Comprehensive determination of potential-dependent heat- and mass-transfer characteristics of disperse materials

A method is proposed for parametric identification of a mathematical model of coupled heat and mass transfer (HMT) in a disperse medium.Notation T temperature of the medium, K - U concentration of substances distributed in the medium, kg/kg - a _m diffusion, m₂/sec - a _m ^T thermodiffusion, m²/(sec·K) - C, C₀, C_q specific heat capacity of the medium, the medium at U=0, and the substance distributed in the medium, J/(kg·K) - y₀ density of the dry material, kg/m³ - thermal conductivity, W/(m·K) - a diffusivity, m²/sec - j_m ^u, j_m ^T, j_m density of the diffusion, thermodiffusion, and total fluxes of the substances, kg/(m²·sec) - q heat flux, W/m² - x space coordinate - time Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 5, pp. 773–779, May, 1989.     

Effect of heat transfer on the limiting characteristics of magnetofluid seals

A procedure is developed for calculating the maximum temperature in the working gap of a magnetofluid seal and the limiting rate of rotation of hermetically sealed shafts.Notation T_max maximum temperature of heating of the sealing fluid, °C - thickness of the sealing layer, m - v₀ linear velocity of rotation of the surface of the hermetically sealed shaft, m/sec - density, kg/m³ - viscosity, N·sec/m² - c specific heat capacity at constant pressure, J/(kg·deg) - coefficient of thermal conductivity, W/(m·deg) - transfer coefficient, W/(m³·deg) - q heat flux, W/m² Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 58–65, January, 1982.     

Influence of radiation on the limits of heterogeneous combustion of a particle in two parallel reactions on its surface

The influence of radiation on critical parameters of heterogeneous ignition and extinction of a carbon particle in air is analyzed with allowance for two heterogeneous reactions.Notation Q _chem surface power of heat release through chemical reactions, W/m² - Q _h overall density of heat flux by molecular convectionQ _m.c. and radiationQ _i, W/m² - d particle diameter, m - t time, sec - T ₁,T ₂,T ₂,T _w particle gas, and reaction chamber wall temperature respectively, K - ₁, ₂ particle and gas density, kg/m³ - c ₁,c ₂ specific heat of particle and gas, J/(kg·K) - n _ox relative mass concentration of oxidant in the gaseous medium - q _i thermal effect of the first (i=1, C+O₂=CO₂) and the second (i=2, 2C+O₂=2CO) chemical reactions, J/kg - _i stoichiometric coefficient - E activation energy, J/mole - k _0i preexponential factor, m/sec - R universal gas constant, J/(mole·K) - Nu Nusselt number - ₂ thermal conductivity coefficient of gas, W/(m·K) - D ₂ diffusion coefficient of gas, m²/sec - ₂₀, ₂₀,D ₀ density, thermal conductivity, and diffusion coefficients of gas atT ₀ - emissivity coefficient - Stefan-Boltzmann constant, W/(m²·K⁴) - , heat- and mass-transfer coefficients, W/(m²·K), m/sec. Indexes: 1, particle - 2 gas - ign ignition - ext extinction - w wall - st steady - cr critical - in initial - c combustion - m maximum - lim limiting I. I. Mechnikov Odessa State University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 466–473, 1995.     

Influence of stefan flow on heat and mass transfer and kinetics of chemical reactions of a carbon particle in air

With account taken of Stefan flow, an analysis of the interrelated heat and mass transfer of a carbon particle in parallel reactions on its surface is performed.Notation T temperature, K - t time, sec - density, kg/m³ - c specific heat, J/(kg·K) - d diameter - R particle radius, m - thermal conductivity coefficient, W/(m·K) - particle emissivity - v Stefan flow velocity, m/sec - r radial coordinate - C _j relative mass concentration of the jth component - µ _j molar weight, kg/mole - k ₁,k ₂ constants of the first and the second reaction rates, m/sec - k ₀₁ andk ₀₂ preexponents - E ₁,E ₂ activation energies, J/mole - D diffusion coefficient, m²/sec - =v _RR/D dimensionless value of the Stefan flow velocity - Q _x surface power of heat release, W/m² - Q _st density of the heat flux via heat conduction and Stefan flow, W/m² - Q _r density of the heat flux via radiation - j _j mass flux density - W rate of the heterogeneous chemical reaction in O₂, kg/(m²·sec). Indexes - 1 particle - 2 gas - w wall - st Stefan - infinitely distant - in initial - R on the particle surface - by heat conduction - r by radiation - j 1, O₂ - j 2, CO₂ - j 3, CO - j 4, N₂ Odessa State University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 4, pp. 576–582, July–August 1995.     

Analytic study of the temperature change in the flowing molten metal in sand casting

A system of differential equations is given for the heat transfer in the flow of a liquid alloy in the channels in casting sand, and a formula is derived for the temperature of the alloy at any given point at an arbitrary instant.Notation c₁ specific heat of liquid alloy, J/kg · deg - ₁ density of alloy, kg/m³ - heat transfer coefficient, W/m² · deg - ₁ effective heat transfer coefficient, W/m² · deg - P channel cross-section circumference, m - F cross-section of channel - t_g temperature at inner channel surface, °K - w flow velocity, m/sec - R half-thickness of channel, m - t₂ temperature of mold wall, °K - _sta time from start of alloy flowing in channel, sec - ₂ thermal conductivity of mold material, W/m · deg - t₀ initial mold temperature, °K - c₂ specific heat of mold material, J/kg · deg - ₂ density of mold, kg/m³ - a₂ thermal diffusivity, m₂/sec - km, b_a coefficients of heat accumulation by mold and alloy, W/sec^1/2/m² · deg - t_in temperature of alloy at inlet, °K Translated from Inzhenerno-Fizicheskii Zhurnal, vol. 20, No. 5, pp. 872–878, May, 1971.     

Heat transfer in hydrocarbon fuel boiling under conditions of natural convection

Data on the heat-transfer coefficient in boiling of five jet fuels, two automotive gasolines, and a diesel fuel are presented over a wide range of regime parameters. The obtained results are described by a unified similarity equation.Notation heat-transfer coefficient, W/(m²·K) - P _s pressure, MPa - q heat flux density, W/m² - V volume, m³ - T _s temperature, K - ₁ and ₂ density of the liquid and vapor phases, kg/m³ - thermal conductivity, W/(m·K) - viscosity of the liquid, m²/sec - surface tension, N/m - C _p heat capacity, J/(kg·K) - r vaporization heat, J/kg - Nu Nusselt number - P Pecklet number.l=C _p T _{s 1}/(r₂)² serves as a governing dimension Kazan' State Techological University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 438–443, May–June, 1995.     

An assessment of expressions for the apparent thermal conductivity of cellular materials

Diverse expressions for the thermal conductivity of cellular materials are reviewed. Most expressions address only the conductive contribution to heat transfer; some expressions also consider the radiative contribution. Convection is considered to be negligible for cell diameters less than 4 mm. The predicted results are compared with measured conductivities for materials ranging from fine-pore foams to coarse packaging materials. The dependencies of the predicted conductivities on the material parameters which are most open to intervention are presented graphically for the various models.Nomenclature a Absorption coefficient - C _v (Jmol^–1 K^–1) Specific heat - E Emissivity - E _L Emissivity of hypothetical thin parallel layer - E ₀ Boundary surfaces emissivity - f Fraction of solid normal to heat flow - fics Fraction of total solid in struts of cell - K(m^–1) Mean extinction coefficient - k(W m^–1 K^–1) Effective thermal conductivity of foam - k _cd(W m^–1 K^–1) Conductive contribution - k _cr(W m^–1 K^–1) Convective contribution - k _g(W m^–1 K^–1) Thermal conductivity of cell gas - k _r(W m^–1 K^–1) Radiative contribution - k _s(W m^–1 K^–1) Thermal conductivity of solid - L(m) Thickness of sample - L _g(m) Diameter of cell - L _s(m) Cell-wall thickness - n Number of cell layers - r Reflection coefficient - t Transmission coefficient - T(K) Absolute temperature - T _m(K) Mean temperature - T _N Fraction of energy passing through cell wall - T ₁(K) Temperature of hot plate - T ₂(K) Temperature of cold plate - V _g Volume fraction of gas - V _w Volume fraction of total solid in the windows - w Refractive index - (m) Effective molecular diameter - (Pa s) Gas viscosity - Structural angle with respect to rise direction - (W m^–2 K^–4) Stefan constant     

Dynamic characteristics of thermoanemometers with glass-covered transducers

This study deals with the frequency characteristics of a glass-covered thermistor serving as transducer in a thermoanemometer and of a constant-resistance thermoanemometer with such probes.Notation A average-in-time coefficient of heat transfer at the glass-fluid boundary, W/m²· °C - A_tot coefficient of steady-state heat transfer at a bare probe (a fictitious quantity introduced for gauging the heat transfer between a glass-covered probe with the moving fluid), W/m²· °C - a thermal diffusivity of glass which insulated the heat sensitive element from the fluid, m²/sec - C_T total thermal capacity of transducer, W· sec/m²· °C - H₁ ratio of moduli in the expressions for current and resistance fluctuations in the transducer, dB - H₂ ratio of moduli in the expressions for heat transfer and resistance fluctuations in the transducer, dB - I quiescent current through thermistor, A - i transform of fluctuation current through thermistor, A - K_v voltage gain of feedback amplifier - k frequency parameter, 1/m - l thickness of glass layer, m - N intrinsic time constant of thermistor, sec - N time constant of constant-resistance thermoanemometer, sec - M intrinsic time constant of thermistor, sec - M time constant of constant-resistance thermoanemometer, sec - p complex variable in the Laplace transformation - Q average-in-time thermal flux from the transducer, W/m² - q transform of thermal flux fluctuations in the transducer, W/m² - R average-in-time operating resistance of thermistor, - R₁ constant resistance in series with the thermistor in the thermoanemometer circuit, - r transform of resistance fluctuations in the thermistor, - S effective surface area of heat transfer from the transducer, m² - T_D steady-state temperature of hot film, °K - T steady-state temperature of insulating glass layer, °K - T_L temperature of fluid, °K - u velocity of oncoming fluid, m/sec - W_T relation between resistance fluctuations and current in the thermistor, in operator form - y space coordinate in the mathematical model of the transducer, m - fluctuation component of heat transfer coefficient, W/m²· °C - temperature coefficient of resistance, 1/°C - thermal conductivity of insulating material, W/m· °C - _d transform of temperature fluctuations in the hot film, °K - transform of temperature fluctuations in the insulating glass layer, °K - coefficient in the transfer function of a thermistor at high frequencies Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 22, No. 6, pp. 1042–1048, June, 1972.     

Tests on a flow cryostat with series cooling

Measurements and calculations on a flow cryostat with serial cooling have given equivalent thermal schemes that have been tested for adequacy and consequent simple working formulas.Notation T_c, T_i, T_w, T_f temperatures of case, body i, tube wall, and flowing coolant in K - T₀ and T_e coolant temperatures at inlet and exit for heat exchanger and pipes in K - T_wi mean pipe wall temperature at points of attachment of bundles from body i in K - T_wn pipe wall temperature at point of attachment for bundle n in K - (_i)_n and _i thermal conductivities of bundle n and all bundles from body i in W/K - _ij thermal conductivity between bodies i and j in W/K - _ci, , _cw thermal conductivities from case to body i and total and radiative conductivities from case to pipe in W/K - _c convective heat-transfer coefficient between pipe and coolant in W/m²·K - _r radiative heat-transfer coefficient between case and pipe in W/m²·K - pipe material thermal conductivity in W/m·K - c specific heat of helium at constant pressure in J/kg·K - q and q_r correspondingly densities of the total heat flux and radiative flux to the pipe in W/m² - P_r heat flux along bundle r in W - M coolant mass flow rate in kg/sec - F tube cross section area in m² - S_i and S_o inside and outside surface areas of pipe in m² - L pipe length in m - ¯x=x/L relative coordinate along pipe axis - ¯x_r relative coordinate for bundle r attachment - R total number of bundles - N_i number of bundles cooling body i - J_i number of bodies linked by heat bridges to body i - _i relative error in calculating the temperature of body i by comparison with numerical result in % - _w mean relative error in heat exchanger temperature calculated numerically by comparison with temperature from (4) taken at ten equally separated points in % - (¯x-¯x_r) Dirac function Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 5, pp. 760–767, May, 1989.     

Analytical technique for the determination of solidification rates during the inward freezing of cylinders

An analytical/experimental approach which permits the determination of solidification rates during the inward solidification of cylinders is proposed. The technique is based on a previous analytical solution that treats the generalized problem of solidification of slabs. This solution is modified by a geometric correlation to compensate for the cylindrical geometry. A number of experiments have been carried out with a special experimental set-up, designed to simulate the inward solidification of cylinders in a water-cooled mould. A series of comparisons of experimental results, numerical predictions and calculations furnished by the proposed technique were made, showing good agreement for any case examined.Nomenclature a _s Thermal diffusivity of solid metal = k _s/c _s d _s (m² sec^–1) - A _i Internal surface area of the mould (m²) - b _s Heat diffusivity of solid metal = (k _s c _s d _s ^1/2(J m^–2 sec^–1/2 K^–1) - c _s Specific heat of solid metal (J kg^–1 K^–1) - d _s Density of solid metal (kg m^–3) - h Newtonian heat transfer coefficien (W m^–2 K^–1) - H Latent heat of fusion (J kg^–1) - k _s Thermal conductivity of solid metal (W m^–1 K^–1) - q Heat flux (W m^–2) - r Radial position (m) - r _o Radius of cylinder (m) - r _f Radius of solid/liquid interface (m) - S Thickness of solidified metal (m) - S _o Thickness of metal side adjunct (m) - t Solidification time (sec) - T Temperature (K) - T _i Surface temperature (K) - T _f Freezing temperature of metal (K) - T _o Temperature of the coolant (K) - T _s Temperature at any point in the solidified metal (K) - V ₁ Volume of remaining liquid metal during the solidification (m³) - V _s Volume of solidified metal (m³) - V _T Total volume of metal in the mould (m³) - x Distance from metal/mould interface (m) - Dimensionless solidification constant.     

A short swirl chamber

The flow in a short air-operated swirl chamber is studied by contactless methods. An engineering technique is suggested to calculate the parameters of a swirled gas flow in this chamber.Notation D ₀,R ₀ peripheral diaraeter and the swirl chamber diameter, m - d ₀,r ₀ diameter and radius of discharge opening of the swirl chamber, m - F total area of intake channels, m² - n power index in the equation for circumferential velocity - V, U, W circumferential, radial, and axial velocities, m/sec - V ₀,U ₀ circumferential and radial velocities at the boundary of the flow core, m/sec - V _in mean-mass velocity in intake channels, m/sec - V _p circumferential velocity at the boundary of the zone of quasipotential flow, m/sec - coefficient of velocity conservation at the boundary of the flow core - G mass flow rate of gas, kg/sec - P static pressure, Pa - T static temperature, K - n ₁ polytrope index - dynamic viscosity, N·sec/m² - P ₀ static pressure at the boundary of the flow core, Pa - T ₀ static temperature at the boundary of the flow core, K - c _p gas heat capacity, J/(kg·K) - R universal gas constant, J/(kg·K) Academic Scientific Complex Luikov Heat and Mass Transfer Institute of the Academy of Sciences of Belarus, Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 5, pp. 827–833, September–October, 1995.     

Thermal boundary resistance at interfaces between sapphire and indium

The Kapitza thermal boundary resistanceR _K has been measured above 1 K on several sapphire-indium boundaries prepared with different methods. By vapor-deposition of indium on sapphire and subsequent cold-welding with bulk indium, reproducible results were obtained. With the indium superconducting, we foundR _KT ^–3 within a certain temperature range, andR _K(1K)=42–44 and 30–36 cm² K/W for polished and rough sapphire surfaces, respectively. The calculation according to the acoustic mismatch theory yieldsR _K(1K)20 cm² K/W. Samples prepared by ultrasonic soldering also follow the relationR _KT ^–3 approximately, and giveR _K(1K)=14–17 cm² K/W. However, it is doubtful whether the calculation presuming a smooth boundary can be applied to the latter samples. Furthermore, we found that the method of vapor deposition and subsequent pouring on molten indium does not give good contacts. Moreover, the electronic contribution to the heat transfer across the boundary has been proved by ruling out other effects.     

Theory for incongruent crystallization: Application to a ZBLAN glass

Equations which describe incongruent nucleation and subsequent crystal growth have been derived. A ZrF₄-BaF₂-LaF₃-AlF₃-NaF glass was used to test the validity of these equations. Nucleation rate measurements were fitted to theory and some growth rate measurements were found in reasonable agreement with theoretical predictions. Both nucleation theory and crystal growth theory were used for computer simulations of the crystallization behaviour during heat treatments. Some heat treatments were performed in a differential scanning calorimeter to verify the theories. The experimental results were in good agreement with the numerical data. Using these theoretical results it is possible to estimate fibre scattering losses due to crystallization. Depending on drawing temperature, estimated losses can vary from 0.014 (310 °C) to 25 (320 °C) or more dB km^–1.Nomenclature a _s the chemical activity of component A in solution referred to the activity of the component in crystalline form - c _c ^A the concentration of A in the crystalline form (mol m^–3) - c _r ^A the concentration of A in the liquid at the interface (mol m^–3) - c ₁ ^A the concentration of A far from the interface in the bulk (mol m^–3) - c _e ^A the equilibrium concentration of A (mol m^–3) - D the diffusion coefficient (m²s^–1) - G the free energy difference between the liquid and the crystal, equal to the molar Gibbs' free enthalpy of component A in solution minus the molar Gibbs' enthalpy of the crystalline form of A (J mol^–1). - -G free energy difference between crystal A and pure liquid A (J mol^–1) - G _a activation energy for growth (J mol^–1) - G _r free energy difference between the liquid (of composition c _r ^A ) at the interface and the pure liquid A - G ₁ free energy difference between the liquid (of compositionc ₁ ^A ) far from the interface and the pure liquid A - H _f heat of fusion of the pure component A (J mol^–1) - I the nucleation frequency (1 m^–3 s^–1) - k Boltzmann constant (J K^–1) - K a constant of the order 10³²–10³³ Pa m^–3 K^–1 - r the radius of the spherical crystal - R gas constant (J mol^–1 K^–1) - t time (s) - T temperature (K) - T T ₁ - T the undercooling of the melt of compositionx ^A (T ₁ is the liquidus of the melt and depends onx _A). - T ₁ liquidus temperature (K) - T _m melting temperature of pure component A (K) - T _p temperature at the top of the DSC peak (K) - u crystal growth rate (ms^–1) - V _m molar volume of the crystallizing phase (mol m^–3) - x _A molar fraction of the precipitating component A in the melt (for an example: see Appendix) - viscosity (Pa s) - jump distance of the order of molecular dimensions (m) - ₀ frequency of vibration (s^–1) - surface tension of the crystal-liquid interface (J m^–2) - the thickness of the diffusion layer     

Temperature similarity of heat transfer processes

New relationships are presented which describe the temperature and humidity of the medium at the edges of the boundary layer in heat and mass transfer processes.Notation A thermal equivalent of mechanical work - g acceleration due to gravity - c_p specific heat of medium - T_f and T_w arithmetic mean temperatures of medium in flow core and at heat transfer surface - w_x and w_y, u_v and v_v projections of mixture and vapor velocities on the X and Y axes - and _T molecular and turbulent thermal conducitvities of medium - andT molecular and turbulent diffusion coefficients - P pressure - r latent heat of condensation - l characteristic geometrical dimension (tube diameter) - l ₀ arbitrary characteristic dimension taken as zero reading - x humidity of mixture - I heat content of mixture - and _v density of mixture and vapor - specific weight - a thermal diffusivity - k diffusion conductivity - Gr Grashof number - Pr Prandtl number     

Evaporation of liquids from cylindrical vessels under conditions of free concentrational convection in a gas phase

An analytical solution is obtained for the axisymmetric problem of free concentrational convection in a vapor-gas mixture with isothermal evaporation of liquids from open cylindrical vessels. Formulas are derived to calculate concentration fields, local and integral mass fluxes of vapor. A comparative analysis of the results of analytical and numerical simulation is carried out for the processes of the evaporation of liquids under the conditions of convective mass transfer.Notation p pressure, Pa - density, kg/m³ - v velocity, m/sec - , dynamic and kinematic viscosity, Pa·sec, m²/sec - D diffusion coefficient, m²/sec - ₁, ₂ mass fractions of vapor and gas in a mixture - g free fall acceleration, m/sec² - M ₁,M ₂ molar masses of vapor and gas, kg/kmole - _r , _z radial and axial components of the velocity of a gas-vapor mixture, m/sec - r, z cylindrical coordinates, m - R, H radius and height of vessel, m - j local mass flux of vapor, kg/(m²·sec) - j vessel cross-sectional area-averaged mass flux of vapor, kg/(m²·sec) - j vessel cross-sectional area-averaged mass flux Chelyabinsk State Technical University, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 403–407, May–June, 1995.     

Temperature jump across a plane interface for a phase transition in a pure liquid

We develop a theoretical model of the development of a temperature jump across the boundary between phases during a phase transition in pure liquids.Notation G₁ mass flux of molecules of the liquid into the liquid - G₂ mass flux of molecules of the liquid into the vapor - G_v mass flux of vapor molecules - T₁ vapor temperature near the liquid surface - T₂ temperature of the liquid - T_v vapor temperature - R universal gas constant - c_p, c_v specific heats - r heat of vaporization - q heat flux density - K ratio c_p/c_v - parameter of the phase transition - F₀ area of the interface - P₁ pressure of the liquid - P₂ phase transition pressure - P_v vapor pressure Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 5, pp. 793–797, May, 1988.     

Numerical calculation of a generalized thermal model of radio-electronic apparatus

A method is proposed for numerical calculation of the temperature field of a generalized model of electronic equipment with high component density.Notation x,y,z,x,y spatial coordinates, m - time, sec - L_x, L_v, L_z dimensions of heated zone, m - _x, _y, _z effective thermal-conductivity coefficients of heated zone, W/m·deg - ₂ thermal conductivity of chassis, W/m·deg - a _z thermal diffusivity of heated zone along z axis, m²/sec - c₁ effective specific heat of heated zone, J/kg·deg - ₁ effective density of heated zone, kg/m³ - c₃, ₃, c₂, ₂ thermophysical characteristics of cooling agent and chassis, J/kg·deg·kg/m³ - q_v(x, ), q(x, y) volume heat-source distribution, W/m³ - q_s (x) surface heat-source distribution, W/m² - p number of cooling agent channels - Fo Fourier number - Bi Biot number - Uⁱ coolant velocity in i-th channel, m/sec - T₁(x, ), T₂(x, ), T₃(x, ) temperature distribution of heated zone, chassis, and coolant, °K - T₃₀, T₁₀(x), T₂₀(x) initial temperatures, °K - T_3in coolant temperature at input to channel, °K - T_T(x) effective temperature distribution of heat loss elements, °K - T_C temperature of external medium, °K - dimensionless heated zone temperature - _v(x) local volume heat exchange coefficient, W/m³·deg - ₁₂(x), _1C(x), _1T(x) heat liberation coefficients - W/m²·sec; ₂₁(x, y), _2c(x, y), _2T(x, y) volume heat-exchange coefficients of chassis with heated zone, medium, and cooling elements, W/m³·deg Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 5, pp. 876–882, May, 1981.     

Thermodynamic Properties and Decomposition of Lithium Hexafluoroarsenate, LiAsF6

The heat capacity of lithium hexafluoroarsenate is determined in the temperature range 50–750 K by adiabatic and differential scanning calorimetry techniques. The thermodynamic properties of LiAsF₆ under standard conditions are evaluated: C _p ⁰(298.15 K) = 162.5 ± 0.3 J/(K mol), S ⁰(298.15 K) = 173.4 ± 0.4 J/(K mol), ⁰(298.15 K) = 81.69 ± 0.20 J/(K mol), and H ⁰(298.15 K) – H ⁰(0) = 27340 ± 60 J/mol. The C _p(T) curve is found to contain a lambda-type anomaly with a peak at 535.0 ± 0.5 K, which is due to the structural transformation from the low-temperature, rhombohedral phase to the high-temperature, cubic phase. The enthalpy and entropy of this transformation are 5.29 ± 0.27 kJ/mol and 10.30 ± 0.53 J/(K mol), respectively. The thermal decomposition of LiAsF₆ is studied. It is found that LiAsF₆ decomposes in the range 715–820 K. The heat of decomposition, determined in the range 765–820 K using a sealed crucible and equal to the internal energy change U _r(T), is 31.64 ± 0.08 kJ/mol.     

Saturation curve equations for normal and heavy water

Compact and precise equations are obtained for the saturation curves of normal and heavy water.Notation p saturated vapor pressure - p_c critical pressure - T absolute temperature - T_c critical temperature - =T/T_c dimensionless temperature - =1 – ; r heat of vaporization - c _p ⁰ isobaric heat capacity of vapor in ideal gas state - c_s liquid heat capacity along saturation curve - v specific volume of vapor - a _i coefficients of Eq. (1) Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 5, pp. 894–897, May, 1981.     

Reduction of the NOx generation through enhancing heat transfer in a furnace

The possibility of reducing the NO_x concentration through enhancing heat transfer in a furnace is demonstrated. A method for approximate calculation of the reduction of the NO_x concentration, with an intermediate radiator placed in the flame, is proposed.Notation T_max maximal temperature of the flame, K - T_rad temperature of the radiator surface, K - C_NO, C_{O 2}, C_{N 2} concentrations of nitrogen oxides and oxygen in combustion products, and of molecular nitrogen, wt.% - R universal gas constant, kJ/(kmol·K) - T temperature in the reaction zone, K - H gas enthalpy, kJ/m³.₀, Stefan-Boltzmann constant, W/(m²·K⁴) - _f emittance of the furnace medium - F running area of the radiating heating surface, m² - heart efficiency of the screens - heat retentivity - F_w surface area of the furnace walls, m² - V_gC_g mean total heat capacity of the combustion products, K - X_max relative location of the temperature maximum in the course of the flame burnt-out expressed in fractions of a full length of the flame (furnace) - T_f gas temperature at the furnace exit, K - Bo Boltzmann number - Q₁ and Q₂ heat absorption of the heating surfaces from the flame without and with a radiator, kJ/m³ - Q_f usable heat release in the furnace, kJ/m³ - H₁ and H₂ gas enthalpies at the exit from the furnace without and with a radiator, kJ/m³ - M parameter accounting for the temperature distribution along the furnace height - C₀ emittance of the black body, W/(m²·K⁴) - T_W temperature of the heat-absorbing surface, K - ₁ and ₂ thermal emission coefficients of the radiator and of the heat-absorbing surface - A₂ absorptivity of the heat-absorbing surface - B fuel flow rate, m²/sec Moscow State Textile Academy. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 3, pp. 337–340, March, 1993