Heat transfer and visualization in large flattened-tube condensers with variable inclination

Condensers;Condensation;Air-Cooled;Inclined;Flattened-Tube;Heat Transfer Coefficient;Visualization

Davies, William Allen ; Hrnjak ; Predrag S.

关键词: Condensers;    Condensation;    Air-Cooled;    Inclined;    Flattened-Tube;    Heat Transfer Coefficient;    Visualization;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/90669/DAVIES-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 】

An experimental study of convective condensation of steam in a large, inclined, finned tube is presented.This study extends previous work in the field on inclined, convective condensation in small, round tubes to large, non-circular tubes with low inlet mass flux of vapor.The steel condenser tube in this study was designed for use in a power-plant air-cooled-condenser array with forced convection of air.The tube was cut in half lengthwise and covered with a polycarbonate viewing window.The half tube had inner dimensions of 214mm x 6.3mm and a length of 10.72m.The viewing window allowed visualization of the steam flow and condensation.This study investigated heat transfer and void fraction results for a mass flux of steam of 7.5 kg/m2-s over a range of inclination angles.The angle of inclination of the condenser tube was varied from 0.3o (horizontal) to 13.2o downward flow.The experiments were performed with uniform crossflowing air with velocity of 2 m/s.Both dropwise and filmwise condensation were observed on the tube wall, and depth of the condensate river at tube bottom was seen to decrease with an increase in inclination angle.Average steam-side heat transfer coefficient was shown to increase with an increase in inclination angle.However, average steam-side heat transfer coefficient was much lower than the predictions of both vertical flat-plate Nusselt condensation, as well as Kroger's correlation for condensation in air-cooled condensers.Overall, the results suggest that an improvement in steam-side heat transfer performance can be achieved by varying the tube inclination angle.Pressure drop results are presented in a companion paper.