1 Copyright © 2012 Mahindra & Mahindra Ltd. All rights reserved. Simulation of Exhaust Gas Heat Recovery System for an Automobile “Patent Pending : 2482/MUM/2013”.
1Copyright © 2012 Mahindra & Mahindra Ltd. All rights reserved.
Simulation of Exhaust Gas Heat Recovery System for an Automobile“Patent Pending : 2482/MUM/2013”.
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IntroductionTo recover heat from exhaust gas and used it to maintainitems temperature at 63°C (Food Safety Temperature Control,UK).
Expected Customer Benefits & Applications: Hot Water Milk, Tea, Coffee Soup Curries Keep food warm Instant food-Maggie Pop Corn ChapattisApplicationTourism Vehicles Bread Toaster Ambulance Safari rides
Hot Box
Cold Water Inlet
Hot Water Outlet
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Hot Box CircuitWater Inlet
Heat exchanger
Hot Box
Hot water Inlet
Return line
Hot Water Outlet
Pump
Switch
Hot BoxHeat Exchanger Unit
Cold Water InletHot Water Outlet
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S.No Length (mm)
Volume (L)
Temperature (o C)
1 500 4.4 2082 450 4 1983 400 3.5 1864 350 3.1 1735 300 2.6 1586 250 2.2 1407 200 1.7 1218 150 1.3 989 100 0.8 73
Table : Optimization of Heat Exchanger length
Figure : Optimization of length of Primary Heat Exchanger
Length Optimization
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Results
Initial After 15 minutesT1 34 95T2 34 90T3 31 37T4 31 34T5 31 39
whereT Temperature in degree CelsiusT1 Exhaust gas temperature before heat exchangerT2 Exhaust gas temperature after heat exchangerT3 Hot Box temperatureT4 Cold water temperatureT5 Hot water temperature
Table 1 : Results of Static testing
Initial After 15 minutesT1 36 121T2 38 111T3 36 45T4 33 35T5 36 50
Table 2. Results of Dynamic testing at 10 kmph
Initial After 15 minutesT1 36 348T2 38 336T3 36 82T4 31 33T5 36 94
Table 3. Results of Dynamic testing at Highway Driving
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Testing Condition LMTD
Static 55.85At 10 kmph 72.75
Highway driving 276.89
Log mean temperature difference (LMTD)
The Log mean temperature difference for a parallel flow double pipeheat exchanger is given by equation:
The log mean temperature difference for the three cases are as given below
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0
50
100
150
200
250
300
350
400
0 1000 2000 3000 4000 5000 6000 7000 8000
Tem
pera
ture
in d
egC
Time in Seconds
T1
T2
T5
T3
T1 T2 T3 T4 T5 LMTDInitial 117.27 112.12 35.66 32.78 32.78
Maximum 347.87 335.82 82.27 32.78 93.87 277.79
Hot Box Temperature Measurements at Highway Driving Condition
T1= Exhaust Gas Temperature before Heat ExchangerT2= Exhaust Gas Temperature after Heat ExchangerT3= Hot Box TemperatureT4= Cold Water TemperatureT5= Hot Water Temperature
AbbreviationsResults
45 minutes for Data logger preparation and Security Clearances
1st Stop2nd Stop
65 deg C Hot Box Temperature
48 minutes for Hot Box to reach 65 deg C despite two stops in between
Conclusion: The target temperature of 65 deg C at Hot Box is achievable. It is possible to achieve 65 deg C at Hot Box in less than 30 minutes in Non Stop driving at Highway Driving.
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Simulation InputInlet Boundary condition:
For Laminar Flow For Turbulent flow
Inlet velocity= 0.17 m/s Inlet velocity = 31 m/s
Inlet temperature= 313 K Inlet temperature = 390.2 K
Symmetry at boundary region Symmetry at boundary region
Wall function at pipe and gas region
No slip condition at wall
Material properties:
Substance Thermal conductivities(W/ m K)
Stainless steel 16
Water 0.58
Exhaust Gas (Carbon dioxide) 0.0146
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Simulation results
Fig: Contours temperature variation in Water regime & Exhaust Gas
Fig: Exhaust Pipe temperature
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Conclusion The use of COMSOL Multi-physics to perform preliminary analysis of heat
transfer mechanism in Exhaust gas heat recovery system is found to give good correlation with the testing results.
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Copyright © 2012 Mahindra & Mahindra Ltd. All rights reserved.
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