Journal of Engineering Thermophysics最新文献

A model of the unsteady flow of a water–oil mixture in a formation-pipeline system is constructed, taking into account mass transfer, and solutions to boundary-value problems are presented. Analytical formulas have been obtained that allow determining the pressure field in the pipe and formation productivity depending on the system parameters. Numerical computations have been performed for the system parameters used in practice.

Facing the challenges of climate change and global warming, the engineering community is paying more attention to the carbon emission reduction for building sector. In this study, various heat supply forms including air source heat pump with R410A or R410A alternatives (R32, R446A, R447B, and R459A), electric heater, gas-fired water heater are evaluated for carbon emissions for environmental performance. All R410A alternatives have a higher COP than R410A. R446A displays the highest COP while R32 the second. R32 showed a higher heating capacity, and R410A also displays a higher capacity than its other alternatives except R32. The carbon emission contributed by the electrical heater is more than 3.5 times than that by the air source heat pump heat supply form. The gas-fired water heater produces ~2.2 times for the value of the carbon emission from the heat pump unit. For air source heat pump emission distribution, the sector of the energy consumption shares the largest, more than 90% share, followed by the sector of the annual refrigerant leakage. R446A unit has a value of 18% carbon emission reduction, and R447B and R459A unit hold an emission reduction value of 13.5 and 12% from R410A heat pump. The annual refrigerant leakage takes up ~6% of the R410A unit total emissions; it only takes less than 3% of the unit total emissions for the unit of R410A alternatives. All air source heat pump unit display a lower total emission value when the COP has been improved. In general, Chengdu displays the lowest emission while Beijing is highest due to the difference for climate conditions.

The paper presents constructed two-layer model of the heat and mass transfer during condensation of saturated vapor on a horizontal half-tube placed in a microporous medium. Analytical solutions for film thickness have been found for conditions of hydrophilicity and hydrophobicity of the microporous medium. It is shown that in case of the effect of capillary forces on heat and mass transfer, these effects are manifested in thinning of the film due to suction for the hydrophilic microporous medium and high film flow velocity along the surface of the half-tube for the hydrophobic medium.

In this study, transfer of heat and flow peculiarities in triangular grooved finless, double and triple triangular grooved finned channels were searched numerically by comparing them with straight channels. Using the Ansys-Fluent computer program, numerical analysis was performed by solving the conservation equations under steady, two-dimensional and laminar flow conditions. To better direct the flow to the lower surfaces of corrugated channels with constant surface temperature, the fins were positioned between the grooves at the top surface of the duct at angles of 30°, 60°, and 90° (θ) with the horizontal and at different heights of 4, 8, and 12 mm (z). The outcomes of the work were examined as variations in the mean Nu number (Nu_{mcorrugated ch.}/Nu_{mstraight ch.}), mean surface temperature (T_{smcorrugated ch.}/T_{smstraight ch.}) and performance evaluation criteria (PEC), taking into account the effects of fin angles and heights. The study’s findings were checked against both the numerical outcomes and the analytical equation of the work in the literature giving the mean Nu number (Nu_m), and it was determined that the outcomes were quite compatible and consistent with each other. The outcomes depicted that for Re = 1200, θ = 90°, and z = 12 mm, the (Nu_{mcorrugated ch.}/Nu_{mstraight ch.}) ratio of TiO₂–water nanofluid in the triple triangular grooved finned channel is 4.28% higher than in the double triangular grooved finned channel. Furthermore, when the fin height of the triple triangular corrugated channel is reduced from 12 to 4 mm for the Re = 1200 and θ = 90°, the increase in the PEC value for the nanofluid reaches 6.02%.

In contrast to gas hydrate with pure water, the presence of salt in the solution inhibited the synthesis of SF₆ hydrate. The dissociation of an SF₆ hydrate layer with SiO₂ nanoparticles at atmospheric pressure was investigated experimentally. During the dissociation process, there were aggregated SiO₂ particles both inside the layer and on its surface. The SiO₂ particles caused more intense ice melting and water formation. During the ice melting and water film formation, the SiO₂ particles partially clogged pores in the sample layer and reduced the porosity of the layer, which prevented the gas from leaving the hydrate. In contrast to pure gas hydrate, the dissociation of hydrate with SiO₂ particles is accompanied by the formation of large gas bubbles on the surface of the powder layer. The presence of SiO₂ particles leads to an increase in the total dissociation time of SF₆ hydrate by 23–30%.

Studies of heating and evaporation of heterogeneous suspension droplets in a high-temperature gas environment, the parameters of which match the conditions in thermal water treatment chambers, form the basis for developing methods to improve the efficiency of these technologies. Using high-speed video recording, we investigated experimentally the heating and evaporation characteristics of multicomponent suspension droplets in a gaseous medium within a temperature range of 330–670 K. The effect of the most significant factors—type and concentration of impurities, and heat flux density—on the heating and evaporation characteristics of suspension droplets has been determined. The experiments revealed dependences of droplet heating and evaporation rates on variations in the external gas environment parameters. Based on these results, we proposed recommendations for applying the experimental findings to advance technologies for the thermal purification of wastewater and process water from solid, insoluble impurities.

Experimental study on heat transfer in bubbly flow in an inclined pipe was performed. The angle of pipe inclination varied from 12° to 80° relative to horizontal. Experiments were performed for two values of superficial liquid velocity. It was shown that the highest values of heat transfer correspond to intermediate angles of inclination. The addition of gas phase results in a significant increase of heat transfer even at low gas flow rates. Results obtained are qualitative similar to those obtained in an inclined rectangular channel. However, the quantitative data are different due to different geometry of the inner wall of the channel.

This work investigated numerically the dynamics of weak far-field shock waves and the possibility of reducing the intensity of shock waves from a body in a spatial configuration through local heating of the incoming supersonic flow near the body. The body was a pointed thin body of revolution, in front of which an aerodynamic surface in the form of a thin disk was located at an angle to the incoming flow. The Mach number of the incoming air flow was 2. The calculations were performed using the combined “phantom body” method. It has been shown that local heating of the incoming flow near the body ensures a decrease in the intensity of the far-field shock waves.

This work presents a nanosecond pulsed laser treatment of silicon surfaces aimed at creating superhydrophilic structures. As a result, two types of surfaces were formed: GraySi and BlackSi, which differ in micromorphology and exhibit superhydrophilic properties. Additional modification of the BlackSi surface by zinc oxide (ZnO) deposition allowed for the formation of a uniform nanostructured layer, leading to a significant improvement of the material’s wicking capability. A quantitative evaluation of the wicking capability of the structures was carried out based on the Wi number, which was 1.9 for GraySi, 2.3 for BlackSi, and 3.6 for BlackSi+ZnO.

This paper presents results on mathematical modeling with respect to a simultaneous evaluating of the emissivity and thermal effect of sublimation for carbon composites material as functions of temperature. Optimal experiment design based on influence of the external heat fluxes and some other parameters to the accuracy of the considered inverse problems solution has been studied.