Combined Experimental-Numerical Approach to Determine Radiation Properties of Particle Suspensions

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Jan Marti ◽  
Matthew Roesle ◽  
Aldo Steinfeld
Keyword(s):  
Numerical Approach ◽  
Particle Suspensions ◽  
Participating Media ◽  
Extinction Coefficients ◽  
Radiation Properties ◽  
Radiation Distribution ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Good Agreement ◽  
Sic Particle

A combination of experimental measurements with a numerical model is used to find the volume-averaged radiation properties—extinction coefficient, scattering albedo and approximated scattering phase function—of SiC particle suspensions with varying particle loadings. The experimentally determined angular radiation distribution of irradiated SiC samples is applied to fit a collision-based Monte Carlo (MC) model with a continuous participating media defining the particle suspension. A validation case with glass microspheres and Mie theory is implemented to verify the modeling procedure. Two types of SiC particles with dissimilar optical characteristics are examined and the respective radiation properties are determined for particle loadings between 0.05 and 0.30. The extinction coefficients of both types of SiC particle are in good agreement with the dependent scattering correlation of Kaviany and Singh.

Combined Experimental-Numerical Approach to Determine Radiation Properties of Particle Suspensions

2013 ◽  
Author(s):  
Jan Marti ◽  
Matthew Roesle ◽  
Aldo Steinfeld
Keyword(s):  
Monte Carlo Model ◽  
Numerical Approach ◽  
Particle Suspensions ◽  
Participating Media ◽  
Radiation Properties ◽  
Radiation Distribution ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Good Agreement ◽  
Sic Particle

A combination of experimental measurements with a numerical model is used to find the intensive radiation properties — extinction coefficient, scattering albedo and scattering phase function — of SiC particle suspensions with varying particle loadings. The experimentally determined angular radiation distribution of irradiated SiC samples is applied to fit a collision-based Monte Carlo model with a continuous participating media defining the particle suspension. A validation case with glass microspheres and Mie theory is used to verify the modeling procedure. Two types of SiC particles with dissimilar optical characteristics are examined and the respective radiation properties are determined for porosities between 0.70–0.95. The extinction coefficients of both types of SiC particle are in good agreement with the dependent scattering correlation of Kaviany and Singh.

scholarly journals On the relationship between the scattering phase function of cirrus and the atmospheric state

2014 ◽  
Vol 14 (10) ◽  
pp. 14109-14157 ◽  
Author(s):  
A. J. Baran ◽  
K. Furtado ◽  
L.-C. Labonnote ◽  
S. Havemann ◽  
J.-C. Thelen ◽  
...  
Keyword(s):  
Model Prediction ◽  
Phase Function ◽  
Weather Prediction ◽  
Ice Crystals ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Nwp Model ◽  
Phase Functions ◽  
The Relationship ◽  
Good Agreement

Abstract. This is the first paper to investigate the relationship between the scattering phase function of cirrus and the relative humidity with respect to ice (RHi), using space-based solar radiometric angle-dependent measurements. The relationship between RHi, and the complexity of ice crystals has been previously studied using data from aircraft field campaigns and laboratory cloud chambers. However, to the best of our knowledge, there have been no studies to date that explore this relationship, through the use of remotely sensed space-based angle-dependent solar radiometric measurements. In this paper, a case study of semi-transparent cirrus is used to explore the possibility of such a relationship. Moreover, for the first time, RHi fields predicted by a high-resolution numerical weather prediction (NWP) model are combined with satellite retrievals of ice crystal complexity. The NWP model was initialised at midnight, on the 25 January 2010, and the mid-latitude RHi field was extracted from the NWP model at 13:00 UTC. At about the same time, there was a Polarization and Anisotropy of Reflectance for Atmospheric science coupled with Observations from a Lidar (PARASOL) overpass, and the PARASOL swath covered the NWP model predicted RHi field. The cirrus case was located over Scotland, and over the North Sea. From the satellite channel based at 0.865 μm, the directionally averaged and directional spherical albedos were retrieved between the scattering angles of about 80° and 130°. An ensemble model of cirrus ice crystals is used to predict phase functions that vary between phase functions that exhibit optical features (called pristine), to featureless phase functions. For each of the PARASOL pixels, the phase function that best minimised differences between the spherical albedos was selected. This paper reports a positive correlation between the scattering phase function and RHi. That is, the pristine and completely featureless phase functions are found to be correlated with RHi < 100%, and RHi> 100%, respectively. Moreover, it is demonstrated that the NWP model prediction of the vertical profile of RHi is in good agreement with independent aircraft-based physical retrievals of RHi. Furthermore, the NWP model prediction of the cirrus cloud-top height and its vertical extent is also found to be in good agreement with aircraft-based lidar measurements.

scholarly journals On the relationship between the scattering phase function of cirrus and the atmospheric state

2015 ◽  
Vol 15 (2) ◽  
pp. 1105-1127 ◽  
Author(s):  
A. J. Baran ◽  
K. Furtado ◽  
L.-C. Labonnote ◽  
S. Havemann ◽  
J.-C. Thelen ◽  
...  
Keyword(s):  
Phase Function ◽  
Ice Crystals ◽  
The North ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Nwp Model ◽  
Phase Functions ◽  
The Relationship ◽  
Good Agreement

Abstract. This is the first paper to investigate the relationship between the shape of the scattering phase function of cirrus and the relative humidity with respect to ice (RHi, using space-based solar radiometric angle-dependent measurements. The relationship between RHi and the complexity of ice crystals has been previously studied using data from aircraft field campaigns and laboratory cloud chambers. However, to the best of our knowledge, there have been no studies to date that explore this relationship through the use of remotely sensed space-based angle-dependent solar radiometric measurements. In this paper, one case study of semi-transparent cirrus, which occurred on 25 January 2010 off the north-east coast of Scotland, is used to explore the possibility of such a relationship. Moreover, for the first time, RHi fields predicted by a high-resolution numerical weather prediction (NWP) model are combined with satellite retrievals of ice crystal complexity. The NWP model was initialised at midnight, on 25 January 2010, and the mid-latitude RHi field was extracted from the NWP model at 13:00 UTC. At about the same time, there was a PARASOL (Polarization and Anisotropy of Reflectance for Atmospheric science coupled with Observations from a Lidar) overpass, and the PARASOL swath covered the NWP-model-predicted RHi field. The cirrus case was located over Scotland and the North Sea. From the satellite channel based at 0.865 μm, the directionally averaged and directional spherical albedos were retrieved between the scattering angles of about 80 and 130°. An ensemble model of cirrus ice crystals is used to predict phase functions that vary between phase functions that exhibit optical features (referred to as pristine) and featureless phase functions. For each of the PARASOL pixels, the phase function that best minimised differences between the spherical albedos was selected. This paper reports, for this one case study, an association between the most featureless phase function model and the highest values of NWP-predicted RHi (i.e. when RHi > 1.0). For pixels associated with NWP-model-predicted RHi < 1, it was impossible to generally discriminate between phase function models at the 5% significance level. It is also shown that the NWP model prediction of the vertical profile of RHi is in good agreement with dropsonde, in situ measurements and independent aircraft-based physical retrievals of RHi. Furthermore, the NWP model prediction of the cirrus cloud-top height and its vertical extent is also found to be in good agreement with aircraft-based lidar measurements.

Combined Radiation and Conduction in Glass Foams

2001 ◽  
Author(s):  
Mark J. Varady ◽  
Andrei G. Fedorov
Keyword(s):  
Heat Transfer ◽  
Foam Layer ◽  
Combustion Gases ◽  
Radiation Properties ◽  
Numerical Iteration ◽  
Flux Approximation ◽  
Scattering Phase ◽  
Bottom Heat ◽  
Scattering Phase Function ◽  
Transfer Properties

Abstract Understanding of heat transfer in glass foams and the development of theoretical tools for predicting heat transfer properties of glass foams is critical to improving the efficiency of glass manufacturing. In this paper, combined radiation and conduction heat transfer in a semitransparent glass foam layer is analyzed. The foam layer is bounded by hot combustion gases on top and glass melt on bottom. Heat transfer is assumed to be one-dimensional perpendicular to the plane-parallel foam layer. A previously developed model is used to calculate effective extinction coefficients and scattering phase function of the foam layer using a void size distribution and assuming all voids to be spherical. These radiation properties are then used along with a Schuster-Schwarzchild two flux approximation to solve the radiative transfer equation (RTE). A method for obtaining the effective thermal conductivity of the foam layer is also presented. The RTE and the energy conservation equations are simultaneously solved using a numerical iteration procedure. The effect of foam thickness and bubble size on the temperature distribution in the foam layer is studied.

Combined Radiation and Conduction in Glass Foams

2002 ◽  
Vol 124 (6) ◽  
pp. 1103-1109 ◽  
Author(s):  
Mark J. Varady ◽  
Andrei G. Fedorov
Keyword(s):  
Heat Transfer ◽  
Foam Layer ◽  
Combustion Gases ◽  
Radiation Properties ◽  
Numerical Iteration ◽  
Flux Approximation ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Transfer Properties ◽  
Isotropic Radiation

Understanding of heat transfer in glass foams and the development of theoretical tools for predicting heat transfer properties of glass foams is critical to improving the efficiency of glass manufacturing. In this paper, combined radiation and conduction heat transfer in a semitransparent glass foam layer is analyzed. The foam layer is thin and of the uniform thickness, bounded by hot combustion gases on top and glass melt on bottom, and exposed to isotropic radiation originating from hot refractories. Heat transfer is assumed to be one-dimensional perpendicular to the plane-parallel foam layer. A previously developed model is used to calculate effective extinction coefficients and scattering phase function of the foam layer using a void size distribution and assuming all voids to be spherical. These radiation properties are then used along with a Schuster-Schwarzchild two-flux approximation to solve the radiative transfer equation (RTE). A method for obtaining the effective thermal conductivity of the foam layer is also presented. The RTE and the energy conservation equations are simultaneously solved using a numerical iteration procedure. The effect of foam thickness and bubble size on the temperature distribution in the foam layer is studied.

scholarly journals Assessing the Role of Particles in Radiative Heat Transfer during Oxy-Combustion of Coal and Biomass Blends

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Gautham Krishnamoorthy ◽  
Caitlyn Wolf
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Radiative Properties ◽  
Test Facility ◽  
Biomass Combustion ◽  
Radiative Fluxes ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Fuel Fragmentation

This study assesses the required fidelities in modeling particle radiative properties and particle size distributions (PSDs) of combusting particles in Computational Fluid Dynamics (CFD) investigations of radiative heat transfer during oxy-combustion of coal and biomass blends. Simulations of air and oxy-combustion of coal/biomass blends in a 0.5 MW combustion test facility were carried out and compared against recent measurements of incident radiative fluxes. The prediction variations to the combusting particle radiative properties, particle swelling during devolatilization, scattering phase function, biomass devolatilization models, and the resolution (diameter intervals) employed in the fuel PSD were assessed. While the wall incident radiative flux predictions compared reasonably well with the experimental measurements, accounting for the variations in the fuel, char and ash radiative properties were deemed to be important as they strongly influenced the incident radiative fluxes and the temperature predictions in these strongly radiating flames. In addition, particle swelling and the diameter intervals also influenced the incident radiative fluxes primarily by impacting the particle extinction coefficients. This study highlights the necessity for careful selection of particle radiative property, and diameter interval parameters and the need for fuel fragmentation models to adequately predict the fly ash PSD in CFD simulations of coal/biomass combustion.

Investigation of Recirculating Casing Treatment for Low-Pressure Ratio Mixed-Flow Micro-Compressor

2020 ◽  
Author(s):  
Kewei Xu ◽  
Gecheng Zha
Keyword(s):  
Pressure Ratio ◽  
Numerical Approach ◽  
Efficiency Loss ◽  
Stall Margin ◽  
Design Point ◽  
Casing Treatment ◽  
Final Design ◽  
Upstream Flow ◽  
Total Pressure Ratio ◽  
Good Agreement

Abstract This paper investigates the recirculating casing treatment (RCT) of a low total pressure ratio micro-compressor to achieve stall margin enhancement while minimizing the design point efficiency penalty. Three RCT injection and extraction configurations are studied, including combined slot-duct, ducts only, and slot only. The numerical approach is validated with a tested micro-compressor using RCT. A very good agreement is achieved between the predicted speedlines and the measured results. To minimize the design point efficiency loss, it is observed that the optimal location of extraction and injection is where the recirculated flow rate can be minimized at the design point. To maximize stall margin, extraction location should favor minimizing the tip blockage such as at the location where the tip flow separation of the baseline blade is fully developed. In addition, the slot configuration that generates pre-swirl to the upstream flow is beneficial to improve stall margin due to reduced incidence. The highest stall margin enhancement achieved is 9.49% with the slot geometry that has the extraction at the 62%C chordwise location, but has a design point efficiency loss of 1.9%. Overall, a small efficiency penalty of 0.6% at the design point is achieved for the final design with the stall margin increased by 6.2%.

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