Validation of RELAP5/MOD3.3 Friction Loss and Heat Transfer Model for Narrow Rectangular Channels (NUREG/IA-0508)

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Publication Information

Manuscript Completed: July 2018
Date Published: March 2019

Prepared by:
Byeonghee Lee*, Su-ki Park*, Andong Shin**, Min Ki Cho**

*Korea Atomic Energy Research Institute
111 Daedeok-daero 989 Beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea

**Korea Institute of Nuclear Safety
62 Gwahak-ro, Yuseong-gu, Daejeon 34142, Republic of Korea

K. Tien, NRC Project Manager

Division of Systems Analysis
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Prepared as part of:
The Agreement on Research Participation and Technical Exchange
Under the Thermal-Hydraulic Code Applications and Maintenance Program (CAMP)

Published by:
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Availability Notice


The friction loss and the heat transfer models in RELAP5/MOD3.3 were assessed using CNNC experiments and KAERI OFEL tests, which are experiments for narrow rectangular channels. The test sections of the experiments were modeled with PIPE, TMDPVOL and TMDPJUN, considering the geometry and boundary conditions. Since the friction loss and heat correlations of RELAP5/MOD3.3 are supplied with a form of "geometry set", the default set for circular geometry and a narrow rectangular set were compared to find an adequate set which properly simulated the experiments.

The assessments included the friction coefficients of the isothermal and non-isothermal channels, and the heat transfer coefficients of forced convection in the channel. The friction and pressure drop in the isothermal channel were well reproduced by RELAP5/MOD3.3 over the whole flow range in the experiments, but a proper shape factor in the laminar flow region was necessary. Also, the non-isothermal friction coefficients matched the experimental results well with the proper viscosity ratio exponent. The heat transfer coefficients in the turbulent flow region matched well with the 101 set, whereas the 102 set tended to overpredict the heat transfer coefficient in the high Re region. The heat transfer coefficients in the low Re region were overpredicted by RELAP5/MOD3.3 due to its internal logic, which simply selects the highest heat transfer coefficient among those of laminar, turbulent, and natural convection. After modifying that logic, the RELAP5/MOD3.3 showed good agreement with the experimental data.

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