Scaled Experiment on Gravity Driven Exchange Flow for the Very High Temperature Reactor
Open Access
- Author:
- Sarangi, Suchismita
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Seungjin Kim, Thesis Advisor/Co-Advisor
Seungjin Kim, Thesis Advisor/Co-Advisor - Keywords:
- gravity driven exchange
vhtr
air ingress
buoyancy driven exchange
water brine - Abstract:
- The process of lock-exchange and gravity driven exchange flow for fluids of differing densities is of particular interest in the postulated Depressurized Loss of Forced Convection (D-LOFC) for the Very High Temperature Gas-Cooled Reactor (VHTR). This event involves the gravity driven ingress of air into the helium filled reactor vessel, ultimately leading to a possible oxidation of graphite components in the vessel. The present study performs a scoping experiment using water and brine as simulant fluids to study the exchange phenomena. To design the test apparatus, a scaling analysis is performed to maintain the exchange time ratio to be unity with the Gas Turbine Modular Helium Reactor (GT-MHR) reference system for the vertical standpipe break. The apparatus consists of two rectangular acrylic compartments connected by pipes and is designed to investigate the effects of the break angle and break length. The break angle is varied from horizontal to vertical at every 15 degrees for L/D = 0.63, 3.0 and 5.0. The volumetric exchange rate is obtained by measuring the time rate of change of mixture density using a hydrometer. A flow visualization study is performed to gain physical understanding of the phenomenon. In general, the present results show similar characteristic phenomena to those found in previous studies for the initial stage of ingress, where the mixture density changes linearly with time. As the ingress progresses, however, it is found that the mixing phenomena inside the compartment and the compartment geometry make significant impacts on the ingress rate. Unlike the previous studies, the present results show that the average exchange rate for the entire ingress event can be up to 70% lower than that obtained from the initial stage alone.