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This paper presents the results of development and experiments with a looped thermosyphon with a microstructured heat transfer surface (3D printed) for the case of a flat evaporator and ethanol coolant. The thermal parameters of this device were tested for the temperature in the range from 20 to 128 °С and for the heat flux ranging from 25 to 530 W and for device filling level of 40 ml (100 % of the evaporator volume). It was found that the heat exchanger with pillar-array surface provides the total thermal resistance about 0.18 K/W (corresponding to the top input heat flux equal to 530 W). The developed micropillar array structure for the inner surface of heat exchanger improves the loop thermosyphon efficiency.

The flows of a viscous liquid film along the outer surface of a vertical cylinder are considered. The study employs a model nonlinear evolutionary equation for film thickness deviation from the undisturbed level. It is valid for describing long-wave perturbations in the case of small fluid flows and large cylinder radii. The branching of spatial wave regimes from the undisturbed flow regime is investigated. Particular attention is paid to special cases when the values of the radii of the cylinders lie in the vicinity of some specific critical points. To study such cases, a model system of equations is obtained from the initial equation. Several solutions of this system are given.

Analytical and numerical solutions for the heating of a composite "hydrocarbon - water" drop with a water microdroplet located in the center of a spherical drop of hydrocarbon are compared. The conjugation conditions are fulfilled at the interface: continuity of temperature and heat flux. At the outer boundary of the droplet, a condition of heat exchange with a hot gas streamlining the droplet is set. The analytical formula is based on the decomposition of the solution in a series of eigenfunctions of the Sturm-Liouville problem. An original conservative difference scheme for the numerical integration of the equations of thermal conductivity inside a composite droplet is constructed to take into account the abrupt change in thermophysical properties at the interface of hydrocarbon-water media. The calculation results obtained using the analytical formula and the numerical integration method are consistent with each other. The numerical scheme includes radiative heat transfer and the effect of evaporation on the heat transfer coefficient. A comparison of the simulation results with experimental data is presented.

High-speed shadow imaging of a gas-droplet flow from a microchannel nozzle device was performed by varying the liquid flow rate from 1 to 50 ml/min and the gas pressure drop from 0.5 to 8 bar. For this purpose, an optical system with a stereomicroscope was assembled to ensure a large depth of field and relatively high resolution. The outflow was studied for two types of nozzles: a three-nozzle device with an internal channel diameter of 200 μm and a custom-made nozzle with a microchannel silicon membrane of 243 μm thickness and a microchannel size of 10×10 μm². Spray angles for a single nozzle and an angle averaged over three nozzles were determined. Dependences of the angles on liquid flow rate for each pressure drop and dependences on pressure drop with varying liquid flow rate were obtained. It is shown that a uniform gas-droplet flow can be organized at the nozzle edge with small droplets using a microchannel membrane.

The results of an experimental investigation on heat transfer and critical heat flux during surface cooling with a dispersed flow of deeply subcooled liquid are presented. The study was carried out using a pressure nozzle with a mass flow rate of water of 24.2 g/s. A record critical heat flux of 13.2 MW/m² was achieved in these experiments. The findings indicate that the onset of boiling within the liquid film formed on the impact surface during spray irrigation leads to a notable reduction in the temperature non-uniformity across the heater.

The paper presents an updated physical-mathematical model for a stationary flow of a water-oil flow through the porous space of a rock core (this space is described as an array of capillary clusters). Here we consider an isothermal statement of problem: the temperature is the key parameters for fluid properties and for the value of pressure drop caused by interaction between the fluid phases. The developed model ensures calculating the relative permeability at different temperatures; this approach is based on standard laboratory data for core testing and on experimental data for single-phase filtration of the fluid at different temperatures (or substituted with appropriate formulas). This model was applied for calculating the relative phase permeabilities at different temperatures for the case of weakly-cemented rock formation. This sample was taken from one of Siberian oil fields with a high viscosity oil. The numerical study was conducted on the effect of temperature on the flow pattern in a variable cross-section capillary channel. Simulation was conducted using the OpenFOAM platform. The temperature-caused change in fluid properties alleviates the intensity of a train flow and promotes the transition of the train flow to the droplet flow.

The paper investigates the possibility to control the two-phase flow of immiscible liquids with a high viscosity ratio of the carrier and dispersed phases in a T-type microchannel, with the dispersed phase being a ferromagnetic liquid, by means of a constant magnetic field. The effects of separation of slugs and microdrops of a ferrofluid, as well as the controllability of the structure of the parallel flow of immiscible liquids, have been found. The obtained results may be used to design microfluidic systems in order to efficiently sort particles, as well as intensify heat and mass transfer processes.

Various approaches to oil film visualization of the flow on the cylinder surface aligned transversely in a supersonic flow in a pulsed wind tunnel are compared. Two types of fine-particle coloring pigments Al₂O₃ and TiO₂ are considered. Two methods of pigment application are used: sprinkling onto the model surface pre-coated with an oil film and applying a mixture of the pigment and oil onto the model surface. The mass fraction of the pigment in the mixture for oil film visualization is varied from 10 to 20%. Photographs of the dynamics of variation of the oil film coating on the model surface are presented, which are taken immediately after application, during the experiment, and upon its completion. Based on the results of the present study, recommendations are formulated on using surface flow oil film visualization with due allowance for specific features of application of this method for experiments in pulsed supersonic wind tunnels.

The present study deals with optical and thermophysical properties of nanofluids based on spherical carbon nanoparticles stabilized in water by sodium dodecyl sulfate. Nanoparticles with the mean diameter of 11 nm are synthesized by means of electric arc spraying in helium at a pressure of 3 Torr. For the concentration of carbon nanoparticles in the nanofluid equal to 0.01%, the extinction coefficient varies from 400 to 200 m^-1 in the wavelength range of 180 - 1100 nm. For mass fractions of nanoparticles within 0 - 0.04%, the viscosity is not found to depend on the concentration. With an increase in the concentration, the thermal conductivity of nanofluids in the same range of concentrations is found to be lower than the thermal conductivity of water by up to 4%.

The paper presents the results of numerical simulation of a round turbulent jet propagation in confined space: the jet at Re = 5.4·10⁴ is supplied into a rectangular cavity with a height to width ratio of 0.16. The URANS and LES calculations reproduce the self-oscillating regime, registered previously in the experiments by Lawson et al. (2005). A significant rearrangement of the flow structure and pressure field occurring at a low-flow jet supply from the narrow side wall allows controlling self-oscillations up to their complete suppression. A map of flow regimes has been obtained for three various positions of the opening, supplying the control jet, depending on the control and primary jets momentum ratio. The calculated data provide a quantitative assessment of the flow controllability by injecting a low-flow jet into the zone of the primary jet propagation perpendicular to its axis.