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ISSN Online: 2688-7231

ISBN Online: 978-1-56700-524-0

Proceedings of the 26thNational and 4th International ISHMT-ASTFE Heat and Mass Transfer Conference December 17-20, 2021, IIT Madras, Chennai-600036, Tamil Nadu, India
December, 17-20, 2021, IIT Madras, Chennai, India

Numerical study of supercritical natural circulation loop under condition of different inclination ad diameter

Get access DOI: 10.1615/IHMTC-2021.1220
pages 815-819

Abstract

Gravity driven natural convection flow under supercritical pressure condition, being having both low flow rate and low heat transfer potential against forced flow conditions is sought after for many engineering applications like solar heater, geothermal system and also as a passive safety system in nuclear reactor cooling system. The present study is focused on Carbon di-oxide based supercritical natural circulation loop under different inclination conditions (0°, 30°, 60°), diameters (6, 8, 10 mm) and operating parameters of sink temperature 295 K at 8 MPa pressure. The key point of analysis is to envisage the FiHTD (Flow induced heat transfer deterioration) phenomenon which occurs when loop average temperature crosses pseudo-critical temperature, leading to sharp decrease in thermal-hydraulic behaviour and sudden increase in the temperature which put serious concern on material safety. Under normal and enhanced operating region, decreasing effective height under inclined condition or for smaller diameter under constant height, friction force dominates over buoyancy force which consequently leads to initiation of FiHTD at relatively low power. This analogy was visualised with the help of temperature contours at heater power of 1000 W. Under favourable conditions, friction factor shows negative trend along the heater length due to increase of Reynolds number. Change of slope from negative to positive signify the occurrence of FiHTD. Though the phenomenon is unavoidable, yet changing the operating condition and loop orientation can lead to delay of FiHTD.
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