Mathematical modeling of heat and mass transfer processes in geocryological forecasts

A condition is found for the selection of a mathematical model of the temperature process and results are presented for the solution of the combined heat- and mass-transfer problem.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 1, pp. 124–129, July, 1987.     

Computer modeling of the heat transfer processes in injection molding

Absract  The results are given of the computer modeling of the heat transfer processes in injection molding. The distribution of temperature in the plant working route and molds for forming ceramic products in the form of nozzles, solid balls, bolls with a hole, and rings have been defined. The initial technological dependences have been calculated of the time of cooling thermoplastic mixtures based on AlN, SiC, and WC to 40°C for products of various shapes and types and sizes. Original Russian Text ? A.A. Leshchuk, T.O. Tsysar’, V.V. Ivzhenko, 2009, published in Sverkhtverdye Materialy, 2009, Vol. 31, No. 2, pp. 34–43.     

An analytical modeling of heat transfer for laser-assisted nanoimprinting processes

Laser-assisted direct imprinting (LADI) technique has been proposed to utilize an excimer laser to irradiate and heat up the substrate surface through a highly-transparent quartz mold preloaded on this substrate for micro- to nano-scaled structure fabrications. While the melting depth and molten duration are key issues to achieve a satisfactory imprinting pattern transfer, many material property issues such as crystalline phase alteration, grain size change and induced film stress variation are strongly affected by transient thermal response. With one-dimensional simplification as a model for the LADI technique, the present paper has successfully derived an analytical solution for the arbitrary laser pulse distribution to predict the relevant imprinting parameters during the laser induced melting and solidification processes. The analytical results agree quite well with the experimental data in the literature and hence can be employed to further investigate the effects of LADI technique from laser characteristics (wavelength, fluence and pulse duration) and substrate materials (silicon and copper) on the molten duration, molten depth and temperature distributions. Three kinds of excimer laser sources, ArF (193 nm), KrF (248 nm) and XeCl (308 nm) were investigated in this study. For the silicon substrate, the melting duration and depth were significantly dictated by the wavelength of laser used, indicating that employing the XeCl excimer laser with longer pulse duration (30 ns in the present study) will achieve the longest molten duration and deepest melting depth. As for the copper substrate, the melting duration and depth are mainly affected by the laser pulse duration; however, the wavelength of laser still plays an insignificant role in LADI processing. Meanwhile, the laser fluence should properly be chosen, less than 1.4 J/cm² herein, so as to avoid the substrate temperature exceeding the softening point of the quartz mold (~1950 K) and to make sure that the mold can still maintain the original features.     

Laboratory modeling of the enhancement of heat and mass transfer processes in chimney-type evaporative cooling towers

We present the results from an experimental investigation of the methods of aerodynamic action on the processes of evaporative cooling of circulating water in a cooling tower.Academic Scientific Complex A. V. Luikov Heat and Mass Transfer Institute of the Academy of Sciences of Belarus, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 2, pp. 143–150, February, 1994.     

Mass transfer in processes of heat technology

It is found experimentally that fields of moisture content with local minima on the moisture distribution curves, explained by the proposed mechanism of mass and heat transfer in conductive and conductive-convective drying of the materials, are atypical. Characteristic fields are given for moisture content and excess pressure in the layer of the colloid capillary-porous materials under infrared irradiation at different stages of drying, sintering, thermal treatment, etc.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 3, pp. 373–379, September, 1990.     

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     

Modeling of radiative heat transfer and mass transfer processes in drop-flow-based heat exchangers for spacecraft

Modeling of radiative heat transfer and mass transfer in drop-flow-based heat exchangers for spacecraft is considered. A Monte Carlo-based numerical model is presented. Results obtained with the aid of the model are analyzed and compared with existing data. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 1, pp. 92–96, January–February, 1998.     

Mathematical modeling of heat and mass transfer in film condensation

The state of the problem of mathematical modeling of the heat and mass transfer during film condensation of a gas is considered.     

Mathematical modeling of combined heat transfer in dispersed materials

We show that combined heat transfer in a dispersed medium can be modeled numerically by treating convective and radiative-conductive heat transfer separately. We refine the radiative heat-transfer model by comparison with experiment.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 5, pp. 781–791, November, 1985.     

Mathematical modeling of complex heat transfer in slit channel

A system of energy-transfer equations in layers of water vapor and a gray medium is given and numerically solved, taking account of radiation turbulent and molecular heat conduction.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 2, pp. 270–278, February, 1979.     

Mathematical model of heat and mass transfer processes in evaporative condensers

This study presents a new mathematical model of heat and mass transfer processes in evaporative condensers. The model consists of four ordinary differential equations with their boundary conditions and some associated algebraic equations. The model was formulated for steady-state heat and mass transfer conditions. A simulation computer program based on the model was written. It was devised for heat calculations in condensers built from bare tubes. The quality of the model was calculated by comparing the results obtained by running the program with experimental results achieved by other authors. The computed results show a good degree of conformity with experimental results. The differences are less than 20% (but in one case, 30%). The computer program may be used to determine heat performance of evaporative condensers of horizontal in-line and staggered bundle systems (if S_q > 2d_z).     

Mathematical modeling of moving contact lines in heat transfer applications

We provide an overview of research on the mathematical modeling of apparent contact lines in non-isothermal systems conducted over the past several decades and report a number of recent developments in the field. The latter involve developing mathematical models of evaporating liquid droplets that account not only for liquid flow and evaporation, but also for unsteady heat conduction in the substrate. The droplet is placed on a flat heated solid substrate and is assumed to be in contact with a saturated vapor. Furthermore, we discuss a careful comparison between mathematical models and experimental work that involves simultaneous measurement of shapes of evaporating droplets and temperature profiles in the solid substrate. The latter is accomplished using thermochromic liquid crystals. Applications to new research areas, such as studies of the effect of evaporation on fingering instabilities in gravity-driven liquid films, are also discussed.     

Water molecules and heat transfer modeling in silicon dew point hygrometer

This paper presents the construction and a new complex model of the fabricated silicon dew point hygrometer. The model describes the behavior of water vapor contained in the measured gas (saturated vapor partial pressure, super cooled water phenomenon), water mass transport (condensation and evaporation processes), heat transport across measurement head, silicon dew detector, and regulator characteristics. The model was created in the SIMULINK environment. Finally, a comparison of measured data and model responses is discussed.     

Generalized modeling and analytical description of meta-constant phenomena in heat conduction and in heat and mass transfer

The derivation is shown of generalized quantities called integroforms, with the aid of which: a) variable coefficients are eliminated from differential equations and boundary conditions; b) one may derive the integral invariants of reciprocal similarity (or identity) transformations “as a whole” for meta-constant phenomena of a given class.     

Use of adjoint functions in investigations of heat conduction and transfer processes

An examination is made of the use of adjoint functions in heat conduction and convection theory. Formulas of perturbation theory are obtained for steady and unsteady cases, an interpretation of the physical meaning of adjoint temperature is given, and some applications of the theory are discussed.Notation (r,) thermal conductivity - t(r,) temperature - t *(r,) adjoint temperature - q_V(r,) density of heat release sources - p(r,) a parameter of adjoint equation - r generalized coordinate - time - (r_s, ) heat transfer coefficient - I linear functional of temperature - (r,;r₀,₀) and *(r,; r₀,₀) Green's function for t(r, ) and t *(r, ) - C(r,) volume specific heat - W(r, ) vector distribution of flow velocities - V, S volume and surface areas of body - R radius of HRE - r, radial and angular coordinates - F_in, F_out inlet and outlet flow areas of channel     

Mathematical modeling of heat and mass transfer in irregular freezing of alloys

A mechanism of formation of structural heterogeneities in crystallization of alloys is considered. A mathematical model of heat and mass transfer in irregular freezing of alloys, a calculation algorithm, and some results of numerical calculations are given.Institute of Technical Thermal Physics, Academy of Sciences of the Ukraine, Kiev. Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 63, No. 6, pp. 752–759, December, 1992.     

Simulation of heat and mass transfer processes and a system approach

The paper presents the basic concepts of a system approach to thermal processes and heat-exchanging apparatuses. The principle of groups that is applied to the analysis of thermal systems and the search for systemic, integrative properties is considered. Integral and local thermal and “mechanical” resistances are one of the forms of the groups. Dimensionless complexes of similarity theory are shown to be one of the forms of the groups at whose critical values integrative properties are manifested. Institute of Technical Thermal Physics, National Academy of Sciences of Ukraine, Kiev. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 6, pp. 1026–1034, November–December, 1992.     

Analytical and numerical modeling of steady periodic heat transfer in extended surfaces

This paper deals with the analytical and numerical approaches that have been used to study periodic or oscillatory heat transfer processes occurring in extended surfaces. The details pertain to harmonic oscillations but many of the methods can be applied to more general periodic functions. For linear problems, the techniques include complex combination, Laplace transforms, finite differences, and boundary elements. For the nonlinear situations, approaches such as finite differences, finite elments, and different combinations of complex temperature, perturbation, series expansions, straightline, and finite differences have proved effective. Following a brief introduction, the applications of each approach are discussed in detail. Both straight and annular fin configurations are covered and the profile shapes include rectangular, trapezoidal, triangular, and convex parabolic. The periodic conditions involve oscillating base temperature, oscillating base heat flux, oscillating environment temperature, convection at the fin's base through a fluid with oscillating temperature, and some combinations of these conditions. The nonlinear problems discussed cover radiating and convecting-radiating fins, fins with variable thermal conductivity and coordinate dependent heat transfer coefficients, and systems with fin-to-fin, fin-to-base, and fin-to-environment radiative interactionsThis article is dedicated to the memory of first author's younger brother, Mohammed Iqbal, Civil Services of Pakistan, who became an innocent victim of human savagery in 1971 in what was then East Pakistan     

An inertia criterion for coupled heat and mass transfer processes

New criterial relations are obtained with allowance for the influence of thermal gradient mass transfer, phase transitions and Kossovich number on the inertia of heat and mass transfer processes.