Univerzitet u Beogradu - Mašinski fakultet, Beograd
Abstract
Razvijen je numerički model za simulaciju i analizu hidrauličkog udara koji je zasnovan na jednodimenzionalnom homogenom modelu dvofaznog strujanja praćenju razdelne površine stuba tečnosti i parnog mehura i modeliranju direktne kondenzacije pare na pothlađenoj tečnosti. Sistem bilansnih jednačina je rešen primenom metode karakteristika. Integracija je vršena duž tri karakteristična pravca: dva pravca određena su pravcem prostiranja talasa pritiska a treći prostiranjem fluidnog delića. Praćenje fluidnog delića i razdelne površine vode i pare izvršeno je rešavanjem energetske jednačine u prostoru sa tačnošću trećeg reda. Količina toplote koju para preda tečnosti pri kondenzaciji određena je integracijom površinskog toplotnog fluksa po razdelnoj površini parne i tečne faze na mestu kontakta pare i pothlađene tečnosti. Model je primenjen na simulaciju i analizu hidrauličkog udara izazvanog u nekoliko eksperimentalih aparatura.A numerical model for the simulation and analysis of the water hammer in the pipe two-phase flow is developed. The modeling is based on one-dimensional homogeneous model of two-phase flow, tracking of the interface between steam volume and water column and modeling of the direct condensation of steam on sub cooled liquid. The mass, momentum and energy conservation equations are solved by the method of characteristics. For these three equations, there are three characteristic directions: two of them are determined by the pressure wave propagation and the third one by the fluid particle propagation. The fluid particle and the steam-water interface tracking are obtained through the energy conservation equation solving in space, with the accuracy of the third degree. The value of thermodynamic quality is used to determine whether the observed computational region is filled with water, two-phase mixture or steam. The term in the energy conservation equation, which contains information about the heat exchanged between steam and liquid phase through condensation, is determined by integration of superficial heat flux over steam-water interface. The model is applied to the simulation and analysis of the air-water interface propagation in the experimental apparatus of oscillating manometer and the condensation induced water hammer in a vertical pipe for draining of steam into the pool filled with sub cooled water
