This document describes the design and analysis of an air-cooled radiator for a diesel engine with a hydrostatic transmission in a special purpose vehicle. It involves calculating the heat loads of the engine and transmission, designing a customized radiator using CAD software to dissipate the heat within given space constraints, and analyzing the radiator design using CFD software. The radiator is designed to have a heat transfer area of 1.23 square meters and incorporates fins to increase surface area for improved heat dissipation performance within the allotted volume of 706mm width, 370mm height and 80mm depth.

1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 138-146 © IAEME
138
DESIGN AND ANALYSIS OF AN AIR COOLED RADIATOR FOR DIESEL
ENGINE WITH HYDROSTATIC TRANSMISSION FOR A SPECIAL
PURPOSE VEHICLE
Chavan DK1
, Maheshwari Sanchit2
, Patil Gaurav2
, Sawant Ajinkya2
, Wani Paritosh2
1
Professor, Mechanical Engineering, MMCOE, Pune, Maharashtra, India
2
Graduate Engineering Student, MMCOE, Pune, Maharashtra, India
ABSTRACT
A Hydraulic Transmission system is a power transmission system in which the transmission
of power takes place through pressurized liquid like water, oil etc. Such systems avoid mechanical
linkages like gears, belts, ropes, chains etc to a great extent. The pressurized fluid is transmitted to
different parts using hydraulic actuators and tubes.
As the fluid power system keeps on functioning, it generates heat due to dissipation of energy
generated in overcoming the viscous and frictional forces. It causes the oil temperature to increase.
Excessive increase in oil temperature leads to variation in flow characteristics of oil and affects the
performance of the system. It also leads to undesirable effects in oil like oxidation, sludge formation
etc.
Hence to limit this, temperature of oil has to be maintained more or less constant. This is
done with the help of heat exchangers called as oil coolers or radiator.
Keywords: Radiator, Engine, Hydrostatic Transmission, Frictional Forces, Design.
1. INTRODUCTION
The core aim of this assignment is to design and develop a tailored radiator for a special
purpose vehicle which runs on Hydrostatic transmission system. Unlike mechanical transmission
system, this radiator would be used for cooling of hydrostatic oil. The major challenge in this
development is to design an effective air cooled radiator for optimum space and weight constraints.
The methodology adopted includes selection of hydraulic prime movers and hydraulic
actuators. This is followed by consideration of heat loads of engine and hydrostatic transmission.
Finally a customized radiator is designed to dissipate the heat generated. Workbenches like
AutoCAD, CATIA, and ANSYS are used for design and analysis.
INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING
AND TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 5, Issue 4, April (2014), pp. 138-146
© IAEME: www.iaeme.com/ijmet.asp
Journal Impact Factor (2014): 7.5377 (Calculated by GISI)
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2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 138-146 © IAEME
139
2. OBJECTIVE
Design and develop a radiator for cooling of oil in Hydrostatic Transmission. The space
constraints in the given problem are:
a. Width available= 706mm
b. Height available= 370mm
c. Depth available= 80mm
3. HYDRAULIC TRANSMISSION SYSTEM UNDER STUDY
Fig 1: Scheme of Hydraulic Transmission System
Legend:
• 1- Diesel engine
• 2-Gear box
• 3-Variable flow pump
• 4-Added pump
• 5-Variable displacement motor
• 6-Planetary gear box
• 7-wheels
• 8,9- Vehicle speed controller
• 10-Microcomputer
3.1 Hydraulic Oil: MIL 5606
Properties:
1. Density (ρ) = 862.037 kg/ m3
2. Specific Heat of oil, Cpo= 2.05kJ/kg o
C
3. Dynamic Viscosity, µ= 8.436e-4 Nm/s

3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 138-146 © IAEME
140
3.2 Engine specification
• Type : CI – turbocharged after cooled Diesel engine
• Cylinder Capacity : 2.8L (4 no’s)
• Max Power : 96KW@3200rpm
3.3 Hydraulic components
A) Hydraulic Pump
• Type: Piston Cylinder Variable Displacement ( 2 Nos.)
• Maximum and minimum Pump Displacement : 75 cc/rev and 18.5 cc/rev respectively
B) Hydraulic Motor
• Type: Piston Cylinder Variable Displacement (2 Nos.)
• Maximum and minimum Pump Displacement : 350 cc/rev and 90 cc/rev respectively
4. HEAT LOAD CALCULATIONS
As a thumb rule for heat exchanger sizing
• heat generation rate ൌ 20% of engine power
• Q ൌ 0.2 ൈ 96
• Q=19.2kW
4.1 Temperature rise
Increase in oil temperature= Heat generated (KW)/(oil specific heat* mass flow rate).
Increase in oil temperature =21.5⁰C
It is required to dissipate this heat generated. This is accomplished by the use of coolers, which are
commonly called heat exchangers.
Selection of heat exchangers:
Selecting a plate fin heat exchanger: these are used as gas to liquid heat exchangers when
high heat transfer rates or high operating pressure are needed.
5. DESIGN
Material used: Al 19000
Table 1: Material Composition
Material Al Cu Mg Si Fe Mn Zn
Composition 99% 0.1% 0.2% 0.5% 0.7% 0.1% 0.1%
5.1 Logarithmic Mean Temperature Difference (LMTD)
tpi = 86.5o
C(oil inlet temp)
tpo =65o
C(oil outlet temp)
tsi =50o
C(air inlet temp)
tso=55o
C(airoutlettemp)
∆ti = tpi-tso =31.5o
C
∆to=tpo-tsi=15o
C
..
.LMTD= (∆ti - ∆to)/ln (∆ti/∆to) = 22.23o
C

4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 138-146 © IAEME
141
Now,
Q=UAF (LMTD)...... (a)
Where
Total Heat Load, Q=19200 W
Overall Heat Transfer Coefficient, U=600 to 800 W/m2
K (Overall heat transfer coefficient
between heavy oil and air)
Hence, taking the mid-range value, U= 700 W/m2
K
Correction Factor F= 1 for cross flow heat exchanger.
Substituting these values in equation (a),
Heat transfer area, A=1.23 m2
To find mass flow rate of air:
By energy balance equation,
maCpa ∆Ta=moCpo ∆To
Mass flow rate of oil, mo = 30 lpm = ((30e-3)861.66)/60 = 0.430 kg/s
Specific Heat of oil, Cpo= 2.05kJ/kg o
C
Change in temperature of oil, ∆To =21.5o
C
Change in temperature of air, ∆Ta =5o
C (assumed)
Specific Heat of air, Cpa = 1.005 kJ/kg o
C
..
.Mass flow rate of air, ma= 3.82 kg/s
5.2 Tube Dimensions
From Aluminium tube standards
Standard pipe Dia(OD)= 33.4mm(D)
Wall thickness= 3.3mm
Thus inner dia= OD- (2wall thickness)=33.4-(2*3.3)
d=26.66mm
Surface Area = 1.23m2
A= πDL
1.23= π x 33.4e-3 x L
Thus L=11.72m
Flow area A = (π/4) (Di) 2
=5.58e-4 m2
mo= ρAV
0.43 = 860.83 x 5.58e-4 x V
..
. V= 0.895 m/s.....Oil flow velocity
Reynold’s Number Re= (ρVD)/µ
Re= 24357.17
..
. Re > 4000
..
. Flow is turbulent.
Thus selecting pipe of this dimension
5.3 Air Velocity to the radiator
Diameter of fan =width of radiator= 0.370m
Density of air at 50o
C = 1.109 kg/m3
Fan = 2 Nos.
ma= (No. of fans) x (Area of one fan) x (Velocity) x (Air Density)
..
. 3.82= 2 x (πx(.372
)/4) x V x 1.109
..
. V = 16.01 m/sec

5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 138-146 © IAEME
142
5.4 Outer Surface temperature
Prandtl Number,
Pr= µCp/ K
Pr = (8.436e-4 x 2050)/ (0.10644)
= 16.24
Now, to find Nusselt Number, we use Dittus- Boelter co-relation:
Nu= 0.023 x Re0.8
x Prn
Nu = (0.023) x (24357.17)0.8
x (16.24)0.3
Nu = 171.47
(Here n=0.3 since fluid is being cooled)
But Nu= hi/k
171.47= (hi x (26.66e-3))/ (0.10644)
hi=684.59 W/m2
k
This is the oil side heat transfer coefficient.
To find outer surface temperature of tubes,
Q = hi x A x ∆T
=hi x π x D x L x [Ts-(Tpi+Tpo)/2]
Ts1 = 96.96o
C (Inner wall temperature)
Fourier’s Law of Heat Conduction through hollow pipe
Q= [2 πLK (T1-T2)]/ ln(D/d)
19200 = 2π x 12.6 x 205 x [(96.96-T2)/ln (16.7/13.3)]
Ts2=96.69 o
C
This is outer surface temperature.
5.5 Air Side Heat Transfer coefficient
Table 2: Material parameters of air at 50o
C
Kinematic viscosity(ν) Thermal
Conductivity(k)
Prandtl no.(Pr) Prandtl no(At Ts2)
(Prs)
24.60 e- 6 m2
/s 28.44 e-3 W/mK 0.7029 0.697
Constants
C= 0.35 (St / Sl)(1/5)
= 0.35
m= 0.4.
Correction factor, C2= 0.8
Diagonal Pitch,Sd = [Sl2 + (St/2) 2
] 0.5
= 46.67 mm … (a)
(St + Do)/2 = (41.75 + 33.4)/2
= 37.575 mm … (b)
As (a) > (b)..
. Vmax occurs in transverse plane
Vmax = [St/(St-D) ] x V = 80.05 m/s
Re max = (Vmax x D)/ ν = 108685.77
Nu = C2 C (Remax)m
(Pr)0.36
(Pr/Prs)1/4
= 367.91
This is Zhukauskas correlation
ho= ( Nu x k ) / Do
= 313.27 W/m2
k.....Air side heat transfer coefficient

6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 138-146 © IAEME
143
Fig 2: 2 row aligned tube arrangement
6. EXTENDED SURFACES: FINS
The rate of heat transfer from solid surface to fluid is given by the equation:
Q = hA (To-T∞)
Where,
h= Convective heat transfer coefficient,
A= Surface area,
(To-T∞) = Temperature difference between solid surface and fluid.
In the above equation the value of ‘h’ is almost constant whenever the heat is convected to
atmosphere and temperature difference cannot be controlled.
Therefore, the only way is to increase the heat transfer rate, Q is by increasing the surface
area A. This surface area of solid is increased by providing external surfaces called fins.
7. CAD MODEL UNDER STUDY
7.1 AutoCAD model
A 2D model of radiator was developed in AutoCAD using the obtained dimensions.
SL=Longitudinal Pitch
ST=Transverse Pitch

7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 138-146 © IAEME
144
Fig 3: 2D model of radiator
7.2 3D Model
A3D model of radiator was developed in CATIA using the obtained dimensions
Fig 4: 3D model of radiator

8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 138-146 © IAEME
145
8. CFD ANALYSIS
3D model of radiator tubes was imported to ANSYS workbench for CFD analysis
Fig 5: CAD model of radiator tube
8.1 Boundary conditions
Table 3: Boundary Conditions
Zone Parameter Value
Inlet Mass flow inlet 0.43kg/s
Temperature 360K
Outlet Pressure Outlet 0 Pa
Walls Heat Transfer Coefficient 313.27 W/m2
K
Free stream temperature 323 K
9. RESULTS
Fig 6: Temp drop through the tubes

9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 138-146 © IAEME
146
Table 4: Results
Parameter measured Theoretical ANSYS
Temperature drop 21.5o
C 23.7o
C
10. CONCLUSIONS
1. Hydraulic actuators like pump and motor were selected to obtain the required tractive effort.
2. Heat load and corresponding temperature rise in oil was calculated.
3. To dissipate the rise in temperature, air cooled radiator was designed by the standard
procedure of LMTD method.
4. Fins were provided to enhance the heat dissipation rate by increasing the surface area of heat
transfer.
5. The design was successfully conformed to the available space.
6. Analysis of the radiator was done using CFD in ANSYS Fluent. The theoretical results and
analytical results were compared to ensure a safe and reliable design
11. REFERENCES
1. Chavan D. K & Tasgaonkar G. S- Study, analysis and design of automobile radiator (heat
exchanger) proposed with cad drawings and geometrical model of the fan ijmperd/vol 3/ issue
2/ june 2013.
2. Fluid Power with applications (seventh edition) by Anthony Esposito.
3. Fundamentals of Heat and Mass Transfer (fifth edition) by Frank P. Incropera and David P.
DeWitt.
4. Computational Fluid Dynamics by John D. Anderson.
5. http://www.alascop.com/pdf/al/6061_pipe.pdf.
6. http://www.lindeengineering.com/internet.global.lindeengineering.global/en/images/P_3_2_e_
12_150dpi19_5772.pdf.
7. Pundlik R. Ghodke and Dr. J. G. Suryawanshi, “Advanced Turbocharger Technologies for
High Performance Diesel Engine - Passanger Vehicle Application”, International Journal of
Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 620 - 632,
ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.
8. Mohd Muqeem and Dr. Manoj Kumar, “Design of an Intercooler of a Turbocharger Unit to
Enhance the Volumetric Efficiency of Diesel Engine”, International Journal of Mechanical
Engineering & Technology (IJMET), Volume 4, Issue 3, 2013, pp. 1 - 10, ISSN Print:
0976 – 6340, ISSN Online: 0976 – 6359.