Secondary Loop System with PCM
under Different Climatic Conditions
Nicholas Lemke, Julia Lemke, Jürgen Köhler
Institut für Thermodynamik
1. Fundamentals
2. Experimental Investigations
3. Simulation – Virtual Test Drive
4. Summary
1. Fundamentals
2. Experimental Investigations
3. Simulation – Virtual Test Drive
4. Summary
4
TIFFE
T
hermal Systems
I
ntegration
F
or
F
uel
E
conomy
Konsortium
Centro Ricerce Fiat SCPA (Projekt-
koordination), Turin
Denso
Thermal Systems S.p.A., Turin
Ford
-Werke GmbH, Köln
Institut für Thermodynamik,
Technische
Universität Braunschweig
Maflow
BRS S.R.L., Mailand
Sintef
Energi AS, Trondheim
4th European Workshop on Mobile Air Conditioning, Vehicle Thermal Systems, Torino (Italy), 1-2 December 2011
Ambient
Passanger
compartment
Ref. cycle
Combination
of the refrigeration cycle with one/two water/glycol cycles
Secondary Loop Systems
HT-
Secondary Loop
LT-
Secondary Loop
Ambient
Passanger
compartment
Refrigerant Water/
Glycol
Water/
Glycol
CRU
Combination
of the refrigeration cycle with one/two water/glycol cycles
CRU with Seconday Loop System - Disadvantages
Decrease of efficiency due to
additional heat
transfers+ irreversibilities
Additional
constructional effort
(pumps,
heat exchangers, …)
CRU with Secondary Loop System - Advantages
Enables application of
flammable/toxic/… refrigerants
Exchangeability of the MAC-System as a
compact unit
Lower internal volume
lower refrigerant charge
(reduction to 5-15%)
Reduced
tubing (lower pressure drop)
Additional
storage effect
additional comfort,…
Easier integration in car
energy management
system
Utilization of
latent heat
∆
∆h
temperature
enthalpy
sensible
sensible
sensible
Phase change
temperature
PCM: Additional
cold storage
within secondary loop (e.g. for start-stop)
PCM key specifications:
Mechanical, chemical and thermal
long-term stability
(compatible with
water-glycol!)
Cycle stability,
reproducible phase change
No /
low sub cooling
necessary
(no hysteresis)
High
energy-
and
power density
Low
cost
at least in large scale
production
temperature
time
subcooling
Suitable
temperatures of phase
change!
Temperature of phase change [°C]
Nitrates
Paraffins
Enth
alp
y
of
ph
ase
chan
ge
[MJ/m³]
Chlorides
Carbonates
Fluorides
Hydroxides
Sugar
alcohols
Salt-
hydrates
Eutectic
water-salt
solutions
Water
Clathrates
Fatty acids
Polyethylene glycoles
T
PC,Evap
0°C (frost)…~10°C (smell)
T
PC,Cond
40°C…45°C
[Mehling]
1. Fundamentals
2. Experimental Investigations
3. Simulation – Virtual Test Drive
4. Summary
Micro-encapsulated PCM:
PCM coated with protective shell,
implemented in carrier fluid (pumpable emulsion: PCS)
200
m
Micro-
encaps. PCM
Macro-
encaps. PCM
Container
Macro-encapsulated PCM:
PCM without protective coating macro-
encapsulated in a container with carrier fluid flowing around
[Borreguero]
Sample 1: Micro-encapsulated paraffin PCM
with a protective polystyrene
shell. ~200
m (PCS), dimensionally stable, T
PC
~42°C
Sample 2:
Paraffin PCM for macro-encapsulation
, coatless.
~5mm (container), dimensionally stable due to additives, T
PC
~6°C
200
m
5 mm
Sample 2:
PCM destinated
for macro-encapsulation
Sample 1:
Micro-
encaps. PCM
Measurement results:
Phase change effect:
Mechanical stability:
new
used
(abrasiveness!)
Sample 2:
PCM dedicated for macro-encapsulation
- material properties
Heating-up
Cooling down
T
PC,manufactorT
PC,heatingT
PC,cooling∆h
PC
108 kJ/kg
Heating/cooling rate:
5K/min
6°C
9,5°C
-1,5°C
DSC
–
D
ifferential
S
canning
C
alorimetry
(influence of
thermal conduction
inside the macroscopic
structure!)
Main function:
Heat rejection (realized
by process thermostat)
Main function:
Investigation of PCM container with
possibility of heat supply (realized by
heating cartridge)
Measurement time [s]
T
em
pe
rat
ure
[
°C]
0
2000
25
20
15
10
5
0
-5
-10
Phase Change
cooling down
Phase Change
heating-up
0
100
200
300
400
500
600
700
-2
0
2
4
6
8
10
12
14
16
18
20
T
e
mp
e
ra
tu
re
[
°C
]
Time [s]
Heating-up:
270W const.
max=6°C
D
t
Additional cooling time
due to PCM latent heat:
50s
(additional water would also
increase the time)
Fluid temperatur, measured
(system with phase change)
Measurement time [s]
T
em
pe
ratu
re
[
°C]
Fluid temperature, extrapolated
(system w/o phase change)
AC off
Aufheizung:
270W konst.
max=6°C
D
t
Kühlungs-Zeitgewinn dank PCM:
Ca. 50s
(Anm.: Größere Wassermenge
würde ebenfalls die Kühldauer
erhöhen)
Fluidtemperatur, gemessen
Measurement time [s]
T
em
pe
ratu
re
[
°C]
Fluidtemperatur, extrapoliert
max=6°C
D
t
Additional cooling time
due to increased fluid quantity:
10s
Implemented PCM quantity: 360g
Sample 2:
PCM dedicated for macro-encapsulation
– measurement results
Fluid temperature, extrapolated
(system without PC)
Fluid temperatur, measured
(system with PC)
Heating-up:
270W const.
HT-Sec.Loop
LT-Sec.Loop
Expansion
valve
Compressor
Condenser
Evaporator
Gauge glass
filling/discharge
device
1. Fundamentals
2. Experimental Investigations
3. Simulation – Virtual Test Drive
Virtual Test Drive – 1 Hour to Munich
Virtual Test Drive – Ambient Climate on July 21
st
(Meteonorm Based Weather)
T
em
pe
ra
ture
[
°C
]
Humidity Ratio x [g/kg]
0
-10
0
10
20
30
40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
10%
20%
30%
40%
100%
90%
80%
70%
60%
50%
Enthalpy [
kJ/kg]
10
0
20
30
40
50
60
70
Pressure:
1.013 bar
Start
Finish
Virtual Test Drive – Urban Heat Island
Influence of cities on the
“Planetary Boundary Layer”
yields an “Urban Heat Island”
(UHI).
Urban Heat Island on an hourly base in
Bochum (10/2006 to 10/2007)
[source: E. Parlow, "The urban heat budget
derived from satellite data,“]
Virtual Test Drive – Urban Heat Island
0
2
4
6
8
10
12
14
10
3
10
4
10
5
10
6
10
7
[Source: Matzarakis „Die thermische Komponente des Stadtklimas“]
North America
Western Europe
Japan
Number of Citizens
Maximum
UHI [
K]
Virtual Test Drive – Ambient Climate on July 21
st
(Meteonorm Based Weather)
T
em
pe
ra
ture
[
°C
]
Humidity Ratio x [g/kg]
0
-10
0
10
20
30
40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
10%
20%
30%
40%
100%
90%
80%
70%
60%
50%
Enthalpy [
kJ/kg]
10
0
20
30
40
50
60
70
Pressure:
1.013 bar
Start
Finish
Virtual Test Drive – Ambient Climate – Effect of “Urban Heat Island” (UHI)
T
em
pe
ra
ture
[
°C
]
Humidity Ratio x [g/kg]
0
-10
0
10
20
30
40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
10%
20%
30%
40%
100%
90%
80%
70%
60%
50%
Enthalpy [
kJ/kg]
10
0
20
30
40
50
60
70
Pressure:
1.013 bar
Start
Modelica / TIL model
Simulation using Modelica and TIL Suite
A/C Cycle
Secondary Loop
IVECO Daily compartment model
+
Ambient
climate data
Simulation using Modelica and TIL Suite
A/C Cycle
Secondary Loop
Cabin Model
PCM
Virtual Test Drive – Simulation Results
0
1000
2000
3000
Time [s]
T
emperature
[
°C]
0
10
20
30
40
Passenger
Compartment
Secondary Loop
Air Inlet
Virtual Test Drive – Simulation Results
0
1000
2000
3000
Time [s]
T
emperature
[
°C]
0
10
20
30
40
Passenger
Compartment
Secondary Loop
+ 1 Liter H
2
O
Air Inlet
Virtual Test Drive – Simulation Results
0
1000
2000
3000
Time [s]
T
emperature
[
°C]
0
10
20
30
40
Passenger
Compartment
Secondary Loop
+ 1 Liter H
2
O
+ 1 Liter PCM
(no additional H
2
O)
Air Inlet
Virtual Test Drive – Simulation Results
0
1000
2000
3000
Time [s]
T
emperature
[
°C]
0
10
20
30
40
Passenger
Compartment
Air Inlet
Secondary Loop
+ 1 Liter H
2
O
+ 1 Liter PCM
(no additional H
2
O)
PCM Loading
Virtual Test Drive – Simulation Results
0
1000
2000
3000
Time [s]
T
emperature
[
°C]
0
10
20
30
40
Passenger
Compartment
Secondary Loop
+ 1 Liter H
2
O
+ 1 Liter PCM
(no additional H
2
O)
PCM Unloading
Air Inlet
Virtual Test Drive – Simulation Results
2400
2500
2600
2800
T
emperature
[
°C]
0
10
20
Passenger
Compartment
Air Inlet
Secondary Loop
+ 1 Liter H
2
O
+ 1 Liter PCM
(no additional H
2
O)
2700
Time [s]
30
2900
Virtual Test Drive – Simulation Results
2400
2500
2600
2800
T
emperature
[
°C]
0
10
20
Passenger
Compartment
Air Inlet
Secondary Loop
+ 1 Liter H
2
O
+ 1 Liter PCM
(no additional H
2
O)
2700
Time [s]
30
odour
nuisance
2900
1. Fundamentals
2. Experimental Investigations
3. Simulation – Virtual Test Drive
Automotive secondary loop systems can be improved using
phase change material (PCM)
Micro-encapsulated
paraffin PCM have not been mechanical
stable
Macro-encapsulated
paraffin PCM seem to be a good choice
Virtual test drive
with PCM showed:
- slower cool down performance but
- improved cooling performance during stop phase
Summary