Thermal Characteristics and Heat Balance Analysis of the FASSIP-06 Ver.3 Rectangular Natural Circulation Loop under Single-Phase Flow Conditions

Abstract:

Natural circulation is a passive cooling mechanism that is attractive for application in thermal engineering systems and advanced nuclear reactors because it is simple, reliable, and does not require pumps or external power sources. However, detailed studies on the thermal characteristics and energy balance of medium-scale experimental facilities remain limited, even though such investigations are essential to validate system performance and support the development of numerical models. This study aims to analyze the performance of the FASSIP-06 Ver.3 facility, which is configured as a rectangular loop with a height of 3.4 m and a width of 0.85 m, operated under single-phase conditions with heater power variations ranging from 750 to 1550 W. Experimental results show that increasing heater power leads to a rise in fluid temperature along the loop until a quasi steady-state condition is achieved. The temperature distribution demonstrates a clear gradient between the hot leg and cold leg, with the highest temperature observed at the heater outlet and the largest drop at the cooler inlet. Heat loss analysis indicates that the major contributions occur at the cooler, the BRT, and the visualization window, while other sections are relatively well insulated. Energy balance evaluation shows that the difference between heater input power and total measured heat loss consistently remains below ±10%, indicating that the system achieves thermal equilibrium.

• Periodical: Defect and Diffusion Forum (Volume 453)
• Pages: 157-164
• DOI: https://doi.org/10.4028/p-IjS4wO
• Online since: July 2026
• Authors: Sunandi Kharisma, Deendarlianto Deendarlianto, Shendy Akbar Maryadi, Kukuh Prayogo, Arif Adtyas Budiman, Adhika Enggar Pamungkas, Putut Hery Setiawan, Mulya Juarsa*
• Keywords: FASSIP-06 Ver.3 Loop, Heat Balance, Natural Circulation, Single-Phase Flow, Thermal Characteristic

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