Abstract The coaxial cylinders method was used to measure the thermal conductivity of the R-125/R-134A (39/61) gas mixture. The experiments were carried out in the temperature range of 320–415 K and in the pressure range of 0.1–1.8 MPa. Coefficients were determined for an equation describing the thermal conductivity as a function of pressure and temperature. Thermal conductivity on the dew line and

Abstract Gas hydrates are a special state of matter because of their properties to concentrate significant volumes of gas in themselves. Different hydrate forming gases have different thermobaric regions of existence. These properties of gas hydrates create a prospect for developing promising industrial technologies for their synthesis and dissociation. This paper reflects the effects of surface-active

Abstract The article presents the results of comparative investigations of operation modes of the DKVR 10-13 steam boiler system. The investigations were performed in two different modes. In the first mode, the boiler worked only on the gas fuel, whereas in the second mode, the boiler worked on the gas fuel and mazout simultaneously. Each mode requires considering the economic and ecological conditions

Abstract We present a numerical model suitable for simulation of shock or blast waves passing through a cloud of water droplets. The model takes into account the droplet breakup, radiation, and evaporation effects. The gas phase (a mixture of air and water vapor) is solved within an Eulerian framework with a set of compressible transport equations. The disperse phase (water droplets) is represented

Abstract This work investigates the motion of the liquid metal on the surface of a heated cylindrical rod. Experiment data are presented, and computational models modified in accordance with the experimental results are described. Exploration of the motion of molten metal over the surface of fuel column simulator both in gravitational runoff and at gas blowoff involved high-speed recording. Formation

Abstract Several challenges coexist in the field of flow boiling in microchannels, ranging from high superheat required for boiling incipience to boiling instabilities and early dryouts. The aim of this study is to mitigate or solve some of the challenges and develop an image-processing algorithm for analysis of boiling oscillations in multiple parallel channels. The experimental results were acquired

Abstract The paper analyzes steady laminar boundary layer flow of low-conductivity Casson fluid over a stretching/shrinking sheet subjected to a transverse magnetic field in the presence of suction/injection when the fluid far away from the surface is at rest. This flow problem is mathematically modelled and the non-Newtonian fluid under consideration obeys the rheological equation of state by the

Abstract The flow in swirling turbulent wakes with varying total excess momentum and angular momentum is described using two second-order mathematical models. The first one includes averaged equations of momenta, turbulence energy balance, and dissipation rate in the far-wake approximation. The closure of the mathematical model relies on Rodi’s algebraic model for Reynolds stresses. The second model

Abstract A triple diffusive convective flow (thermal diffusion and dual species diffusion) in a viscous fluid flowing within a vertical duct is investigated under the Robin boundary conditions at the duct walls. Viscous heating and homogenous chemical reaction effects are included. The mass transfer (solutal) buoyancy effects due to concentration gradients of the dispersed components are taken into

Abstract The aim of the present investigation is framing the effect of thermal radiation and slip on a magnetohydrodynamic (MHD) Casson nanofluid flow over a stretching surface under the influence of variable viscosity and convective boundary condition. First, non-dimensionally developed boundary layer equations are deduced with suitable transformations. Then they are solved numerically by the Runge–Kutta–Fehlberg

Abstract Experimentally obtained ranges of decreasing of temperature of combustion products after pulsed injection of an aerosol consisting of fine water droplets and time intervals with reduced (as compared to the initial) temperature of gases are presented. Fast-response thermocouples and panoramic optical methods of tracer visualization are applied. To ensure the possibility of using the experimental

Abstract The paper present experimental results for temperature fields in heterogeneous droplets of liquids, freely falling in a preheated gaseous medium, before their micro-explosive fragmentation. The optical technique of Planar Laser Induced Fluorescence was applied. Unlike the known results of other authors, such fields were obtained for the first time without using holders for droplets, the latter

Abstract In plate fin heat exchangers, fins of special shapes on the plates generate high turbulent flow in the flow channels formed by the plates, which enables achievement of high heat transfer coefficients. The present work uses a conjugated heat transfer approach to evaluate numerically the heat transfer improvement and pressure drop in plate fin heat exchangers due to zigzag (type B) and inner

Abstract This paper presents experimental results on occurrence of large-scale maldistribution of parameters of liquid and vapor flows in a regular-packing distillation column. Experiments on separation of mixtures of R114/R21 freons were conducted in a Mellapak 350.Y packing of 0.9 m in diameter. Temperature distributions across column cross sections at different heights were obtained. The experimental

Abstract The presented mathematical model enables calculation of the wave surface profile, as well as the fields of velocity and temperature, in falling wavy liquid films. Numerical simulation of wave formation and heat transfer intensity was performed for falling films of liquid nitrogen. Different activation functions for input perturbations were checked for films with different parameters. The dependencies

Abstract This experimental and numerical work explains why a vortex breakdown bubble first emerges and then disappears as the fluid rotation speeds up. To this end, we explore a flow in a sealed cylindrical container with one end disk rotating and all other walls stationary. The rotation drives the meridional circulation: the fluid filling the container moves away from the rotating disk along the sidewall

Abstract This paper presents the results of measurement and calculation within an upgraded Zuber model of critical heat flux (CHF) during nucleate boiling in thin horizontal layers of liquid. The layer height was increased in regimes of developed nucleate boiling. The two-phase layer was foam with vapor columns ascending at the corners of a rectangular square lattice. In the calculations, the foam

Abstract The investigation is focused on the phenomenon of heat transfer deterioration (HTD), inhibiting the use of supercritical fluids in the processes in which high-power local heat release is possible. The ordinary discussion is based solely on the data of quasi-stationary measurements. In order to clarify the intrinsic nature of HTD as an essentially non-stationary phenomenon, it is worthwhile

Abstract The title of this paper echoes the title of a paragraph in the famous book by Frisch on classical turbulence. In the relevant chapter, the author discusses the role of the statistical dynamics of vortex filaments in the fascinating problem of turbulence and the possibility of a breakthrough in constructing an advanced theory. This aspect arose due to the large amount of evidence, both experimental

Abstract The thermal conductivity of cerium in the solid and liquid states, including the phase transition, in the temperature range of 293–1800 K was measured for the first time by the laser-pulse method with an accuracy of 2–5%. Comparison of the results with the available literature data was made. Data for the 293–400 K temperature range were obtained for the first time. Reference tables on the

Abstract Aspire of this study is to study the effect of heat source, suction/injection, and chemical reaction on dissipative and radiative MHD flow of a Casson fluid over an exponentially permeable stretching sheet. Series solutions are obtained for converted non-dimensional ordinary differential equations using an analytical technique known as the homotopy analysis method (HAM). A decisive approach

Abstract The article presents the results of a comprehensive fundamental numerical study of the problem of conjugate mixed convection with surface radiation from a vertical electronic board with multiple different discrete heat sources. The governing equations for the fluid flow and heat transfer, which are considered in their full strength, are transformed from a primitive variable form to a stre

Abstract The paper presents the results of investigation of the products of oxidation of sludge-lignin (waste from the Baikal pulp and paper mill) in H\(_{2}\)O/O\(_{2}\) mixture in the autoclave and semi-flow modes at uniform heating of the reactor up to 750 K. The time dependencies of the reactor wall temperature and the power of ohmic heaters imply that the oxidation starts at 440 K and the maximum

Abstract The article presents an improved numerical method developed for calculating turbulent flows basing on the algorithm SIMPLE, Rhie–Chow interpolation on non-staggered grids, and monotonic second and third order accurate TDV schemes. The use of high-order difference schemes for calculation of viscous flows enables achievement of significantly better resolution of the algorithm on coarse grids

Abstract This work presents a numerical study of incompressible, laminar, two-dimensional, mixed convection flows in horizontal channels with two rectangular alternated blocks mounted in the surfaces. The influence of the geometry and positioning of the blocks on the heat transfer rate is evaluated using Constructal Design. The problem is subjected to two geometric constraints associated with the areas

Abstract At present, electronic systems are thermally designed on the basis of the assumption that all the parameters and factors that determine the thermal processes are fully known and unambiguously determined, id est, that they are determinate. However, the practice of creation and operation of real electronic systems shows that the real values of determining parameters and factors, as well as the

Abstract The conjugated temperature distributions of a microchannel fluid flow between two semi-infinite parallel plates are obtained analytically. The variables separation and transformation techniques are implemented to introduce the degenerate hypergeometric differential equation, the solution of which is given in terms of Kummer’s functions. The eigenvalues of the corresponding transcendental characteristic

Abstract A new approach for modeling chemical processes in industrial column apparatuses is presented. An exact approach for solving the equations in the convective type models is used. The use of experimental data for the average concentration at the column end for a specific process and column makes it possible to find out model parameters related with radial non-uniformity of velocity. These parameters

It is experimentally shown that diverging nozzles with a cone angle of 12o -14° and a length of 10-15 mm provide the finest atomization of metastable superheated liquid with a submicron droplet fraction at a level of 65-70%.

This article presents values of heat transfer coefficients at pool boiling of aqueous solution of lithium bromide on smooth and fin tubes. The experimental studies were performed under conditions typical of absorption chiller with single-stage desorption. More exactly, the condensation pressure was about 7.8–8.5 kPa, and the concentration of lithium bromide solution was 60–61 wt%. The outer diameter

The well-known description of hydrodynamic instability of planar interfacial boundary at liquid combustion is applied to analysis of stability of a stationary analytical solution for the shape of the phase interface during propagation of self-sustaining evaporation front along a flat heater in superheated liquid. The applicability of the criterion of hydrodynamic instability of planar interphacial

This investigation discusses the effects of first order chemical (generative/destructive) reaction on the transport in a species of variable mass conductance in a Williamson liquid of variable diffusion coefficient. The problem is modeled using conservation laws with temperature dependent variable diffusion coefficients models. Several numerical experiments are carried out to analyze the effects of

Problem statement This study investigates the relationship between heating and humidity of silica sand materials in vibrating drying machines. Hence, a prototype of drying plant for one-meter length is designed, including choosing the parameters of the drying machine and computing the factors that affect drying process in addition to studying materials’ characteristics and hot air flow effect. Approach

Generation of the power on low earth orbit satellites remains based particularly on photogeneration (solar cells), whereas other sources of energy, such as heat, remain unexploited. Indeed, exchange of heat is considered generally on board spacecraft as hostile, destructive and undesirable, thereby different means are used to reduce its effect on board spacecraft. Heat being an important source of