摘要
The cooling of a(pebble bed)spent fuel in a high-temperature gas-cooled reactor(HTGR)is adversely affected by an increase in the temperature of the used gas(air).To investigate this problem,a configuration consisting of three copper spheres arranged in tandem subjected to a forced mistflow inside a cylindrical channel is considered.The heat transfer coefficients and related variations as a function of Reynolds number are investigated accord-ingly.The experimental results show that when compared to those with only airflow,the heat transfer coefficient of the spherical elements with mistflow(j=112 kg/m2 hr,Re=55000)increases by 180%,75%,and 20%,respec-tively for thefirst,second,and third spherical element(the corresponding heat transfer enhancement ratio being 2.3,1.4,and 1.1).Additional numerical simulations reveal that the presence of stagnant zones with intense vortex formation around each spherical element contributes significantly to determine the heat transfer behavior.
