Heat Transfer and Forces for Free-Molecule Flow on a Concave Cylindrical Surface

1964 ◽  
Vol 86 (1) ◽  
pp. 1-9 ◽  
Author(s):  
E. M. Sparrow ◽  
V. K. Jonsson ◽  
T. S. Lundgren ◽  
T. S. Chen
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Cylindrical Surface ◽  
High Speed ◽  
Angle Of Attack ◽  
Accommodation Coefficient ◽  
Free Molecule ◽  
Adiabatic Wall ◽  
The Difference ◽  
Molecule Flow

An analysis has been carried out to determine the local and overall heat-transfer rates, the adiabatic wall temperature, and the forces exerted when a high-speed, free-molecule flow is incident on a concave cylindrical surface. The flow may impinge on the surface at an arbitrary angle of attack. Additionally, the thermal accommodation coefficient may be arbitrary, and the degree of concavity of the surface may be varied at will from a semicircular cross section to a relatively flat circular arc. The concavity causes molecules to interreflect back and forth between surface elements. Even with the interreflections, the heat-transfer rate continues to depend linearly on the difference between the wall temperature and the adiabatic wall temperature. The interreflections are found to have a greater effect on both the heat transfer and the force results as the accommodation co-efficient decreases and as the degree of concavity and the angle of attack increase.

Free-Molecule Tube Flow and Adiabatic Wall Temperatures

1963 ◽  
Vol 85 (2) ◽  
pp. 111-118 ◽  
Author(s):  
E. M. Sparrow ◽  
V. K. Jonsson ◽  
T. S. Lundgren
Keyword(s):  
Mass Flow ◽  
Wall Temperature ◽  
Energy Transport ◽  
Circular Tube ◽  
Tube Length ◽  
Tube Flow ◽  
Free Molecule ◽  
Adiabatic Wall ◽  
Flow Through ◽  
Molecule Flow

The processes of mass and convective-energy transport in free-molecule flow are shown to bear useful similarities with the process of energy transport by thermal radiation. These similarities have been applied as a basis for deriving the mass and energy transfer characteristics for free-molecule flow in a circular tube. The net mass flow through tubes of various length-diameter ratios has been calculated as a function of the pressures and temperatures at the inlet and exit of the tube. A throughflow may occur even if the inlet and exit pressures are the same, provided that a temperature difference exists. For a length-diameter ratio in excess of 45, a fully developed mass flow relation applies. The distribution of the adiabatic wall temperature along the tube length has also been determined as a function of system pressures and temperatures and of the tube dimensions. Rather large variations of adiabatic wall temperature may occur for long tubes. The throughflow of energy shows characteristics similar to the throughflow of mass.

A Novel CFD Method to Estimate Heat Transfer Coefficient for High Speed Flows

2016 ◽  
Vol 66 (3) ◽  
pp. 203 ◽  
Author(s):  
A. Bhandarkar ◽  
Malsur Dharavath ◽  
M.S.R. Chandra Murty ◽  
P. Manna ◽  
Debasis Chakraborty
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Isothermal Condition ◽  
Heat Fluxes ◽  
Aerodynamic Heating ◽  
Transfer Coefficients ◽  
Adiabatic Wall ◽  
Speed Test ◽  
The Difference ◽  
Cfd Method

<p>Accurate prediction of surface temperature of high speed aerospace vehicle is very necessary for the selection of material and determination of wall thickness. For aerothermal characterisation of any high speed vehicle in its full trajectory, it requires number of detailed computational fluid dynamics (CFD) calculations with different isothermal calculations. From the detailed CFD calculations for different flow conditions and geometries, it is observed that heat transfer coefficients scale with the difference of adiabatic wall temperature and skin temperature. A simple ‘isothermal method’, is proposed to calculate heat flux data with only two CFD simulations one on adiabatic condition and other on isothermal condition. The proposed methodology is validated for number of high speed test cases involving external aerodynamic heating as well as high speed combusting flow. The computed heat fluxes and surface temperatures matches well with experimental and flight measured values.</p>

High Resolution Heat Transfer Measurements on the Stator Endwall of an Axial Turbine

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
Benoit Laveau ◽  
Reza S. Abhari ◽  
Michael E. Crawford ◽  
Ewald Lutum
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
High Resolution ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Wall Temperature ◽  
Adiabatic Wall ◽  
Axial Turbine ◽  
The Heat Transfer Coefficient

In order to continue increasing the efficiency of gas turbines, an important effort is made on the thermal management of the turbine stage. In particular, understanding and accurately estimating the thermal loads in a vane passage is of primary interest to engine designers looking to optimize the cooling requirements and ensure the integrity of the components. This paper focuses on the measurement of endwall heat transfer in a vane passage with a three-dimensional (3D) airfoil shape and cylindrical endwalls. It also presents a comparison with predictions performed using an in-house developed Reynolds-Averaged Navier–Stokes (RANS) solver featuring a specific treatment of the numerical smoothing using a flow adaptive scheme. The measurements have been performed in a steady state axial turbine facility on a novel platform developed for heat transfer measurements and integrated to the nozzle guide vane (NGV) row of the turbine. A quasi-isothermal boundary condition is used to obtain both the heat transfer coefficient and the adiabatic wall temperature within a single measurement day. The surface temperature is measured using infrared thermography through small view ports. The infrared camera is mounted on a robot arm with six degrees of freedom to provide high resolution surface temperature and a full coverage of the vane passage. The paper presents results from experiments with two different flow conditions obtained by varying the mass flow through the turbine: measurements at the design point (ReCax=7.2×105) and at a reduced mass flow rate (ReCax=5.2×105). The heat transfer quantities, namely the heat transfer coefficient and the adiabatic wall temperature, are derived from measurements at 14 different isothermal temperatures. The experimental data are supplemented with numerical predictions that are deduced from a set of adiabatic and diabatic simulations. In addition, the predicted flow field in the passage is used to highlight the link between the heat transfer patterns measured and the vortical structures present in the passage.

A Method of Solving Three Temperature Problem of Turbine With Adiabatic Wall Temperature

2021 ◽  
Author(s):  
Zeyu Wu ◽  
Xiang Luo ◽  
Jianqin Zhu ◽  
Zhe Zhang ◽  
Jiahua Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Wall Temperature ◽  
Reference Temperature ◽  
Inlet Temperature ◽  
Adiabatic Wall ◽  
Rotating Cavity ◽  
Temperature Problem ◽  
Turbulence Parameters

Abstract The aeroengine turbine cavity with pre-swirl structure makes the turbine component obtain better cooling effect, but the complex design of inlet and outlet makes it difficult to determine the heat transfer reference temperature of turbine disk. For the pre-swirl structure with two air intakes, the driving temperature difference of heat transfer between disk and cooling air cannot be determined either in theory or in test, which is usually called three-temperature problem. In this paper, the three-temperature problem of a rotating cavity with two cross inlets are studied by means of experiment and numerical simulation. By substituting the adiabatic wall temperature for the inlet temperature and summarizing its variation law, the problem of selecting the reference temperature of the multi-inlet cavity can be solved. The results show that the distribution of the adiabatic wall temperature is divided into the high jet area and the low inflow area, which are mainly affected by the turbulence parameters λT, the rotating Reynolds number Reω, the high inlet temperature Tf,H* and the low radius inlet temperature Tf,L* of the inflow, while the partition position rd can be considered only related to the turbulence parameters λT and the rotating Reynolds number Reω of the inflow. In this paper, based on the analysis of the numerical simulation results, the calculation formulas of the partition position rd and the adiabatic wall temperature distribution are obtained. The results show that the method of experiment combined with adiabatic wall temperature zone simulation can effectively solve the three-temperature problem of rotating cavity.

scholarly journals Local Heat Transfer Coefficient and Adiabatic Wall Temperature Measurement Beneath Arrays of Staggered and Inline Impinging Jets

1994 ◽  
Author(s):  
Kenneth W. Van Treuren ◽  
Zuolan Wang ◽  
Peter T. Ireland ◽  
Terry V. Jones ◽  
S. T. Kohler
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Impinging Jets ◽  
Hole Diameter ◽  
Channel Height ◽  
Published Data ◽  
Target Plate ◽  
Adiabatic Wall

Recent work, Van Treuren et al. (1993), has shown the transient method of measuring heat transfer under an array of impinging jets allows the determination of local values of adiabatic wall temperature and heat transfer coefficient over the complete surface of the target plate. Using this technique, an inline array of impinging jets has been tested over a range of average jet Reynolds numbers (10,000–40,000) and for three channel height to jet hole diameter ratios (1, 2, and 4). The array is confined on three sides and spent flow is allowed to exit in one direction. Local values are averaged and compared with previously published data in related geometries. The current data for a staggered array is compared to those from an inline array with the same hole diameter and pitch for an average jet Reynolds number of 10,000 and channel height to diameter ratio of one. A comparison is made between intensity and hue techniques for measuring stagnation point and local distributions of heat transfer. The influence of the temperature of the impingement plate through which the coolant gas flows on the target plate heat transfer has been quantified.

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