Numerical Study of Heat Transfer in High Speed Microflows

2003 ◽  
Author(s):  
Reni Raju ◽  
Subrata Roy
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Numerical Study

Unsteady and Calming Effects Investigation on a Very High Lift LP Turbine Blade: Part I — Experimental Analysis

2002 ◽  
Author(s):  
Thomas Coton ◽  
Tony Arts ◽  
Michae¨l Lefebvre ◽  
Nicolas Liamis
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Numerical Study ◽  
Turbine Rotor ◽  
High Lift ◽  
Turbine Rotor Blade ◽  
Pressure Loss Coefficient ◽  
Lp Turbine ◽  
Exit Mach Number ◽  
Very High

An experimental and numerical study was performed about the influence of incoming wakes and the calming effect on a very high lift low pressure turbine rotor blade. The first part of the paper describes the experimental determination of the pressure loss coefficient and the heat transfer around the blade mounted in a high speed linear cascade. The cascade is exposed to incoming wakes generated by high speed rotating bars. Their aim is to act upon the transition/separation phenomena. The measurements were conducted at a constant exit Mach number equal to 0.8 and at three Reynolds number values, namely 190000, 350000 and 650000. The inlet turbulence level was fixed at 0.8%. An additional feature of this work is to identify the boundary layer status through heat transfer measurements. Compared to the traditionally used hot films, thin film heat flux gages provide fully quantitative data required for code validation. Numerical computations are presented in the second part of the paper.

Cooling Enhancement of a Heat Source Through Flow Pulsation and Porous Block

Volume 4 ◽  
2004 ◽  
Author(s):  
Po-Chuan Huang ◽  
Shy-Her Nian ◽  
Chao-Fu Yang
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
High Speed ◽  
Numerical Study ◽  
Particle Diameter ◽  
Pulsating Flow ◽  
Flow Pulsation ◽  
Cycle Space ◽  
Porous Block ◽  
Cooling Enhancement

A numerical study of forced pulsating flow in a parallel-plate channel with a porous-block-attached strip heat source at the bottom wall is presented. Comprehensive time-dependent flow and temperature data are calculated and averaged over a pulsation cycle in a periodic steady state. The results show that the cycle-space averaged Nusselt number for pulsating flow is higher than that for steady flow. The heat transfer enhancement factor increases with particle diameter, and pulsation frequent, but decreases with pulsation amplitude. The method combining flow pulsation with particle-porous heat sink can be considered as an augment heat transfer tool for cooling high-speed electronic devices.

scholarly journals Numerical Study on Transient Heat Transfer of a Quartz Lamp Heating System

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Yan Yu ◽  
Pingjian Ming ◽  
Song Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Finite Volume Method ◽  
Finite Volume ◽  
High Speed ◽  
Numerical Study ◽  
Heating System ◽  
Aerodynamic Heating ◽  
Thermal Testing ◽  
Volume Method

Thermal ground testing is an accepted and frequently used method for simulating the aerodynamic heating of high speed flight vehicles. A numerical method based on a finite volume method for a quartz lamp heating system, used in thermal testing, is proposed. In this study, the unstructured finite-volume method (UFVM) for radiation has been formulated and implemented in a fluid flow solver GTEA on unstructured grids. For comparison and validation of the proposed method, a 2D furnace with cooling pipes was chosen. The results obtained from the proposed FVM agreed well with the exact solutions. Numerical results show that the quartz lamp can be simplified as a slat with the same temperature radiation source, and a simplified 2D thermal testing case was then simulated with the coupling effects of radiation, convection, and conduction heat transfer. Different temperature loading curves and ratios of intervals between the lamps and lamp length (l/s) were studied using the proposed method. The radiation heat flux on the metal surface was a wave-shaped curve. Comparing the different interval ratios, we found that the smaller the interval ratio, the larger the maximum value and the smaller the difference between the maximum and minimum heat flux.

Unsteady and Calming Effects Investigation on a Very High-Lift LP Turbine Blade—Part I: Experimental Analysis

2003 ◽  
Vol 125 (2) ◽  
pp. 281-290 ◽  
Author(s):  
Thomas Coton ◽  
Tony Arts ◽  
Michae¨l Lefebvre ◽  
Nicolas Liamis
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Numerical Study ◽  
Turbine Rotor ◽  
High Lift ◽  
Turbine Rotor Blade ◽  
Pressure Loss Coefficient ◽  
Lp Turbine ◽  
Exit Mach Number ◽  
Very High

An experimental and numerical study was performed about the influence of incoming wakes and the calming effect on a very high-lift low-pressure turbine rotor blade. The first part of the paper describes the experimental determination of the pressure loss coefficient and the heat transfer around the blade mounted in a high-speed linear cascade. The cascade is exposed to incoming wakes generated by high-speed rotating bars. Their aim is to act upon the transition/separation phenomena. The measurements were conducted at a constant exit Mach number equal to 0.8 and at three Reynolds number values; namely, 190,000, 350,000, and 650,000. The inlet turbulence level was fixed at 0.8%. An additional feature of this work is to identify the boundary layer status through heat transfer measurements. Compared to the traditionally used hot films, thin film heat flux gages provide fully quantitative data required for code validation. Numerical computations are presented in the second part of the paper.

scholarly journals Experimental and numerical study on sensible heat transfer at droplet/wall interactions

2017 ◽  
Author(s):  
Ana Sofia Moita ◽  
Emanuele Teodori ◽  
Pedro Pontes ◽  
António Luís Nobre Moreira ◽  
Anastasios Georgoulas ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
High Speed ◽  
Numerical Study ◽  
Temperature Fields ◽  
Sensible Heat ◽  
Droplet Spreading ◽  
The Impact

The present study addresses a detailed experimental and numerical investigation on the impact of water dropletson smooth heated surfaces. High-speed infrared thermography is combined with high-speed imaging to couple the heat transfer and fluid dynamic processes occurring at droplet impact. Droplet spreading (e.g. spreading ratio) and detailed surface temperature fields are then evaluated in time and compared with the numerically predicted results. The numerical reproduction of the phenomena was conducted using an enhanced version of a VOF- based solver of OpenFOAM previously developed, which was further modified to account for conjugate heat transfer between the solid and fluid domains, focusing only on the sensible heat removed during  droplet spreading. An excellent agreement is observed between the temporal evolution of the experimentally measured and the numerically predicted spreading factors (differences between the experimental and numerical values were always lower than 3.4%). The numerical and experimental dimensionless surface temperature profiles along the droplet radius were also in good agreement, depicting a maximum difference of 0.19. Deeper analysis coupling fluid dynamics and heat transfer processes was also performed, evidencing a strong correlation between maximum and minimum temperature values and heat transfer coefficients with the vorticity fields in the lamella, which lead to particular mixing processes in the boundary layer region. The correlation between the resulted temperature fields and the droplet dynamics was obtained by assuming a relation between the vorticity and the local heat transfer coefficient, in the first fluid cell i.e. near the liquid-solid interface. The two measured fields revealed that local maxima and minima in the vorticity corresponded to spatially shifted local minima and maxima in the heat transfer coefficient, at all stages of the droplet spreading. This was particularly clear in the rim region,which therefore should be considered in future droplet spreading models.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5024

Numerical Study on a Single Square Cylinder Subjected to Vortex-Induced Vibration in HTR-PM

2016 ◽  
Author(s):  
Qiankun Xiao ◽  
Li Shi ◽  
Xiaoxin Wang ◽  
Xiaowei Luo ◽  
Xinxin Wu
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Numerical Study ◽  
Flow Direction ◽  
Turbulence Models ◽  
Detached Eddy Simulation ◽  
Square Cylinder ◽  
Vortex Induced Vibration ◽  
Eddy Simulation ◽  
High Reynolds

The heat transfer tube bundles of the steam generator in high temperature reactor pebble bed module (HTR-PM) are subjected to high speed helium flow, which might lead to vortex-induced vibration (VIV). In the present paper, to investigate the vibration of square cylinder under flow effect, vortex shedding phenomena of a stationary square cylinder at a high Reynolds number equal to 6.8 × 104 is simulated by detached eddy simulation (DES) turbulence models. A comparatively close agreement with previous experimental results is achieved. Combining computational fluid dynamics (CFD) and computational structural dynamics (CSD) methods, a fluid-structure-interaction (FSI) model for VIV of the square cylinder is then established, and vibration response perpendicular to flow direction were investigated. Moreover, the safe range of the natural frequency of the square cylinder to avoid synchronized vibration with VIV is analyzed. The results of this paper can provide an important guidance to the design of the heat transfer tubes and their supports in HTR-PM.

scholarly journals Numerical Study for Optimizing Heat Transfer in High Speed Rotating Components

1998 ◽  
Vol 4 (3) ◽  
pp. 151-161 ◽  
Author(s):  
S. Wittig ◽  
S. Kim ◽  
Th. Scherer ◽  
I. Weissert
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
High Speed ◽  
Numerical Study ◽  
Rotating Disks ◽  
Rotating System ◽  
Local Flow ◽  
Flow Through ◽  
Air Flows ◽  
Cooling Air

Cooling of high speed rotating components is a typical situation found in turbomachinery as well as in automobile engines. Accurate knowledge of discharge coefficients and heat transfer of related components is essential for the high performance of the whole engine. This can be achieved by minimized cooling air flows and avoidance of hot spots. In high speed rotating clutches for example aerodynamic investigations improving heat transfer have not been considered in the past. Advanced concepts of modern plate design try to reduce thermal loads by convective cooling methods. Therefore, secondary cooling air flows have to be enhanced by an appropriate design of the rotor stator system with orifices. CFD modelling is used to improve the basic understanding of the flow field in typical geometries used in these systems.The computational results are obtained by a 3-D-finite-volume-code based on body fitted structured grids. The Navier Stokes equations are solved by a pressure-correction method combined with the standard k-e-turbulence model. Considering the rotation of orifices in disks or shafts, the frame of reference has to be changed to the rotating system. The flow through orifices in high speed rotating disks can be calculated with a high level of accuracy in comparison with experiments as shown in Wittig et al. [1994].Numerical results of the flow in a high speed rotating system are presented with emphasis on geometrical variations. Calculations are carried out in order to find an optimum design in terms of position and size of the orifices in the housing. These variations induce different physical phenomena. Special consideration is directed towards the basic problems of the flow through orifices in high speed rotating disks and shafts and the flow inside rotor-stator systems. As expected, the very complex flow fields are dominated by rotational effects. In addition it is shown that differences occur between the configuration of optimized mass flow rate and the geometry with a maximum of total heat transfer. Obviously, optimization procedures are dependent on the knowledge of the local flow field and cannot be performed without advanced CFD-methods. It is demonstrated that the approach presented here is suitable for these tasks.

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