TY - GEN
T1 - CTF void drift validation
AU - Gergar, M.
AU - Avramova, M.
AU - Salko, R.
PY - 2015
Y1 - 2015
N2 - CTF, a version of the thermal-hydraulic subchannel code COBRA-TF being jointly developed by The Pennsylvania State University (PSU) and Oak Ridge National Laboratory (ORNL) for applications in the Consortium for Advanced Simulation of Light Water Reactors (CASL), has been used to perform isothermal subchannel calculations in order to determine the void distribution in an experimental 2x2 rod bundle facility. The experiments were run with an air and water mixture as the working fluid in order to study the void drift phenomenon, which involves vapor bubbles migrating from small cross-sectional area subchannels to larger cross-sectional area subchannels. These simulations were performed in order to validate the void drift model used in CTF. Since CTF does not directly solve the noncondensable gas conservation equations to obtain gas void (i.e., air in the air-water mixture), the inlet enthalpy of the CTF model was modified to from experimental values to sustain the desired vapor void fraction at the bundle inlet. The bundle average void fraction was then held constant with respect to axial location to simulate the noncondensa ble nature of air in the experiment by iterating the inlet fluid enthalpy. The modeling of the droplet flow field was disabled and the void distribution of the bundle was determined both with and without the void drift model enabled in order to demonstrate the efficacy of the model. The CTF results calculated with the void drift option enabled exhibited the same trend as found in the experiment. Additionally, the average absolute error between the experimental and CTF results demonstrated that the corner subchannel void was consistently overpredicted while the center subchannel void was consistently underpredicted. However, the CTF-to-experiment error was consistently within the ±6% experimental error uncertainty when the void drift option was enabled. Conversely, the relative error was outside of this experimental uncertainty when the void drift modeling option was disabled.
AB - CTF, a version of the thermal-hydraulic subchannel code COBRA-TF being jointly developed by The Pennsylvania State University (PSU) and Oak Ridge National Laboratory (ORNL) for applications in the Consortium for Advanced Simulation of Light Water Reactors (CASL), has been used to perform isothermal subchannel calculations in order to determine the void distribution in an experimental 2x2 rod bundle facility. The experiments were run with an air and water mixture as the working fluid in order to study the void drift phenomenon, which involves vapor bubbles migrating from small cross-sectional area subchannels to larger cross-sectional area subchannels. These simulations were performed in order to validate the void drift model used in CTF. Since CTF does not directly solve the noncondensable gas conservation equations to obtain gas void (i.e., air in the air-water mixture), the inlet enthalpy of the CTF model was modified to from experimental values to sustain the desired vapor void fraction at the bundle inlet. The bundle average void fraction was then held constant with respect to axial location to simulate the noncondensa ble nature of air in the experiment by iterating the inlet fluid enthalpy. The modeling of the droplet flow field was disabled and the void distribution of the bundle was determined both with and without the void drift model enabled in order to demonstrate the efficacy of the model. The CTF results calculated with the void drift option enabled exhibited the same trend as found in the experiment. Additionally, the average absolute error between the experimental and CTF results demonstrated that the corner subchannel void was consistently overpredicted while the center subchannel void was consistently underpredicted. However, the CTF-to-experiment error was consistently within the ±6% experimental error uncertainty when the void drift option was enabled. Conversely, the relative error was outside of this experimental uncertainty when the void drift modeling option was disabled.
KW - CTF
KW - Void drift
KW - Void fraction
UR - http://www.scopus.com/inward/record.url?scp=84964054297&partnerID=8YFLogxK
M3 - Conference contribution
AN - SCOPUS:84964054297
T3 - International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015
SP - 6064
EP - 6075
BT - International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015
PB - American Nuclear Society
T2 - 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2015
Y2 - 30 August 2015 through 4 September 2015
ER -