Results of Experimental Investigation of Heat Transfer with Emulsions with Low-Boiling Disperse Phase

摘要

The results are given of a theoretical investigation of heat transfer from thin wires to emulsions in which the disperse phase is low-boiling compared to the dispersion medium. A special feature of heat transfer to such emulsions is observed in the mode of nucleate boiling, when only the droplets of the disperse phase of emulsion are boiling. The transition from the convective mode of heat transfer to nucleate boiling requires high values of temperature gradient ΔT=T{sub}W- T{sub}0 at which the temperature of the heat-transfer surface T{sub}W is higher than the temperature T{sub}s of saturated vapors of the disperse phase by 100℃ and more. Here, T{sub}0 is the temperature of the heat-transfer agent away from the heat-transfer surface. Note that, for pure liquids and solutions, the value of delay of the beginning of boiling ΔT=T{sub}W- T{sub}0 as a rule does not exceed 1-5℃. Another feature of heat transfer to the emulsions being treated is a wide temperature range of the mode of nucleate boiling (over 100℃); the upper limit of this temperature range is defined by the temperature of transition to film boiling of the dispersion medium of the emulsion being investigated that has already boiled by this instant of time. The value of delay of the beginning of boiling is affected significantly by additions of surfactants and adsorbents.