Investigation of the destruction of the heating surface coated by porous structure in elements оf thermal power units



Genbach А.А., Bondartsev D.Yu., Iliev   I.K.


Abstract. A model of vapor bubble dynamics was established, which are appeared at the solid surface in porous structures and steam generating wall. The model is based on movie and still photography by high-speed camera SKS-1М. The analytical model was established on theory of thermo elasticity when a heat flow goes to core of the vapor bubble, which has a “dry” spot and micro layer shaped like a frustum of a cone. Limit state of the weak heat conductive porous coating and metal plate were determined. Heat flows were calculated from time of spontaneous appearance of steam seed (10-8) up to time of material destruction (102 + 103 с), i.e time interval was described from the relaxation process up to macro process (destructionBreakup of surfaces under impact of the compression force activates much earlier than under the tension force. Probably breakup will occur under impact of compression force and shear force. Intervals of heat flow where such breakups take place are different for quartz surfaces qmax ≈ 7×107 W/m2,  qmin ≈ 8×104 W/m2 and boundary qmax ≈ 1×107 W/m2, qmin ≈ 21×104 W/m2.. When specific heat flow in the heated layer gets increased, and therefore time for heating gets reduced, that leads to compression stress increase. Despite high resistance to breakup compression from compressive heat stresses it occurs in more favorable conditions immediately and in miniscule low volumes.
Key words: model of vapor bubble dynamics, capillary porous surfaces, intervals of heat flows, heat conductivity equation, heat and power units.


МРНТИ 44.31.31.. №2(2018г.)

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