| Summary: | An experimental investigation has been made of the effect of mass transfer on the heat transfer and drag force for evaporating and burning liquid drops. An experimental technique was developed which allowed freely falling drops of size less than 0.5 m.m. to be studied. A photographic record of a drop's flight down a furnace containing stationary air was obtained for the liquids: - water, heptane, pentane, benzene, ethyl alcohol and methyl alcohol. Experiments were carried out at varying furnace temperatures up to 1000°C; all the fuel drops ignited at about 700°C, and above this temperature burning drops with envelope flames were studied. From the drop size and distance-time records, the Nusselt number, drag coefficient and Reynolds number were calculated. For drops at low evaporation rates, the values for the Nusselt number were close to the values obtained by previous investigators who had used relatively large suspended drops evaporating into low temperatures. Ls the rate of evaporation increased, the values for the Nusselt number decreased. Similarly for burning drops it was found that as the mass transfer rate increased, the Nosselt values were lowered. The drag coefficient values for drops at low evaporation rates were close to the standard curve for solid spheres. As the intensity of mass transfer increased, the drag coefficient values were reduced. From the experimental results it has been shown how the reduction of the Nusselt number and drag coefficient can be correlated with the intensity of mass transfer.
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