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Numerical comparison of thermalhydraulic aspects of supercritical carbon dioxide and subcritical water based natural circulation loop

Flow-induced heat transfer deterioration can be delayed by increasing system pressure or lowering sink temperature. Bulk temperature level throughout the loop with water as working fluid is higher than supercritical carbon dioxide. This is until the heat transfer deterioration, and hence the use of a single-phase loop is prescribed beyond that limit. | Numerical comparison of thermalhydraulic aspects of supercritical carbon dioxide and subcritical water based natural circulation loop N u c l e a r E n g i n e e r i n g a n d T e c h n o l o g y 4 9 ( 2 0 1 7 ) 1 0 3 e1 1 2 Available online at ScienceDirect Nuclear Engineering and Technology journal homepage: www.elsevier.com/locate/net Original Article Numerical Comparison of Thermalhydraulic Aspects of Supercritical Carbon Dioxide and Subcritical Water-Based Natural Circulation Loop Milan Krishna Singha Sarkar and Dipankar Narayan Basu* Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam e 781039, India article info abstract Article history: Application of the supercritical condition in reactor core cooling needs to be properly Received 16 February 2016 justified based on the extreme level of parameters involved. Therefore, a numerical study Received in revised form is presented to compare the thermalhydraulic performance of supercritical and single- 6 September 2016 phase natural circulation loops under low-to-intermediate power levels. Carbon dioxide Accepted 7 September 2016 and water are selected as respective working fluids, operating under an identical set of Available online 20 October 2016 conditions. Accordingly, a three-dimensional computational model was developed, and solved with an appropriate turbulence model and equations of state. Large asymmetry in Keywords: velocity and temperature profiles was observed in a single cross section due to local Heat Transfer Deterioration buoyancy effect, which is more prominent for supercritical fluids. Mass flow rate in a su- Natural Circulation percritical loop increases with power until a maximum is reached, which subsequently Single Phase corresponds to a rapid deterioration in heat transfer coefficient. That can be identified as Supercritical the limit of operation for such loops to avoid a high temperature,