scholarly journals Heat dissipation from a stationary brake disc, Part 2: CFD modelling and experimental validations

2017 ◽  
Vol 232 (10) ◽  
pp. 1898-1924 ◽  
Author(s):  
Marko Tirovic ◽  
Kevin Stevens
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Dissipation ◽  
Axial Flow ◽  
Flow Visualisation ◽  
Brake Disc ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Static Conditions

Following from the analytical modelling presented in Part 1, this paper details a comprehensive computational fluid dynamics modelling of the three-dimensional flow field around, and heat dissipation from, a stationary brake disc. Four commonly used turbulence models were compared and the shear stress turbulence model was found to be most suitable for these studies. Inferior cooling of the anti-coning disc type is well known but the core cause in static conditions was only now established. The air flow exiting the lower vane channels at the inner rotor diameter changes direction and flows axially over the hat region. This axial flow acts as a blocker to the higher vane inlets, drastically reducing convective cooling from the upper half of the disc. The complexity of disc stationary cooling is further caused by the change of flow patterns during disc cooling. The above axial flow effects slowly vanish as the disc temperatures reduce. Consequently, convective heat transfer coefficients are affected by both, the change in the flow pattern and decrease in air velocities due to reduced air buoyancy as the disc cools down. As in Part 1, the special thermal rig was used to validate the computational fluid dynamics results quantitatively and qualitatively. The former used numerous thermocouples positioned strategically around the brake disc, with the latter introducing the concept of laser generated light plane combined with a smoke generator to enable flow visualisation. Predicted average heat transfer coefficients using computational fluid dynamics correlate well with the experimental values, and even two-dimensional analytical values (as presented in Part 1) reasonably closely follow the trends. The results present an important step in establishing cooling characteristics related to the electric parking brake application in commercial vehicles, with future publications detailing heat transfer from the entire brake assembly.

Computational Fluid Dynamics Simulations of Flow and Heat Transfer in a Preswirl System: Influence of Rotating-Stationary Domain Interface

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Joachim Karnahl ◽  
Jens von Wolfersdorf ◽  
Kok-Mun Tham ◽  
Mike Wilson ◽  
Gary Lock
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Direct Connection ◽  
Swirl Ratio ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Parameters ◽  
Flow And Heat Transfer ◽  
Stationary Approach

This paper presents computational fluid dynamics (CFD) predictions of flow and heat transfer for an over-swirled low-radius preswirl system and comparison with experimental data. The rotor-stator CFD model comprises a stationary domain with the preswirl nozzles and a rotating domain with the receiver holes. The fluid-dynamic conditions feature an over-swirled system with a swirl ratio at the nozzle radius βp = 1.4−1.5 and rotational Reynolds number ReΦ = 0.8 × 106 and 1.2 × 106. Three different treatments for the rotating and stationary domain interface are used to evaluate the influence on the flow and heat transfer behavior: a stationary approach (including Coriolis forces in the rotating domain) with “direct connection” and fixed angle between preswirl nozzle and receiver holes; a stationary approach with circumferential averaging of the velocity at radial bands; and a full transient simulation with the rotating domain capturing the unsteady flow due to the rotating receiver holes. Results at different circumferential angles show high variability in pressure and velocity distributions at the preswirl inlet nozzle radius. Circumferential averaging of these flow parameters lead to an alignment of the pressures and velocities between the three different interface approaches. Comparison with experimental pressure and swirl-ratio data show a quantitative agreement but the CFD results feature a systematic overestimation outward of the preswirl nozzle radius. Heat transfer coefficient distributions at the rotor surface show the effect of the different interface approaches and dependence on the flow structure (for example the impinging jet and vortex structures). The three different interface approaches result in significant differences in the computed heat transfer coefficients between pairs of receiver holes. Circumferentially averaged heat transfer coefficients inward of the receiver holes radius show good agreement between the transient and stationary direct connection interfaces, whereas those for the circumferential averaging interface differ, contrary to the flow parameters, due to smoothing of local effects from the preswirl jets.

scholarly journals Heat dissipation from a stationary brake disc, Part 1: Analytical modelling and experimental investigations

2017 ◽  
Vol 232 (9) ◽  
pp. 1707-1733 ◽  
Author(s):  
Kevin Stevens ◽  
Marko Tirovic
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Dissipation ◽  
Brake Disc ◽  
Transfer Coefficients ◽  
Cooling Period ◽  
Heat Transfer Coefficients ◽  
Parking Brake ◽  
Convective Heat Transfer Coefficients

The main aim of the research is to support the development of the commercial vehicle electric parking brake. Though nowadays widely used on passenger cars, electric parking brake applications on commercial vehicles present completely different challenges. With the brake mass, thermal capacity and required clamp forces an order of magnitude higher, safe parking demands much more attention. In the first instance, the priority is placed upon predicting heat dissipation from the brake disc only. The research is presented in two parts; part one (presented here) focuses on analytical modelling and experimental verification of predicted disc temperatures over long cooling periods, with part two investigating the air flow, velocities and convective heat transfer coefficients using computational fluid dynamics modelling, also followed by experimental validations. To begin the analytical analysis, a study was conducted into the variance in mean local convective heat transfer coefficients over a simplified brake disc friction surface, by investigating typical dimensionless air properties. A nonlinear equation was derived for the average surface convective heat transfer coefficient ([Formula: see text]) variability with temperature drop for the entire cooling phase. Starting from fundamental principles, first-order differential equations were developed to predict the bulk disc temperature. By including variation of the convective and radiative heat dissipation throughout the cooling period, a good correlation was achieved with measured values, to within 10%. Experiments were conducted on a specifically designed thermal rig which uses 15 kW induction heater to heat the disc. Numerous experiments proved the results are very repeatable, throughout the cooling period. It was established, for the grey cast iron brake disc with a fully oxidised surface, the emissivity value are practically constant at ɛ = 0.92. Although the research is being conducted on a brake disc, the results have generic application to any disc geometry, whatever the application.

Analysis of automotive disc brake cooling characteristics

2003 ◽  
Vol 217 (8) ◽  
pp. 657-666 ◽  
Author(s):  
G P Voller ◽  
M Tirovic ◽  
R Morris ◽  
P Gibbens
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Thermal Contact ◽  
Thermal Power ◽  
Disc Brake ◽  
Transfer Coefficients ◽  
Fe Modelling ◽  
Heat Transfer Coefficients ◽  
Brake Application ◽  
Cfd Analyses

The aim of this investigation was to study automotive disc brake cooling characteristics experimentally using a specially developed spin rig and numerically using finite element (FE) and computational fluid dynamics (CFD) methods. All three modes of heat transfer (conduction, convection and radiation) have been analysed along with the design features of the brake assembly and their interfaces. The spin rig proved to be very valuable equipment; experiments enabled the determination of the thermal contact resistance between the disc and wheel carrier. The analyses demonstrated the sensitivity of this mode of heat transfer to clamping pressure. For convective cooling, heat transfer coefficients were measured and very similar results were obtained from spin rig experiments and CFD analyses. The nature of radiative heat dissipation implies substantial e ects at high temperatures. The results indicate substantial change of emissivity throughout the brake application. The influence of brake cooling parameters on the disc temperature has been investigated by FE modelling of a long drag brake application. The thermal power dissipated during the drag brake application has been analysed to reveal the contribution of each mode of heat transfer.

scholarly journals Heat Transfer Characteristics of Aluminum Sputtered Fabrics

2018 ◽  
Vol 13 (3) ◽  
pp. 155892501801300 ◽  
Author(s):  
Hye Ree Han ◽  
Yaewon Park ◽  
Changsang Yun ◽  
Chung Hee Park
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Ambient Air ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Hot Plate ◽  
Multilayer Systems ◽  
Heat Transfer Coefficients ◽  
Transfer Characteristics ◽  
Shape Memory Polyurethane

Al was sputtered onto four substrates: nylon, polyester, cotton/polyester, and shape memory polyurethane nanoweb, and the heat-transfer characteristics of the resultant materials were investigated by surface temperature measurements. The thickness of the Al layer increased linearly with sputtering time. The heat-transfer mechanisms of the multilayer systems in terms of conduction, convection, and radiation were investigated under steady-state conditions using a hot plate as a heat source in contact with Al-sputtered fabrics. The Al-sputtered fabric was placed on the hot plate, which was maintained at 35°C, and exposed to open air, which was maintained at 15°C. The temperatures of the air-facing surfaces of hot plate-Al-fabric-air (i.e., Al-phase-down) and hot plate-fabric-Al-air (i.e., Al-phase-up) systems were used to investigate the heat-transfer mechanism. It was found that heat dissipation to ambient air was much higher for the Al-phase-up system than for the Al-phase-down system. Heat-transfer coefficients of the Al surfaces were calculated and found to increase with the thickness of the Al layer. Furthermore, different conductive thermal resistances were observed for different fabrics prepared with the same Al-sputtering time. Consequently, differences in their thicknesses pore sizes, and thermal conductivities were suggested to have significant effects on their heat-transfer properties.

Influence of Surface Heating Condition on Local Heat Transfer in Enclosed Corotating Disks With Axial Throughflow

1993 ◽  
Author(s):  
S. Y. Kim ◽  
J. C. Han ◽  
G. L. Morrison ◽  
E. Elovic
Keyword(s):  
Heat Transfer ◽  
Axial Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Outer Radius ◽  
Surface Heating ◽  
Heating Condition ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Rotating Cavity

Local heat transfer in a rotating cavity with axial throughflow was experimentally investigated. The rotating cavity was bounded by two plane disks and a cylindrical rim (shroud). The ratio of the rim span to the disk outer radius was 0.4 and the ratio of the disk inner radius to outer radius was 0.25. This study investigated the effects of axial coolant flow rate, rotation speed, and disk surface heating condition on the local heat transfer coefficient distributions inside the cavity. Three cavity surface heating conditions were tested: case 1 - upstream and downstream disks with radially increasing temperature but colder than rim; case 2 - upstream and downstream disks at uniform temperature but colder than rim; and case 3 - upstream and downstream disks and rim at uniform temperature. Tests were systematically performed for the axial flow Reynolds numbers between 2500 and 25,000, the rotational Reynolds numbers between 0 and 5.11 × 105, and the rotational Grashof numbers between 5 × 106 and 1.3 × 1010, respectively. The results show that the local heat transfer coefficients for the non-rotating cavity increase with increasing axial flow Reynolds number. However, the local heat transfer coefficients initially decrease and then increase with increasing rotational Reynolds number. In general, the heat transfer coefficients on the rim for case 2 surface heating condition are higher than those for case 1 and case 3 whereas the heat transfer coefficients on the upstream and downstream disks for case 3 surface heating condition are higher than those for case 1 and case 2.

Turbulent Heat Transfer Characteristics of Supercritical Carbon Dioxide for a Vertically Upward Flow in a Pipe Using Computational Fluid Dynamics and Artificial Neural Network

2021 ◽  
Author(s):  
Rajendra Prasad K S ◽  
Krishna V ◽  
Sachin Bharadwaj ◽  
Babu Rao Ponangi
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Turbulence Model ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Ansys Fluent ◽  
Artificial Neural ◽  
Turbulent Models

Abstract Modelling of turbulence heat transfer for supercritical fluids using Computational Fluid Dynamics (CFD) software is always challenging due to the drastic property variations near critical point. Use of Artificial Neural Networks (ANN) along with numerical methods have shown promising results in predicting heat transfer coefficients of heat exchangers. In this study, accuracy of four different turbulent models available in the commercial CFD software - Ansys Fluent is investigated against the available experimental results. The k-e Re Normalization Group (RNG) model with enhanced wall treatment is found to be the best-suited turbulence model. Further, K-e RNG Turbulence Model is used in CFD for parametric analysis to generate the data for ANN studies. A total of 1,34,698 data samples were generated and fed into the ANN program to develop an equation that can predict the heat transfer coefficient. It was found that, for the considered range of values the absolute average relative deviation is 3.49%.

Heat Transfer Enhancement of Reactor Utilizing Taylor-Poiseuille Flow

2014 ◽  
Author(s):  
Li Ye ◽  
Huajun Peng ◽  
Bo Zhou ◽  
Mo Yang ◽  
Zheng Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Regime ◽  
Poiseuille Flow ◽  
Axial Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Taylor Number ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Numerical studies have been conducted to determine the heat transfer performances in a Taylor-Poiseuille flow regime. The flow is confined between two different heated, concentric cylinders. The inner cylinder is allowed to rotate while the outer one remains fixed, an axial flow is added. The influences of rotation Taylor number and axial Reynolds number on heat transfer coefficients are investigated. Results show that temperature in the flow regime presents a remarkable sinusoidal periodicity as the result of the axial arrangement of Taylor vortices, so does the local heat transfer coefficients. Heat transfer efficiency gets strengthened with increasing Taylor number, while damped with increasing Reynolds number. The accuracy of the simulation is validated by compared to the existing linear stability analysis.

scholarly journals Thermal Analysis and Optimization of Nano Coated Radiator Tubes Using Computational Fluid Dynamics and Taguchi Method

Coatings ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 804
Author(s):  
Sudalai Suresh Pungaiah ◽  
Chidambara Kuttalam Kailasanathan
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Thermal Analysis ◽  
Computational Fluid Dynamics ◽  
Orthogonal Array ◽  
Heat Dissipation ◽  
Heat Removal ◽  
Taguchi Methods ◽  
Coolant Fluid ◽  
The Impact

Automotive heat removal levels are of high importance for maximizing fuel consumption. Current radiator designs are constrained by air-side impedance, and a large front field must meet the cooling requirements. The enormous demand for powerful engines in smaller hood areas has caused a lack of heat dissipation in the vehicle radiators. As a prediction, exceptional radiators are modest enough to understand coolness and demonstrate great sensitivity to cooling capacity. The working parameters of the nano-coated tubes are studied using Computational Fluid Dynamics (CFD) and Taguchi methods in this article. The CFD and Taguchi methods are used for the design of experiments to analyse the impact of nano-coated radiator parameters and the parameters having a significant impact on the efficiency of the radiator. The CFD and Taguchi methodology studies show that all of the above-mentioned parameters contribute equally to the rate of heat transfer, effectiveness, and overall heat transfer coefficient of the nanocoated radiator tubes. Experimental findings are examined to assess the adequacy of the proposed method. In this study, the coolant fluid was transmitted at three different mass flow rates, at three different coating thicknesses, and coated on the top surface of the radiator tubes. Thermal analysis is performed for three temperatures as heat input conditioning for CFD. The most important parameter for nanocoated radiator tubes is the orthogonal array, followed by the Signal-to-Noise Ratio (SNRA) and the variance analysis (ANOVA). A proper orthogonal array is then selected and tests are carried out. The findings of ANOVA showed 95% confidence and were confirmed in the most significant parameters. The optimal values of the parameters are obtained with the help of the graphs.

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