Condensation charging of aerosol particles in the course of their formation in the gas phase

The behavior of aerosols formed over boiling melts of substances (boiling temperature 500–1800 K) in a stream of a carrier gas at 300 K was studied. Microparticles of size from 0.2 to 10 μm, partially aggregated, were detected in the aerosol. In an applied electric field with an intensity of 150–1000 V cm⁻¹, the particles migrated toward the negatively charged electrode at a velocity of 5–15 cm s⁻¹. The velocity of their motion was a linear function of the field intensity and depended on the melt boiling temperature in accordance with the Arrhenius equation. Experimental data were interpreted on the basis of a concept that, in the course of the growth of each microparticle, vapor molecules adsorbed by it decompose into ions with nonequivalent transfer of cations and anions into the particle volume, i.e., the microparticles undergo growth charging at the activation energy of the cation release from the particle surface into vapor of approximately 0.5 eV.     

Nucleate boiling

The study deals with the effect of the surface conditions on the nucleate boiling curve. A relation is proposed which describes the complete nucleate boiling curve.Notation q thermal flux - q* thermal flux at which the liquid boils after one-phase convection - q_c thermal flux during one-phase convection - q_cr1, q_cr2 first and the second critical thermal flux - T saturation temperature - T superheat of the heating surface relative to the saturation temperature - T* superheat prior to boiling of the liquid after one-phase convection - T_cr1 superheat during the first boiling crisis - T_cr3min minimum superheat at which the third boiling crisis can occur - P pressure - P_cr critical pressure - heat transfer coefficient during nucleate boiling - R_cr radius of a critical vapor forming nucleus - coefficient of surface tension - r latent heat of evaporation - thermal conductivity of the liquid - kinematic viscosity of the liquid - , densities of the liquid and the vapor - g gravitational constant - k Boltzmann constant - N Avogadro number - h Planck's constant Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 3, pp. 394–401, March, 1981.     

The first critical heat-flux density of kerosene in stepwise and steady-state releases of heat

Experimental results on determination of stationary and nonstationary first critical densities of heat fluxes for the TS-1 hydrocarbon fuel are presented. As a consequence of the investigations carried out in a wide range of subcoolings and pressures, it has been established that for kerosene, just as for water, hydrogen, and helium, the first nonstationary critical heat-flux density q_cr.1n coincides with the stationary one q_cr1. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 6, pp. 57–60, November–December, 2006.     

Heat transfer and critical heat fluxes in the boiling of aqueous solutions of polyethylene oxide at reduced pressures under natural-convection conditions

Experimental data are presented on heat transfer and critical heat fluxes in the boiling of aqueous solutions of polyethylene oxide of different concentrations under conditions of natural convection at atmospheric and reduced temperatures.Notation q heat flux - q_cr critical heat flux - q_cr.s critical heat flux during boiling under subheating conditions - T overheating of heating surface relative to-saturation temperature - T_S subheating of liquid core to the saturation temperature - heat-transfer coefficient - P pressure - , densities of the liquid and vapor - c_p isobaric specific heat of water - r heat of vaporization Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 1, pp. 24–28, July, 1984.     

The effectiveness of using one variant of the finite-element method for solving nonlinear nonstationary heat-conduction problems

It is established that the use of a previously proposed variant of the finite-element method for solving nonlinear nonstationary heat-conduction problems is efficient (in the sense of computer time expenditures) when the half-width of the band β of the resulting matrix in the system of linear algebraic equations does not exceed a certain value of β_cr. As a result of a numerical experiment for an axially symmetric case we obtain β_cr ≈ 47, which demonstrates the effectiveness of this variant of the finite-element method for solving a wide range of practical problems of heat-conduction theory. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 2, pp. 284–289, March–April, 1997.     

Effect of hydrogen on orientation dependence of critical shear stress and mechanism of straining in single crystals of stable stainless steel

The effect of hydrogen on the critical shear stress (τ_cr), dislocation structure, and mechanisms of straining (slip vs. twinning) in single crystals of Fe-26Cr-32Ni-3Mo (wt %) austenite stainless steel has been studied. It is shown for the first time that hydrogenation leads to the appearance of the orientation dependence of τ_cr, which is absent in the initial hydrogen-free crystals. This dependence of τ_cr is related to a decrease in the stacking fault energy, which determines a change of the mechanism of straining from slip to twinning.     

Numerical study of a laminar melt flow driven by a rotating magnetic field in enclosed cylinders with different aspect ratios

Summary This paper is devoted to the numerical study of axisymmetric rotating flow in enclosed cylinders with aspect ratios R (diameter divided by height) equal to 0.25, 0.33, 0.5, 1, 2, 3 and 4. The steady motion of the liquid is caused by the action of a low-frequency, low-induction rotating magnetic field with magnetic Taylor numbers lying in the range from 0.0025 · Ta _cr to 0.9 · Ta _cr , where Ta _cr refers to the critical magnetic Taylor number. We found that the ratio between global meridional to global azimuthal flow velocity passes a distinct maximum which depends on the aspect ratio. It marks the transition from the viscous to the inertial regime. Their characteristic features are examined by analysis of the angular velocity and the torques exerted by the boundaries, in dependence on Ta and the aspect ratio.     

Boiling Heat Transfer Enhancement by Using Micro-pin-finned Surface for Electronics Cooling

For efficiently cooling electronic components with high heat flux, experiments were conducted to study the flow boiling heat transfer performance of FC-72 over square silicon chips with the dimensions of 10 × 10 × 0.5 mm³. Four kinds of micro-pin-fins with the dimensions of 30 × 60, 30 × 120, 50 × 60, 50 × 120 μm² (thickness, t × height, h) were fabricated on the chip surfaces by the dry etching technique for enhancing boiling heat transfer. A smooth surface was also tested for comparison. The experiments were made at three different fluid velocities (0.5, 1 and 2 m/s) and three different liquid subcoolings (15, 25 and 35 K). The results were compared with the previous published data of pool boiling. All micro-pin-fined surfaces show a considerable heat transfer enhancement compared with a smooth surface. Flow boiling can remarkably decrease wall superheat compared with pool boiling. At the velocities lower than 1 m/s, the micro-pin-finned surfaces show a sharp increase in heat flux with increasing wall superheat. For all surfaces, the maximum allowable heat flux, q _max , for the normal operation of LSI chips increases with fluid velocity and subcooling. For all micro-pin-finned surfaces, the wall temperature at the critical heat flux (CHF) is less than the upper limit for the reliable operation of LSI chips, 85°C. The largest value of q _max can reach nearly 148 W/cm² for micro-pin-finned chips with the fin height of 120 μm at the fluid velocity of 2 m/s and the liquid subcooling of 35 K. The perspectives for the boiling heat transfer experiment of the prospective micro-pin-finned surfaces, which has been planned to be made in the Drop Tower Beijing/NMLC in the future, are also presented.     

Flow Boiling Heat Transfer in Two-Phase Micro Channel Heat Sink at Low Water Mass Flux

Boiling heat transfer at water flow with low mass flux in heat sink which contained rectangular microchannels was studied. The stainless steel heat sink contained ten parallel microchannels with a size of 640 × 2050 μm in cross-section with typical wall roughness of 10–15 μm. The local flow boiling heat transfer coefficients were measured at mass velocity of 17 and 51 kg/m²s, heat flux on 30 to 150 kW/m² and vapor quality of up to 0.8 at pressure in the channels closed to atmospheric one. It was observed that Kandlikar nucleate boiling correlation is in good agreement with the experimental data at mass flow velocity of 85 kg/m²s. At smaller mass flux the Kandlikar model and Zhang, Hibiki and Mishima model demonstrate incorrect trend of heat transfer coefficients variation with vapor quality.     

Properties of Perfluorobenzene near the Critical Point

The density of vapor and liquid perfluorobenzene along the liquid–vapor coexistence curve has been studied by a gamma-ray attenuation technique over the temperature range from 299 to 517 K. According to measurements, the coordinates of the critical point are T_C = 516.66 ± 0.05 K and ρ _C = 550.5 ± 2 kg · m⁻³. The critical exponent β of the coexistence curve equals 0.343 ± 0.005, which agrees closely with the non-classical value. The results of our measurements were compared with data available in the literature. The height dependence of the density of a two-phase sample was investigated in relation to the temperature and time. These experiments made it possible to determine the isothermal compressibility of liquid and vapor phases near the critical point.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Quantum Turbulence Generated and Detected by a Vibrating Quartz Fork

Flow due to a commercially available vibrating quartz fork is studied in gaseous helium, He I, He II and ³He–B, over a wide range of temperatures and pressures. On increasing the driving force, the flow changes in character from laminar (characterized by a linear velocity versus drive dependence) to turbulent (characterized by a square root velocity versus drive dependence). In classical fluids, we characterize this transition by a critical Reynolds number, Re _c =U _cr δ/ν, where U _cr is the critical velocity, ν stands for the kinematic viscosity, $\delta=\sqrt{2\nu/\omega}$ is the viscous penetration depth and ω is the angular frequency of oscillations. U _cr of order 10 cm/s observed in He II and 1 mm/s in ³He–B agree with those found with other vibrating objects such as spheres, wires and grids, as well as with available numerical simulations of vortex motion in an applied ac flow.     

Characteristic features of the boiling of emulsions having a low-boiling dispersed phase

The results of investigation of heat transfer from thin wires to a boiling emulsion, the dispersed phase of which is formed from a liquid with a boiling temperature much lower than the boiling temperature of the dispersion medium, are presented. Two variants of boiling of such an emulsion are possible: boiling of the dispersed phase alone and simultaneous boiling of the dispersed phase and dispersion medium. In the present work, only the first variant has been studied; it is distinguished by the following most important features: high superheat of the dispersed-phase droplets ΔT_sup of the emulsion and a wide temperature range of bubble boiling (50–200°C). For conventional heat carriers (pure liquids and solutions), the value of ΔT_sup does not exceed 1–10°C, with the bubble-boiling interval lying within the range from 5 to 20°C. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 6, pp. 81–84, November–December, 2006.     

A Thermodynamic Property Model for the Binary Mixture of Methane and Hydrogen Sulfide

A thermodynamic property model with new mixing rules using the Helmholtz free energy is presented for the binary mixture of methane and hydrogen sulfide based on experimental P_ρ T_x data, vapor–liquid equilibrium data, and critical-point properties. The binary mixture of methane and hydrogen sulfide shows vapor–liquid–liquid equilibria and a divergence of the critical curve. The model represents the existing experimental data accurately and describes the complicated behavior of the phase equilibria and the critical curve. The uncertainty in density calculations is estimated to be 2%. The uncertainty in vapor–liquid equilibrium calculations is 0.02 mole fraction in the liquid phase and 0.03 mole fraction in the vapor phase. The model also represents the critical points with an uncertainty of 2% in temperature and 3% in pressure. Graphical and statistical comparisons between experimental data and the available thermodynamic models are discussed     

Heat Transfer in Condensation of Vapor Moving inside Vertical Tubes

A review of works devoted to the study of heat transfer in condensation of moving vapor in cocurrent flow of vapor and film is presented. Generalization of a wide range of experimental data obtained by different authors showed that in wave regimes of film flow conditions take place under which an increase in vapor velocity does not lead to enhancement of heat transfer, as compared to heat transfer in condensation of motionless vapor. In turbulent film flow, an intense entrainment of the film from the crests of waves into the vapor core begins when W > We_cr, thus leading to considerable enhancement of heat transfer.     

An Equation of State for Fluoroethane (R161)

Fluoroethane (R161, C₂H₅F, 353-36-6) is a potential alternative refrigerant with excellent cycle performance, with zero ozone-depletion potential and low global warming potential. In this study, the thermodynamic property formulation for fluoroethane has been developed with the use of available experimental thermodynamic property data. In determining the equation of state, multiproperty fitting methods were used including single-phase pressure–density–temperature (pρT), vapor pressure, and saturated liquid-density data. The equation of state has been developed to conform to the Maxwell criterion for two-phase liquid–vapor equilibrium states, and is valid for temperatures from 130 K to 450 K, and pressures to 5 MPa. The extrapolation behavior of the equation of state at high temperatures and high pressures is reasonable. As there are very few compressed liquid-density experimental data published, the uncertainties in density of the equation of state are estimated to be 2.0 % in the compressed-liquid region and 0.5 % in the gas and supercritical regions. Uncertainties in vapor pressure are 0.5 % above 200 K and increase at lower temperatures. The uncertainties for all properties are higher in the critical region, except vapor pressure. Detailed comparisons between experimental and calculated data have been performed in this study.     

Boiling of liquid in the cell of a jet printer

An approximate calculation of the main parameters of boiling of a liquid in the cell of a jet printer — the ejection velocity of a liquid drop and the limiting permissible (critical) heat flow density supplied to the thermoresistor — is carried out. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 2. pp. 218–221, March–April, 1998.     

Heat exchange processes near the boundary of a film boiling nucleus

Results are presented of an experimental investigation of the change in temperature, heat flux to the liquid, and rate of displacement of the isotherms near a film boiling nucleus propagating over a plane surface. The experiment was carried out in a liquid nitrogen bath at atmospheric pressure on the saturation line. The heater was a sapphire plate 1.2 mm thick having a heat transfer surface area of 77×22 mm². The following facts were established: 1) near the boundary of the film boiling nucleus a new heat exchange mechanism takes place caused by the instability of the liquid microlayer; 2) the maximum heat flux to the liquid is considerably greater than the critical heat flux; 3) the vapor film in the film boiling region grows gradually with increasing distance from the boundary, i.e., there is a smooth transition in terms of heat exchange intensity before the equilibrium film boiling level is reached. Pis’ma Zh. Tekh. Fiz. 25, 39–46 (November 12, 1999)     

Vapor Pressure over KI–CoI2 Melts

The vapor pressure in the KI–CoI₂ system is determined by isobaric boiling point measurements. Calculated vapor pressure isotherms of the KI–CoI₂ system show negative deviations from linearity. The vapor composition over pure CoI₂ is determined, and the temperature-dependent vapor pressure of CoI₂ is assessed. The boiling point of pure CoI₂ is found to be 1160 K.     

Influence of Water Vapor Pressure on Superconducting Properties of YBCO Film by TFA-MOD

We fabricated YBa₂Cu₃O_7−x (YBCO) films on LaAlO₃ (LAO) substrates using metal organic deposition of precursor solutions containing metal trifluoroacetates (TFA-MOD). The effect of water vapor pressure on the microstructure, degree of texture, and critical current of prepared YBCO films was evaluated. The firing process was performed in the water vapor pressure range from 7 to 31 kPa. According to the results of the XRD, SEM and X-ray ω scan analyses, the causes of critical properties’ change with the different water pressure were explained. The YBCO film prepared at the lower water pressure showed the low critical current because of the a–b axis grain. The films fired at 20 kPa showed the highest critical current of 3.8 MA/cm².     

Special features of boiling of a slightly subcooled liquid

Slightly subcooled boiling is characterized by the fact that vapor bubbles that form at active sites on the heater surface grow continuously and, having attained a maximum size, separate and float. The frequency of bubble separation, which determines the rate of heat transfer, depends on the degree of subcooling of the boiling liquid. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 6, pp. 993–995, November–December, 1998.