Advaned Cooling System for Heavy Vehicles
Transcript of Advaned Cooling System for Heavy Vehicles
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
1/24
Advanced cooling system for
heavy vehicles heat exchangers/coolers
Wamei Lin
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
2/24
Outline
Introduction of my project
Energy distribution in vehicle
Methods for saving energy
New material for heat exchangersConclusion of graphite foam heat
exchanger
Future work
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
3/24
Introduction of my project The aim of my PhD project is to develop a new cooling
system for heavy vehicles, so that the fuel consumptionand CO2 emission would be reduced.
This project includes two parts:
Flow field: Chalmers University of Technology (LennartLfdahl, Lisa Larsson)
Heat transfer: Lund university (Bengt sundn, Wamei
Lin)
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
4/24
Energy distribution in vehicle In order to save fuel
consumption in vehicles,
what can be done?
(1)Can we reuse some energyfrom the engine coolant?
(2)Can we recover someenergy from the exhaust gas?
(3)Can we recover somemechanical energy?
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
5/24
Engine cooling Radiator: to make sure the
engine works at its optimaltemperature (80-90C).
Intercooler: to cool downthe fresh air, whosetemperature is increasedafter through a
turbocharger.
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
6/24
Methods for saving energyEngine cooling: thermal management
14.5 kW power wassaved in a standarddiesel vehicle (Cho
2007)
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
7/24
Methods for saving energyExhaust gas (vary between 250 and 680)
(1) Heatingcompartment
(2) Absorption cooling:
7.1 billion gallons ofgasoline was saved inU.S. vehicles (2002J ohnson)
(3) Thermoelectric
device:
Peltier-Seebeck effect.
3-8% of fuelconsumption can be
saved (2007 Smith)
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
8/24
Methods for saving energy
During the braking process, we canstore the mechanical energy and use itto drive vehicle later.
(1)Transfer the mechanical energy intoelectricity
(2)During the braking process, thekinetic energy is used to generate ahigh pressure gas, which is used todrive vehicles later.
80% of kinetic energy lost in thebraking process can be recovered
The mechanical work
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
9/24
With the increasing power of vehicles and the increase of electric orhybrid electric vehicles, less heat will be dissipated in the exhaust gas,more heat has to be brought away by the cooling system.
Heatingcompartment
Absorptioncooling
Thermoelectricdevice (3-10%fuel reduced)
Thermalmanagement
Methods for saving energy
The regenerativebraking system (10-25% fuel reduced)
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
10/24
New material for heat exchangers
The thermal management development
Aluminum and copper
heat exchanger(180 W/(m.K) for aluminum
6061 and 400 W/(m.K) forcopper)
The utilization ofmicrocellular foam materialssuch as metal or graphitefoams
(the enhancement of heat transferby huge fluid-solid contact surfacearea and the fluid mixing)
Coolingpowerincreasing
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
11/24
Graphite foam
New material for heat exchangers
An
appropriatematerial forthe thermal
management
High thermal
conductivity:(Ksolid=1700W/(m.K).
Keff=150W/(m.K) >Keff.Al=2-26W/(m.K))
Low density:0.2-0.6g/cm3,20% of that of
AluminumLarge specific
surface area:5000-50000m2/m3
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
12/24
New material for heat exchangers
Problems
The high pressure drop
The effective area of heat transfer is reduced; A large input of pumping power, a low coefficiency of performance.
Weak mechanical properties
The tensile strength of graphite foam with porosity of 75 % is only0.69 MPa. However, the tensile strength of nickel foam with thesame porosity is 18.44 Mpa.
The dust blocking
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
13/24
New material for heat exchangers In order to reduce the pressure drop of graphite foams, four different
configurations of foams (pin-finned, blind-holes, corrugated andbaffle) are analyzed.
Graphite
foam
Porosity () Pore
diameter
(Dp) (um)
Specific
surface
area
()(m2/m3)
Effective
thermal
conductivity
(keff)(W/m.K)
Permeability
() (m2)
Forchheimer
coefficient
(CF)
POCO 0.82 500 5240 120 6.13x10-10
0.4457
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
14/24
Verification of the simulation model
The pressure drop values ofthe present simulation modelare justified to be comparableto experiment.
The Nusselt numbers of thepresent simulation model areslightly higher than theexperimental results.
0
5
10
15
0 0.02 0.04 0.06 0.08 0.1
Frontal velocity (m/s)
Pressuredrop(kPa)
Experiment [6]
Simulation0
20
40
60
80
100120
140
160
0 0.02 0.04 0.06 0.08 0.1
Frontal velocity (m/s)
NusseltnumberN
u
Experiment [6]
Simulation
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
15/24
Pressure drop of graphite foam The pressure loss through
the graphite foam is basedon the Forchheimer
extended Darcy equation
f f F
i i i
CdPu u u
dx
The corrugated and pin-finned foams have lowerpressure drop, due to theshort flow length
(corrugated) and smoothflow path (pin-finned).
The configuration hasimportant effect on thepressure drop of foams.
15times
Frontal air velocity (m/s)
0
50
100
150
200
250
300
350
400
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Pressuredrop(P
a)
corrugated
blind-holes
baffle
pin-finned
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
16/24
Thermal performance of graphite foam
Nusselt number (Nu) is calculatedby
Np h removed
f f b base inlet
h D D Qu
k k A T
Due to the low flow resistancethrough the corrugated and the
pin-finned foams, more cold air canreach the surface inside the foamand bring away the heat from thefoam.Thus, the effective heat transfersurface is larger in the corrugatedand the pin-finned foams
removedQ . .effhA T
The corrugated and pin-finnedfoams have higher Nu
Frontal air velocity (m/s)
0
20
40
60
80
100
120
140
160
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Nus
seltnumberNu
corrugated
blind-holes
baffle
pin-finned
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
17/24
Comparison between graphite foam and
aluminium louver fin
Lp(mm)
(degree)
Fp(mm)
Tp(mm)
Lw(mm)
FL(mm)
1 29 2.5 14 12 50
removed removed
pum in in
Q QCOP
P u A P
1000
removed
HEX
QPD
m
1000
removed
HEX
QCF
V
(1) coefficient of performance (COP,how much heat can be removed bya certain input pump power)
(2) power density (PD, how muchheat can be removed by a certainmass of fins)
(3) compactness factor (CF, howmuch heat can be removed in acertain volume)
Aim of comparison
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
18/24
Comparison of COP (coefficient of
performance)
The louver finheat exchanger
has a largerCOP valuethan thecorrugated andpin-finned foamheat
exchangers atlow velocity.
Frontal velocity (m/s)
10
60
110160
210
260
310
360410
460
510
5 6 7 8 9 10 11 12 13 14 15
COP
pin-finned
louver fin
corrugated
At highvelocity,the COP
values aresimilar
Thus, by applying an appropriate configuration for graphitefoam, it is possible to reduce the input pumping power, andhave similar COP value as aluminium louver fin.
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
19/24
Comparison of PD (power density)
Frontal velocity (m/s)
20
30
40
50
60
70
80
90
100
5 6 7 8 9 10 11 12 13 14 15
PD(kW/kg
pin-finned
louver fin
corrugated The corrugatedand pin-finnedfoams havehigher PD valuesthan the louver
fin
This means that the corrugated or pin-finned graphitefoamheat exchanger is lighter than the louver fin heatexchanger, when the removed heat is the same.(Because of the low density)
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
20/24
Comparison of CF (compactness factor )
When the removed heat is the same, the volume of thecorrugated or pin-finned foam is much smaller than that of thelouver fin.
Because of the open cells in the foam, the heat transfer surface is
larger in the corrugated or pin-finned foam than in the louver fin.
The CF value of
the corrugated orpin-finned foam ishigher than that ofthe louver fin.
Frontal velocity (m/s)
2000
4000
6000
8000
10000
1200014000
16000
18000
5 6 7 8 9 10 11 12 13 14 15
CF(kW/m3
pin-finned
louver fin
corrugated
Highcompactness in graphite
foam
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
21/24
Conclusion of graphite foam heat
exchanger Low pressure drop and high thermal performance have
been provided by the corrugated and pin-finned graphitefoams.
The corrugated and pin-finned graphite foams have
higher PD and CF values than the aluminium louver fin.This implies a light or compact cooling system in vehicles.
By using an appropriate configuration of the graphitefoam, it is possible to have the similar COP value as thealuminum louver fin.
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
22/24
Future work New structure for heat exchangers
Due to space limitation, it might be good to change the position of heatexchanger. But when the position of the heat exchanger is changed,maybe a new structure of the heat exchanger is appropriate for the newposition.
1) Maybe a countercurrent exchanger is good for the radiator which is on thetop of driver compartment.
2) Designing a new configuration of heat exchanger, first the aluminum heatexchanger will be considered and analyzed. Later the graphite foam heatexchanger will be considered.
radiator 2
compartment
radiator 3
Radiator 1:
countercurrent
exchanger
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
23/24
Ideas about countercurrent HEX
a.Louverfin(crossflow) b.Louverfin(countercurrentflow)
d.Wavefin(countercurrentflow)c.Pinfin(countercurrentflow)
-
7/29/2019 Advaned Cooling System for Heavy Vehicles
24/24
Thank youDiscussion and Questions