[Paper Review] New Weighted Sum of Gray Gases (WSGG) Models for Radiation Calculation in Carbon Capture Simulations: Evaluation and Different Implementation Techniques

Osama A. Marzouk, E. David Huckaby|arXiv (Cornell University)|Nov 27, 2024

Radiative Heat Transfer Studies5 citations

TL;DR

The paper compares four recently developed WSGGM models for H2O–CO2 mixtures against the air-fuel WSGGM, evaluates interpolation schemes, and uses finite-volume RT solutions to assess accuracy against a spectral line-based reference.

ABSTRACT

We apply several weighted sum of gray gases models (WSGGMs) to calculate the radiative absorption coefficient for gas mixtures containing H2O and CO2. Our main objectives are to analyze and compare four WSGGMs which have been recently developed for oxy-fuel combustion. The models are compared with the widely-used air-fuel WSGGM of Smith et al. In addition to direct comparison of the absorption coefficients, we compare finite-volume solutions of the radiative equation of transfer in a 2m x 2m x 4m box with a specified inhomogeneous temperature field and a homogeneous mixture of the H2O, CO2 and N2. Calculations using a spectral line-based WSGGM (SLW) are used as a reference solution to estimate the accuracy. For each WSGGM, we apply two interpolation methods for determining the model coefficients at arbitrary H2O-to-CO2 ratios. For wet-recycle oxy-fuel combustion, we found that the deviation of the air-fuel WSGGM was not significantly larger than several of the newer models. However, with dry recycle (90 vol%-CO2) the air-fuel WSGGM model underpredicts the radiative flux and radiative heat source in contrast to the other models which overpredict these fields. Piecewise linear interpolation consistently improves the predictions of the air-fuel WSGGM, but only has a modest effect on the predictions of the oxy-fuel WSGGM's.

Motivation & Objective

• Analyze and compare four WSGGMs developed for oxy-fuel combustion in the context of carbon capture gas mixtures (H2O/CO2/N2).
• Evaluate the accuracy of these models against a spectral-line-based WSGGM (SLW) reference.
• Assess the impact of two coefficient-interpolation methods for arbitrary H2O-to-CO2 ratios on model predictions.

Proposed method

• Compute radiative absorption coefficients for H2O–CO2–N2 mixtures using four WSGGMs and the air-fuel WSGGM as a baseline.
• Use a 2 m × 2 m × 4 m finite-volume box with inhomogeneous temperature field to compare radiative flux and source terms.
• Use SLW as reference to estimate accuracy of WSGGMs.
• Apply two interpolation methods for model coefficients at arbitrary H2O-to-CO2 ratios (including piecewise linear interpolation).
• Analyze results for wet-recycle and dry-recycle oxy-fuel cases (e.g., 90 vol% CO2).

Experimental results

Research questions

• RQ1 How do the four newer WSGGMs perform in predicting radiative absorption for H2O–CO2–N2 mixtures compared with the air-fuel WSGGM and the SLW reference?
• RQ2 What is the impact of coefficient interpolation on model accuracy, especially for varying H2O/CO2 ratios?
• RQ3 How do wet-recycle and dry-recycle oxy-fuel scenarios affect model accuracy and flux predictions?
• RQ4 Do newer WSGGMs mitigate under- or over-predictions seen with the traditional air-fuel WSGGM in carbon capture contexts?

Key findings

• Deviations of the air-fuel WSGGM are not significantly larger than several newer models for wet-recycle oxy-fuel conditions.
• Under dry recycle (90 vol% CO2), the air-fuel WSGGM underpredicts radiative flux and radiative heat source compared with the other models, which overpredict.
• Piecewise linear interpolation consistently improves the air-fuel WSGGM predictions.
• Interpolation has only a modest effect on the predictions of the oxy-fuel WSGGMs.
• SLW serves as a reference solution to estimate accuracy of the WSGGMs.
• Other WSGGMs tend to overpredict radiative fields under dry-recycle conditions whereas air-fuel WSGGM underpredicts.