Study of turbulent heat transfer of aviation kerosene flows in a curved pipe at supercritical pressure

The now and heat transfer characteristics of China No. 3 aviation kerosene in a heated curved tube under supercritical pressure are numerically investigated by a finite volume method. A two-layer turbulence model, consisting of the RNG k-epsilon two-equation model and the Wolfstein one-equation model, is used for the simulation of turbulence. A 10-species kerosene surrogate model and the NIST Supertrapp software are applied to obtain the thermophysical and transport properties of the kerosene at various temperature under a supercritical pressure of 4 MPa. The large variation of thermophysical properties of the kerosene at the supercritical pressure make the flow and heat transfer more complicated, especially under the effects of buoyancy and centrifugal force. The centrifugal force enhances the heat transfer, but also increases the friction factors. The rise of the velocity caused by the variation of the density does not enhance the effects of the centrifugal force when the curvature ratios are less than 0.05. On the contrary, the variation of the density increases the effects of the buoyancy. (C) 2010 Elsevier Ltd. All rights reserved.

Turbulent heat transfer and coherent vortical structures in gas turbine film cooling

Unsteady coherent structures and turbulent heat transfer in a film cooling flow is studied by using detached eddy simulation (DES). Detailed computations for an inclined jet in crossflow by a single row of 35 degree round holes on a flat plate were performed at blowing ratios of 0.5 and 1.0, and a density ratio of 2.0. The correlation between the coherent vortical structures and the unsteady heat transfer is carefully examined. The instantaneous flow fields and heat transfer distributions are found to be characterized by the formation of large coherent vortical structures. These structures enhance the thermal mixing process and turbulent heat transfer to the wall. From the inspection of both unsteady adiabatic film cooling effectiveness and heat transfer coefficient, these two are found to have substantial local fluctuations due to the large unsteadiness of coherent structures. The fluctuation of the adiabatic effectiveness and heat transfer coefficient, for example, can be as high as 15 and 50 percent of the time-mean value, respectively. It could result in the detrimental effect on film cooling performance.

Numerical Study Of Heat Transfer Mechanism In Turbulent Supercritical Co2 Channel Flow

Direct numerical simulation (DNS) of supercritical CO2 turbulent channel flow has been performed to investigate the heat transfer mechanism of supercritical fluid. In the present DNS, full compressible Navier-Stokes equations and Peng-Robison state equation are solved. Due to effects of the mean density variation in the wall normal direction, mean velocity in the cooling region becomes high compared with that in the heating region. The mean width between high-and low-speed streaks near the wall decreases in the cooling region, which means that turbulence in the cooling region is enhanced and lots of fine scale eddies are created due to the local high Reynolds number effects. From the turbulent kinetic energy budget, it is found that compressibility effects related with pressure fluctuation and dilatation of velocity fluctuation can be ignored even for supercritical condition. However, the effect of density fluctuation on turbulent kinetic energy cannot be ignored. In the cooling region, low kinematic viscosity and high thermal conductivity in the low speed streaks modify fine scale structure and turbulent transport of temperature, which results in high Nusselt number in the cooling condition of the supercritical CO2.

Numerical Study of Heat Transfer Mechanism in Turbulent Supercritical CO2 Channel Flow

Direct numerical simulation (DNS) of supercritical CO2 turbulent channel flow has been performed to investigate the heat transfer mechanism of supercritical fluid. In the present DNS, full compressible Navier-Stokes equations and Peng-Robison state equation are solved. Due to effects of the mean density variation in the wall normal direction, mean velocity in the cooling region becomes high compared with that in the heating region. The mean width between high-and low-speed streaks near the wall decreases in the cooling region, which means that turbulence in the cooling region is enhanced and lots of fine scale eddies are created due to the local high Reynolds number effects. From the turbulent kinetic energy budget, it is found that compressibility effects related with pressure fluctuation and dilatation of velocity fluctuation can be ignored even for supercritical condition. However, the effect of density fluctuation on turbulent kinetic energy cannot be ignored. In the cooling region, low kinematic viscosity and high thermal conductivity in the low speed streaks modify fine scale structure and turbulent transport of temperature, which results in high Nusselt number in the cooling condition of the supercritical CO2.

Numerical study of turbulent fluid flow and heat transfer in lateral perforated extended surfaces

Numerical study has been performed in this study to investigate the turbulent convection heat transfer on a rectangular plate mounted over a flat surface. Thermal and fluid dynamic performances of extended surfaces having various types of lateral perforations with square, circular, triangular and hexagonal cross sections are investigated. RANS (Reynolds averaged Navier–Stokes) based modified k–ω turbulence model is used to calculate the fluid flow and heat transfer parameters. Numerical results are compared with the results of previously published experimental data and obtained results are in reasonable agreement. Flow and heat transfer parameters are presented for Reynolds numbers from 2000 to 5000 based on the fin thickness.

Heat Transfer to molten lead-bismuth eutectic in turbulent pipe flow /

"Contract No. AT-(40-1)-1061 Part 2."

Effect of gas entrainment on the heat transfer characteristics of mercury under turbulent flow conditions : final report /

"Gas entrainment, indicated by visual bubbles in the mercury, led to low heat transfer rates which were increased by increasing the static pressure. Suitable changes in the flow system resulted in a reduction of this entrainment effect and an increase in heat transfer performance."--Page iii.

Turbulent forced convection heat transfer in circular tubes containing sodium hydroxide.

"ORNL-1370."

An experimental study of heat transfer at high temperature differences in turbulent air flow between a rotating cylinder and a stationary concentric auter cylinder,

Final report no. AFOSR 3207.