Weighted Sum ◽  
Gas Temperature ◽  
Zone Method ◽  
Plant Site ◽  
Good Agreement ◽  
Steam Production

In this study an expression for soot absorption coefficient is introduced to extend the weighted-sum-of-gray gases data to the furnace medium containing gas-soot mixture in a utility boiler 150 MWe. Heat transfer and temperature distribution of walls and within the furnace space are predicted by zone method technique. Analyses have been done considering both cases of presence and absence of soot particles at 100% load. To validate the proposed soot absorption coefficient, the expression is coupled with the Taylor and Foster's data as well as Truelove's data for CO2-H2O mixture and the total emissivities are calculated and compared with the Truelove's parameters for 3-term and 4-term gray gases plus two soot absorption coefficients. In addition, some experiments were conducted at 100% and 75% loads to measure furnace exit gas temperature as well as the rate of steam production. The predicted results show good agreement with the measured data at the power plant site.

Heat Transfer by Combined Forced Convection and Thermal Radiation in a Heated Tube

1962 ◽  
Vol 84 (4) ◽  
pp. 301-311 ◽  
Author(s):  
M. Perlmutter ◽  
R. Siegel
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchange ◽  
Thermal Radiation ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Tube Wall ◽  
Tube Length ◽  
Tube Surface ◽  
Gas Temperature

An analysis is made to study the heat exchange by combined forced convection and thermal radiation in a tube when there is a specified heat flux imposed at the tube wall. The gas flowing in the tube is assumed transparent to radiation, so that the radiation which is included takes place between the elements of the internal tube surface and between this tube surface and the environment at each end of the tube. The inside surface of the tube is a black emitter and the outside is assumed perfectly insulated. The heat-transfer coefficient for convection alone from the tube wall to the gas is assumed constant. The energy equation governing the heat exchange is solved by two methods which provide results that are in good agreement with each other. Numerical examples of the wall and gas-temperature variations along the tube show the influence of the system parameters such as inlet gas temperature, tube length, and convective heat-transfer coefficient. A simple method is outlined, which can be used under some conditions to obtain an approximate wall-temperature distribution.

Radiative Transfer in Hartmann MHD Flow

1979 ◽  
Vol 101 (3) ◽  
pp. 502-506 ◽  
Author(s):  
T. F. Smith ◽  
P. H. Paul
Keyword(s):  
Radiative Transfer ◽  
Mhd Flow ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Radiative Properties ◽  
Temperature Profiles ◽  
Gas Temperature ◽  
Real Gas ◽  
Gaseous Products ◽  
Transfer Term

The high temperatures and gaseous products resulting from combustion of hydrocarbon fuels in magnetohydrodynamic generators have provided an impetus to develop more accurate methods for prediction of gas temperature profiles and heat fluxes at the generator walls. One area where an improvement may be realized is in the evaluation of radiative transfer between the gas and surrounding walls. Analyses and results are presented to examine the importance of the radiative transfer term appearing in the gas energy balance for classical Hartmann MHD flow. Results for both real (nongray) and gray gas radiative properties are presented. Inclusion of radiation is found to increase the surface heat flux as well as to alter gas temperature profiles. Furthermore, real gas results differ significantly from those for a gray gas.

Passive Absorption/Emission Spectroscopy for Gas Temperature Measurements in Gas Turbine Engines

2011 ◽  
Author(s):  
Hejie Li ◽  
Guanghua Wang ◽  
Nirm Nirmalan ◽  
Samhita Dasgupta ◽  
Edward R. Furlong
Keyword(s):  
Gas Turbine ◽  
Emission Spectroscopy ◽  
Gas Absorption ◽  
Temperature Measurements ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Gas Temperature ◽  
Measurement Results ◽  
Passive Absorption ◽  
Hot Surface

A novel technique is developed to simultaneously measure hot surface and gas temperatures based on passive absorption/emission spectroscopy (PAS). This non-intrusive, in situ technique is the extension of multi-wavelength pyrometry to also measure gas temperature. The PAS technique uses hot surface (e.g., turbine blade) as the radiation source, and measures radiation signals at multiple wavelengths. Radiation signals at wavelengths with minimum interference from gas (mostly from water vapor and CO2) can be used to determine the hot surface temperature, while signals at wavelengths with gas absorption/emission can be used to determine the gas temperature in the line-of-sight. The detection wavelengths are optimized for accuracy and sensitivity for gas temperature measurements. Simulation results also show the effect of non-uniform gas temperature profile on measurement results. High pressure/temperature tests are conducted in single nozzle combustor rig to demonstrate sensor proof-of-concept. Preliminary engine measurement results shows the potential of this measurement technique. The PAS technique only requires one optical port, e.g., existing pyrometer or borescope port, to collect the emission signal, and thus provide practical solution for gas temperature measurement in gas turbine engines.

The Influence of Real Gas Radiation On the Stability and Development of Benard Convection in a Two-Dimensional Layer

2021 ◽  
Author(s):  
Brent W. Webb ◽  
Vladimir Solovjov
Keyword(s):  
Rayleigh Number ◽  
Critical Rayleigh Number ◽  
Radiative Heating ◽  
Two Dimensional ◽  
Gas Temperature ◽  
Layer Depth ◽  
Real Gas ◽  
Gas Radiation ◽  
Induced Flow ◽  
Buoyancy Induced Flow

Abstract The influence of real gas radiation on the thermal and hydrodynamic stability is investigated in a two-dimensional layer of radiatively participating H2O and/or CO2 heated from below. The non-gray radiation effects of the two species are treated rigorously using a global spectral approach, the Spectral Line Weighted-sum-of-gray-gases model. The phenomena are explored by solving the full coupled laminar equations of motion, energy, and radiative transfer from the low-Rayleigh number, pure conduction-radiation regime through the onset of buoyancy-induced flow to the developed Bénard convection regime. The evolution of the thermal, velocity, and radiative heating fields is studied, and the critical Rayleigh number is characterized as a function of species mole fraction, average layer gas temperature, layer depth, wall emissivity, and the total gas pressure. It is found that participating radiation in the medium has the effect of stabilizing the layer, delaying transition to buoyancy-induced flow. The development of buoyancy-induced flow and temperature, along with the radiative heating are presented. It is found that the critical Rayleigh number in the radiatively participating gas layer can be more than an order of magnitude higher than the classical convection-only scenario. The onset of instability is found to depend on the species mole fractions, average gas temperature in the layer, wall emissivity, layer depth, and total pressure. Generally, all other variables being the same, H2O has a greater stabilizing influence on the layer than CO2.

scholarly journals Real gas state equations comparative analysis for low-temperature calculations

2019 ◽  
Vol 140 ◽  
pp. 05007 ◽  
Author(s):  
Mikhail Sokolov ◽  
Nikolay Sadovsky ◽  
Anatoly Zuev ◽  
Lyubov Gileva ◽  
Minh Hai Nguyen
Keyword(s):  
Comparative Analysis ◽  
Low Temperature ◽  
Exact Equation ◽  
Gas Temperature ◽  
State Equations ◽  
Two Phase ◽  
Accurate Identification ◽  
Real Gas ◽  
Mass Transfer Processes ◽  
Definition Of

In this paper, various real gas state equations are considered and their comparative analysis is carried out. The following state equations are studied in the work: Benedict-Webb-Rubin modification equation, Ridlich-Kwong Real Gas equation, Peng-Robinson Real Gas equation, and the modified Ridlich-Kwong real gas state equations proposed by Barsuk S.D. We have made a direct comparison of these calculation methods with most accurate identification. In addition, the paper analyzes the equations features, with applicability limits definition of each state equations. For the chosen one, as the most universal and exact equation, the calculations were made for the liquid phase and the real gas two-phase state. Based on the data obtained, polynomials were developed for various parameters depending on the gas temperature, which can later be used to build various mathematical models. Our conclusions show main advantages of selected equation for real gases and the reasons for choosing it for modeling low-temperature heat and mass transfer processes.

scholarly journals Steady Laminar Heat Transfer in a Circular Tube with Conduction in Tube Wall

1974 ◽  
Vol 38 (2) ◽  
pp. 144-150 ◽  
Author(s):  
Shigeru Mori ◽  
Mikio Sakakibara ◽  
Akira Tanimoto
Keyword(s):  
Heat Transfer ◽  
Circular Tube ◽  
Tube Wall ◽  
Steady Laminar

Pressure drop due to the motion of a sphere near the wall bounding a Poiseuille flow

1973 ◽  
Vol 60 (1) ◽  
pp. 81-96 ◽  
Author(s):  
Peter M. Bungay ◽  
Howard Brenner
Keyword(s):  
Pressure Drop ◽  
Poiseuille Flow ◽  
Circular Tube ◽  
Tube Wall ◽  
Previous Method ◽  
Pronounced Increase ◽  
Additional Pressure ◽  
Sphere Radius ◽  
Neutrally Buoyant ◽  
Quiescent Fluid

An expression is derived for the (low Reynolds number) additional pressure drop created by a relatively small sphere moving near the wall of a circular tube through which there is a Poiseuille flow. Two specific applications are examined: (i) the sedimentation of a homogeneous non-neutrally buoyant sphere in a quiescent fluid; and (ii) the motion of a neutrally buoyant sphere. In the latter case a pronounced increase in the additional pressure drop is predicted when the separation between the sphere and the tube wall is reduced to zero.This analysis, which includes the behaviour for a sphere in contact with the tube wall, supplements previous ‘method of reflexions’ treatments valid only when the distance from the sphere centre to the wall is large compared with the sphere radius.

The Zone Method: A New Explicit Matrix Relation to Calculate the Total Exchange Areas in Anisotropically Scattering Medium Bounded by Anisotropically Reflecting Walls

2002 ◽  
Vol 124 (4) ◽  
pp. 696-703 ◽  
Author(s):  
J. M. Goyhe´ne`che ◽  
J. F. Sacadura
Keyword(s):  
Complex Geometry ◽  
Anisotropic Scattering ◽  
Radiative Properties ◽  
Scattering Medium ◽  
Zone Method ◽  
Indirect Exchange ◽  
Matrix Relation ◽  
Definition Of ◽  
New Formulation ◽  
Total Exchange

A new explicit matrix relation for the calculation of the total exchange areas (TEA) in emitting, absorbing and anisotropically scattering semi-transparent medium bounded by emitting, absorbing and anisotropically reflecting walls has been established. It has been used to directly determine the TEA as a function of radiative properties and geometry of the medium and its boundaries. Computation calls for direct exchange areas (DEA) and indirect exchange areas (IEA). A new definition of these exchange areas reduces their integration order and provides practical energy balance relations for their computation in the case of complex geometry elements. The new formulation is applied in the case of an emitting, absorbing and linearly anisotropic scattering semi-transparent slab bounded by black surfaces. This method is also applicable to nongray medium using the weighted sum of gray gases model.

scholarly journals FEATURES OF SPATIAL DISTRIBUTION OF THE SPECIFIC HEAT CAPACITY OF SUPERCRITICAL WATER DURING ITS FLOW IN VERTICAL BARE TUBES

2021 ◽  
Vol 43 (3) ◽  
pp. 15-23
Author(s):  
N.М. Fialko ◽  
A.V. Nosovsksyi ◽  
S.O. Aleshko ◽  
I.L. Pioro ◽  
D.P. Khmil
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Spatial Distribution ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Supercritical Water ◽  
Tube Wall ◽  
Tube Length ◽  
Radial Coordinate ◽  
Upstream Flow

The results of computer modeling of the spatial distribution of the specific heat capacity under condition of the upstream flow of supercritical water in vertical bare tubes are given. The features of the motion along the tube length the front of the pseudo-phase transition "pseudoliquid-pseudogas" are considered. The position of this front determines the location of the extremums of the specific heat capacity of water. The regularities of changes in the radial distributions of heat capacity along the length of the tube and longitudinal distributions for different values of the radial coordinate are investigated. The data of a comparative analysis of this distribution at various values of the specific heat flux supplied to the tube wall are presented

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