Natural circulation in parallel vertical channels with different heat inputs

When forced circulation of the coolant is lost in a Gas Cooled Reactor, natural circulation takes place in the reactor core. The natural circulation among the many parallel vertical channels with different temperatures is quite complicated because the flow rate and direction depend on the time history of the channel temperatures. Since only a few previous studies were concerned with this problem, an experimental and analytical study was made on the natural circulation in many parallel channels with different heat inputs. The experimental apparatus consisted of four vertical channels filled with water. Each channel was furnished with a heater pin and heated by various combinations of time-varying heat inputs. Flow velocity of the water was measured, and an abrupt change of the flow direction was observed. An analytical code predicted well the experimental results. (author)