Investigation of Plenum-To-Plenum Heat Transfer and Gas Dynamics under Natural Circulation in a Scaled-Down Dual Channel Module Mimicking Prismatic VHTR Core Using CFD

In this study, two CFD packages, STAR-CCM+ and COMSOL were used to simulate scaled experimental facilities mimicking a dual channel natural circulation behavior in VHTR\u27s and mimicking prismatic VHTR core and plena operation under natural circulation conditions to simulate the natural flow conditions in P2P, identify stream line, and velocity variations in the upper plenum and the two channels at given initial conditions for two different cases of 0.8 MPa and 4.2 MPa. A dual channel module represents a scaled down prismatic block reactor mimicking OSU-HTTF with a scaling down ratio of 1/4 axially and 1/4 radially with a diameter similar to OSU-HTTF cooler channel (0.625 inch) and length of channel is identical to 1/4 to the length of channels of OSU-HTTF of reactor core diameter 1 foot with reference OSU-HTTF. Dual-channel module was meshed with 1 million cells for the two cases. Simulations were carried out for Helium at pressure values of 0.8 MPa and 4.2 MPa