Film Cooling and Heat Transfer in Nozzles

1988 ◽  
Vol 110 (1) ◽  
pp. 57-65 ◽  
Author(s):  
J. Stoll ◽  
J. Straub
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Film Cooling ◽  
Wall Heat Flux ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Film Stability ◽  
Hot Air ◽  
Theoretical Investigations ◽  
Favorable Pressure Gradient

In this paper experimental and theoretical investigations on heat transfer and cooling film stability in a convergent–divergent nozzle are presented. Compressed air is injected into hot air in the inlet region of the nozzle and the influence of the strong favorable pressure gradient in the nozzle on turbulent heat transfer and mixing is examined. The experiments cover measurements of wall pressures, wall temperature, and wall heat flux. Calculations with parabolic finite difference boundary layer code have been performed using a well-known k–ε-turbulence model with an extension paying regard to acceleration. As a result the calculated wall heat flux is compared with the measured heat flux.

TURBULENT HEAT TRANSFER AT A SHARP CHANGE IN WALL HEAT FLUX

1990 ◽  
Author(s):  
A. M. Nasibulov ◽  
B. V. Perepelitsa ◽  
Yu. M. Pshenichnikov ◽  
N. S. Safarova ◽  
E. M. Khabakhpasheva
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Wall Heat Flux ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Sharp Change

Experiments on Turbulent Heat Transfer in a Tube With Circumferentially Varying Thermal Boundary Conditions

1967 ◽  
Vol 89 (3) ◽  
pp. 258-268 ◽  
Author(s):  
A. W. Black ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boundary Conditions ◽  
Wall Heat Flux ◽  
Turbulent Heat Transfer ◽  
Working Fluid ◽  
Turbulent Heat ◽  
Turbulent Diffusivity ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

An experimental investigation, supported by analysis, was performed to determine the heat transfer characteristics for turbulent flow in a circular tube with circumferentially varying wall temperature and wall heat flux. Air was the working fluid. The desired boundary conditions were achieved by electric heating within the wall of a tube whose thickness varied circumferentially. In this way, ratios of maximum-to-minimum wall heat flux as large as two were attained. Local heat transfer coefficients, deduced from the experimental data, display a circumferential variation that is substantially smaller than the heat flux variation. In general, lower heat transfer coefficients correspond to circumferential locations of greater heating, while higher coefficients correspond to locations of lesser heating. The predictions of prior analyses appear to overestimate the circumferential variation of the heat transfer coefficient. A specially designed probe was employed to measure the radial and circumferential temperature distributions within the flowing airstream. On the basis of these measurements, as well as from the heat transfer results, it is concluded that, in the neighborhood of the wall, the tangential turbulent diffusivity is greater than the radial turbulent diffusivity. The axial thermal development was found to be more rapid on the lesser-heated side of the tube than on the greater-heated side. Experimentally determined circumferential-average heat transfer coefficients agreed well with the predictions of analysis.

scholarly journals Three-point MEMS heat flux sensor for turbulent heat transfer measurement in internal combustion engines

2018 ◽  
Vol 20 (7) ◽  
pp. 696-705 ◽  
Author(s):  
Kazuhito Dejima ◽  
Osamu Nakabeppu ◽  
Yuto Nakamura ◽  
Tomohiro Tsuchiya ◽  
Keisuke Nagasaka
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Standard Deviation ◽  
Heat Fluxes ◽  
Wall Heat Flux ◽  
Turbulent Heat Transfer ◽  
Heat Flux Sensor ◽  
Turbulent Heat ◽  
Mems Sensor ◽  
Flux Sensor

A heat flux sensor was developed with micro-electro-mechanical systems (MEMS) technologies for investigating turbulent heat transfer characteristics in engines. The sensor has three thin-film resistance temperature detectors (RTDs) of a square 315 µm on a side on a 900 µm diameter circle in rotational symmetry. The performances of the MEMS systems sensor were tested in an open combustion chamber and a laboratory engine. In the open chamber tests, it was revealed that the MEMS sensor can measure the wall heat fluxes reflecting flow states of gas phase. In addition, the noise was evaluated as 3.8 kW/m2 with the standard deviation against the wall heat flux of a few hundred kW/m2. From these results, it was proved that the MEMS sensor has the potential to observe turbulent heat transfer on the order over 10 kW/m2 in the engine. In the laboratory engine test, the wall heat flux for continuous 200 cycles was measured with a good signal-to-noise ratio. The noise was evaluated as 13.4 kW/m2 with the standard deviation despite the noisy environment. Furthermore, it was proved that the MEMS sensor has the comparable scale with the turbulence in the engine because the three adjacent detectors measured similar but different phase oscillations in the local instantaneous heat fluxes. In addition, a heat flux vector reflecting the state of the local instantaneous heat transfer was visualized by the adjacent three-point measurement. It is expected that the three-point MEMS sensor will be a useful tool for the engine heat transfer research.

Direct numerical simulation of turbulent heat transfer across a sheared wind-driven gas–liquid interface

2016 ◽  
Vol 804 ◽  
pp. 646-687 ◽  
Author(s):  
Ryoichi Kurose ◽  
Naohisa Takagaki ◽  
Atsushi Kimura ◽  
Satoru Komori
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Mass Transfer ◽  
Heat Flux ◽  
Streamwise Velocity ◽  
Liquid Interface ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Turbulent Eddies

Turbulent heat transfer across a sheared wind-driven gas–liquid interface is investigated by means of a direct numerical simulation of gas–liquid two-phase turbulent flows under non-breaking wave conditions. The wind-driven wavy gas–liquid interface is captured using the arbitrary Lagrangian–Eulerian method with boundary-fitted coordinates on moving grids, and the temperature fields on both the gas and liquid sides, and the humidity field on the gas side are solved. The results show that although the distributions of the total, latent, sensible and radiative heat fluxes at the gas–liquid interface exhibit streak features such that low-heat-flux regions correspond to both low-streamwise-velocity regions on the gas side and high-streamwise-velocity regions on the liquid side, the similarity between the heat-flux streak and velocity streak on the gas side is more significant than that on the liquid side. This means that, under the condition of a fully developed wind-driven turbulent field on both the gas and liquid sides, the heat transfer across the sheared wind-driven gas–liquid interface is strongly affected by the turbulent eddies on the gas side, rather than by the turbulent eddies and Langmuir circulations on the liquid side. This trend is quite different from that of the mass transfer (i.e. $\text{CO}_{2}$ gas). This is because the resistance to heat transfer is normally lower than the resistance to mass transfer on the liquid side, and therefore the heat transfer is controlled by the turbulent eddies on the gas side. It is also verified that the predicted total heat, latent heat, sensible heat and enthalpy transfer coefficients agree well with previously measured values in both laboratory and field experiments. To estimate the heat transfer coefficients on both the gas and liquid sides, the surface divergence could be a useful parameter, even when Langmuir circulations exist.

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