2013 1(12)

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Pages:

77 - 82

Language:

RU

Ref.:

10


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2013_1(12)_14.pdf

 

 

MODELLING OF BOILING UP OF A METASTABLE LIQUID WITH APPEARANCE OF THE EVAPORATION FRONTS

Aktershev S.P., Ovchinnikov V.V.

Institute of Thermophysics SB RAS, Novosibirsk, Russia


Citation:

Aktershev, S.P. and Ovchinnikov, V.V., (2013) Modelling of boiling up of a metastable liquid with appearance of the evaporation fronts, Modern Science: Researches, Ideas, Results, Technologies, Iss. #1(12), PP. 77 - 82.


Keywords:

boiling up; superheated liquid; evaporation front; condensation front; numerical simulation


Abstracts:

It was found out experimentally that superheating above some threshold values facilitates transition from the conditions of one-phase convection to film boiling (so-called, third crisis of a convective heat transfer). This scenario of the third crisis of heat transfer is possible in various heat transfer equipment. The boiling up at this regime starts from appearance of a spherical vapor bubble on the heater wall. After a while two conic vapor cavities jointed to primary bubble appear on a line of contact of a bubble with a heater wall. The front point of cavity (evaporation front) moves along the heater with constant velocity, which depends on overheat and can attain the value of tens meters per second. The evaporation front was observed both at quasistationary and transient heating for various substances (water, cryogenic and organic liquids, liquid metals). In spite of many experimental data on the velocity of front propagation for various liquids, mechanism of its formation practically is not studied. Various available models allow calculate only velocity of steady propagation of evaporation depending on parameters of liquid before boiling up and do not describe dynamics of boiling up in the presence of evaporation front. In the presented paper the boiling up of highly superheated liquid in the presence of evaporation front is simulated by a numerically. The calculations made are compared to available experimental data for various substances both in the saturation conditions, and in the conditions underheating of a liquid in volume. Results of numerical modeling have shown that proposed model well presents both growth of a primary vapor bubble, and the form of a cone-shaped vapor cavity. For a case of underheating of a liquid in volume the model describes effect of detaching of a cone-shaped cavity from a primary bubble during its condensation and extending of the «vapor rest» along a heater.


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