DETERMINATION OF HEAT TRANSFER COEFFICIENT OF BRAKE ROTOR DISC USING CFD SIMULATION

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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 7, Issue 3, May–June 2016, pp.276–284, Article ID: IJMET_07_03_025
Available online at
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ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
DETERMINATION OF HEAT TRANSFER
COEFFICIENT OF BRAKE ROTOR DISC
USING CFD SIMULATION
Sanket Kothawade, Aditya Patankar, Rohit Kulkarni and Sameer Ingale
Department of Mechanical Engineering,
Pimpri Chinchwad College of Engineering, Pune, India.
ABSTRACT
Safety aspect in automotive engineering is of prime importance and given
priority in design and development of vehicle. This vehicle development needs
to meet safety requirement. Braking system along with good suspension
systems, good handling and safe cornering, is one of the most critical system
in the vehicle. The objective of this work is to design, analyze and investigate
the temperature distribution of rotor disc during braking operation using
suitable numerical tools. The numerical study uses the finite element analysis
techniques to predict the temperature distribution on the full and ventilated
brake disc. This analysis is further used to identify the critical temperature of
the rotor by varying geometric design of the disc. The analysis also gives us,
the heat flux distribution for the disc rotors with various groove patterns.
Numerical analysis of the rotor disc of disc brake is aimed at evaluating the
performance of disc brake rotor under severe braking conditions and there by
assist in disc rotor design and analysis. Hence best suitable design is
suggested based on the performance and temperature distribution criteria.
Key words: Braking System, Heat flux distribution, Rotor disc, Temperature
distribution, CFD.
Cite this Article: Abhishek Kr. Singh and Durg Vijay Rai, The Variation In
Physical Properties Affects The Vertical Compressive Strength of The
Rudraksha-Bead (Elaeocarpus Ganitrus Roxb). International Journal of
Mechanical Engineering and Technology, 7(3), 2016, pp. 276–284.
http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=7&IType=3
1. INTRODUCTION
Braking system is an energy converting system that converts vehicle movement into
heat while stopping the rotation of the wheels. This is done by causing friction at the
wheels.
There are two basic types of friction that explain how brake systems work: kinetic
or moving, and static or stationary. The amount of friction produced is proportional to

Determination of Heat Transfer Coefficient of Brake Rotor Disc using CFD Simulation
the pressure applied between the two objects, the type of materials in contact & the
smoothness of their rubbing surfaces. Friction converts the kinetic energy into heat.
The greater the pressure applied to the objects, the more friction & heat produced, &
the sooner the vehicle is brought to a stop [1].
Belhocine Ali and Bouchetara Mostefa (2013) [3], analyzed the thermo
mechanical behavior of the dry contact between the brake disc and pads during the
braking phase. The thermal-structural analyze is then used to determine the
deformation and the Von Mises stress established in the disc, the contact pressure
distribution in pads.
D. Murali Mohan Rao, Dr. C. L. V. R. S. V. Prasad, T. Ramakrishna (2013) [4],
studied that the frictional heat generated during braking application can cause
numerous negative effects on the brake assembly such as brake fade, premature wear,
thermal cracks and Disc Thickness Variation (DTV). He stated that numerical
simulation for the coupled transient thermal field and stress field is carried out
sequentially by thermal-structural coupled method based on ANSYS to evaluate the
stress fields and of deformations which are established in the disc which is another
significant. He compared the results obtained by the simulation with those of the
specialized literature.
Behnam Ghadimi, Fars Kowsary and M.Khorami (2012) [5], investigated the
thermal analysis of the wheel-mounted brake disc R920K for the ER24PC
locomotive. The brake disc and ﬂuid zone were simulated as a 3D model with a
thermal coupling boundary condition. The braking process was simulated in
laboratory and the experimental data was used to verify the simulation results. During
the braking, he observed that the maximum temperature is in the middle of braking
process instead of the braking end point. Moreover, a large lagging was observed for
ﬁns temperature which renders no cooling at the beginning of the braking
2. DESIGN PARAMETERS AND CALCULATIONS
The calculation and verification of braking force is a crucial step in the design process
of an automobile as the braking system directly factors as a good control and safety
feature in the product. While designing, the main objective is to generate more
braking force than ideally required to account for inefficiencies in mechanical
linkages and hydraulic systems.
Considering an off-road vehicle, the maximum coefficient of friction between tire
and road is 0.7 [1]. The maximum possible deceleration without wheel lockup is thus
limited to the 0.7G. Stopping distance for a vehicle should be as minimum as possible
without affecting the driver control. The stopping distance depends on the velocity at
which vehicle is moving and the maximum possible deceleration.
2.1. Braking Force (Fb)
The braking force is directly proportional to the maximum possible deceleration and
the gross weight of the vehicle. The braking force equation can be given as [1]:
2.2. Braking Force on Single Wheel (Fb1)
Dynamic weight transfer in wheeled vehicles is the measurable change of load borne
by different wheels during acceleration (both longitudinal and lateral). This includes
braking, and deceleration. No motion of the center of mass relative to the wheels is

necessary. Hence, the braking force on single wheel is directly proportional to the
dynamic weight transfer and the total braking force divided by two since in a four
wheel vehicle there are two discs each at the front wheels [1].
2.3. Minimum Size of Disc:
The minimum size of disc is calculated by using the following relation [1]:
)
Where Am and Aw are area of master cylinder and caliper cylinders respectively,
Table 1 Initial Design Parameters
NO Parameter Value
1 Gross weight of Vehicle 220 kg
2 Dynamic weight transfer on front 0.65
3 Diameter of master cylinder (dm) 19 mm
4 Diameter of caliper cylinder (dw) 28 mm
5 Mechanical leverage (Rp) 4
6 Force exerted on pedal (f) 300N
Substituting the initial design parameters in the above relations, we get
Table 2 Calculated Design Parameters
NO Parameter Value
1 Braking force (Fb) 1510.74 N
2 Braking force on front wheel (Fb1) 491 N
3 Area of master cylinder (Am) 283.5 mm2
4 Area of caliper cylinder (Aw) 981.7 mm2
5 Minimum outer radius of disc (r) 41.88mm
Further, it is necessary to determine and decide the inner and outer diameter of the
rotor disc. The inner and outer diameter of the rotor disc depends on the minimum
swept area required for applying brakes and the dimensions of the brake pad. It also
depends on the assembly constraints of the wheel assembly.
Considering the case of a vehicle having following assembly specifications:
Diameter of the wheel = 22”

For the above specifications and calculated values the rotor dimensions selected
are as follows.
Outer diameter of disc (Do) = 160 mm
Inner diameter of disc (Di) = 110 mm
2.4. Required Actuating Force:
Actuating force required to be generated by the brake caliper is the brake force on the
single assembly divide by the coefficient of friction between brake pad and disc [1].
Wbraked = 491/0.4
Wbraked = 1227.5 N
As the force is exerted by both the brake pads,
Wbraked = 2455 N
2.5. Rotor Material
Stainless steel although a little more expensive has a lot more positives. It doesn’t
rust, or at least not to any great extent. It is very robust; it is tolerant to almost all
brake pads and particularly to sintered brake pads. It is highly resistant to wear, it
doesn’t shatter and it resists heat very well. Hence the material selected for disc is
SS410.
Table 3 Properties of SS410
NO Parameter Value
1 Density 7.845 g/cc
2 Tensile Strength 1475 MPa
3 Yield Strength 1005 MPa
4 Thermal Conductivity 24.9 W/ m-K
5 Coefficient of Thermal Expansion 9.9 μm/m/°C
6 Specific Heat Capacity 460 J/ Kg-k
3. HEAT TRANSFER COEFFICIENTS
It is used in calculating the heat transfer, typically by convection or phase transition
between a fluid and a solid. The heat transfer coefficient has SI units in watts per
square meter Kelvin: W/ (m2K).
3.1. Analytical Calculations
Since the forced convection takes place on the contact surface during every rotation of
a disc (out of pad area on the rubbing path) as well as on the cylindrical external and
internal surface. The convective heat transfer coefficient h is of the form [1]:
Where Reynolds number is given by Re

ρ = Density of Material.
v = velocity of air
When Re > 2.4 * 105 the convective heat transfer coefficient h is of the form,
Ka = Thermal conductivity of air
Do = Outer diameter of disc
3.2. Numerical Analysis
The finite volume commercial CFD software fluent version 15 is used for analysis.
This commercial CFD tool is widely used in the numerical simulation of different
flow conditions with various complexities. It is chosen in this study because of its
proven capability in flows similar to those investigated here. In present simulation the
flow fields are calculated by solving the Realizable k-" turbulence model. This
involves splitting the geometry into many sub volumes and then integrating the
differential equations over these volumes to produce a set of coupled algebraic
equations for the velocity components, and pressure at the centroid of each volume.
The solver guesses the pressure field and then solves the discretized form of
momentum equations to find new values of the pressure and velocity components.
This process carries on, in an iterative manner, until the convergence criterion is
satisfied. Following methodology is used for CFD analysis
Figure 1 Methodology for CFD Simulation
3.2.1. Assumptions made for CFD analysis
The assumptions made for CFD analysis are as follows.
1. The flow medium is air.
2. Flow is steady and turbulent.
3. Properties of air are taken at standard temperature pressure conditions.
4. 90% of frictional heat transferred to disc.
5. Heat Flux is uniform over pad area.
6. Radiation effects are neglected.
7. Constant properties (density, Conductivity, specific heat, and viscosity)
• Geometric modeling
• Grid Generation
Preprocessing
• Initial Condition and Boundary
Condition
• Selection of Flow models
Solver
• Contour PlotsPost-Processing

3.2.3. Modeling of brake disc for CFD simulation
A quarter disc models are created for CFD simulation. As the disc is symmetric
about both the axis the quarter disc model provides reasonably correct solution with
decrease in the solver time. The enclosure was made around the quarter model taking
into consideration that it may not affect the solution. Hence, the grid was sufficient
large. The disc cross section does not change along its thickness. Hence, disc was
modeled with half thickness. Symmetry boundary condition was used across the
thickness so the grid size was reduced to half. At the interface of the disc and
surrounding air boundary layer is generated by means of Prisms. Fine mesh is
obtained by use of proximity and curvature.
Figure 2 Grid Generation
Figure 3 Boundary Layer Generations at Interface
3.2.4. Initial conditions
Considering the standard ambient conditions for temperature as
T (x, y, z) = 27°C at time t = 0

3.2.5. Boundary conditions
In a braking system, the mechanical energy is transformed into a calorific energy.
This energy is characterized by a total heating of the disc and pads during the braking
phase. The heat quantity in the contact area is the result of plastic micro deformations
generated by the friction forces. Generally, the thermal conductivity of material of the
brake pads is smaller than of the disc. We consider that the heat quantity produced
will be completely absorbed by the brake disc. The heat flux evacuated of this surface
is equal to the power friction. The initial heat flux entering the disc is calculated by
the following formula [2]:
q = 36504 W/m2
Inlet velocity (v) = 8.33 m/s
Heat flux into disc surface = 36504 W/m2
4. RESULTS AND DISCUSSIONS
Figure 4 Contour Plots for Disc with 4 Grooves

Table 4 Variation of Heat Transfer Coefficient
Disc with 4 grooves 182 W/m2
K
K
K
K
The above results show that with the provision of grooves improves the heat
transfer coefficient at the vicinity of the grooves. Hence, further increasing the
number of the grooves enhances the heat dissipation rate. Further, provision of petals
over the outer edge of the disc increase the surface area as well improves the heat
transfer coefficient.

5. CONCLUSION
The following comments could be concluded:-
1. CFD simulation provides an insight to flow physics at vicinity at effect of the grooves
on the heat transfer coefficient
2. Due to provision of grooves there is considerable increase in heat transfer coefficient
at vicinity of grooves, increased heat transfer coefficient increases the heat dissipation
rate.
3. The analytical solution of heat transfer coefficient and Numerical Solution are Close,
the difference in the values is due to provision of grooves which is not taken into
consideration while analytical calculation.
REFERENCES
[1] Limpert, R.Brake design and safety, 2ndEdition, Society of Automotive
Engineers. Inc, Warrendale, Pa.
[2] Reimpel, J. Braking technology, Vogel, Verlag, Würzburg, 1998
[3] Belhocine, A. and Bouchetara, M.Study of The Thermal Behaviour of Dry
Contacts in The Brake Discs, FME Transactions 41(59-65), 2013
[4] Rao, D. M. M.,Dr.Prasad,C. L. V. R. S. V., Ramakrishna, T.Experimental and
Simulated Studies on Temperature Distribution For Various Disc Brakes”,
International journal of Research in Mechanical Engineering and Technology,
3(1), Nov-April 2013
[5] Ghadimi, B., Kowsary, F. and Khorami, M. Thermal Analysis of Locomotive
Wheel-Mounted Brake Disc, Elsevier LtdB. Ghadimi et al. / Applied Thermal
Engineering 51(948-952), 2013.
[6] S. Kandwal, Rajeev Pandey and Dr. S. Singh, CFD Analysis and
Enhancement of Heat Transfer in Rectangular Channel using Blockage
with Elongated Hole. International Journal of Mechanical Engineering and
Technology, 6(7), 2015, pp. 40–52.
[7] K. Obual Reddy, M. Srikesh, M. Kranthi Kumar and V. Santhosh Kumar,
CFD Analysis of Economizer to Optimize Heat Transfer. International
Journal of Mechanical Engineering and Technology, 5(3), 2015, pp. 66–76.
[8] Hardik D. Rathod, Ashish J. Modi and Prof. (Dr.) Pravin P. Rathod, Effect
of Different Variables on Heat Transfer Rate of Four-Stroke Si Engine
Fins - Review Study. International Journal of Mechanical Engineering and
Technology, 4(2), 2013, pp. 328–333.

DETERMINATION OF HEAT TRANSFER COEFFICIENT OF BRAKE ROTOR DISC USING CFD SIMULATION

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