RAS Institute of Thermal Physics

Yekaterinburg, Russia

RAS Institute of Thermal Physics

Yekaterinburg, Russia

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Chernysheva M.A.,RAS Institute of Thermal Physics | Yushakova S.I.,RAS Institute of Thermal Physics | Maydanik Y.F.,RAS Institute of Thermal Physics
Energy | Year: 2014

An implementation of a cooling system with a loop heat pipe for thermal control of supercomputers is considered. For this purpose two copper-water loop heat pipes (LHPs) with an effective length of 400mm and ID/OD diameters of the vapor lines of 3/4 and 4/5mm correspondingly were designed and tested. The LHPs were equipped with a flat-oval evaporator with one-sided heat supply. The evaporator had a thickness of 7mm, a length (including the compensation chamber) of 80mm and a width of 42mm. The influence of the cooling temperature of the condenser on the LHP operating characteristics was the central issue of this research. Tests were conducted in the range of the cooling temperature from 20 to 80°C. The heat load supplied to the evaporator was varied from 20 to 600W. A mathematical model for prediction of the LHP's operating temperature has been developed. It takes into consideration three operating modes of a loop heat pipe. Modeling results and their analysis are presented. © 2014 Elsevier Ltd.


Gasanov B.M.,RAS Institute of Thermal Physics
International Journal of Heat and Mass Transfer | Year: 2016

High-speed filming has been used to investigate the process of nucleate boiling of emulsions with a low-boiling disperse phase on a platinum wire 0.10 mm in diameter. Investigations have been conducted on an emulsion with which a disperse phase and a dispersion medium participate in boiling, and on an emulsion with which only a disperse phase boils. Vaporization at the boiling of an n-pentane/water and an n-pentane/glycerine emulsion at the surface of a wire has been studied. The boiling of disperse phase droplets in a thermal boundary layer by the mechanisms of heterogeneous and homogeneous nucleation has been shown. A model of avalanche-like boiling of superheated disperse phase droplets in a thermal boundary layer has been checked. © 2015 Elsevier Ltd.


Baidakov V.G.,RAS Institute of Thermal Physics
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

Based on the results of computer simulation of transport coefficients in a Lennard-Jones fluid, it has been shown that in (p,T) coordinates, lines of constant values of coefficients of self-diffusion D and excess shear viscosity Δη extended into the region of superheated liquid and supersaturated vapor have an envelope. Each of the ensembles of such lines is divided into two parts by a critical isoline, where the conditions = c=const (=D,Δη) are fulfilled. One part of this ensemble has as an envelope the branch of the spinodal that refers to superheated liquid; the other part has the branch of the spinodal of supersaturated vapor. The critical point of liquid-vapor equilibrium is the cusp of the spinodal, at which the critical isolines have a common tangent line with the spinodal and the binodal. Thus, at the approach to the spinodal, the relations ( D/p)T→ and ( Δη/p)T→ hold. © 2012 American Physical Society.


Pavlov P.A.,RAS Institute of Thermal Physics | Skripov P.V.,RAS Institute of Thermal Physics
International Journal of Thermophysics | Year: 2014

This paper studies the phenomenon of spontaneous boiling-up of polymeric liquids on heating at rates (T)up to 107 K·s−1. A model of the thermal equation of state for (polymer + monomer) systems and a procedure for determination of the spontaneous boiling-up temperature T* for polymeric liquids, taking decomposition into account, are proposed. The experimental data on T* for a number of polymer melts are compared with results calculated from the model. © 1999, Plenum Publishing Corporation.


Baidakov V.G.,RAS Institute of Thermal Physics | Kozlova Z.R.,RAS Institute of Thermal Physics
Chemical Physics Letters | Year: 2010

Molecular-dynamics computer simulation has been used to calculate the self-diffusion coefficient of a Lennard-Jones fluid in the interval of reduced temperatures T = 0.35-2.0, through mean-squared particles displacements and the velocity autocorrelation function. Calculations have been performed for systems in stable and metastable states up to the boundary of spontaneous nucleation in a model of a fluid consisting of 2048 particles. The values of the self-diffusion coefficient on the spinodals of a superheated liquid and supersaturated vapor have been determined. It has been established that in the region of supercooled states of the liquid phase on an isotherm the logarithm of the self-diffusion coefficient is a linear function of the pressure. © 2010 Elsevier B.V. All rights reserved.


Koverda V.P.,RAS Institute of Thermal Physics | Skokov V.N.,RAS Institute of Thermal Physics
Physica A: Statistical Mechanics and its Applications | Year: 2014

The system of two nonlinear stochastic equations simulating 1/f fluctuations during the interaction of nonequilibrium phase transitions in the presence of an external periodic action has been studied by numerical methods. It is shown that in the system there appears stochastic resonance, which leads to an amplification of the output periodic signal under the action of noise. To a random process with a 1/f power spectrum corresponds the maximum Gibbs-Shannon informational entropy. At stochastic resonance the informational entropy is minimum. A new behavior of a two-dimensional system at stochastic resonance has been revealed: at low frequencies of a periodic action with an increased white noise intensity the system trajectories are limited by two mutually perpendicular directions - anisotropic stochastic resonance. With a further increase in the white noise intensity in the system one can observe "ordinary" stochastic resonance, when the increasing intensity of fluctuations in the vicinity of the driving frequency is smeared in the directions. © 2013 Elsevier B.V. All rights reserved.


Maydanik Yu.F.,RAS Institute of Thermal Physics | Chernysheva M.A.,RAS Institute of Thermal Physics | Pastukhov V.G.,RAS Institute of Thermal Physics
Applied Thermal Engineering | Year: 2014

The paper contains an analytical review of developments, results of tests and simulation of loop heat pipes (LHPs) with disk-shaped, rectangular and flat-oval evaporators. Two main directions have been noted in the development of flat evaporators, which may be arbitrarily separated into evaporators with opposite replenishment (EORs) and evaporators with longitudinal replenishment (ELRs). The bodies of such evaporators are made of stainless steel, copper, aluminum. For making wicks use is made of sintered powders and mesh of stainless steel, nickel, titanium, copper, polytetrafluoroethylene (PTFE) and ceramics. Monoporous and biporous capillary structures are considered. Water, ammonia, methanol, ethanol, and acetone have been tested as working fluids. The best results were shown by the combination "copper-copper-water" at temperatures above 70 °C, when on trials an evaporator thermal resistance of less than 0.01°C/W and a heat flux close to 1000 W/cm2 were achieved. For temperatures below 70°C the most efficient combination is "stainless steel-nickel-ammonia". © 2014 Elsevier Ltd. All rights reserved.


Baidakov V.G.,RAS Institute of Thermal Physics
Low Temperature Physics | Year: 2013

This review addresses the kinetics of spontaneous boiling-up of liquefied gases and their solutions. It discusses the theories of thermal and quantum nucleation in metastable liquids. The experimental methods for studying the nucleation kinetics are outlined. The experimental data on the attainable superheating temperature for cryogenic liquids and solutions of liquefied gases are presented in a wide range of pressures, including negative ones. The properties of new-phase nuclei near the boundary of attainable superheating are discussed. The kinetics of initiated and heterogeneous nucleation is considered. The experimental data on detection of quantum tunneling of nuclei are presented. The experimental data are compared with the theories of thermal and quantum nucleation. © 2013 AIP Publishing LLC.


Chernysheva M.A.,RAS Institute of Thermal Physics | Maydanik Y.F.,RAS Institute of Thermal Physics
Applied Thermal Engineering | Year: 2012

This paper presents a three-dimension mathematical model of a flat evaporator of a loop heat pipe which takes into account the peculiarities of the evaporator configuration and the specific character of a one-side heat load supply. All the main structural elements of the evaporator, such as its body, wick, vapor-removal grooves, barrier layer and compensation chamber, are included in the model. The intensity of heat-exchange processes during evaporation in the active zone is determined by local drops between the temperature at the wick surface and the vapor temperature. The effects of drying the wick in the evaporation zone are also taken into account. The problem was solved by a numerical method. The results of calculations are presented for a copper evaporator and water as a working fluid in the heat load range from 20 to 1100 W. A comparative analysis of calculated and experimental data has been made. © 2011 Elsevier Ltd. All rights reserved.


Koverda V.P.,RAS Institute of Thermal Physics | Skokov V.N.,RAS Institute of Thermal Physics
Physica A: Statistical Mechanics and its Applications | Year: 2012

An analysis of masterslave hierarchy has been made in a system of nonlinear stochastic equations describing fluctuations with a 1f spectrum at coupled nonequilibrium phase transitions. It is shown that for a system of stochastic equations there exist different probability distribution functions with power-law (non-Gaussian) and Gaussian tails. The governing equation of a system has a probability distribution function with Gaussian tails. Therefore, distribution functions for governing equations may be used for finding the GibbsShannon entropy. The local maximum of this entropy has been found. It corresponds to the tuning of the parameters of the equations to criticality and points to the stability of fluctuations with a 1f spectrum. The Tsallis entropy and the Renyi entropy for the probability distribution functions with power-law tails have been calculated. The parameter q, which is included in the determination of these entropies has been found from the condition that the coordinates of the maximum GibbsShannon entropy coincide with the maxima of the Tsallis and Renyi entropies. © 2011 Elsevier B.V. All rights reserved.

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