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Chinnov E.A.,RAS Kutateladze Institute of Thermophysics
Technical Physics Letters | Year: 2012

The evolution of three-dimensional (3D) waves into thermocapillary-wave structures in a locally heated water film flowing down a vertical plate has been experimentally studied. The interaction of hydrodynamic perturbations with thermocapillary instabilities was monitored using a high-speed high-resolution IR imager. The existence of thermocapillary structures has been observed for the first time at high Reynolds numbers (Re = 150) in regime A, which is characterized by high temperature gradients on the film surface and a definite value of the "most dangerous" wavelength of instability that arises when the heat flux density exceeds a certain threshold. It is established that structures periodically appear in which the distance between temperature maxima is much shorter than that observed before. As the heat flux density is increased, the thermal entry length exhibits a sharp drop when thermocapillary instabilities arise in the vicinity of the upper edge of the heater. © 2012 Pleiades Publishing, Ltd.


Kulik V.M.,RAS Kutateladze Institute of Thermophysics
International Journal of Heat and Fluid Flow | Year: 2012

The rate and amplitude of compliant coating deformation by turbulent pressure pulsations were calculated. Complex compliance determined by a 2D model has two components: along and across the coating. Dependence of the components of dimensionless compliance on the ratio between wavelength λ and coating thickness H was determined for 0.3 < λ/H< 30 and dependence of these components on the ratio of flow velocity V to shear velocity Ct0 was determined for 0.1


Chinnov E.A.,RAS Kutateladze Institute of Thermophysics
International Journal of Heat and Mass Transfer | Year: 2014

The temperature distributions and wave characteristics of the water film flowing down a vertical plate with a heater of 100 × 150 mm at Re = 150, 300, 500 are studied. The field of film thicknesses at different heat flux values was measured using the fluorescence method. The temperature field on the film surface was measured by an infrared scanner. The experimental data were obtained for variations in temperature over the liquid film surface with time during the propagation of waves. Thermocapillary forces that arise on heating lead to the formation of rivulets separated by thin layer troughs, with three-dimensional (3D) waves propagating over the crests of rivulets. Averaging of measurements allowed the values of the transverse film deformation and distance between the rivulets to be determined. In the interrivulet zone Marangoni number increases with a rise of the heat flux. The amplitudes of 3D waves in a water film flowing down a vertical heated plate have been measured. The film thickness and 3D wave amplitudes on the heater grow with increasing heat flux and distance downstream the flow, but the relative wave amplitude remains unchanged. In the heated regions between rivulets, the relative amplitude of waves increases with decreasing average thickness (or local Reynolds number). Analysis of results obtained for large Reynolds numbers showed that the relative amplitudes of waves in the regions between rivulets at high heat fluxes are much greater than those for small Reynolds numbers and in isothermal falling films. Two mechanisms of thermocapillary forces influence on the motion of the wavy liquid film are marked. For the first time, the exhibition of such a strong thermocapillary effects is revealed in the heated liquid film at high Reynolds numbers. © 2013 Elsevier Ltd. All rights reserved.


Misyura S.Ya.,RAS Kutateladze Institute of Thermophysics
International Journal of Heat and Mass Transfer | Year: 2014

Dynamics of nucleate boiling in droplets of bidistillate on different wall surfaces was studied experimentally. These experiments were carried out on the rough copper and on the polished surface with plasma spraying of a golden film. The surface state was investigated by an electron microscope and 3D image processing software. Characteristic microroughness responsible for minimal superheating at nucleate boiling was determined. Heat transfer on the polished surface was significantly worse than on the rough wall. Thermal measurements were performed by means of a multiple increase in thermal imaging. When boiling on the polished surface, the self-organized ordered structures are formed there. © 2013 Elsevier Ltd. All rights reserved.


Fedyaeva O.N.,RAS Kutateladze Institute of Thermophysics | Vostrikov A.A.,RAS Kutateladze Institute of Thermophysics
Journal of Supercritical Fluids | Year: 2012

The conversion of bitumen (the gross-formula CH1.56N 0.01S0.007) in supercritical water (SCW) flow at 400 °C, 30 MPa with and without addition of zinc and aluminum shavings into bitumen has been studied. For the conversion without addition of 〈Zn〉 and 〈Al〉 the yield of volatile and liquid products was 3.1 and 47.3%, respectively, in relation to the weight of bitumen. As a result of a chemical interaction of H2O molecules with bitumen, oxygen atoms appeared in these products and conversion residue; the amount of hydrogen in them being increased. When 〈Zn〉 or 〈Al〉 was added, the conversion and hydrogenation of bitumen significantly increased owing to hydrogen evolution during the oxidation of metals by SCW. This oxidation via the synthesis of ZnO and Al2O3 nanoparticles was accompanied by on-site heating of reactants. Moreover, when adding 〈Zn〉 and 〈Al〉 into bitumen, the yield of the volatile products increased up to 15.3 and 38.2%, respectively. The addition of 〈Zn〉 resulted in the yield increase of the liquid products up to 62.3%, of the resins up to 33.5%, the content of oxygen in the products being increased too. While the addition of 〈Al〉 resulted in the yield decrease of the resins up to 7.5% and the yield increase of the oil up to 36.1%, no oxygen atoms in the structure of the liquid products being detected. A portion of sulfur was removed from bitumen via the SCW conversion with addition of 〈Zn〉 in terms of the ZnO + H2S = ZnS + H2O reaction. These and other peculiarities of the conversion and hydrogenation of bitumen in situ are reported in the present paper. © 2012 Elsevier B.V.


Pakhomov M.A.,RAS Kutateladze Institute of Thermophysics | Terekhov V.I.,RAS Kutateladze Institute of Thermophysics
International Journal of Thermal Sciences | Year: 2012

The numerical model for description of flow dynamics and heat transfer in an impinging axisymmetric gas-droplets jet is presented. The Eulerian model uses for computations of the impinging gas-droplets jet. In this paper the two-phase turbulent jet is numerically predicted by the set of axisymmetic Reynolds averaged Navier-Stokes equations. The flow structure and heat transfer in the gas-droplets impinging spray with low mass fraction of droplets (M L1 ≤ 1%) is studied numerically. Gas phase turbulence is modeled with the use of Reynolds stress transport model for two-phase flow. Droplets addition causes a significant increase in heat transfer intensity (almost twice) in comparison with a single-phase impinging air jet in the stagnation zone. In the region of wall jet the heat transfer intensity in the two-phase impinging jet decreases and approaches the value of a single-phase impinging jet. © 2012 Elsevier Masson SAS. All rights reserved.


Pakhomov M.A.,RAS Kutateladze Institute of Thermophysics | Terekhov V.I.,RAS Kutateladze Institute of Thermophysics
International Journal of Heat and Mass Transfer | Year: 2010

The work presents the results of numerical investigation of the flow structure and heat transfer of impact mist jet with low concentration of droplets (M L1 ≤ 1%). The downward gas-droplets jet issued from a pipe and strikes into at a center of the circular target wall. Mathematical model is based in the solution to RANS equations for the two-phase flow in Euler approximation. For the calculation of the fluctuation characteristics of the dispersed phase equations of Zaichik et al. (1997) [35] model were applied. Predictions were performed for the distances between the nozzle and target plate x/(2R) = 1-10 and the initial droplets size (d 1 = 5-100 μm) at the fixed Reynolds number based on the nozzle diameter, Re = 26,600. Addition of droplets causes significant increase of heat transfer intensity in the vicinity of the jet stagnation point compared with the one-phase air impact jet. © 2010 Elsevier Ltd. All rights reserved.


Chinnov E.A.,RAS Kutateladze Institute of Thermophysics
Technical Physics Letters | Year: 2015

Dynamics of temperature fluctuations on the surface of a vertically falling heated film of water are analyzed at Reynolds number 500 under conditions of motion of developed three-dimensional waves. It is shown that the high-frequency component of temperature fluctuations decays as long as the film moves in the heater bottom part. Some temperature perturbations are carried away into the rivulet region due to transverse thermocapillary forces. At high densities of heat fluxes, only the maximum temperature fluctuations generated by the largest waves reach the heater bottom. In this case, the averaged integral energy of temperature fluctuations in the interrivulet region is reduced. © 2015, Pleiades Publishing, Ltd.


Grant
Agency: Cordis | Branch: FP7 | Program: MC-IIFR | Phase: FP7-PEOPLE-IIF-2008 | Award Amount: 15.00K | Year: 2011

The main goal of the proposal is to elaborate a new technology for active cooling of high heat flux equipment, using thin, intensively evaporating liquid films driven by the action of a forced gas flow in a narrow channel. The main practical motivation of the project is to develop a design capability and design tools that would enable effective cooling of powerful microelectronics for terrestrial and space applications. This capability must be based upon the development of a fundamental understanding of the parameters enabling high heat transfer rates in such thin film systems. It is proposed to develop such fundamental understanding through conducting systematical experimental studies, including studies in microgravity during aircraft parabolic flights. The experiments will be performed on test sections with flat and microstructured local heaters, which will be brought to the host institution (ULB) by the applicant. ULB possesses all necessary experimental facilities to organize and study shear-driven liquid film flows. In the experiments several state-of-the-art techniques will be used (Schlieren methods, Infrared thermography, Fiber optical thickness probe, High speed CCD camera). The proposed research is supposed to make significant advances in basic knowledge of liquid film heat transfer and rupture, and eventually may lead to a new practical cooling technology with broad area of applications in the marketplace. The proposed research, as well as applicants scientific experience, is relevant to the research interest and activities of MRC group of ULB. MRC-ULB has close collaboration with Euro Heat Pipes S.A., aiming at elaboration and creation of an advanced film cooling system for powerful microelectronics. Part of the proposed research is in the framework of ESA-sponsored MAP BOILING project of MRC-ULB. The proposed activity will reinforce mutually beneficial cooperation between ULB and IT, which has been lasting for more than 10 years.


Grant
Agency: Cordis | Branch: FP7 | Program: CP-FP | Phase: AAT.2010.1.1-1.;AAT.2010.1.1-3. | Award Amount: 4.02M | Year: 2010

The objective of AFDAR is to develop, assess and demonstrate new image-based experimental technologies for the analysis of aerodynamic systems and aerospace propulsion components. The main development focus is on new three-dimensional methods based on Particle Image Velocimetry (PIV) to measure the flow field around aircraft components, and on the high-speed version of the planar technique for the analysis in time-resolved regime of transient/unsteady aerodynamic problems. The progress beyond the state of the art with respect to current technologies is summarized by three aimed breakthroughs: 1) three-dimensional volumetric measurements over wings and airfoils; 2) time-resolved measurements and aerodynamic analysis several orders of magnitude faster than today; 3) turbulence characterization in aerodynamics wind-tunnels at resolution orders of magnitude higher than today by Long-Range Micro-PIV. The project ultimately aims to support the design of better aircraft and propulsion systems by enabling the designer to use experimental data during the development cycle of unprecedented completeness and quality. The work also covers the simultaneous application of PIV-based techniques and other methods to determine aeroacoustic noise emissions from airframe and to improve combustion processes to lower NOx, CO2 and soot emissions from engines. The consortium is led by a Dutch Technical University and lists 10 partners including a Russian research Institute and an Australian University. Three industries are involved in this work either as participant or contributing under subcontract and providing testing facilities. As final results of the project, a detailed analysis of the new measurement systems will be delivered and a number of demonstrations will be performed to validate the concepts in industrial environments. Special emphasis is given to the dissemination of results by meetings, publications and workshops.

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