TY - JOUR
T1 - Radiative heating of supercritical carbon dioxide flowing through tubes
AU - Khivsara, Sagar D.
AU - Srinivasan, Vinod
AU - Dutta, Pradip
N1 - Publisher Copyright:
© 2016 Elsevier Ltd
PY - 2016/10/25
Y1 - 2016/10/25
N2 - Brayton power cycles using high temperature, high pressure supercritical carbon dioxide (s-CO2) as the working fluid have been increasingly considered as attractive candidates for solar-thermal power plants. Several configurations of heat exchangers and solar receivers are under investigation, with predicted tube temperatures ∼1000 K. The inclusion of radiation modeling to capture the effect of absorption bands of s-CO2 and the radiative heat transfer among the equipment surfaces makes the computation costly and time consuming, and is often neglected on the basis of convection being the dominant transport mechanism. In this work, a numerical study has been performed to characterize the heat transfer in simultaneously developing laminar flow of s-CO2 through a circular pipe. The combined effects of convection and radiation are presented by varying the Reynolds number, pipe diameter, length to diameter ratio, wall emissivity and the total wall heat flux. It is shown that neglecting the effects of radiative heat transfer, and in particular the participation of s-CO2 in thermal transport can lead to large errors in predicting wall temperature, and by extension, the component lifetime. The error in wall temperature also leads to erroneous predictions on losses to the environment. The calculations indicate that there is a range of flow conditions over which the design process needs to incorporate radiation modeling.
AB - Brayton power cycles using high temperature, high pressure supercritical carbon dioxide (s-CO2) as the working fluid have been increasingly considered as attractive candidates for solar-thermal power plants. Several configurations of heat exchangers and solar receivers are under investigation, with predicted tube temperatures ∼1000 K. The inclusion of radiation modeling to capture the effect of absorption bands of s-CO2 and the radiative heat transfer among the equipment surfaces makes the computation costly and time consuming, and is often neglected on the basis of convection being the dominant transport mechanism. In this work, a numerical study has been performed to characterize the heat transfer in simultaneously developing laminar flow of s-CO2 through a circular pipe. The combined effects of convection and radiation are presented by varying the Reynolds number, pipe diameter, length to diameter ratio, wall emissivity and the total wall heat flux. It is shown that neglecting the effects of radiative heat transfer, and in particular the participation of s-CO2 in thermal transport can lead to large errors in predicting wall temperature, and by extension, the component lifetime. The error in wall temperature also leads to erroneous predictions on losses to the environment. The calculations indicate that there is a range of flow conditions over which the design process needs to incorporate radiation modeling.
KW - Brayton cycle
KW - Participating media
KW - Radiation heat transfer
KW - Supercritical CO
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U2 - 10.1016/j.applthermaleng.2016.05.049
DO - 10.1016/j.applthermaleng.2016.05.049
M3 - Article
AN - SCOPUS:84969164657
SN - 1359-4311
VL - 109
SP - 871
EP - 877
JO - Applied Thermal Engineering
JF - Applied Thermal Engineering
ER -