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The Effect of Loop Inclination on Natural Circulation Mass Flow Rate and Heat Removal Inside Rectangular Passive Cooling Loop

Atom Indonesia · Vol. 51 No. 3 (2025) · pp. 259–271

DOI
10.55981/aij.2025.1467
ISSN
2356-5322, 0126-1568
Published
2025-12-08
Publisher
National Research and Innovation Agency
Language
eng
License
creativecommons.org/licenses/by-nc-sa/4.0

Abstract

The use of passive cooling systems as a reactor safety measure has become a key approach to preventing future incidents similar to the Fukushima Daiichi NPP accident. These systems operate based on natural circulation, a process driven by temperature differences and elevation between the heat source and heat sink. Key design factors, such as the inclination angle of the rectangular loop, significantly influence this circulation. This study aims to investigate the effects of different inclination angles of the rectangular loop and variations in the initial water temperature in the Water Heating Tank (WHT) on the flow rate and heat removal capability. The research was conducted experimentally using a natural circulation rectangular loop facility, FASSIP-04 Ver.0, which has an inner diameter of 26.64 mm, a rectangular loop height of 2280 mm, and a width of 780 mm. The experimental variations were achieved by adjusting the water temperature inside the WHT to 50°C, 70°C, and 90°C. Meanwhile, the inclination angle of the loop was set to 30°, 60°, and 90° mass flow rate and heat removal capability was influenced by both the loop inclination angle and the water temperature in the WHT. The highest values were observed at a 90° inclination angle and a set temperature of 90°C, with a mass flow rate of 0.0241 kg/s, and heat removal rates of qH = 0.791 kW, qC = 0.489 kW. The resulting buoyancy force was stronger under these conditions, leading to greater heat removal through natural circulation compared to free convection, thereby increasing both mass flow rate and heat removal efficiency.

Keywords

Collaboration network of the authors

40 authors · 154 co-authorship links · 54 across different organisations · showing the 40 most connected

Hover or tap a name to highlight its co-authors. Double-click to open the author's page.

  • National Nuclear Energy Agency of Indonesia
  • Universitas Gadjah Mada
  • National Research and Innovation Agency
  • University of Indonesia
  • Research Organization for Nuclear Energy
  • University of Technology Sydney
  • Udayana University
  • Affiliation unknown
  • Different organisations
  • Same organisation
  • Affiliation unknown
  • Thicker line = more joint articles · bigger circle = more articles
Show as table
Co-authorOrganisationJoint articles
N. PutraAffiliation unknown3
Anhar Riza AntariksawanNational Nuclear Energy Agency of Indonesia3
E. P. AristaUniversitas Gadjah Mada3
A. S. Al-aminUniversitas Gadjah Mada3
Hyundianto Arif GunawanNational Research and Innovation Agency3
Pricylia ValentinaNational Research and Innovation Agency3
Sri IsmarwantiNational Nuclear Energy Agency of Indonesia2
Mukhsinun Hadi KusumaNational Nuclear Energy Agency of Indonesia2
Tanti ArdiyatiNational Nuclear Energy Agency of Indonesia2
T.M.I. MahliaUniversity of Technology Sydney2
Julwan Hendry PurbaNational Nuclear Energy Agency of Indonesia2
Surip WidodoNational Nuclear Energy Agency of Indonesia2
Wiratni BudhijantoUniversitas Gadjah Mada2
Indarto IndartoUniversitas Gadjah Mada2
Ainur RosidiNational Nuclear Energy Agency of Indonesia1
Wayan Nata SeptiadiUdayana University1
Irwin Pratama PutraUniversity of Indonesia1
Ranggi SahmuraUniversity of Indonesia1
P W JokoNational Nuclear Energy Agency of Indonesia1
H IsmuNational Nuclear Energy Agency of Indonesia1
Edy SNational Nuclear Energy Agency of Indonesia1
Kiswanta KiswantaNational Nuclear Energy Agency of Indonesia1
D. HaryantoNational Nuclear Energy Agency of Indonesia1
J.P. WitokoNational Nuclear Energy Agency of Indonesia1
GI GiarnoNational Nuclear Energy Agency of Indonesia1
RA. KoestoerAffiliation unknown1
Sinta Tri HabsariAffiliation unknown1
Dewanto SaptoadiUniversity of Indonesia1
Topan SetiadipuraNational Nuclear Energy Agency of Indonesia1
H.M. KusumaNational Nuclear Energy Agency of Indonesia1

Affiliations come from OpenAlex; journal OAI-PMH metadata carries none. Authors without an OpenAlex ID are matched by name, which can merge or split people.

Metadata source: OAI-PMH (metadata jurnal) https://atomindonesia.brin.go.id/index.php/aij/oai, first harvested 8 Nov 2026, last seen 8 Nov 2026.
Original metadata (oai_dc) 
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	<dc:title xml:lang="en-US">The Effect of Loop Inclination on Natural Circulation Mass Flow Rate and Heat Removal Inside Rectangular Passive Cooling Loop</dc:title>
	<dc:creator>Budiyanto, N. R.</dc:creator>
	<dc:creator>Deendarlianto, D</dc:creator>
	<dc:creator>Yuliaji, D.</dc:creator>
	<dc:creator>Oktaviandi, R.</dc:creator>
	<dc:creator>Raharjo, E. P. A.</dc:creator>
	<dc:creator>Mariyadi, S. A.</dc:creator>
	<dc:creator>Pamungkas, A. E.</dc:creator>
	<dc:creator>Setiawan, P. H.</dc:creator>
	<dc:creator>Budiman, A. A.</dc:creator>
	<dc:creator>Juarsa, M.</dc:creator>
	<dc:subject xml:lang="en-US">Inclination angel; Natural circulation; Passive cooling; Heat removal; Mass flow rate; FASSIP-04 Ver.0</dc:subject>
	<dc:description xml:lang="en-US">The use of passive cooling systems as a reactor safety measure has become a key approach to preventing future incidents similar to the Fukushima Daiichi NPP accident. These systems operate based on natural circulation, a process driven by temperature differences and elevation between the heat source and heat sink. Key design factors, such as the inclination angle of the rectangular loop, significantly influence this circulation. This study aims to investigate the effects of different inclination angles of the rectangular loop and variations in the initial water temperature in the Water Heating Tank (WHT) on the flow rate and heat removal capability. The research was conducted experimentally using a natural circulation rectangular loop facility, FASSIP-04 Ver.0, which has an inner diameter of 26.64 mm, a rectangular loop height of 2280 mm, and a width of 780 mm. The experimental variations were achieved by adjusting the water temperature inside the WHT to 50°C, 70°C, and 90°C. Meanwhile, the inclination angle of the loop was set to 30°, 60°, and 90° mass flow rate and heat removal capability was influenced by both the loop inclination angle and the water temperature in the WHT. The highest values were observed at a 90° inclination angle and a set temperature of 90°C, with a mass flow rate of 0.0241 kg/s, and heat removal rates of qH = 0.791 kW, qC = 0.489 kW. The resulting buoyancy force was stronger under these conditions, leading to greater heat removal through natural circulation compared to free convection, thereby increasing both mass flow rate and heat removal efficiency.</dc:description>
	<dc:publisher xml:lang="en-US">National Research and Innovation Agency</dc:publisher>
	<dc:contributor xml:lang="en-US">RIIM batch-1 LPDP Mandatori BRIN</dc:contributor>
	<dc:date>2025-12-08</dc:date>
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	<dc:source xml:lang="en-US">Atom Indonesia; Vol 51, No 3 (2025): DECEMBER 2025; 259-271</dc:source>
	<dc:source>2356-5322</dc:source>
	<dc:source>0126-1568</dc:source>
	<dc:source>10.55981/aij.v51i3</dc:source>
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	<dc:rights xml:lang="en-US">Copyright (c) 2025 Atom Indonesia</dc:rights>
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