Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Evaluation of the SRI and the WSGG models in high pressure supercritical CO2 media
Submission Author:
Felipe Ramos Coelho , SP
Co-Authors:
Felipe Ramos Coelho, Vitor Olson, Francis França, Alexandre Kupka da Silva
Presenter: Felipe Ramos Coelho
doi://10.26678/ABCM.COBEM2023.COB2023-2282
Abstract
Engineering applications involving the use of supercritical CO2 (s-CO2), such as thermal power cycles and thermal energy storage systems, have been gaining an increasing interest in the recent years. In the thermodynamic conditions common in such applications, the s-CO2 can participate significantly in the overall radiative heat transfer, even in conditions that consider moderately low temperatures. Despite this, most studies involving these engineering applications of s-CO2 neglect the radiative heat transfer phenomenon, mainly due the computational cost required for its calculations. To aggravate this, there are currently few alternatives in the literature of less CPU intensive approximate radiation models that are applicable to these conditions. With this in mind, the present work evaluates two distinct approaches to account for radiative transfer in s-CO2 applications: the spectrally reduced integration (SRI) method and the weighted-sum-of-gray-gases (WSGG) model. The WSGG is a global gas model that replaces the highly irregular behavior of the absorption coefficient of CO2 by a few gray gases. Despite its simplicity, this model is able to result in satisfactory levels of accuracy, especially when considering its low computational cost. It is also expected that the high pressure and moderately low temperatures studied will improve the accuracy of the WSGG – as the behavior of the CO2 absorption spectrum in such conditions becomes closer to what is observed in gray gases. The SRI, on the other hand, is a highly accurate methodology that is suitable to generate benchmark solutions of the radiative transfer in participating gas media. Furthermore, independent studies show that the ratio between accuracy and CPU time is even better when dealing with high pressure gas media composed of only CO2. Thus, the present study aims to provide new WSGG correlations as an alternative for faster approximate calculations in s-CO 2 media while also evaluating the applicability of the SRI for benchmark solutions in such conditions. In summary, it is expected that both methodologies will present satisfactory performance, each in its own merit, depending on whether the user favors high accuracy or faster solution time.
Keywords
Supercritical CO2, Radiative heat transfer, High pressure, Spectrally reduced integration, weighted-sum-of-gray-gases
