Optimizing Parameters of a High-Efficiency Steam Condenser from a Steam-Gas Mixture with a Large Content of Noncondensing Gases

Abstract

A method and a program for calculating a steam condenser from a steam-gas mixture (SGM) while maintaining its velocity along the depth of the pipe bundle have been developed. At a constant velocity of the SGM, as the steam condenses, a high intensity of heat and mass transfer remains due to the dynamic effect of the flow, but there is a loss of pressure at the same time, as a result of which the saturation temperature of steam in the SGM decreases. The program was used to calculate the optimal steam velocity in a condenser with a high content of noncondensable gases. The optimization took into account the ratio between intensification heat and mass transfer with an increase in the SGM rate and decrease in temperature saturation steam in the mixture due to an increase in pressure loss. The target function was the minimum heat-transfer surface area for a given degree of vapor condensation in the tube bundle. Calculations have been carried out at a pressure of 5-30 kPa at the inlet to the tube bundle, the temperature of cooling water at the inlet to the condenser 12-30°C, water velocity in the pipes 1-4 m/s, length of pipes 4-12 m, and concentration of noncondensable gases (NCG) at the inlet 1-20% at an SGM flow rate of 1 kg/s. An assessment of the influence of deposits on the surface of pipes on the intensity of heat transfer during operation, as well as the influence of the accuracy of calculating the heat-transfer coefficient on the results of calculating the optimal speed, has been carried out. The dependences of the surface area of the heat-exchange surface on the velocity of the SGM and the dependence of the optimal velocity of the SGM on the temperature and speed of the cooling water, the condensation pressure, and other parameters have been obtained. The optimal value of the SGM velocity lies in the region of more than 40 m/s, which must be taken into account when designing capacitors.