Effect of inclination on pressure drop and flow regimes in large flattened-tube steam condensers

air-cooled condenser;inclination;pressure drop;condensation;flattened tube

Kang, Yu ; Hrnjak ; Predrag Stojan

关键词: air-cooled condenser;    inclination;    pressure drop;    condensation;    flattened tube;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/95329/KANG-THESIS-2016.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This thesis presents an experimental study of the inclination effect on pressure drop and flow regime during condensation of steam in a large flattened tube used in air-cooled condensers (ACC) for power plants. Steam with mass flux of about 7 kg m-2 s-1 was condensed inside a 10.7 m long, flattened test tube with inclination angle varied from horizontal up to 70o. The original full-sized steel tube was cut in half along the centerline, and the removed part was replaced by a polycarbonate window to enable simultaneous flow visualization in situ with heat transfer and pressure drop measurements. A uniform velocity profile of 2.03 ± 0.12 m s-1 was imposed on the air side to extract heat from the steam in a cross flow direction. The experimental results showed that increasing the inclination angle led to reductions of pressure drop due to the improvement in the gravity-assisted drainage of condensate inside the test tube. At such low mass fluxes, tube inclination significantly influenced the flow pattern which was observed to be a well separated stratified flow throughout the tube at all inclination angles for downward flow. Because of the creation of the visualization window, the tube width was less than that used in industry, and thus a model that accounts for the differences in tube geometry between the full and test tube was developed and used to convert experimental pressure drop results to the full-sized tube under the same operating conditions. A prediction of pressure drop performance of the same steam condensing system under vacuum condition was also discussed. The negative dependence of pressure drop on inclination angle also prevailed in both converted results in atmospheric condition and the predicted ones in vacuum condition.