Experimental Study Of Single-phase Forced Convection Heat Transfer In Pebble-Bed Channels With Internal Heat Source

Fluid flow and heat transfer phenomena in porous media with a broad engineering background, has become the most active field of frontier research at the current subjects such as engineering thermo-physics. New concept of micro-pebble bed water cooled reactor has high economic and security which can be expected to be significantly higher than the current water cooled reactors in volume thermal power. Study on forced convective heat transfer in pebble bed channels with internal heat source timely, is of great significance to promote the development of water cooled pebble bed reactors.In this paper, the pebble bed channel was packed by balls with particle diameter of 3mm or 8mm.Non-contact intermediate frequency induction heating provides internal heat source for the pebble bed, with distilled water as the cooling medium.First, the induction heating power distribution in the pebble bed channel was investigated by experiments with oxidized stainless balls (φ=3mm). Induction heating power was evenly distributed within the bed, with good symmetry. Axial induction heating power is higher in the middle, lower in the both ends, with non-uniformity of about 35%, while radial induction heating power decreases from core to the wall, with non-uniformity of about 10%.Second, the experimental studies of single-phase forced convection heat transfer in the pebble-bed were operated under 4 kinds of balls. The average coefficient of the forced convection heat transfer inside the pebble-bed channels is very high, and it decreases with the increasing of inlet water temperature and heating power, but increases with the increase of packed ball diameter. Based on the experimental data, correlations are developed for the single-phase forced convection heat transfer in pebble-bed with internal heat source, and the prediction error on the experimental results of±11%.Finally, summarized the issues encountered in the experimental measurements, and propose the solutions or improvements. Such as stratification in the calibration of the long and short mini-sheathed thermocouples using NI measurement system; The interference of intermediate frequency electromagnetic field on the signals of thermocouples and turbine flowmeter, under the strong electromagnetic fields of induction heating.