Experimental Studies on Thermal and Hydraulic Performance of Fuel Stack of VHTR, (III): Experimental and Analytical Results of HENDEL Multi-Channel Test Rig with 12 Independently Heated Fuel Rods

Experimental studies on heat transfer and fluid-dynamic characteristics of a mock-up fuel stack of the Very High Temperature Gas Cooled Reactor (VHTR) were carried out by the use of a multi-channel test rig of Helium Engineering Demonstration Loop (HENDEL). Heat generation rate of each simulated fuel rod was varied independently to simulate a power distribution of the VHTR core in a horizontal plane. In parallel with this experiment, a three-dimensional thermal analysis code was developed in order to check the experimental temperature distribution of the fuel stack. Experimental results showed that the distribution of coolant flow rate varied with the temperature distortion in the fuel stack. The variation of calculated temperature distribution in the fuel stack was about 20-35°C in each case, indicating that the temperature distortion in the fuel stack was flattened by thermal conduction through the graphite.