Burnout and intensification of heat transfer in a four-red bundle in freon-12 and water flows

Results of experimental investigation of burnout and intensification of heat transfer in a four-rod bundle in freon-12 and water flows are presented. Experiments are carried out at mass rates of 1000-2500 kg/(m2xc), pressures of 6.86-12.74 MPa, coolant temperatures at the channel entry of 240-300 deg C for water and pressures of 1.06-2.46 MPa, temperatures of 20-65 deg C for freon. Pressure at the channel exit, coolant expense and temperature at the channel entry were kept constant during experiments. Burnout was attained by smooth increase of electric power and was fixed by indexes of thermal pairs placed in tubes. The comparison of experimental results for freon-12 and water showed that regularities of burnout arising and dependence of critical heat flux (critical power) on regime parameters are qualitatively similar. The experiments showed that dynamics of burnout development for bundles with standard lattices and with lattice-turbulators is essentially different. In the first case burnout starting was accompanied by sharp change of heat transfer surface temperature. In the second case under similar conditions surface temperature increased smoothly in strict correspondance with conducted power. Data evaluation coefficient of freon-12 burnout is specified to water