Experimental study on condensation heat transfer of steam on vertical titanium plates with different surface energies

• Published in: Experimental thermal and fluid science Vol. 35; no. 1; pp. 211 - 218
• Main Authors: Baojin, Qi, Li, Zhang, Hong, Xu, Yan, Sun
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.01.2011; Elsevier
• Subjects: Applied sciences; Condensation pattern; Condensing; Covering; DROPLETS; Dropwise and film co-existing condensation; DROPWISE CONDENSATION; Energy; Energy. Thermal use of fuels; ENGINEERING; Exact sciences and technology; HEAT FLUX; HEAT TRANSFER; Heat transfer coefficients; Heat transfer model; Heat transfer models; MODIFICATIONS; PLATES; SIMULATION; STEAM; SUBCOOLING; SURFACE ENERGY; SURFACES; Theoretical studies. Data and constants. Metering; TITANIUM; Titanium; Heat transfer model; Dropwise and film co-existing condensation; Condensation pattern; Subcooling; Film condensation; Instrumentation; Experimental study; Dropwise condensation; Vertical plate; Surface energy; Heat transfer
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2010.09.003

Visual experiments were employed to investigate heat transfer characteristics of steam on vertical titanium plates with/without surface modifications for different surface energies. Stable dropwise condensation and filmwise condensation were achieved on two surface modification titanium plates, respectively. Dropwise and rivulet filmwise co-existing condensation form of steam was observed on unmodified titanium surfaces. With increase in the surface subcooling, the ratio of area ( η) covered by drops decreased and departure diameter of droplets increased, resulting in a decrease in condensation heat transfer coefficient. Condensation heat transfer coefficient decreased sharply with the values of η decreasing when the fraction of the surface area covered by drops was greater than that covered by rivulets. Otherwise, the value of η had little effect on the heat transfer performance. Based on the experimental phenomena observed, the heat flux through the surface was proposed to express as the sum of the heat flux through the dropwise region and rivulet filmwise region. The heat flux through the whole surface was the weighted mean value of the two regions mentioned above. The model presented explains the gradual change of heat transfer coefficient for transition condensation with the ratio of area covered by drops. The simulation results agreed well with the present experimental data when the subcooling temperature is lower than 10 °C.