The evaporation rate of a liquid spray in a turbulent gas stream is of interest in connection with direct contact heat transfer and combustion equipment. Any fundamental approach to this problem has usually dealt with single drops evaporating in an “infinite” atmosphere. The evaporation of sprays from actual atomisers is obviously a more complicated process and few attempts have been made to find in how far single drop data may be applied, or to measure the evaporation from a whole spray.

The main difficulties lie in devising a satisfactory method of measuring the evaporation rate. Selden and Spencer, injected the liquid into a bomb filled with hot gas under pressure and measured the decrease in pressure with time on a special indicator.