Abstract: An improved two-phase flow pattern map is proposed for evaporation in horizontal tubes. The new map was developed based on flow pattern data for five different refrigerants covering a wide range of mass velocities and vapor qualities. The new map is valid for both adiabatic and diabatic (evaporating) flows and accurately identifies about 96% of the 702 data points. In addition, the new flow pattern map includes the prediciton of the onset of dryout at the top of the tube during evaporation inside horizontal tubes as a function of heat flux and flow parameters.

Abstract: A new heat transfer model for intube flow boiling in horizontal plain tubes is proposed that incorporates the effects of local two-phase flow patterns, flow stratification and partial dryout in annular flow. Significantly, the local peak in the heat transfer coefficient versus vapor quality can now be determined from the prediction of the location of onset of partial dryout in annular flow. The new method accurately predicts a large, new database of flow boiling data, and is perticularly better than existing mehods at high vapor qualities (x > 85%) and for stratified types of flows.

Abstract: Attempts have recently been made to numerically simulate film boiling on a horizontal surface. It has been observed from experiments and numerical simulations that during film boiling the bubbles are released alternatively at the nodes and antinodes of a Taylor wave. Near the critical state, however, hydrodynamic transition in bubble release pattern has been reported in the literature. The purpose of this work is to understand the mechanism of the transition in bubble release pattern through complete numerical simulation of the evolution of the vapor-liquid interface. The interface is captured by a level set method which is modified to include the liquid-vapor phase change effect. It is found from the numerical simulation that at low wall superheats the interface moves upwards, bubbles break off, and the interface drops down alternatively at the nodes and antinodes. However, with an increase in wall superheat, stable vapor jets are formed on both the nodes and antinodes and bubbles are released from the top of the vapor columns. The numerical results are compared with the experimental data, and visual observations reported in the literature are found to be in good agreement with the data.

Abstract: A simple and effective surface modification technique, namely palladium-treated thermal oxidation (PTO), has been developed in the present research. Comparative investigations on both corrosion and wear resistance have been carried out on surface-engineered titanium-based materials by conventional plasma nitriding (PN), thermal oxidation (TO), and the newly developed palladium-treated thermal oxidation (PTO). Both the TO- and PTO-treated materials have a significantly superior corrosion resistance in boiling HCl solutions compared to the PN-treated and untreated materials. The lifetime for the protective surface layer breakdown of the TO-treated titanium in boiling 20% HCl solution is about 13 times that of the PN-treated titanium, whereas the lifetime of the PTO-treated material has been increased further by a factor of 2.6 over the TO-treated material. The PTO-treated material has shown a better anti-scuffing capacity than the TO-treated material under oil-lubricated conditions. Characterisation of both the TO- and PTO-treated surface layers was performed using glow discharge spectrometry (GDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Abstract: Subcooled flow boiling covers the region beginning from the location where the wall temperature exceeds the local liquid saturation temperature to the location where the thermodynamic quality reaches zero, corresponding to the saturated liquid state. Three locations in the subcooled flow have been identified by earlier investigators as the onset of nucleate boiling, the point of net vapor generation, and the location where x = 0 is attained from enthalpy balance equations. The heat transfer regions are identified as the single-phase heat transfer prior to ONB, partial boiling (PB), and fully developed boiling (FDB). A new region is identified here as the significant void flow (SVF) region. Available models for predicting the heat transfer coefficient in different regions are evaluated and new models are developed based on our current understanding

Abstract: A summary of a comprehensive experimental study on flow boiling heat transfer is presented for five refrigerants (R134a, R123, R402A, R404A and R502) evaporating inside plain horizontal, copper tube test sections. The test data were obtained for both 12.00 mm and 10.92 mm diameters using hot water as the heating source. Besides confirming known trends in flow boiling heat transfer data as a function of test variables, it was also proven that the heat flux level at the dryout point at the top of the tube in annular flow has a very significant downstream effect on heat tranfer coefficients in the annular flow regime with partial dryout.

Abstract: The present invention relates to a fibrous material which includes a plurality of polylactide containing fibers. The plurality of polylactide containing fibers can be considered low shrinkage or high shrinkage. The plurality of polylactide containing fibers are considered low shrinkage fibers if they provide a boiling water shrinkage propensity of less than about 20 %. The plurality of polylactide containing fibers are considered high shrink fibers if they provide an average fiber boiling water shrinkage propensity of greater than about 10 % and a heat of fusion of less than about 25 J/g. The invention additionally relates to the use of an extrusion process to provide low shrinkage fibers and high shrinkage fibers. The invention futher relates to the use of these fibers in desirable products.

Abstract: An experimental study was done on the effect of dissolving a surfactant in water sprays used to cool a hot surface. A copper surface was heated to an initial temperature of 240°C and then rapidly cooled rising a spray of either pure water or an aqueous solution containing 100 ppm by weight of sodium dodecyl sulfate. The variation of surface temperature was measured during cooling, and spray impact was photographed. Addition of the surfactant was found to enhance nucleate boiling heat flux by up to 300 percent. The surface temperature required to initiate vapor bubble nucleation was reduced from 118°C to 103°C. These effects were attributed to the surfactant promoting bubble nucleation and foaming in spray droplets. Nucleate boiling heat transfer enhancement was observed at all liquid mass fluxes and droplet velocities in the range of our experiments. The surfactant slightly reduced transition boiling heat transfer, and also reduced the temperature at which spray droplets started to wet the surface. Changing the orientation of the surface with respect to gravity had no effect on heat transfer

Abstract: Thermally enhanced remediation of trichloroethylene (TCE) from a 50 cm deep silty soil was demonstrated in a two-dimensional laboratory tank. Volatilized TCE was captured by vapor extraction in an overlaying coarse sand layer. Soil vapor extraction was first tested alone at 23 °C, showing very little efficiency due to the low-permeable layer and an estimated cleanup time of more than 1 year. By injecting electric current, the temperature was increased to 85 and 100 °C in steps, and the fluxes of TCE increased by factors of 2.6 and 19, respectively. After 37 days of heating, the mass of TCE in the soil was reduced from 35 to 0.072 g, corresponding to 99.8% mass removal. Average soil TCE concentrations were reduced from 273 to 0.6 mg/kg. Steam production by boiling of pore water and a 9-fold increase in the Henry's law constant of TCE were identified as the major mechanisms for overcoming mass-transfer limitations. The silty soil did not dry out due to water addition at the current electrodes, which is prom...

Abstract: Experimental evidence available in the literature indicates that the pool boiling heat transfer with binary mixtures is lower than the respective mole- or mass-fraction-averaged value. Although afew investigators have presented analytical work to model this phenomenon, empirical methods and correlations are used extensively. In the present work, a theoretical analysis is presented to estimate the mixture effects on heat transfer. The ideal heat transfer coefficient used currently in the literature to represent the pool boiling heat transfer in the absence of mass diffusion effects is based on empirical considerations, and has no theoretical basis. In the present work, a new pseudo-single component heat transfer coefficient is introduced to account for the mixture property effects more accurately. The liquid composition and the interface temperature at the interface of a growing bubble are predicted analytically and their effect on the heat transfer is estimated. The present model is compared with the theoretical model of Calus and Leonidopoulos (1974), and two empirical models, Calus and Rice (1972) and Fujita et al. (1996). The present model is able to predict the heat transfer coefficients and their trends in azeotropeforming mixtures (benzene/ methanol, R-23/R-13 and R-22/R-12) as well as mixtures with widely varying boiling points (water/ethylene glycol and methanol/water).

Abstract: A parametric study of coupled neutronic-thermohydraulic stability of natural circulation boiling water reactors (BWRs) is performed As an example, the stability characteristics of the Dutch Dodewa

Abstract: Intube evaporation tests for R-407C and R-407C/oil are reported for a plain copper tube The tests were run at a nominal inlet pressure of 645 bar (935 psia) at mass velocities of 100, 200 and 300 kg/m2s (73581, 147162 and 220743 lb/h ft2) over nearly the entire vapor quality range Pure R-407C performed very similar to pure R-134a run previously in similar tests at all three mass velocities, differing only at high vapor qualities where the peaks in href vs x were shifted slightly For local vapor qualities from 10-70%, oil tended to have little effect on local R-407C/oil heat transfer coefficients at the lowest mass velocity while at the higher mass velocities the effect was to increase or decrease the coefficients within ±20% of the pure R-407C values At vapor qualities higher than 70%, the effect of the oil was very dramatic, decreasing performance by as much as 80-90% even with small amounts of oil Two-phase pressure drops were increased by the presence of oil, especially at high vapor qualities Two methods for predicting local boiling coefficients of refrigerant-oil mixtures were presented Using the refrigerant-oil mixture viscosity in place of the pure refrigerant viscosity in the recent Kattan-Thome-Favrat flow boiling model and flow pattern map without further modification predicted the R-134a/oil and R-407C/oil data quite accurately The Friedel two-phase friction multiplier was found to work adequately for pure R-134a and pure R-407C Finally a new local refrigerant- oil viscosity ratio was developed that accurately predicted two-phase pressure drops of R-134a/oil and R-407C/oil mixtures at high vapor qualities

Abstract: A theoretical model describing coupled neutronic-thermohydraulic power oscillations in natural circulation boiling water reactors (BWRs) is developed. The governing equations for the thermohydrauli...

Abstract: A new chemical enhanced oxidation method for gallium arsenide (GaAs) in liquid phase near room temperature (40°C–70°C) is proposed and investigated. Featureless oxide layers with good uniformity and reliability can be grown efficiently on GaAs without any extra energy source. A relatively high oxidation rate (1000 A/h), about 50 times higher than that obtained during oxidation in boiling water has been realized. Based on the results of X-ray photoelectron spectroscopy (XPS), excellent chemical stability after thermal annealing as well as good chemical stoichiometry have been realized. The oxide was determined to be composed of Ga2O3 and As2O3.

Abstract: A self cooling beverage container or can. Different embodiments of a self cooling can are shown including the use of an endothermic reaction perhaps between ammonium nitrate and water. In another embodiment a volatile liquid is evaporated. In another embodiment water is maintained in a low pressure environment and allowed to boil. The vapour which is produced from the boiling water is absorbed by a desiccant maintaining the boiling process. The cooling process may be initiated by the pressure release of a carbonated beverage can during opening of the can.