EVAPORATION RATE OF FREE PARAFFIN HYDROCARBON DROPLETS IN A HIGH-TEMPERATURE AND HIGH-PRESSURE GAS-STREAM

A series of evaporation rate constants has been obtained for fine free droplets of paraffin hydrocarbons, n-heptane, iso-octane and n-undecane in the range of 623 to 1 023 K in temperature and 0.1 to 0.5 MPa in pressure as the ambient conditions. To obtain the time histories of droplet diameter a fine droplet stream generated by an electrically controlled piezoelectric element was synchronized with a flash light, and enlarged droplet images were taken on a still camera. The evaporation rate constant increases with ambient pressure and temperature and is expressed by empirical equations. A mixed-hydrocarbon droplet of n-heptane and n-undecane was also examined in terms of the evaporation rate constant, and the evaporation history, the so-called D2-t relation, displays a bending line with two separate straight lines of respective constituents.