EXPERIMENTAL-STUDY ON FLOW-RATE MEASUREMENT OF BUOYANCY-DRIVEN EXCHANGE FLOW

An experimental investigation was carried out for the buoyancy-driven exchange flow in a narrow vertical pipe concerning the air ingress pro cess during a standpipe rupture in a high-temperature gas-cooled react or. In the current study, the evaluation method of exchange flow was d eveloped by measuring the velocity in the pipe using a laser Doppler v elocimeter. The experiments were performed under atmospheric pressure with nitrogen as a working fluid. The Rayleigh numbers range from 2.0 x 10(4) to 2.1 x 10(5). The exchange flow fluctuated irregularly with time and space in the pipe. It was found that the exchange-velocity di stribution along the horizontal axis changed from one- to two-humped c urves with increasing Rayleigh number. In the case that the lower plen um wall was cooler than the heated disk, the volumetric exchange flow rate was smaller than that in the case where the lower plenum wall and heated disk were kept at the same temperature.