Abstract: Evaporation and boiling heat transfer coefficients are presented for thin, distilled water films flowing over the outside of horizontal, electrically heated brass tubes. Tests were conducted with a thin-slot water distribution system for 2.54- and 5.08-cm-dia smooth tubes. Both local and average heat transfer data were obtained for nonboiling and boiling conditions corresponding to feedwater temperatures ranging from 49 to 127C and heat-flux values ranging from 30 to 80 kW/m{sup 2}. Feedwater flow rates ranged from 0.135 to 0.366 kg/s per meter length per side of the tube. Both nonboiling and boiling correlations of the average heat transfer coefficients were developed and compared.

Abstract: In the first part of this work, nucleate boiling of aqueous solutions of sodium lauryl sulfate (SLS) over relatively wide ranges of concentration and heat flux was carried out in a pool boiling apparatus. The experimental results show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient h considerably higher, and that there is an optimum additive concentration for higher heat fluxes. Beyond this optimum point, further increase in additive concentration makes h lower. In the second part of this work, nucleate boiling heat transfer rate for n-propanol-water binary mixtures with various amounts of sodium lauryl sulfate were measured in the same pool boiling apparatus. The importance of the mass diffusion effect, which is caused by preferential evaporation of the more volatile component at the vapor-liquid interface on the boiling of the binary mixture, has been confirmed. However, it is shown that the effect exerted by the addition of a surfactant dominates over the mass diffusion effect in dilute binary mixtures.

Abstract: Under certain circumstances, the water on which a burning pool of liquid fuel is supported may begin to boil. The water vapor that is released and escapes through the fuel surface tends to atomize the oil, which results in an emulsive-droplet flame above the fuel surface. This phenomenon, called boilover, has been observed for large scale pool fires, but the mechanism causing it to occur has not been fully investigated yet. This paper describes fundamental aspects of the effect of a boiling water sublayer on the behavior of pool fires. A burner system in which the burning surface of the fuel can be fed into the flame so that the fuel/water interface with respect to the edge of the container remains fixed was used. Ten different single-component and six different multicomponent fuels were tested. Conventional flow visualization techniques were applied to study the liquid motion, and results for an ethylbcnzene pool in a 4.8cm diameter pan are presented. Data obtained include temperatures and mass ...

Abstract: A two stage catalytic cracking process wherein a heavy cycle gas oil fraction (HCGO) nominal boiling range 315°C to 565°C (600°F to 1050°F), API gravity of -10° to +10° and 65 to 95 vol% aromatics is recycled to extinction between an ebullated bed hydrocracking zone (50) and a fluidized catalytic cracking zone (2) to yield a liquid fuel and lighter boiling range fraction (19,62) as the light fraction from each zone The catalyst in the fluidized catalytic cracking zone is maintained at a micro activity 68 to 72 while cracking a virgin gas oil to HCGO (20) HCGO is then mixed with vacuum residuum (40) and hydrocracked in an ebullated bed reactor The mid range fraction (64) is recycled to the fluidized catalytic cracking zone The 540°C⁺ (1000°F⁺) (66) fraction is blended with a fuel oil

Abstract: Steady-State subcooled water flow boiling experiments were carried out in a uniformly heated horizontal circular channel with a 0.45-MPa exit pressure and with the mass velocity varying from 1.56 t...

Abstract: This review covers the dynamics and tendency toward rupture of thin evaporating liquid films on a heated surface. Very large heat transfer coefficients can be obtained. The applications include various boiling heat transfer and film cooling devices. A relatively new area for study is heat transfer through ultrathin films, which are less than 100 nm in thickness, and hence subject to van der Waals and other long-range molecular forces. Some recent work employing lubrication theory to obtain an evolution equation for the growth of a surface wave is described. Earlier phenomenological work is briefly discussed, as well as the connection between forced-convection subcooled nucleate boiling and thin-film heat transfer.

Abstract: Mass balance calculations based on metal contents in hot spring mud deposits yield minimum metal contents in hot spring mud deposits yield minimum metal concentrations for the Rotokawa deep geothermal fluid which are compared with calculated (thermodynamic) mineral solubilities and direct analytical metal concentrations. The deep fluid is saturated with respect to native gold and argentite, but unsaturated with respect to cinnabar, native mercury, and stibnite. Adiabatic boiling leads to rapid partial precipitation of argentite from silver chloride complexes while silver and gold bisulfide complexes persist and become unstable only at shallower levels. Stibnite and cinnabar precipitation can only be expected at low temperatures and shallow levels. Mercury partitions into the vapor phase during boiling and a major fraction escapes to the atmosphere.

Abstract: We investigated the hypothesis that the critical heat flux (CHF) occurs when some point on a heated surface reaches a temperature high enough that liquid can no longer maintain contact at that point, resulting in a gradual but continuous increase in the overall surface temperature for most power-controlled systems. This hypothesis unifies the occurrence of the CHF with the quenching of hot surfaces by relating them to the same concept: the ability of a liquid to contact a hot surface, generally defined as some fraction of the liquid's homogeneous nucleation temperature, depending on the contact angle. The proposed hypothesis about the occurrence of the CHF is investigated through a study of the boiling mechanism of the second transition region of nucleate pool boiling of water on copper. An idealized two-dimensional transient conduction heat transfer model was developed to investigate the heat transfer mechanism. The initial macrolayer thickness on the dry portion of the heater, in the second transition region, was found to be bounded between 0 and 11 [mu]m. The radius of the dry patch varied from 15 to 23 mm (60 and 92 percent of the heater radius, respectively) for initial macrolayer thicknesses of 0 and 11 tim, respectively.more » The results indicated that the critical liquid-solid contact temperature at the onset of CHF (the surface temperature at the center of the dry patch) must be lower than the homogeneous nucleation temperature of the liquid for the pool boiling of water on a clean horizontal surface. The liquid-solid contact Temperature was dependent on the initial dry patch liquid macrolayer thickness, varying from 180[degrees]C to 157[degrees]C for initial macrolayer thicknesses of 0 and 11 [mu]m, respectively. Independent assessment of these values shows good agreement with extrapolated contact temperature data at the onset of film boiling.« less

Abstract: The cork used for stoppers (reproduction cork) is subjected to a boiling operation before processing, which consists of immersing the cork boards in boiling water for approximately one hour. An experimental study of the hot water treatment was undertaken with the purpose of characterizing the alterations that it may cause in the structure, dimensions, mass and compression properties of cork. Various parameters related to the treatment were investigated, including water temperature, time, cork quality, and the kinetics of open air-drying. The major structural alteration due to boiling is the attenuation of cell-wall corrugations. This leads to an expansion of 10-15% in the radial direction and 5-7% in directions perpendicular to this, including the axial and tangential directions. The mass is virtually unaffected. Boiling causes a softening of cork and also a reduction of its elastic anisotropy. These and other observed changes in the stress-strain curves in compression can be explained in terms of the structural changes.

Abstract: In many problems involving boiling in a porous medium, such as geothermal energy, meltdown in nuclear reactors, and heat pipes, the porous medium consists of single-phase (liquid) and two-phase (liquid + vapor) regions separated by a phase-change interface. Experimental evidence suggests that the phase-change interface is strongly influenced by liquid-phase natural convection and that liquid can flow in both directions across the interface. This paper describes a numerical scheme for problems involving boiling in a porous medium, including the effects of natural convection. The equations in the liquid region and the two-phase region are coupled by the dynamics of the phase-change interface. The present investigation represents the first attempt at obtaining numerical solutions in the liquid and two-phase regions, together with the position of the interface.

Abstract: Publisher Summary Nucleate boiling is a complicated phenomenon accompanied with a phase change from liquid to vapor. The nucleate boiling heat transfer is one of the most important modes of heat exchange occurring in several constituent devices of thermal plant. The augmentation of nucleate boiling heat transfer significantly contributes towards the efficient use of the thermal energy. The chapter describes a correlation method of nucleate boiling heat transfer by considering the factors that affect the heat-transfer processes. It presents the effect of surface configuration on the nucleate boiling along with the nucleate boiling heat transfer in a narrow space and in a liquid film. The chapter also illustrates potential measures for augmentation of nucleate boiling heat transfer and some results obtained. As the nucleate boiling heat transfer is greatly influenced by surface conditions, the unified rule of the nucleation factor for several surface conditions, which is similar to the emissivity encountered in the heat transfer by thermal radiation, needs to be developed in the future.

Abstract: This invention pertains to processes for manufacturing in an environmentally friendly way, continuous, supported ion exchange membranes from (I) liquids containing vinyl and related monomeric electrolytes and high boiling solvents therefor, said solvents also being swelling agents for said membranes; and (II) an indefinitely long, foraminous substrate and to the products of such processes.