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.
|Original language||English (US)|
|Number of pages||7|
|Journal||Applied Thermal Engineering|
|State||Published - Oct 25 2016|
Bibliographical noteFunding Information:
This research is based upon work supported by the Solar Energy Research Institute for India and the U.S. (SERIIUS) funded jointly by the U.S. Department of Energy subcontract DE AC36-08G028308 (Office of Science, Office of Basic Energy Sciences, and Energy Efficiency and Renewable Energy, Solar Energy Technology Program, with support from the Office of International Affairs) and the Government of India subcontract IUSSTF/JCERDC-SERIIUS/2012 dated 22nd November 2012.
- Brayton cycle
- Participating media
- Radiation heat transfer
- Supercritical CO