Energy release from sodium spray combustion

Energy release associated with sodium spray combustion was determined and a computer code was developed to analyze combustion of sodium particles in the atmosphere depleted of oxygen. Liquid sodium heated at 300∼500 deg. C was injected as much as 400 gr into a closed vessel of 2 m3. Atmosphere in the vessel was controlled by mixing nitrogen gas with dry air and wet air 0∼21% in oxygen concentration and 0∼75 in humidity. Temperatures and pressure of the atmosphere were recorded to observe their rises and drops with time during and after sodium injection. Peak pressure rose with increases in oxygen concentration and temperature of injected sodium being more sensitive to the concentration than the temperature. The peak pressure did not reach a level which was obtained from theoretical energy release from sodium spray combustion because of incomplete combustion and heat transfer to the vessel wall. It was assumed in the computer code that heat and mass transfer was controlled respectively by heat conduction and mass diffusion inside a reaction zone and the transfer was governed by convection outside the reaction zone. Calculation results revealed that combustion rate per unit area on the sodium particle was in proportion to oxygen concentration in the ambient gas but in reverse to the particle sizes, and that decreasing rate of square of particle sizes was about 7x10-4 cm2/s, being smaller in one order of the value of fuel oils. Change in the pressure obtained from the calculation was on the whole in agreement with that observed in the experiment. (author)