Analytical and Numerical Modeling of Diffusion Processes in Smoke Pipes of Heat Generating Plants

Abstract

Method and results of calculation of diffusion processes in smoke pipes of heat generating plants are considered. The technique consists of six stages, including modeling of gas-dynamic and heat-mass-exchange processes based on differential equations of motion, continuity of flow, preservation of energy.

Differential motion equations are written for the turbulent mode. An integral form of the diffusion equation was used to calculate the moisture exchange parameters in the pipe wall. The flow with heat exchange was simulated in Flow Vision software complex. A computer program developed by the authors was used to calculate diffusion processes in the pipe wall.

In order to test the method, the diffusion processes were calculated in a reinforced concrete stack assembly with a height of 30 m and a diameter of 1.2 m at the parameters of the coldest month. As a result of the calculations, it has been found that the zones of possible condensation are located in the outer layers of the pipe wall or on its outer surface. The significant effect of the flow rate of flue gases in the pipe on the temperature and humidity conditions of the walls is noted.

The difference of this technique from the known methods consists in taking into account the factors that significantly influence the temperature and humidity mode of the chimney, primarily the dimensional features of the chimney, the transient processes, the thermophysical and gas-dynamic characteristics of the gases to be removed, and the composition of natural gas. The technique, at the design stage, makes it possible to predict diffusion processes in smoke pipes of heat generating plants, as well as to determine operating modes of operating plants.