158 Abstracts for The 3rd World Conference Investigation on the Bundle Effects of Boiling Heat Transfer in Tube Bundle Using Nitrogen Bubble Simulation M. H. Shi X. Y. Zong W. P. Yu Department of Power Engineering Southeast University Nanjing, Jiangsu, China An experimental investigation to clarify the bubble flow and the effects of rising bubbles on boiling heat transfer in tube bundle was conducted by using nitrogen bubble simulation. The experimental results showed that the ris- ing bubbles from the different parts of the lower tube surface have different flow characteristics and only a part of rising bubbles can impact and slide over the test tube and form a microlayer between a sliding bubble and boiling surface. The effects of sliding bubbles on enhanc- ing heat transfer were evaluated at different heat fluxes. An Experimental Study of Nucleate Boiling Heat Transfer from Flame Spraying Surface of Tube Bundle in Rl13/Rll-Oil Mixtures Yong-Ping Gan Qi Chen Xiao-Yan Yuan Department of Thermal Science Engineering Beijing Potytechnic University Beljing, China Shu-Rong Tian Kyushu University Kasuga Fukuoka, Japan An experimental investigation of pool nucleate boiling from a flame-spraying aluminum-enhanced tube (SAE tube, China. Pat. No. CN85100996A) is reported. The test fluids were Rl13, Rll3-Rll mixtures, and Rll3-Rll-oil mixtures. Data were taken at atmospheric pressure and at heat flux from 0.1 kW/m 2 to 100 Kw/m 2. The enhanced surface showed a 5- to 10-fold increase in the heat trans- fer coefficient when compared to a plain tube because the flame-spraying tube onset of nucleate boiling occurred at very low superheat. There was no temperature overshoot. The tube bundle was tested experimentally with pure Rl13 and Tll3-Rll mixtures as working fluid with or without oil contamination. Changes in heat transfer caused by gradually increased oil concentration are shown and discussed for the common range of boiling condition. Predicting the Onset of Nucleate Boiling in a Vertical Thermosiphon Reboiler Mohd Kamil Hamid Ali S. S. Alam Department of Chemical Engineering Aligarh Muslim University Aligarh, India The heating surface and liquid temperature distributions were experimentally obtained to identify the onset of boiling conditions in a single vertical tube thermosiphon reboiler with distilled water, methanol, benzene, toluene, and ethylene glycol as test liquids. The uniform heat flux values were used in the range of 4.1-43.0 kW/m 2, while inlet liquid subcooling varied from 0.5-11.6°C. The liquid submergence levels were maintained around 100, 75, 50, and 30%. The maximum superheat attained near the onset of boiling was taken from the wall temperature distributions and correlated with heat flux and physical properties of test liquids using the expression of Yin and Abdelmessih. A dimensionless correlation relating these values with heat flux, inlet liquid subcooling, and submer- gence was proposed. Minimum Heat Flux Point Condition in Pool Boiling of Binary Mixtures as Determined by the Quenching Method Jyh-Fuh Chen Horng-Shyang Lin Yu-Min Yang Department of Chemical Engineering National Cheng Kung University Tainan, Taiwan Boiling curves for pure water, pure n-propanol and ten of their mixtures including the azeotrope were obtained by quenching a 1.25-cm diameter chromium-electroplated copper sphere from 560°C in the saturated liquids. Pool boiling minimum heat flux (MHF) point condition (qmin, ATmi n) values were determined from these boiling curves. The experimental results show that there are two maxima of qmin, the more significant one occurs at a concentration below the azeotropic point and the other occurs at a concentration above the azeotropic point. The case is also true for ATmin but with less noticeable maxima. This curious behavior of the binary mixtures is at- tributed to the mass diffusion effect, which is caused by the exhaustion of the more volatile component near the vapor-liquid interface and can be represented by a theo- retical dimensionless function F: in which x, y are the mass fraction in liquid and vapor phase, respectively, a, D, C~, h~g are the thermal diffu- . . . . . . . Y J. SWlty, mass dlffUSlVlty, liquid speofic heat, and latent heat of vaporization, respectively. T is the saturation tempera- ture of a liquid. The appropriateness of taking mass diffusion effect into consideration by F function is justi- fied through correlating the experimental MHF point data with equation concerning F. Measurements of Boiling Heat Transfer From Cylindrical Fins R. H. Yeh S. P. Liaw J. Y. Hong Department of Marine Mechanical Engineering National Taiwan Ocean University Keelung, Taiwan Boiling heat transfer on a cylindrical fin was investigated experimentally in this study. Copper fins with a diameter of 25 mm and lengths of 100, 85, 70, 55, and 40 mm were used to protrude into a pool of saturated distilled water and isopropyl alcohol at atmospheric pressure. Experi- ments were conducted in both heating and cooling pro- cesses. The total heat transfer rate and safety operating