Thermofluidic Characteristics of a Porous Ventilated Brake Disk

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
H. B. Yan ◽  
T. Mew ◽  
M.-G. Lee ◽  
K.-J. Kang ◽  
T. J. Lu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Substantial Reduction ◽  
Three Dimensional ◽  
Cooling Capacity ◽  
Vehicle Speed ◽  
Brake Disk ◽  
Cooling Flow ◽  
Flow Mixing ◽  
Bulk Diamond

We introduce a new class of ventilated brake disk which incorporates an open cellular core: wire-woven bulk diamond (WBD). Transient and steady-state thermofluidic characteristics are presented. As reference, a commercially available pin-finned brake disk is also considered. At a braking power of 1.9 kW, representative of a medium sized truck descending a 2% gradient at a vehicle speed of 40 km/h (i.e., 200 rpm), the WBD cored brake disk reduces the overall brake disk temperature by up to 24% compared to the pin-finned brake disk. Results also reveal that in typical operating ranges (up to 1000 rpm), the WBD core provides up to 36% higher steady-state overall cooling capacity over that obtainable by the pin-finned core. In addition, the three-dimensional morphology of the WBD core gives rise to a tangentially and radially more uniform temperature distribution. Although the WBD core causes a higher pressure drop, this is balanced by the benefit of a stronger suction of cooling flow. Flow mixing in an enlarged heat transfer area by the WBD core is responsible for the substantial heat transfer enhancement. The WBD core is mechanically strong yet light while providing a substantial reduction in a brake's operating temperature.

Fundamental Issues and Recent Advancements in Analysis of Aircraft Brake Natural Convective Cooling

1998 ◽  
Vol 120 (4) ◽  
pp. 840-857 ◽  
Author(s):  
M. P. Dyko ◽  
K. Vafai
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Flow Field ◽  
Three Dimensional ◽  
Convective Cooling ◽  
Cooling Flow ◽  
Physical Mechanisms ◽  
Braking System ◽  
Flow And Heat Transfer ◽  
Convection Cooling

A heightened awareness of the importance of natural convective cooling as a driving factor in design and thermal management of aircraft braking systems has emerged in recent years. As a result, increased attention is being devoted to understanding the buoyancy-driven flow and heat transfer occurring within the complex air passageways formed by the wheel and brake components, including the interaction of the internal and external flow fields. Through application of contemporary computational methods in conjunction with thorough experimentation, robust numerical simulations of these three-dimensional processes have been developed and validated. This has provided insight into the fundamental physical mechanisms underlying the flow and yielded the tools necessary for efficient optimization of the cooling process to improve overall thermal performance. In the present work, a brief overview of aircraft brake thermal considerations and formulation of the convection cooling problem are provided. This is followed by a review of studies of natural convection within closed and open-ended annuli and the closely related investigation of inboard and outboard subdomains of the braking system. Relevant studies of natural convection in open rectangular cavities are also discussed. Both experimental and numerical results obtained to date are addressed, with emphasis given to the characteristics of the flow field and the effects of changes in geometric parameters on flow and heat transfer. Findings of a concurrent numerical and experimental investigation of natural convection within the wheel and brake assembly are presented. These results provide, for the first time, a description of the three-dimensional aircraft braking system cooling flow field.

Verification of Finite Volume Computations on Steady-State Fluid Flow and Heat Transfer

2001 ◽  
Vol 124 (1) ◽  
pp. 11-21 ◽  
Author(s):  
J. Cadafalch ◽  
C. D. Pe´rez-Segarra ◽  
R. Co`nsul ◽  
A. Oliva
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Steady State ◽  
Finite Volume ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Independent Solution ◽  
Post Processing ◽  
Square Duct ◽  
Flow And Heat Transfer

This work presents a post-processing tool for the verification of steady-state fluid flow and heat transfer finite volume computations. It is based both on the generalized Richardson extrapolation and the Grid Convergence Index GCI. The observed order of accuracy and a error band where the grid independent solution is expected to be contained are estimated. The results corresponding to the following two and three-dimensional steady-state simulations are post-processed: a flow inside a cavity with moving top wall, an axisymmetric turbulent flow through a compressor valve, a premixed methane/air laminar flat flame on a perforated burner, and the heat transfer from an isothermal cylinder enclosed by a square duct. Discussion is carried out about the certainty of the estimators obtained with the post-processing procedure. They have been shown to be useful parameters in order to assess credibility and quality to the reported numerical solutions.

Steady-State Behavior of a Three-Dimensional Pool-Boiling System

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Michel Speetjens
Keyword(s):  
Steady State ◽  
Model Problem ◽  
Separation Of Variables ◽  
Pool Boiling ◽  
Three Dimensional ◽  
Electronics Cooling ◽  
Nucleate Boiling ◽  
Cooling Capacity ◽  
State Behavior ◽  
Steady State Behavior

Pool-boiling serves as the physical model problem for electronics cooling by means of phase-change heat-transfer. The key for optimal and reliable cooling capacity is better understanding of the conditions that determine the critical heat-flux (CHF). Exceeding CHF results in the transition from efficient nucleate-boiling to inefficient film-boiling. This transition is intimately related to the formation and stability of multiple (steady) states on the fluid-heater interface. To this end, the steady-state behavior of a three-dimensional pool-boiling system has been studied in terms of a representative mathematical model problem. This model problem involves only the temperature field within the heater and models the heat exchange with the boiling medium via a nonlinear boundary condition imposed on the fluid-heater interface. The steady-state behavior is investigated via a bifurcation analysis with a continuation algorithm based on the treatment of the model with the method of separation of variables and a Fourier-collocation method. This revealed that steady-state solutions with homogeneous interface temperatures may undergo bifurcations that result in multiple solutions with essentially heterogeneous interface temperatures. These heterogeneous states phenomenologically correspond with vapor patches (“dry spots”) on the interface that characterize transition conditions. The findings on the model problem are consistent with laboratory experiments.

Temperature Prediction Methodology for a Missile Flying at Low and High Altitudes

2014 ◽  
Vol 592-594 ◽  
pp. 1794-1800
Author(s):  
G. Vijayakumar ◽  
Ashwani Kumar Kachroo
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Wall Temperature ◽  
Thermal Environment ◽  
Three Dimensional ◽  
High Rate ◽  
Heat Transfer Analysis ◽  
Vehicle Speed ◽  
Time Duration ◽  
Flight Data

Missiles fly at supersonic and hypersonic speeds. Airframe forms the aerodynamic shape of the missile and houses several components essential for mission with suitable structural supports. The missile airframe is subjected to high rate of heating caused by kinetic heating due to very high vehicle speed. Heat transfer analysis of the missile airframe structure is required to be performed for wall temperature predictions to select the material of missile construction with suitable wall thickness and also to check design adequacy for ensuring the safe operation in the severe thermal environment experienced during flight. This paper describes the methodology of evaluation of heat flux distribution over missile wall, prediction of missile wall temperature distribution considering airframe as heat sink and validation of the methodology against flight data. Heat flux has been estimated using classical engineering methods for both stagnation as well as off-stagnation regions including the effect of angle of attack, rarified flow, thermal radiation and solar heating. Transient three dimensional heat transfer analysis with convective and radiative boundary conditions has been carried out for predicting the missile wall temperature profiles. Parametric study has been carried out, considering various parameters such as material of construction, thickness and time duration. The prediction methodology has been validated and a close match is observed between the predictions and flight data.

Computational Predictions of Heat Transfer and Film-Cooling for a Turbine Blade With Nonaxisymmetric Endwall Contouring

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Stephen P. Lynch ◽  
Karen A. Thole ◽  
Atul Kohli ◽  
Christopher Lehane
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Turbine Engine ◽  
Cooling Flow ◽  
Endwall Contouring ◽  
Dynamics Simulations ◽  
Endwall Film Cooling

Three-dimensional contouring of the compressor and turbine endwalls in a gas turbine engine has been shown to be an effective method of reducing aerodynamic losses by mitigating the strength of the complex vortical structures generated at the endwall. Reductions in endwall heat transfer in the turbine have been also previously measured and reported in literature. In this study, computational fluid dynamics simulations of a turbine blade with and without nonaxisymmetric endwall contouring were compared to experimental measurements of the exit flowfield, endwall heat transfer, and endwall film-cooling. Secondary kinetic energy at the cascade exit was closely predicted with a simulation using the SST k-ω turbulence model. Endwall heat transfer was overpredicted in the passage for both the SST k-ω and realizable k-ε turbulence models, but heat transfer augmentation for a nonaxisymmetric contour relative to a flat endwall showed fair agreement to the experiment. Measured and predicted film-cooling results indicated that the nonaxisymmetric contouring limits the spread of film-cooling flow over the endwall depending on the interaction of the film with the contour geometry.

Heat Transfer Enhancement in Ventilated Brake Disk Using Double Airfoil Vanes

2011 ◽  
Vol 3 (4) ◽  
Author(s):  
A. Nejat ◽  
M. Aslani ◽  
E. Mirzakhalili ◽  
R. Najian Asl
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Simple Model ◽  
Transfer Enhancement ◽  
Brake Disk ◽  
Pumping Efficiency ◽  
Angular Velocities ◽  
The Heat Transfer Coefficient ◽  
Novel Design

The aim of this research is to enhance the heat transfer of ventilated brake disks using modified vanes. The investigated braking scenario is a hold braking deceleration during a downhill drive. A simple model for computing the steady state vane’s temperature is presented. The heat transfer coefficient (HTC) of the brake disk’s ventilation is estimated by means of a verified CFD computation. A novel design for the vanes is proposed using an airfoil profile to improve the air pumping efficiency increasing the flow velocity between vanes. For further improving the ventilating capacity, a secondary airfoil vane is introduced to the primary airfoil vane design. The computed results estimate 17% to 29% improvement in HTC number for new vane design at different disk’s angular velocities.

Heat Transfer Normal to Paired Arterioles and Venules Embedded in Perfused Tissue During Hyperthermia

1988 ◽  
Vol 110 (4) ◽  
pp. 277-282 ◽  
Author(s):  
C. K. Charny ◽  
R. L. Levin
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Three Dimensional ◽  
Numerical Data ◽  
Tissue Temperature ◽  
Three Dimensional Model ◽  
Sources And Sinks ◽  
The Mean ◽  
Krogh Cylinder ◽  
Subsequent Incorporation

A numerical model of the heat transer normal to an arteriole-venule pair embedded in muscle tissue has been constructed. Anatomical data describing the blood vessel size, spacing, and density have been incorporated into the model. This model computes temperatures along the vessel walls as well as the temperature throughout the tissue which comprises an infinitely long Krogh cylinder around the vessel pair. Tissue temperatures were computed in the steady-state under resting conditions, while transient calculations were made under hyperthermic conditions. Results show that for both large- (1st generation) and medium-sized (5th generation) vessel pairs, the mean tissue temperature within the tissue cylinder is not equal to the mean of the arteriole and venule blood temperatures under both steady-state and transient conditions. The numerical data were reduced so that a comparison could be made with the predictions of a simple two-dimensional superposition of line sources and sinks presented by Baish et al. [1]. This comparison reveals that the superposition model accurately describes the heat transfer effects during hyperthermia, permitting subsequent incorporation of this theory into a realistic three-dimensional model of heat transfer in a whole limb during hyperthermia.

Computational Predictions of Heat Transfer and Film-Cooling for a Turbine Blade With Non-Axisymmetric Endwall Contouring

2010 ◽  
Author(s):  
Stephen P. Lynch ◽  
Karen A. Thole ◽  
Atul Kohli ◽  
Christopher Lehane
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Turbine Engine ◽  
Cooling Flow ◽  
Endwall Contouring ◽  
Dynamics Simulations ◽  
Endwall Film Cooling

Three-dimensional contouring of the compressor and turbine endwalls in a gas turbine engine has been shown to be an effective method of reducing aerodynamic losses by mitigating the strength of the complex vortical structures generated at the endwall. Reductions in endwall heat transfer in the turbine have been also previously measured and reported in the literature. In this study, computational fluid dynamics simulations of a turbine blade with and without non-axisymmetric endwall contouring were compared to experimental measurements of the exit flowfield, endwall heat transfer and endwall film-cooling. Secondary kinetic energy at the cascade exit was closely predicted with a simulation using the SST k-ω turbulence model. Endwall heat transfer was overpredicted in the passage for both the SST k-ω and realizable k-ε turbulence models, but heat transfer augmentation for a non-axisymmetric contour relative to a flat endwall showed fair agreement to the experiment. Measured and predicted film-cooling results indicated that the non-axisymmetric contouring limits the spread of film-cooling flow over the endwall depending upon the interaction of the film with the contour geometry.

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