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.

Fluid flow and heat transfer of a stratified system during natural convection – influence of chamfered corners

2019 ◽  
Vol 29 (2) ◽  
pp. 470-486 ◽  
Author(s):  
Alireza Rahimi ◽  
Aravindhan Surendar ◽  
Aygul Z. Ibatova ◽  
Abbas Kasaeipoor ◽  
Emad Hasani Malekshah
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Immiscible Fluids ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose This paper aims to investigate the three-dimensional natural convection and entropy generation in the rectangular cuboid cavities included by chamfered triangular partition made by polypropylene. Design/methodology/approach The enclosure is filled by multi-walled carbon nanotubes (MWCNTs)-H2O nanofluid and air as two immiscible fluids. The finite volume approach is used for computation. The fluid flow and heat transfer are considered with combination of local entropy generation due to fluid friction and heat transfer. Moreover, a numerical method is developed based on three-dimensional solution of Navier–Stokes equations. Findings Effects of side ratio of triangular partitions (SR = 0.5, 1 and 2), Rayleigh number (103 < Ra < 105) and solid volume fraction (f = 0.002, 0.004 and 0.01 Vol.%) of nanofluid are investigated on both natural convection characteristic and volumetric entropy generation. The results show that the partitions can be a suitable method to control fluid flow and energy consumption, and three-dimensional solutions renders more accurate results. Originality/value The originality of this work is to study the three-dimensional natural convection and entropy generation of a stratified system.

Three Dimensional Numerical Simulation of the Natural Convection in an Annulus With an Internal Slotted Cylinder

2011 ◽  
Author(s):  
Mo Yang ◽  
Jin Wang ◽  
Kun Zhang ◽  
Ling Li ◽  
Yuwen Zhang
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Dimensional Model ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Rayleigh Numbers

Detailed numerical analysis is presented for three-dimensional natural convection heat transfer in annulus with an internal concentric slotted cylinder. The internal slotted cylinder and the outer annulus are maintained at uniform but different temperatures. Governing equations are discretized using control volume technique based on staggered grid formulation and solved using SIMPLE algorithm with QUICK scheme. Flow and heat transfer characteristics are investigated for a Rayleigh number range of 10 to 106 while Prandtl number (Pr) is taken to be 0.7. The results indicate, at Rayleigh numbers below 105, the system shows two dimensional flow and heat transfer characteristics. On the other hand, the flow and heat transfer shows three dimensional characteristics while for Rayleigh numbers greater than 5×105. Comparison with experimental results indicated that the numerical solutions by three dimensional model can obtain more accuracy than the numerical solutions by two dimensional model. Besides, Numerical results show that the average equivalent conductivity coefficient of natural convection heat transfer of this problem can be enhanced by as much as 30% while relative slot width is more than 0.1.

scholarly journals Numerical Simulation of the Natural Convection with Presence of the Nanofluids in Cubical Cavity

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Mohamed Sannad ◽  
Abourida Btissam ◽  
Belarche Lahoucine
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Volume Fraction ◽  
Numerical Study ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Flow And Heat Transfer ◽  
Heating Section ◽  
The Right

This article consists of a numerical study of natural convection heat transfer in three-dimensional cavity filled with nanofluids. This configuration is heated by a partition maintained at a hot constant and uniform temperature TH. The right and left vertical walls are kept at a cold temperature TC while the rest is adiabatic. The fluid flow and heat transfer in the cavity are studied for different sets of the governing parameters, namely, the nanofluid type, the Rayleigh number Ra = 103, 104, 105, and 106, and the volume fraction Ф varying between Ф = 0 and 0.1. The obtained results show a positive effect of the volume fraction and the Rayleigh number on the heat transfer improvement. The analysis of the results related to the heat transfer shows that the copper-based nanofluid guarantees the best thermal transfer. In addition, the increase of the heating section size and Ra leads to an increased amount of heat. Similarly, increasing the volume fraction improves the intensification of the flow and increases the heat exchange.

Natural Convection of Nanofluid in a Triangle Cavity with Different Angular Positions

2020 ◽  
Vol 12 (3) ◽  
pp. 325-329
Author(s):  
Mohsen Rostami ◽  
Mohammad Saleh Abadi
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Natural Convection ◽  
Flow Field ◽  
Boundary Conditions ◽  
Angular Position ◽  
Numerical Results ◽  
Heat Transfer Characteristics ◽  
Current Structure ◽  
Flow And Heat Transfer

The effects of the angular position on the flow and heat transfer of the nanofluid in a triangular cavity is investigated numerically. A triangular cavity is chosen with the same boundary conditions as the published results are available. The comparison between the current numerical results with the available data is made to show the accuracy of the numerical simulation. The current structure of triangular cavity is rotated to investigate the effects of various angular positions on the flow and heat transfer characteristics of nanofluid. For this purpose, the equations of continuity, momentum and energy are solved numerically. The results show that the hot fluid is more freely penetrated into the domain by increasing of the angular position. The velocity of fluid in the flow field becomes maximum for the angle of 120 . Also, the creation of vortices in the flow field depends on the value of angular position.

An Experimental Study of Natural Convection Cooling of an Array of Heated Protrusions in a Vertical Channel in Water

1989 ◽  
Vol 111 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Y. Joshi ◽  
T. Willson ◽  
S. J. Hazard
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Power Dissipation ◽  
Three Dimensional ◽  
Vertical Channel ◽  
Steady Flows ◽  
Transfer Rates ◽  
Fluid Velocities ◽  
Convection Cooling ◽  
Flow Visualizations

An experimental investigation of steady state and transient natural convection from a column of eight in-line rectangular heated protrusions in a vertical channel in water is presented. Flow visualizations and element surface temperature measurements were carried out for several power dissipation levels in the range of 0.2–1.5 W per component and channel spacings from 6.4 to 23 mm. The three-dimensional steady flows were visualized in two mutually perpendicular planes. Average component temperatures determined from the measurements on the five fluid exposed faces were used to obtain nondimensional heat transfer rates. Heat transfer data for all channel spacings except the smallest did not differ from the measurements for an isolated surface by more than 14 percent. For the smallest spacing, the component surface temperatures increased significantly due to a reduction in the fluid velocities. Measurements and flow visualizations during the transient indicated an initial diffusive transport period, followed by the evolution of convective effects. No overshoots in component temperatures were found. Steady transport responses with selectively powered components are also examined.

Natural Convection Cooling of Multiple Heat Sources in Parallel Open-Top Cavities Filled With a Fluorinert Liquid

1998 ◽  
Vol 120 (1) ◽  
pp. 73-81 ◽  
Author(s):  
M. Behnia ◽  
A. A. Dehghan ◽  
H. Mishima ◽  
W. Nakayama
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Alumina Ceramic ◽  
Heat Sources ◽  
Flow And Heat Transfer ◽  
Discrete Heat Sources ◽  
Vertical Walls ◽  
Convection Cooling ◽  
Lower Heat

Natural convection immersion cooling of discrete heat sources in a series of parallel interacting open-top cavities filled with a fluorinert liquid (FC–72) has been numerically studied. A series of open-top slots which are confined by conductive vertical walls with two heat sources on one side are considered. One of the slots is modeled and simulated. The effect of the separation between the heat sources on the flow and heat transfer characteristics of the wall and the effect of strength of the lower heat source (which location is upstream of the other one) on the flow and heat transfer of the upper heat source are considered. The wall thermal conductivity considered ranges from adiabatic to alumina-ceramic. The results of bakelite and alumina-ceramic are shown, which are commonly used as wiring boards in electronic equipment. It is found that conduction in the wall is very important and enhances the heat transfer performance.

Natural Convection in a Partitioned Cubic Enclosure

1992 ◽  
Vol 114 (2) ◽  
pp. 410-417 ◽  
Author(s):  
K. C. Karki ◽  
P. S. Sathyamurthy ◽  
S. V. Patankar
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Flow And Heat Transfer ◽  
Dimensional Simulation ◽  
Oriented Parallel ◽  
Rayleigh Numbers

Numerical solutions are obtained for fluid flow and heat transfer in a cubic enclosure with a vertical adiabatic partition. The two zones of the enclosure are connected by a single rectangular opening. The partition is oriented parallel to the isothermal sidewalls, one of which is heated and the other cooled while the remaining walls are adiabatic. Results have been presented for air for the Rayleigh numbers in the range 104−107. The width of the opening is held fixed while the height, relative to the enclosure height, is varied from 0.25 to 0.75. The effects of various parameters on the flow structure and heat transfer are investigated. The results of the three-dimensional simulation have also been compared with those for the corresponding two-dimensional configurations.

Piezoelectric Fans: Heat Transfer Enhancements for Electronics Cooling

2008 ◽  
Author(s):  
James Petroski ◽  
Mehmet Arik ◽  
Mustafa Gursoy
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Flow Field ◽  
Heat Sink ◽  
Three Dimensional ◽  
Electronics Cooling ◽  
Coefficient Of Performance ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Piezoelectric Fans

Piezoelectric fans have been investigated for electronics cooling over the last decade. The primary usage or method has been to place the vibrating fan near the surface to be cooled. The piezofan used in the current study is composed of a piezo actuator attached to a flexible metal beam. It is operated at up to 120VAC and at 60 Hz. While most of the research in the literature focused on cooling bare surfaces, larger heat transfer rates are of interest in the present study. A proposed system of piezoelectric fans and heat sink is presented as a more efficient method of system cooling with these fans. In this paper, a heat sink and piezoelectric fan system demonstrated a capability of cooling an area of about 75 cm2 (about 1 C/W) where electronic assemblies can be mounted. The heat sink not only provides surface area, but also flow shaping for the unusual three-dimensional flow field of the fans. A volumetric coefficient of performance (COPv) is proposed, which allows a piezofan and heat sink system volume to be compared against the heat dissipating capacity of a similar heat sink of the same volume for natural convection. A piezofan system is shown to have a COPv of five times of a typical natural convection solution. The paper will further discuss the effect of nozzles in flow shaping obtained via experimental and computational studies. A three-dimensional flow field of the proposed cooling scheme with a piezofan is obtained via laser Doppler anemometry (LDA) flow visualization method. Velocities at the heat sink in the order of 1.5 m/s were achieved through this critical shaping. Finally, the overall system characterization to different heat loads and fan amplitudes will be discussed.

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