V. I. Terekhov

The mechanism of heat transfer in nanofluids: state of the art (review). Part 2. Convective heat transfer

In the second part of review, we have considered the problems related to momentum and heat transfer in nanofluids. Results on hydrodynamic friction, forced and free convection in the laminar and turbulent flows are analysed; heat transfer at boiling is considered. The available models describing heat transfer intensification and suppression in nanofluids are studied. It is shown that for some problems on convective heat transfer there is a contradiction in data of different authors; possible reasons for this contradiction are analysed.

Heat transfer in turbulent separated flows in the presence of high free-stream turbulence

Abstract Hydrodynamic features of the gas flows past a rib and past a downward step in characteristic separation-flow regions, and distributions of pressures, temperatures, and heat-transfer coefficients behind the obstacles in such flows were experimentally studied. A comparative analysis of the intensifying action of ribs and steps on convective heat transfer is given. We also examined the effect of enhanced external turbulence on thermal and dynamic characteristics of the separated flows. An increased level of free-stream turbulence suppresses the flow separation. The high free-stream turbulent intensifying effect turned out to be more pronounced for the flow past a downward step.

The mechanism of heat transfer in nanofluids: state of the art (review). Part 1. Synthesis and properties of nanofluids

Here is the review of experimental and theoretical results on the mechanism of heat transfer in nanofluids. A wide scope of problems related to the technology of nanofluid production, experimental equipment, and features of measurement methods is considered. Experimental data on heat conductivity of nanofluids with different concentrations, sizes, and material of nanoparticles are presented. Results on forced and free convection in laminar, and turbulent flows are analyzed. The available models of physical mechanisms of heat transfer intensification and suppression in nanofluids are presented. There are significant divergences in data of different researchers; possible reasons for this divergence are analyzed.

Effects of flow turbulence on film cooling efficiency

Abstract Results of experimental investigations on film cooling effectiveness in high-turbulent flow are represented in this paper. The turbulence intensity changed within the range Tu o = 0.2–15% and the injection parameter was 0.1 m m m > 1) the turbulence effect weakens. The experimental data generalization and its comparison with the results of the calculation carried out by asymptotic theory are given.

Effect of flow acceleration and initial turbulence level on velocity fluctuations

The effect of various levels of initial turbulence on the decay of the velocity fluctuations in convergent channels with different contraction ratios has been experimentally investigated. The results of the experiments indicate that the level of turbulence has a strong influence on the longitudinal velocity fluctuations and a weaker effect on the transverse fluctuations. The experimental data demonstrate the inapplicability of the rapid distortion theory and the need for that theory to take into account the energy dissipation, the integral scale and the degree of anisotropy.

An experimental study of submerged jets at low reynolds numbers

Results of an experimental study of submerged subsonic air jets exiting from axially symmetric and plane channels in the Reynolds number range of 100–6000 are presented. Data on visualizing the flow picture and zone of the laminar-turbulent transition have been obtained. The measurement results are compared with well-known experimental data for gas macro- and microjets. The coordinate of the transition to the turbulence for microjets is shown to be able to reach high values, and a generalization of the experimental data is presented.

Structure of pulse dispersed jet upon change in its frequency characteristics

Intensities of heat and mass transfer for continuous and pulse spray in interaction with the vertical surface of a heat exchanger differ considerably from one another when the time-averaged spraying rate [1–6] is kept constant. This difference is determined by characteristic properties of gas-drop flows of continuous and pulse sprays and their interaction with the heat-exchanging surface. Results of experimental studies of basic hydrodynamic parameters of pulse drop flow are presented: velocity and drop size dispersions, spectral characteristics of the kinetic energy of the spray at various distances from the source, and influence of the gas concurrent flow on these parameters. A difference in the heat transfer is shown upon variation of the pulse drop flow parameters from the heat transfer at the stationary supply of spray.

Some Features of a Turbulent Separated Flow and Heat Transfer Behind a Step and a Rib. 1. Flow Structure

The influence of the shape and size of the obstacle on separated flow and heat transfer is studied experimentally. Results of investigation and comparative analysis of the hydrodynamic structure of a separated flow behind a step and a rib are presented. A principally different character of transfer processes in the separated flow behind obstacles of these types is demonstrated. The flow structure in the secondary vortex region is considered.

Laminar natural convection between vertical isothermal heated plates with different temperatures

Numerical investigation of laminar free convection heat transfer in the vertical parallel plate channel with asymmetric heating is presented. Both inlet and exit effects are included into the analysis. A numerical solution is obtained for a Prandtl number of 0.71 and for modified Rayleigh number

Boundary-Layer Structure with Hydrogen Combustion with Different Injection Intensities

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