Study of fragile capillary-porous coatings in power installations

Abstract

For carrying out the high-technological processes in heat power installations the fragile capillary-porous coatings up to a limiting condition of heat exchange surface were researched. The coatings made of metallic materials (copper and stainless steel) and of natural mineral media (quartz, granite and teschenit) were studied. A model of the nucleation of steam bubbles in the cells of the porous coatings was developed during vaporization of coolant from their explosive emergence, taking into account the development of the “dry” spots before the damage; also the dynamic angle was defined in the range of (74÷80) degrees. The limiting state of the medium according to the model of the bubbles is studied when solving the problem of thermal elasticity. During the destruction of the coating caused by only a compression a number of curves corresponding to a definite thickness of the coming-off coating particle were obtained. Intervals of the specific heat fluxes coming to steam bubbles are established. In these intervals there is a destruction of a porous coating and metal surfaces at the joint action of capillary and gravity potentials.