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.

The Impact of Fin Deformation on Condensation Heat Transfer Coefficients in Internally Grooved Tubes

2013 ◽  
Author(s):  
Sunil Mehendale
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Thermal Contact ◽  
Heat Pumps ◽  
Condensation Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Condensing Heat Transfer ◽  
The Impact ◽  
Tube Expansion

In HVACR equipment, internally enhanced round tube (microfin) designs such as axial, cross-grooved, helical, and herringbone are commonly used to enhance the boiling and condensing performance of evaporators, condensers, and heat pumps. Typically, such tubes are mechanically expanded by a mandrel into a fin pack to create an interference fit between the tube outside surface and the fin collar to minimize the thermal contact resistance between tube and fin. However, during this expansion process, the internal enhancements undergo varying amounts of deformation, which degrades the in-tube thermal performance. Extensive data on condensing heat transfer coefficients in microfin tubes have been reported in the open literature. However, researchers have seldom used expanded tubes to acquire and report such data. Hence, it is always questionable to use such pristine tube data for designing heat exchangers and HVACR systems. Furthermore, the HVACR industry has been experiencing steeply rising copper costs, and this trend is expected to continue in coming years. So, many equipment manufacturers and suppliers are actively converting tubes from copper to aluminum. However, because of appreciable differences between the material properties of aluminum and copper, as well as other manufacturing variables, such as mandrel dimensions, lubricant used, etc., tube expansion typically deforms aluminum fins more than copper fins. Based on an analysis of the surface area changes arising from tube expansion, and an assessment of the best extant in-tube condensation heat transfer correlations, this work proposes a method of estimating the impact of tube expansion on in-tube condensation heat transfer. The analysis leads to certain interesting and useful findings correlating fin geometry and in-tube condensation thermal resistance. This method can then be applied to more realistically design HVACR heat exchangers and systems.

Analysis of heat transfer between solids at low temperatures

1976 ◽  
Vol 54 (17) ◽  
pp. 1749-1771 ◽  
Author(s):  
J. D. N. Cheeke ◽  
H. Ettinger ◽  
B. Hebral
Keyword(s):  
Heat Transfer ◽  
Thermal Contact ◽  
Impedance Matching ◽  
Debye Model ◽  
Phonon Transport ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Critical Cone ◽  
Acoustic Mismatch ◽  
The Heat Transfer Coefficient

A detailed analysis is given of the acoustic mismatch formulation first given by Little for the thermal contact resistance between solids for the case of phonon transport in a Debye model. Extrema in the heat transfer coefficients as a function of the refractive index of the interface are shown to be due to either impedance matching conditions or to the presence of the critical cone. Detailed numerical tables are presented which permit rapid evaluation of the heat transfer coefficient to an accuracy of 5% or better.

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.

Heat Transfer to Supercritical Water in Advanced Power Engineering Applications: An Industrial Scale Test Rig

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Gerrit A. Schatte ◽  
Andreas Kohlhepp ◽  
Tobias Gschnaidtner ◽  
Christoph Wieland ◽  
Hartmut Spliethoff
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Supercritical Water ◽  
Test Section ◽  
Power Plants ◽  
Thermal Power ◽  
Internal Diameter ◽  
Test Rig ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Heat transfer to supercritical water in heated tubes and channels is relevant for steam generators in conventional power plants and future concepts for supercritical nuclear and solar-thermal power plants. A new experimental facility, the high pressure evaporation rig, setup at the Institute for Energy Systems (Technische Universität München) aims to provide heat transfer data to fill the existing knowledge gaps at these conditions. The test rig consists of a closed-loop high pressure cycle, in which de-ionized water is fed to an instrumented test section heated by the application of direct electrical current. It is designed to withstand a maximum pressure of 380 bar at 580 °C in the test section. The maximum power rating of the system is 1 MW. The test section is a vertical tube (material: AISI A213/P91) with a 7000 mm heated length, a 15.7 mm internal diameter, and a wall thickness of 5.6 mm. It is equipped with 70 thermocouples distributed evenly along its length. It enables the determination of heat transfer coefficients in the supercritical region at various steady-state or transient conditions. In a first series of tests, experiments are conducted to investigate normal and deteriorated heat transfer (DHT) under vertical upward flow conditions. The newly generated data and literature data are used to evaluate different correlations available for modeling heat transfer coefficients at supercritical pressures.

Detailed Heat Transfer Measurements in a Model of an Integrally Cast Cooling Passage

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Ioannis Ieronymidis ◽  
David R. H. Gillespie ◽  
Peter T. Ireland ◽  
Robert Kingston
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Contact ◽  
Casting Process ◽  
High Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Cooling Passage

Detailed measurements of the heat transfer coefficient (htc) distributions on the internal surfaces of a novel gas turbine blade cooling configuration were carried out using a transient liquid crystal technique. The cooling geometry, in which a series of racetrack passages are connected to a central plenum, provides high heat transfer coefficients in regions of the blade in good thermal contact with the outer blade surface. The Reynolds number changes along its length because of the ejection of fluid through a series of 19 transfer holes in a staggered arrangement, which are used to connect ceramic cores during the casting process. Heat transfer coefficient distributions on these holes surface are particularly important in the prediction of blade life, as are heat transfer coefficients within the hole. The results at passage inlet Reynolds numbers of 21,667, 45,596, and 69,959 are presented along with in-hole htc distributions at Rehole=5930, 12,479, 19,147; and suction ratios of 0.98, 1.31, 2.08, and 18.67, respectively. All values are engine representative. Characteristic regions of high heat transfer downstream of the transfer holes were observed with enhancement of up to 92% over the Dittus–Boelter level. Within the transfer holes, the average htc level was strongly affected by the cross-flow at the hole entrance. htc levels were low in these short (l/d=1.5) holes fed from regions of developed boundary layer.

scholarly journals Analysis of combustion, heat and fluid flow in a biomass furnace

2019 ◽  
Vol 128 ◽  
pp. 03003
Author(s):  
Björn Pfeiffelmann ◽  
Michael Diederich ◽  
Fethi Gül ◽  
Ali Cemal Benim ◽  
Andreas Hamberger ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Power ◽  
Transfer Coefficients ◽  
Combustion Heat ◽  
Heat Transfer Coefficients ◽  
Water Side ◽  
Numerical Formulation ◽  
Measured Flow ◽  
Flow Heat ◽  
Computational Procedures

A waste wood burning boiler with 200kW thermal power is investigated by experiments and numerically. Temperature measurements are performed in the furnace and in the heat exchanger sectionsin the downstream. Exit exhaust gas composition is also measured. Flow, heat transfer and combustion in the furnace, and forced convection on the water side are numerically analyzed. The water side calculations are used to obtain boundary conditions for the furnace by heat transfer coefficients. For validating the adopted mathematical/numerical formulation, the predictions are compared with measurements.A satisfactory agreement between the predictions and measurements is observed, confirming the validity of the applied computational procedures.

Jet Impingement Heat Transfer Enhancement by U-Shaped Crossflow Diverters

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
Srivatsan Madhavan ◽  
Kishore Ranganath Ramakrishnan ◽  
Prashant Singh ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Jet Impingement ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Pumping Power ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Impingement Heat Transfer ◽  
Baseline Case

Abstract Array-jet impingement is typically used in gas turbine blade near-wall cooling, where high rates of heat dissipation is required. The accumulated crossflow mass flux results in significant reduction in jet effectiveness in the downstream rows, leading to reduced cooling performance. In this paper, a jet impingement system equipped with U-shaped ribs (hereafter referred as “diverter”) was used for diverting the crossflow away from the jets emanating from the nozzle plate. To this end, a baseline configuration of array-jet impingement onto smooth target surface is considered, where the normalized jet-to-jet spacing (x/dj = y/dj) was 6 and the normalized jet-to-target spacing (z/dj) was 2. Crossflow diverters with thickness t of 1.5875 mm and height h of 2dj (= z) were installed at a distance of 2dj from the respective jet centers. Detailed heat transfer coefficients have been calculated through transient liquid crystal experiments carried out over Reynolds numbers ranging from 3500 to 12,000. It has been observed that crossflow diverters protect the downstream jets from upstream jet deflection, thereby maximizing their stagnation cooling potential. An average of 15–30% enhancement in Nusselt number is obtained over the flow range tested. This benefit in heat transfer came at a cost of increased pumping power to maintain similar flow rate in the system. At a given pumping power, crossflow diverters yielded an enhancement of 9–15% in heat transfer compared with the baseline case.

An Improved Analytical Approach to Steam Turbine Heat Transfer

2004 ◽  
Author(s):  
Howard M. Brilliant ◽  
Anil K. Tolpadi
Keyword(s):  
Heat Transfer ◽  
Steam Turbine ◽  
Steam Turbines ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Operating Cycle ◽  
Local Flow ◽  
Heat Transfer Coefficients ◽  
Thermal Growth ◽  
Cfd Analyses

Improvements to the design of advanced steam turbines require an improved understanding of the heat transfer within the various components of the unit. Physics-based ANSYS models for typical high pressure and intermediate pressure units have been developed. The boundary conditions were derived from full-load, steady state flow analyses, steam turbine performance code outputs and computational fluid dynamics (CFD) analyses to develop normalized (non-dimensional) local flow conditions, with the normalizing parameters based on key cycle parameters. These normalized local flow conditions and cycle parameters were then used to define local transient boundary temperatures and heat transfer coefficients for input to the thermal ANSYS model. Transient analyses of components were performed. The results were compared with temperature measurements taken during the operating cycle of an operational steam turbine to validate and improve the methodology and were applied to structural models of the components to predict their thermal growth and the net impact on the clearance between the rotor and diaphragms and other secondary flow paths in the steam turbine, including seals.

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