Structure and dynamics of ovalbumin gels

Solvent effects on dynamical and thermal behaviors of ovalbumin (OVA) gels induced by thermal denaturation at high temperature of 160°C were studied from dynamic shear modulus measurement, shear creep and creep recovery measurement, and DSC measurement. Two organic solvents, glycerin (G) and ethylene glycol (EG), and their mixtures with water (W)(G/W and EG/W) were used as solvent for preparation of gels. Stable gels formed in pure glycerin took a fractal structure at OVA concentration C range of 15–45wt% at a temperature specific to respective C, whereas a fractal structure was not observed for gels prepared in EG, G/W, and EG/W. The results were consistent with thermal denaturation behaviors of OVA in these solvents. Morphologies of two gels prepared in water and glycerin were explored using high resolution SEM, which showed that a basic unit responsible for formation of OVA gels was spheres with a diameter ranging from 20 to 40 nm, being much larger than 5.6 nm of the diameter of native OVA, and a fractal structure was related to network formation accompanied by melting of those spheres.Dedicated to Prof. John D. Ferry on the occasion of his 85th birthday.     

An experimental study of the evaporation characteristics of emulsified liquid droplets

This paper presents the results of an experimental investigation, into the effect of water in diesel and kerosene emulsions, on the evaporation time of a single droplet, on hot surfaces (stainless-steel and aluminum). Experiments are performed at atmospheric pressure, and initial water volume concentrations of 10, 20, 30, and 40%. The wall temperatures ranging from 100–460 °C, to cover the entire spectrum of heat transfer characteristics from evaporation to film boiling. Results show that, qualitatively, the shapes of emulsion evaporation curves are very similar to that of pure liquids. Quantitavely, there are significant differences. The total evaporation time, for the emulsion droplets is lower than that for diesel and kerosene fuels, and decreased as water initial concentration increases, up to surface temperatures less than the critical temperature. The value of the critical surface temperature (maximum heat transfer rate), decreases as initial concentration of water increases. In the film-boiling region, the evaporation time for the emulsion droplets is higher than for diesel and kerosene droplets, at identical conditions.List of Symbols h_fg latent heat of vaporization, KJ/kg - m mass of the droplet, gm - T_b boiling temperature, °C - T_c critical temperature, °C - T_L Leidenfrost temperature, °C - T_s initial surface temperature of the hot surface, °C     

Experimental studies on mixed convection heat transfer in laminar flow through a plain square duct

This paper reports the findings of experimental studies on combined free and forced convection through a plain square duct in laminar region. The test fluid flows through an inner square duct, hot water at high flow rate circulated through a annular channel formed between square duct and circular tube, in counter current fashion to attain a nearly uniform wall temperature conditions. The importance of mixed convection is judged by the value of the Richardson number (Ri). It was observed that at low Reynolds number, heat transfer was mainly governed by mixed convection. However at higher values of Reynolds number, heat transfer was significantly dominated by forced convection. It was found that Reynolds number higher than 1050 for water and 480 for ethylene glycol resulted in laminar forced convention heat transfer. The empirical correlation developed for Nusselt number in terms of Grashoff number and Graez number, was found to fit with experimental Nusselt number within ±11 and ±12?% for water and ethylene glycol respectively.     

Effects of the anomalous temperature dependence of water density on surface gravity current

This paper reports experimental results on the propagation of a plane water jet at a temperature above the maximum-density temperature (4° C) along the free surface of initially quiescent water at a temperature of about 0°C. For comparison, experiments were performed in which the temperatures of the lower and higher layers were more than 4°C, other conditions being equal. The experiments revealed a number of new hydrodynamic effects, including peculiar flow instability and a fine structure of the density field at large times.Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 1, pp. 63–69, January–February, 2005     

A cryostat for use with a thermal conductivity hot wire system

Summary A cryostat for use with a thermal conductivity hot wire system is described in which temperatures between –70°C and –130°C can be maintained constant to within (0.01°C). Control of temperature is made by adjusting the vacuum between a five component mixture and liquid oxygen. Extra control is made by adjusting the current through a heating coil immersed in the cryostat mixture. The temperature indicator is a platinum wire surrounding the tubes.     

Investigation of the different base fluid effects on the nanofluids heat transfer and pressure drop

A numerical study of laminar forced convective flows of three different nanofluids through a horizontal circular tube with a constant heat flux condition has been performed. The effect of Al₂O₃ volume concentration 0 ≤ φ ≤ 0.09 in the pure water, water-ethylene glycol mixture and pure ethylene glycol as base fluids, and Reynolds number of 100 ≤ Re ≤ 2,000 for different power inputs in the range of 10 ≤ Q(W) ≤ 400 have been investigated. In this study, all of the nanofluid properties are temperature and nanoparticle volume concentration dependent. The governing equations have been solved using finite volume approach with the SIMPLER algorithm. The results indicate an increase in the averaged heat transfer coefficient with increasing the mass of ethylene glycol in the water base fluid, solid concentration and Reynolds number. From the investigations it can be inferred that, the pressure drop and pumping power in the nanofluids at low solid volumetric concentration (φ < 3%) is approximately the same as in the pure base fluid in the various Reynolds numbers, but the higher solid nanoparticle volume concentration causes a penalty drop in the pressure. Moreover, this study shows it is possible to achieve a higher heat transfer rate with lower wall shear stress with the use of proper nanofluids.     

Effect of an Anomalous Temperature Dependence of the Water Density on Circular Jet Propagation

It is shown experimentally that an originally circular jet with a temperature greater than 4°C transforms into a thin sheet when propagating in water at a temperature of about 0°C and sinks rather than ascends. At large times, a peculiar fine structure of the hydrophysical fields is detected. This is due to the difference between the molecular diffusivities of heat and dissolved salts, as well as the breakdown of large-scale to small-scale vortices.__________Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, 2005, pp. 39–47.Original Russian Text Copyright © 2005 by Bukreev.     

Hydrodynamics and boiling phenomena of water droplets impinging on hot solid

The collision of single water droplets with a hot Inconel 625 alloy surface was investigated by a two-directional flash photography technique using two digital still cameras and three flash units. The experiments were conducted under the following conditions: the pre-impact diameters of the droplets ranged from 0.53 to 0.60 mm, the impact velocities ranged from 1.7 m/s to 4.1 m/s, and the solid surface temperatures ranged from 170 °C to 500 °C. When a droplet impacted onto the solid at a temperature of 170 °C, weak boiling was observed at the liquid/solid interface. At temperatures of 200 or 300 °C, numerous vapor bubbles were formed. Numerous secondary droplets then jetted upward from the deforming droplet due to the blowout of the vapor bubbles into the atmosphere. No secondary droplets were observed for a surface temperature of 500 °C at the low-impact Weber numbers (∼30) associated with the impact inertia of the droplets. Experiments using 2.5-mm-diameter droplets were also conducted. The dimensionless collision behaviors of large and small droplets were compared under the same Weber number conditions. At temperatures of less than or equal to 300 °C, the blowout of vapor bubbles occurred at early stages for a large droplet. At a surface temperature of 500 °C, the two dimensionless deformation behaviors of the droplets were very similar to each other.     

Experimental study to obtain the viscosity of CuO-loaded nanofluid: effects of nanoparticles’ mass fraction,temperature and basefluid’s types to develop a correlation

In this study, the impacts of temperature, nanoparticles mass fraction, and basefluid types were investigated on the dynamic viscosity of CuO-loaded nanofluids. The nanoparticles were dispersed in deionized water, ethanol, and ethylene glycol as basefluids separately and the measurements were performed on samples with nanoparticles loads ranging from 0.005 to 5 wt%, and the temperature range of 25 to 70 °C. TEM analysis were performed on dried nanoparticles and the results showed the average mean diameter of CuO nanoparticles ranged from 10 to 50 nm. The results of DLS analysis confirmed the results of nanoparticles size obtained by TEM analysis in mentioned basefluids and Zeta-Potential tests exhibited the high stability of the nanoparticles in the basefluids environment. The results indicate that by adding tiny amount of CuO nanoparticles to basefluids, relative viscosity of nanofluid increases. By the increase in nanoparticles load higher than 0.1 wt% the effect of both nanoparticles mass fraction and temperature would be more tangible, while for nanoparticles mass fraction lower than 0.1 wt% no significant change in viscosity was observed. In addition, the results declare that viscosity of nanofluid remains constant at various applied shear rates indicating Newtonian behavior of nanofluid at various nanoparticles load and temperature. According to experimental data, it is also evident that with the increase in temperature, the value of relative dynamic viscosity decreases significantly. Also it is concluded that for CuO/ethanol nanofluid, more interfacial interaction is resulted that causes higher relative dynamic viscosity while for CuO/water lower interfacial interaction between nanoparticles surface and water molecules are resulted which leads to the lower values for this parameter. The results of this study implied that with increase the temperature from 25 to 70 °C at the condition where nanoparticles mass fraction was chosen to be 5 wt%, the value of dynamic viscosity of CuO/ethanol, CuO/deionized water, CuO/ethylene glycol declined 69%, 66%, and 65% respectively. Finally, a correlation was proposed for the relative dynamic viscosity of nanofluid based on the CuO nanoparticles mass fraction and temperature of the basefluid and nanoparticles.     

Comparison of the thermal performances of two nanofluids at low temperature in a plate heat exchanger

The objective of this study is to compare experimentally the thermal performances of two types of commercial nanofluids. The first is composed of oxides of alumina (γAl₂O₃) dispersed in water and the second one is aqueous suspensions of nanotubes of carbons (CNTs). The viscosity of the nanofluids is measured as a function of the temperature between 2 and 10 °C. An experimental device, containing three thermal buckles controlled in temperature and greatly instrumented permits to study the thermal convective transfers. The evolution of the convective coefficient permits to study the convective thermal transfers. The evolution of the convective coefficient is presented according to the Reynolds number, at low temperature from 0 to 10 °C and for the two aforementioned nanofluids. An assessment of the pressure drops in the circuit as well as of the powers of the circulator and outputs is dealt with.     

Hot-wire calibration over a large temperature range

The hot-wire calibration method as proposed by Cimbala and Park (1990) has been showen to be accurate within a temperature range of 20–45°C. This is a significant extension of the range used by Cimbala and Park (27.5– 34.5°C). The accuracy of the calibration is not affected by the ambient temperature. The calibration curve obtained seems to hold over a long period of time, thus reducing the need for frequent calibrations. Due to contamination the accuracy eventually decreases and the probe has to be re-calibrated.     

FREE CONVECTION FLOW OF WATER AT 4℃ PASSING AN INFINITE POROUS PLATE WITH CONSTANT SUCTION IN A ROTATING SYSTEM

In this work an analysis of steady free convection flow of water at 4℃ passing a vertical infinite porous plate in a rotating system is considered. Approximate solutions for the coupled nonlinear equations are obtained for the velocity and the temperature. The effect of E’ (Eckman number) is discussed, when P (prandtl number)=11.4, which corresponds to water at 4℃.     

Neue Bestimmung des kritischen Punktes von leichtem und schwerem Wasser

Zusammenfassung Im Rahmen der internationalen Wasserdampfforschung [1, 2, 3] wurden in den letzten Jahren genaue Messungen verschiedener Zustandsgrößen von leichtem und teilweise auch von schwerem Wasser vorgenommen. In diesem Zusammenhang war auch die Kenntnis genauerer Werte für die kritischen Zustandsgrößen von großem Interesse.In einer zylindrischen, waagerecht liegenden Druckkammer mit durchsichtigen Beobachtungsfenstern wurden beim langsamen Durchlaufen des kritischen Punktes mit sehr geringfügigen Temperaturänderungen von 0,01 bis 0,03 °C/h fortlaufend Temperaturen und Drücke gemessen. Gleichzeitig wurde die Phasentrennfläche zwischen Flüssigkeit und Dampf beobachtet, die beim Durchlaufen des kritischen Zustandes in einem sehr kleinen Temperatur- und Druckbereich verschwindet bzw. wiedererscheint.Es ergaben sich folgende Werte für die kritischen Temperaturen und Drücke von H₂O und D₂O: H₂O t_krit=(373,91±0,03) °C P_krit=(220,45±0,03) bar D₂O t_krit=(370,66±0,03) °C P_krit=(216,59±0,03) bar.Die Temperaturangaben beziehen sich auf die Internationale Praktische Temperaturskala von 1948.

---

New determination of the critical point of water and heavy water

The apparatus used for determining the critical data of water and heavy water consists in principle of a horizontal cylindrical pressure chamber of INCONEL X-750. Observation windows of synthetic saphire (Al₂O₃) are located at the ends.During the experiments the critical point was passed with very small rates of temperature change of about 0.01 to 0.03 °C/h. The disappearance and appearance of the meniscus could be observed continuously with a telescope enlarging 10 times, with simultaneous measurement of pressure and temperature.The following results were obtained for the critical temperature and critical pressure of H₂O and D₂O: H₂O t_crit=(373.91±0.03) °C P_crit=(220.45±0.03) bar D₂O t_crit=(370.66±0.03) °C P_crit=(216.59±0.03) bar.These temperatures are related to the International Practical Temperature Scale of 1948.

---

---

Über diese Arbeit wurde auf dem VDI-Thermodynamik-Kolloquium 1967 in Bad Neuenahr berichtet.     

Molecular tagging thermometry with adjustable temperature sensitivity

We report an extension to the technique of molecular tagging thermometry which allows for adjustable temperature sensitivity. The temperature dependence of laser-induced phosphorescence of the water-soluble phosphorescent triplex (1-BrNp•Mβ-CD•ROH) is used to conduct temperature measurements in aqueous flows. It is shown that the temperature sensitivity of phosphorescence intensity can be adjusted by changing the time delay between the laser excitation pulse and the start of the phosphorescence emission acquisition. For example, for a phosphorescence integration period of 1 ms, the temperature sensitivity of the measured phosphorescence intensity varies in the range 8.15–18.2% per °C at 25°C as the time delay changes from 1 to7 ms. This temperature sensitivity is much higher than that of most fluorescent dyes used for temperature measurements (e.g. less than about 2% per °C for Rhodamine B). The implementation and application of this new approach are demonstrated by conducting temperature measurements in the wake of a heated cylinder.     

A note on the rubber-like properties of gelatin

Summary The shape of the load-elongation curve and the temperature coefficient of the elastic modulus have been examined for the unidirectional extension of cross-linked gelatin films swollen in an alcohol-water mixture. The load-elongation curve for extensions up to 300% was of the form predicted by the kinetic theory of elasticity. The temperature coefficient of the stress at constant extension was positive and over the temperature range 50° to 70°C was proportional to absolute temperature. Between 50°C and 0°C the temperature coefficient of the stress was much greater. Over this temperature range the elastic modulus, as measured by extending a film at different temperatures, increased greatly as the temperature was lowered. It is suggested that the large temperature coefficient of the stress at temperatures below 50 °C is due to the formation of gelling cross-links causing straightening of the gelatin chains.

---

Zusammenfassung Die Form der Spannungs-Dehnungskurve und der Temperaturkoeffizient des Elastizitätsmoduls wurde für lineare Streckung von vernetzten Gelatine-Filmen bestimmt, die in Alkohol-Wasser-Mischungen gequollen waren. Bis zu einer Dehnung von 300% hatte die Kurve die aus der kinetischen Elastizitätstheorie zu erwartende Form. Der Temperaturkoeffizient der Spannung für konstante Dehnung war positiv und im Temperaturbereich 50–70° C proportional der absoluten Temperatur; zwischen 0 und 50° C war er viel größer. In diesem Temperaturbereich vergrößert sich der Elastizitätsmodul, gemessen durch Dehnung des Films bei verschiedenen Temperaturen, beträchtlich mit sinkender Temperatur. Es wird angenommen, daß der große Temperaturkoeffizient der Spannung bei Temperaturen unterhalb 50° C auf die Bildung gelierender Querbindungen zurückzuführen ist, die die Gelatineketten ausrichten.

---

---

Communication No. 1955 H from the Kodak Research Laboratories.     

On the quenching of steel and zircaloy spheres in water-based nanofluids with alumina,silica and diamond nanoparticles

The quenching curves (temperature vs time) for small (∼1 cm) metallic spheres exposed to pure water and water-based nanofluids with alumina, silica and diamond nanoparticles at low concentrations (?0.1 vol%) were acquired experimentally. Both saturated (ΔT_sub = 0 °C) and highly subcooled (ΔT_sub = 70 °C) conditions were explored. The spheres were made of stainless steel and zircaloy, and were quenched from an initial temperature of ∼1000 °C. The results show that the quenching behavior in nanofluids is nearly identical to that in pure water. However, it was found that some nanoparticles accumulate on the sphere surface, which results in destabilization of the vapor film in subsequent tests with the same sphere, thus greatly accelerating the quenching process. The entire boiling curves were obtained from the quenching curves using the inverse heat transfer method, and revealed that alumina and silica nanoparticle deposition on the surface increases the critical heat flux and minimum heat flux temperature, while diamond nanoparticle deposition has a minimal effect on the boiling curve. The possible mechanisms by which the nanoparticles affect the quenching process were analyzed. It appears that surface roughness increase and wettability enhancement due to nanoparticle deposition may be responsible for the premature disruption of film boiling and the acceleration of quenching. The basic results were also confirmed by quench tests with rodlets.     

Freezing heat transfer in water-saturated porous media in a vertical rectangular vessel

Numerical and experimental study is performed for the freezing of water-saturated porous media in a vertical rectangular vessel. The governing equations are solved by using a variable transformation and employing a finite difference scheme. The SOR method is utilized to solve numerically the equations. Different size and types of spherical beads are used as the porous media. The temperature of cold wall is kept at –10°C, while that of the hot wall is varied from 2°C to 22°C. Comparisons of the analytical results with the experimental ones are made. The effects of the Stefan number, the Darcy number, the modified Prandtl number and the ratio of the temperature of cold wall to the temperature of hot wall are discussed for freezing of the water-saturated porous media.Diese numerische und experimentelle Untersuchung das Gefrieren in mit Wasser gesättigten porösen Medien in einem vertikalen rechteckigen Behälter. Die Erhaltungsgleichungen werden mit einem Variablen-Transformations-Verfahren und einem Differenzen-Verfahren gelöst. Zur numerischen Lösung der Differentialgleichung wird die SOR Methode verwendet. Als poröses Medium wurden verschiedene Typen und Größen von kugelförmigen Perlen benutzt. Die kalte Wand wurde auf –10°C gehalten, die Temperatur der warmen Wand lag zwischen 2 und 22°C. Die errechneten Ergebnisse wurden mit den experimentell Ermittelten verglichen. Die Einflüsse der Stefan-, Darcy- und Prandtl-Zahlen sowie des Verhältnisses der Temperatur der warmen zur kalten Wand auf das Gefrieren in gesättigten porösen Medien wurden diskutiert.     

A torsional creep instrument and a torsional pendulum,both with accurate temperature control

Summary This paper describes a torsional pendulum and a torsional creep instrument. With the pendulum shear moduli between 10⁶ and 10¹⁰ N/m² can be measured at frequencies from 0.1 to 20 Hz. The creep instrument is suitable for measurement of shear compliances lower than 10^–7 m²/N in the time range from 1 to 10⁵ seconds. In both instruments, specimens are kept at the right temperature by blowing heated nitrogen gas through a surrounding thermostatic chamber. The signal of a platinum resistance thermometer, provided in each chamber, automatically controls the heating of the gas. Temperatures from –180 to +300 °C can be maintained with an absolute accuracy of ±1 °C and a long term stability of ±0.05 °C. It is shown that one cannot directly compare one and the same shear property, calculated from the shear modulus as measured with the pendulum as well as from the shear compliance as measured with the creep instrument. This is due to differences in the temperature of one thermostatic chamber over against the other. Finally, the paper presents a method to reduce these differences to ±0.1 °C, although the absolute accuracy of temperature control remains ±1 °C.

---

Zusammenfassung Die Arbeit beschreibt ein Torsionspendel und eine Torsions-Kriechapparatur. Mit dem Pendel können Schermoduli zwischen 10⁶ und 10¹⁰ N/m² bei Frequenzen zwischen 0,1 und 20 °C gemessen werden. Die Kriechapparatur ist geeignet für die Messung von Scherkomplianzen kleiner als 10^–7 m²/N in Zeiten zwischen 1 bis 10⁵ sec. In beiden Geräten werden die Proben durch das Einblasen von erhitztem Stickstoff durch eine umgebende thermostatische Kammer bei der richtigen Temperatur gehalten. Die Anzeige eines Platin-Widerstandsthermometers, das in jeder Kammer angebracht ist, kontrolliert automatisch die Erwärmung des Gases. Es können Temperaturen zwischen –180 und +300 °C mit einer absoluten Genauigkeit von ±1 °C und einer Langzeitstabilität von ±0,05 °C eingestellt werden. Es wird gezeigt, daß ein direkter Vergleich der gleichen Schereigenschaft, die zum einen aus dem mit dem Pendel gemessenen Schermodul und zum anderen aus der mit der Kriechapparatur ermittelten Kriechkomplianz errechnet wird, nicht möglich ist. Das beruht auf Temperaturdifferenzen zwischen den thermostatisierten Kammern.Abschließend stellt die Arbeit eine Methode vor, um diese Differenzen auf ±0,1 °C zu senken. Die absolute Genauigkeit der Temperaturkontrolle bleibt bei ±1 °C.

---

---

Paper presented at the Conference on Experimental Rheology, University of Bradford, April 17–19, 1968.     

Viscous properties of polymer melts and elastomers exemplified by ethylene-propylene copolymer

Summary The copolymer of ethylene and propylene possesses a sufficiently high thermo-oxidative resistance, making it possible to study its viscous properties, determine the appearance of elastic turbulence and wall slippage and to measure the rate of the latter over a wide interval of temperatures ranging from room temperature to 260 °C.At low shear stresses and rates the copolymer behaves like aNewtonian liquid with a viscosity of about 10⁸ poise at room temperatures.Elastic turbulence and wall slippage are displayed in sharp form when the viscosity of the copolymer is lowered to its critical value, which depends very little on the temperature and may be accepted as averaging 2.2×10⁴ poise. The corresponding critical shear stress values vary about 10-fold. The criteria of appearance of elastic turbulence suggested in (12, 14) do not agree with experimental data. The entrance losses during the flow of the copolymer through capillaries are low right until elastic turbulence sets in, after which it becomes practically impossible to measure them by the method of capillaries of different length. The average wall slippage rate values of the copolymer at shear stresses above 10⁶ dyne/cm² amount to tens of cm/sec. They increase very abruptly with rising temperature.The temperature dependence of the viscosity and the dynamic characteristics of the copolymer indicate that it has a phase transition at temperatures of about 100–120 °C, which must be related to melting of blocks contained in the copolymer macromolecules, having a structure close to that of high-pressure polyethylene. This shows that the rheological method of studying block-type polymer and grafted polymers is promising.