Thermal Conductivity of Pear, Sweet-cherry, Apricot, and Cherry-plum Juices as a Function of Temperature and Concentration

ABSTRACT:  The thermal conductivity of 4 fruit (pear, sweet-cherry, apricot, and cherry-plum) juices was measured with a coaxial-cylinder (steady-state) technique. Measurements were made, temperature range 20 to 120 °C, at concentrations between 12.2 and 50 °Brix. The uncertainty of the thermal conductivity measurements was estimated to be less than 2%. A semitheoretical method for the prediction of thermal conductivity of juices was proposed. It was found that the prediction Model IV,  λ ( T , x )/λ ( T ₀, x ) = ( T / T ₀) ⁿ   , where  λ  is the thermal conductivity, x is the concentration, and T is the temperature, developed in this work can be adopted with satisfaction. The thermal conductivity of juices can be predicted just by knowing the thermal conductivity  λ₀  at a reference temperature   T ₀  .     

Thermal-Conductivity Measurements of Aqueous Orthophosphoric Acid Solutions in the Temperature Range from (293 to 400) K and at Pressures up to 15 MPa

A new improved guarded parallel-plate thermal-conductivity cell for absolute measurements of corrosive (chemically aggressive) fluids under pressure has been developed. Using the new modified guarded parallel-plate apparatus the thermal conductivity of aqueous orthophosphoric acid solutions was measured over the temperature range from (293 to 400) K and pressures up to 15 MPa. Measurements were made for three compositions of \(\text {H}_{3}\text {PO}_{4}\) (8 mass%, 15 mass%, and 50 mass%) along three isobars of (0.101, 5, and 15) MPa. The combined expanded uncertainty of the thermal-conductivity \((\lambda )\) measurements at the 95 % confidence level with a coverage factor of \(k=2\) is estimated to be 2 %. The uncertainties of the temperature, pressure, and concentration measurements were 15 mK, 0.05 %, and 0.01 %, respectively. The temperature, concentration, and pressure dependences of the thermal conductivity of the solution were studied. The measured values of thermal conductivity were compared with the available reported data and the values calculated from various correlation and prediction models. A new wide-range correlation model (extended Jones–Dole type equation with pressure-dependent coefficients) for the \(\text {H}_{3}\text {PO}_{4}\) (aq) solution was developed using the present experimental data.     

Method of calculating the heat capacity of a binary mixture near the critical line

The behavior of the heat capacity at constant volume is analyzed for solutions of NaCl in water near the liquid-gas critical line using the pseudospinodal hypothesis.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 1, pp. 112–117, January, 1988.     

Densities and Excess,Apparent, and Partial Molar Volumes of Binary Mixtures of BMIMBF<Subscript>4</Subscript> + Ethanol as a Function of Temperature,Pressure, and Concentration

The densities of five BMIMBF₄ (1-butyl-3-methylimidazolium tetrafluoroborate) + ethanol binary mixtures with compositions of (0.0701, 0.3147, 0.5384, 0.7452, and 0.9152) mole fraction BMIMBF₄ and of pure BMIMBF₄ have been measured with a vibrating-tube densimeter. Measurements were performed at temperatures from 298 K to 398 K and at pressures up to 40 MPa. The total uncertainty of density, temperature, pressure, and concentration measurements were estimated to be less than 0.1 kg · m⁻³, 15 mK, 5 kPa, and 10⁻⁴, respectively. The uncertainties reported in this article are expanded uncertainties at the 95% confidence level with a coverage factor of k = 2. The measured densities were used to study derived volumetric properties such as excess, apparent, and partial molar volumes. It is shown that the values of excess molar volume for BMIMBF₄ + ethanol mixtures are negative at all measured temperatures and pressures over the whole concentration range. The effect of water content on the measured values of density is discussed. The volumetric (excess, apparent, and partial molar volumes) and structural (direct and total correlation integrals, cluster size) properties of dilute BMIMBF₄ + ethanol mixtures were studied in terms of the Krichevskii parameter. The measured densities were used to develop a Tait-type equation of state.     

Transesterification of rapeseed and palm oils in supercritical methanol and ethanol

The results of the rapeseed and palm oils transesterification with supercritical methanol and ethanol were presented. The studies were performed using the experimental setups which are working in batch and continuous regimes. The effect of reaction conditions (temperature, pressure, oil to alcohol ratio, reaction time) on the biodiesel production (conversion yield) was studied. Also the effect of preliminary ultrasonic treatment (ultrasonic irradiation, emulsification of immiscible oil and alcohol mixture) of the initial reagents (emulsion preparation) on the stage before transesterification reaction conduction on the conversion yield was studied. We found that the preliminary ultrasonic treatment of the initial reagents increases considerably the conversion yield. Optimal technological conditions were determined to be as follows: pressure within 20-30 MPa, temperature within 573-623 K. The optimal values of the oil to alcohol ratio strongly depend on preliminary treatment of the reaction mixture. The study showed that the conversion yield at the same temperature with 96 wt.% of ethanol is higher than with 100 wt.% of methanol.     

Experimental Study of the Density and Viscosity of n-Heptane at Temperatures from 298 K to 470 K and Pressure upto 245 MPa

The density and viscosity of $n$ -heptane have been simultaneously measured over the temperature range from 298 K to 470 K and at pressures up to 245 MPa using the hydrostatic weighing and falling-body techniques, respectively. The expanded uncertainty of the density, pressure, temperature, and viscosity measurements at the 95 % confidence level with a coverage factor of $k= 2$ is estimated to be 0.15 % to 0.30 %, 0.05 %, 0.02 K, and 1.5 % to 2.0 % (depending on temperature and pressure ranges), respectively. The measured densities were used to develop a Tait-type equation of state for liquid $n$ -heptane. Theoretically based Arrhenius–Andrade and Vogel–Tamman–Fulcher type equations with pressure-dependent coefficients were used to describe the temperature and pressure dependences of the measured viscosities for liquid $n$ -heptane. The measured values of the density and viscosity were compared in detail with reported data and with the values calculated from a reference EOS and correlation models for the viscosity.     

Heat capacity of rocket propellant (RP-1 fuel) at high temperatures and high pressures

Isobaric heat capacity of rocket propellant (RP-1 fuel) has been measured with a vacuum adiabatic calorimeter immersed in a precision liquid thermostat. Measurements were made in the temperature range from 293 to 671 K and at pressures up to 60 MPa. The uncertainty of heat capacity, pressure, and temperature measurements were estimated to be 2-2.5%, 0.05%, and 15 mK, respectively. The measured values of heat capacity were compared with the values calculated from a surrogate mixture model (equation of state, EOS). The average absolute deviation (AAD) between the present data and the values calculated with EOS was 0.81%.     

Al2O3 and TiO2 atomic layer deposition on copper for water corrosion resistance

Al(2)O(3) and TiO(2) atomic layer deposition (ALD) were employed to develop an ultrathin barrier film on copper to prevent water corrosion. The strategy was to utilize Al(2)O(3) ALD as a pinhole-free barrier and to protect the Al(2)O(3) ALD using TiO(2) ALD. An initial set of experiments was performed at 177 °C to establish that Al(2)O(3) ALD could nucleate on copper and produce a high-quality Al(2)O(3) film. In situ quartz crystal microbalance (QCM) measurements verified that Al(2)O(3) ALD nucleated and grew efficiently on copper-plated quartz crystals at 177 °C using trimethylaluminum (TMA) and water as the reactants. An electroplating technique also established that the Al(2)O(3) ALD films had a low defect density. A second set of experiments was performed for ALD at 120 °C to study the ability of ALD films to prevent copper corrosion. These experiments revealed that an Al(2)O(3) ALD film alone was insufficient to prevent copper corrosion because of the dissolution of the Al(2)O(3) film in water. Subsequently, TiO(2) ALD was explored on copper at 120 °C using TiCl(4) and water as the reactants. The resulting TiO(2) films also did not prevent the water corrosion of copper. Fortunately, Al(2)O(3) films with a TiO(2) capping layer were much more resilient to dissolution in water and prevented the water corrosion of copper. Optical microscopy images revealed that TiO(2) capping layers as thin as 200 ? on Al(2)O(3) adhesion layers could prevent copper corrosion in water at 90 °C for ~80 days. In contrast, the copper corroded almost immediately in water at 90 °C for Al(2)O(3) and ZnO films by themselves on copper. Ellipsometer measurements revealed that Al(2)O(3) films with a thickness of ~200 ? and ZnO films with a thickness of ~250 ? dissolved in water at 90 °C in ~10 days. In contrast, the ellipsometer measurements confirmed that the TiO(2) capping layers with thicknesses of ~200 ? on the Al(2)O(3) adhesion layers protected the copper for ~80 days in water at 90 °C. The TiO(2) ALD coatings were also hydrophilic and facilitated H(2)O wetting to copper wire mesh substrates.