The steady behavior of the supercritical carbon dioxide natural circulation loop

• Published in: Energy (Oxford) 2024-05, Vol.294, p.130735, Article 130735
• Main Authors: Draskic, Marko, Bugeat, Benjamin, Pecnik, Rene
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Experiments; Natural circulation; Predictive equation; Supercritical fluid
• ISSN: 0360-5442
• DOI: 10.1016/j.energy.2024.130735

The steady state behavior of thermodynamically supercritical natural circulation loops (NCLs) is investigated in this work. Experimental steady state results with carbon dioxide are presented for supercritical pressures in the range of 80–120 bar, and temperatures in the range of 20–65 °C. Distinct thermodynamic states are reached by traversing a set of isochors. An equation for the prediction of the steady state of NCLs at supercritical pressures is presented, and its performance is assessed using empirical data. Changes of mass flow rate as a result of independent changes of thermodynamic state, heating rate, driving height and viscous losses are shown to be accurately captured by the proposed equation. Furthermore, close agreement between the predicted and measured mass flow rate is found when the measured equipment losses are taken into account for the comparison. Subsequently, the findings are put forward in aid of the development of safe, novel supercritical natural circulation facilities. •Experimental investigation of natural circulation loop (NCL) with supercritical CO2.•A steady-state mass flow rate equation is proposed for supercritical pressure NCLs.•An experimental sensitivity analysis substantiates the validity of the equation.•The applicability of the equation to large-scale systems is elaborated on.