New Method of Experimentally Determining Heat Transfer Coefficients in Direct-Contact Bubble Evaporation.

A measurement technique is presented that uses a new dilatometer measuring device to determine the instantaneous bubble volume and thereby calculate the instantaneous heat transfer coefficients for vaporizing bubbles in an immiscible liquid. Data were taken on single droplets of refrigerant-114 evaporating in water with a nominal initial diameter of 0. 8 mm at a temperature difference of 4 K. The results indicate that the heat transfer data for R-114 may be different in the region at the end of evaporation where the vaporization ratio is greater than 50%. The technique used is consistent, accurate and the experimental method is easy to perform