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MODELING THE EFFECTS OF ADDING GRAPHITE FLAKES
TO FAM-Z02 IN AN ADSORBER BED
Mahdi Nemati Mehr
Amir Sharafian
Khorshid Fayazmanesh
Wendell Huttema
Majid Bahrami
October 5, 2016
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2
Objectives
• Developing a CFD model to predict system performance under different operational conditions
• Understanding heat and mass transfer inside the adsorber bed
• Performing a comprehensive parametric study to see the effects of different parameters on the performance of the adsorption cooling system
• Studying the effects of graphite flakes additive to the adsorbent on the ACS performance
• Investigating the impact of using graphite-based heat exchangers as the adsorber bed
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Motivations and Opportunities
3
The U.S. consumed about 140.43 billion liters of fuel a year for AC systems of light duty vehicles in 2015[1].
[1] Independent Statistics and and Analysis, How much gasoline does the United States consume?, US Energy Information Administration (EIA), March 2016 [2] R. Farrington, J. Rugh. Impact of vehicle air-conditioning on fuel economy, tailpipe emissions, and electric vehicle range. Proceeding of the Earth Technologies Forum, Washington, D.C., October 31, 2000. [3] US Department of Energy, Energy Efficiency and Renewable Energy, www.fueleconmy.gov
During the SFTP-SC03 driving cycle, a vapor compression refrigeration cycle of light-duty vehicle results in increasing[2]:
• CO emissions by 71%
• NOx emissions by 81%
• Non-methane hydrocarbons by 30%
Parasitic Loss 4% - 6%
Power to Wheels 18% - 25%
Drivetrain Loss 5% - 6%
[3]
Engine Loss 68% - 72%
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Schematic of Experimental Test Setup
4
Parameter Value
Working pairs FAM Z02 – water
Heating fluid inlet temperature 90°C
Cooling fluid inlet temperature 30°C
Coolant fluid inlet temperature 20°C
Chilled water inlet temperature 20°C
Heat transfer fluid mass flow rate to adsorber bed Not measured
Heat transfer fluid Silicone oil
Balance
P
TCS
20°C
Evap
ora
tor
P
TCS
T T
90°C 30°C
Co
nd
ense
r
TCS: Temperature control system
Ad
sorb
er
Be
d
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5
Literature Review
Working pairs Reference
Zeolite - Water [1][2][3][4][5][6][7][8][9]
Silica gel – Water [9][10][11][12][13]
Ammonia - Activated Carbon [2]
Ethanol – Activated Carbon [13]
Geometry Reference
1D [1][2][3][4][5][11]
2D [6][7][8][9][10][12]
3D [13][14]
[1] L.M. Sun, et al., Heat Recover. Syst. CHP. 15 (1995) 19–29. [2] N.B. Amar, et al., Appl. Therm. Eng. 16 (1996) 405–418. [3] L.Z. Zhang, Sol. Energy. 69 (2000) 27–35. [4] L. Marletta, et al., Int. J. Heat Mass Transf. 45 (2002) 3321–3330. [5] G. Restuccia, et al., Appl. Therm. Eng. 22 (2002) 619–630. [6] K.C. Leong, Y. Liu, Int. J. Heat Mass Transf. 47 (2004) 4761–4770. [7] K.C. Leong, Y. Liu, Appl. Therm. Eng. 24 (2004) 2359–2374. [8] Y. Liu, K.C. Leong, Int. Commun. Heat Mass Transf. 35 (2008) 618–622. [9] D.B. Riffel, et al., Int. J. Heat Mass Transf. 53 (2010) 1473–1482. [10] G.G. Ilis, et al., Int. Commun. Heat Mass Transf. 38 (2011) 790–797. [11] İ. Solmuş, et al., Int. J. Refrig. 35 (2012) 652–662. [12] A.O. Yurtsever, et. al., Appl. Therm. Eng. 50 (2013) 401–407. [13] H. Niazmand, I. Dabzadeh, Int. J. Refrig. 35 (2012) 581–593. [14] H. Talebian, et al., Int. Conf. Mech. Eng. Adv. Technol., 2012: pp. 1–7
Gaps in literature: - FAM-Z02 as working pair - Few 3D models - No models with effects of thermal contact
resistance (TCR)
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6
Assumptions
Assumptions:
• Ideal gas behavior for adsorbate gas [1-14]
• Uniformly sized spherical particles [1-14]
• Constant thermo-physical properties for materials (except density of adsorbate)
[1-14]
• Thermal equilibrium between particles and adsorbate [1-14]
• Thermal contact resistance
Numerical Tool:
• ANSYS Fluent was used to solve the Navier-Stokes, energy, and uptake equations
• User defined scalar (UDS) module was used in order to simulate uptake rate (ω)
• Mass generation, heat generation, and scalar generation were simulated using
user defined functions (UDF)
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7
Governing Equations
• Continuity
• Momentum
• Energy
. 1 0
refrigerant
refrigerant adsorbent
dv
t dt
2. .2
Cvvv p v v v
t K
2.
3Tv v vI
, , ,1 1adsorbent p adsorbent p refrigerant refrigerant p refrigerant adsorbent adsorption
T dC C vC T h k T
t dt
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8
Governing Equations
• Uptake
[1] A. Sharafian, M. Bahrami, Renewable and Sustainable Energy Reviews, 48 (2015) 857-869. [2] M.J. Goldsworthy, Microporous Mesoporous Material, 196 (2014) 59–67. [3] M. Intini, M. Goldsworthy, S. White, C.M. Joppolo, Applied Thermal Engineering, 80 (2015) 20–30.
mass of adsorbed material kg of adsorbate
mass of adsorbent kg of adsorbent
02
15exps a
equp adsorbent
D Ed
dt R TR
,eq T pf
00
1
00
1
, 11
exp / 1 !1
1 exp / !
s
ss
jnj
jeq jn
s j
j
n
hpK jp RT
n hpK jp RT
0
1
0
max
exp
exp
1
v
n n
v
eq
hk p
RT
hk p
RT
water-FAMZ02 [2]
water-FAMZ02 [3] water-silica gel [1]
[1]
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9
Thermal Contact Resistance (TCR)
𝛿 + 2𝛿𝑇𝐶𝑅
kyy=kads
kxx= kzz=0
ρ=cp=0
kads, ρads, cp,ads
kyy=kads
kxx= kzz=0
ρ=cp=0
kads, ρads, cp,ads
𝛿
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10
Geometry
Periodic Line
Vac
uu
m C
ham
be
r W
all
Pipe
Symmetry Line Periodic
Line
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11
HEX and Vacuum Chamber Arrangement
Heat transfer
fluid
Adsorbent Gap between
HEX and vacuum chamber
Vacuum chamber wall
Front View Side View
HEX fin
TCR
Ad
sorb
ent
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12
Initial and Boundary Conditions
Initial Conditions: - The final solution does not depend on initial conditions due to cyclic operation of ACSs.
- Incorrect initial conditions can result in
divergence (esp. for pressure)
Boundary Conditions: - Pressure at outlet / inlet → Represents pressure at evaporator / condenser
- Temperature at outlet / inlet → Representative for temperature of vapor coming from
(or going to ) at evaporator (condenser)
- Temperature at heat exchanger walls → Represents temperature of heating/cooling fluid
0.05
0.07
0.09
0.11
0.13
0 20 40 60 80 100 120 140
Up
take
(kg
/kg)
Time (min)
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0
5
10
15
20
25
30
35
0 30 60 90 120 150
Wat
er U
pta
ke %
(kg
/kg)
Time (min)
Numerical
Experimental
13
Results – Equilibrium Uptake
Adsorption
Desorption
0
5
10
15
20
25
30
35
0 30 60 90 120 150
Wat
er U
pta
ke %
(kg
/kg)
Time (min)
Experimental
Numerical
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14
Results – Cyclic Operation
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 5 10 15 20
Up
take
Dif
fere
nce
% (
kg/k
g)
Cycle Time (minute)
Experimental
Numerical
14% 5%
7%
Δω: the difference between the maximum and the minimum values of the uptake
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15
Graphite Doped Adsorbent
0
1
2
3
4
5
6
7
8
9
10
0 300 600 900 1200 1500
Δω
(kg
/kg)
Cycle time (s)
0% graphite5% graphite10% graphite20% graphite
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16
Conclusions and Future Works
Conclusions
• A full three-dimensional finite volume based computational fluid dynamic model was
developed.
• It was shown that if thermal conductivity improvement is performed by adding some non-
adsorptive material like graphite, it could decrease the adsorption performance of the
adsorber bed
Future Works
• Adding the effects of uptake value on thermo-physical properties of an adsorbent.
• Studying the effects of the ideal evaporator and condenser.
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18
Boundary Conditions
1
2
2 3
2
Rectangular Wave (Ideal Case)
1
2
2 3
2
Fourier Series of Rectangular Wave
1
2
2 3
2
Trapezoidal Wave
2 3
2
1
2
Actual Case
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19
Graphite HEX vs. Aluminum HEX
Fin TCR Adsorbent
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20
Graphite HEX vs. Aluminum HEX
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Boundary Conditions
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
20
30
40
50
60
70
80
90
100
0 150 300 450 600 750 900
Pre
ssu
re a
t b
ou
nd
ary
(Pa)
Co
olin
g/h
eati
ng
tem
per
atu
re (
C)
Time (s)
Temperature Pressure
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22
Results - Graphite HEX vs. Aluminum HEX
14
15
16
17
18
0 150 300 450 600 750 900
Up
take
% (
kg/k
g)
Time (s)
Aluminum Graphite
2.39%
2.21 %
1.58 %
2.06%
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23
Results - Graphite HEX vs. Aluminum HEX
Cycle Time (s)
Δω with Aluminum HEX (SCP)
Δω with Graphite HEX
(SCP)
Enhancement of Δω
300 1.58 % (132) 2.02 % (168) 31 %
480 3.11 % (161) 3.56 % (185) 15.7 %
600 4.12 % (171) 4.62 % (192) 12.1 %
900 6.57 % (154) 7.05 % (175) 7.3 %
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Qih Qibd +
Vapor Compression Refrigeration (VCR) vs. Adsorption Cooling System (ACS)
24
Evap
ora
tor
Q evap
Co
nd
ense
r
Q cond
Expansion valve
Adsorber beds
Compressor
W comp
Qic Qiba +
ih: isosteric heating ibd: isobaric desorption ic: isosteric cooling iba: isobaric adsorption
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Adsorption Refrigeration Cycle
25
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ACS Working Pairs
26
ACS refrigerant (adsorbate):
• Water
• Methanol
• Ethanol
• Ammonia [6] http://www.ucicarbons.com/medical-benefits-activated-carbon/ [7] http://www.weiku.com/products/15374902/_gt_All_kinds_of_desiccant_Desiccant_pack_moisture_absorber_.html [8] http://www.rwlwater.com/zeolite-holds-key-to-waste-heat-use/
ACS sorbent material (adsorbent):
Silica gel [7] Activated carbon [6] Zeolite [8]
𝜕𝜔
𝜕𝑡= 𝐾 𝜔𝑒𝑞 − 𝜔
𝜔𝑒𝑞 = 𝐹 𝑇, 𝑃
LDF model:
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27
How to improve adsorption cycle
• Adsorbate/Adsorbent Pair • Material • Physical shape (consolidated, powder, pelletized particles)
• Heat Exchanger Design
• Dimensions • Weight • Mass transfer resistance
• Thermodynamic cycle
• Heat Recovery • Mass Recovery • Heat and Mass Recovery • Temperature range
• Heat source (Exhaust gas, Coolant) • Refrigerant
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Adsorption Concepts
Adsorption is the adhesion of atoms, ions, or molecules of gas, liquid, or dissolved
solids to a solid surface
28
Two main processes: • Cooling → Adsorption → Evaporation at evaporator
• Heating → Desorption → Condensation at condenser
Exothermic Process
Endothermic Process
Ad
sorb
ent
Adsorbate Adsorbents Adsorbates
silica gel zeolite
activated carbon
FAM-Z02
water methanol/ethanol
ammonia
mass of adsorbed material kg of adsorbate
mass of adsorbent kg of adsorbent
Uptake:
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Advantages and Disadvantages
29
Advantages of ACS [1,2]: • Utilization of waste heat • Few moving parts (valves) less maintenance is required • Non toxic materials • Environmental friendly refrigerants
[1] M. O. Abdullaha, I. A. W. Tana, L. S. Limb., Renewable and Sustainable Energy Reviews (2011); 15: 2061–2072. [2] H. Demir, M. Mobedi, S. Ulku., Renewable and Sustainable Energy Reviews (2008); 12: 2381–2403. [3] R.Z. Wang, J.Y. Wu, Y.X. Xu, W. Wang., Energy Conversion and Management (2001); 42: 233–249.
Major challenges facing commercialization of ACS [2,3]:
• Low working pressure in many cases (1 kPa – 7kPa for the case of water) • Small specific cooling power values
• Small COP values
• Bulky and heavy systems
evap
ads cyc
QSCP
m
evap
ih ibd
QCOP
Q Q
10<typ.<270
0.02<typ.<0.6
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Adsorber Bed Designs
30
Spiral plate Hairpin
Annulus tube
Plate
Plate fin
Finned tube
Plate-tube Tube
Shell and tube
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31
Literature Review on Mass Measurement
[1] Glaznev I, et al., Heat Transf Eng 2010;31:924–30. [2] Aristov YI, et. al.,. Chem Eng Sci 2006;61:1453–8. [3] Aristov YI, et al, . Int J Heat Mass Transf 2008;51:4966–72. [4] Glaznev IS, Aristov YI. Int J Heat Mass Transf 2008;51:5823–7. [5] Okunev BN, et al. Int J Heat Mass Transf 2010;53:1283–9. [6] Glaznev IS, Aristov YI. Int J Heat Mass Transf 2010;53:1893–8. [7] Dawoud B. J Chem Eng Japan 2007;40:1298–306. [8] Schnabel L, et al., Appl Therm Eng 2010;30:1409–16. [9] Freni A, et al., Appl Therm Eng 2015;82:1–7. [10] Dawoud B, Aristov YI. Int J Heat Mass Transf 2003;46:273–81. [11] Dawoud B, et al., Int J Heat Mass Transf 2007;50:2190–9. [12] Solmuş İ, et al., Appl Energy 2010;87:2062–7. [13] Santamaria S, et al., Appl Energy 2014;134:11–9. [14] Sapienza A, et al., Appl Energy 2014;113:1244–51. [15] Storch G, et al., Adsorption 2008;14:275–81. [16] Dawoud B. Appl Therm Eng 2013;50:1645–51. [17] Riffel DB, et al., Int J Heat Mass Transf 2010;53:1473–82.
Mass of adsorbent Reference Working pair
Less than 1 g
[1]
[2][3][4][5][6]
[7][1]
[8]
[9]
silica gel - water
silica gel + CaCl2 (SWS-1L)-water
FAM-Z02-water
zeolite-water
activated carbon-methanol
1 g < mass of adsorbent < 100 g
[10] [10] [11][8][12][13] [9][14]
silica gel-water silica gel + CaCl2 (SWS-1L)-water zeolite-water SAPO 34-water
100 g < mass of adsorbent < 1 kg [15] [16]
zeolite 13X-water FAM-Z02-water
1 kg < mass of adsorbent [17] [17] [16]
silica gel-water zeolite-water FAM-Z02-water
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Adsorber Bed Design – 3 fin per inch – Design I
32
Header
Collector
Parameter Value
No. of supply pipes 1
Supply pipes size 1/2 in
No. of return pipes 6
Return pipes size 3/8 in
No. of fins 17
Fin spacing 9 mm
Fin diameter 6 in
Fin thickness 1/16 in
Fin material Copper
Parameter Value
Cycle time 60 – 90 – 120 – 180 min
Mass of adsorbent 0.620 kg
Design Parameters
Working Parameters
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Adsorber Bed Design – 10 fin per inch – Design II
33
Parameter Value
No. of passes 1
Branch pipes size ½ in
Fitting Size ¾ in
No. of return pipes 6
Fin spacing 10 fpi
Overall Size 12 ¾ x 18 x 1 ½ in
Fin width 1 ½ in
Fin thickness 0.2 mm
Fin material Aluminum
Parameter Value
Cycle time 8 – 10 – 20 – 30 – 60 –
90 – 120 min
Mass of adsorbent 1.5 kg
Design Parameters
Working Parameters
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In-situ Uptake Measurement Setup – Design I
34
Evaporator/ Condenser (at 20°C)
Chiller Pressure transducers
Aluminum lid Hosing Scale
Adsorber bed
Heat transfer fluid (at 30 and 90°C)
Introduction EXPERIMENTAL SETUP Numerical Modeling Conclusion
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In-situ Uptake Measurement Setup – Design II
35
FAM Z02 in new adsorber bed
Adsorber bed Evaporators 1 and 2
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Challenges
36
• Low working pressure of adsorption system (1 kPa – 7 kPa)
• Designing vacuum chamber
• Leaking )Helium leak detector(
• Changes of the density of the heat transfer fluid (silicone oil) with temperature
• Changes of hosing stiffness with temperature
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Measured Parameters
37
25
35
45
55
65
75
85
95
0 10 20 30 40 50 60
Te
mp
era
ture
( C
)
Time (min)
Design IICycle time = 60 min
T bed_i
T bed_o
Adsorption Desorption
0
50
100
150
200
250
300
350
0 10 20 30 40 50 60
Mass (
g)
Time (min)
Design IICycle time = 60 min
Measured mass
Mass change ofsilicone oil
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 10 20 30 40 50 60
Pevap/c
ond
(kP
a)
Time (min)
Cycle time = 60 min
Design I
Design II
Psat. at 20 C
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FAM Z02- Equilibrium Uptake
38
0
5
10
15
20
25
30
35
40
0 30 60 90 120 150 180 210 240
Wa
ter
up
take
% (
kg
/kg
)
Time (min)
FAM-Z02Tdes = 90 CTads = 30 CTevap/cond = 20 C
Design I
Design II
TGA measurement
0
5
10
15
20
25
30
35
0 30 60 90 120 150 180 210 240
Wate
r upta
ke%
(kg/k
g)
Time (min)
FAM-Z02Tdes = 90 CTads = 30 CTevap/cond = 20 C
Design I
Design II
TGA measurement
Adsorption
Desorption
[1]
[1] [1] Okamoto K, et. al., Int. Symp. Innov.
Mater. Process. Energy Syst., Singapore,
2010.
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FAM Z02- Cyclic Operation
39
0
2
4
6
8
10
12
14
16
18
20
0 20 40 60 80 100 120 140 160 180
Δω
% (k
g/k
g a
dso
rbe
nt)
Cycle time (min)
FAM-Z02Tdes = 90 CTads = 30 CTevap/cond = 20 C
Design I
Design II
0
20
40
60
80
100
120
140
0 20 40 60 80 100 120 140 160 180
SC
Pid
eal(W
/kg)
Cycle time (min)
FAM-Z02Tdes = 90 CTads = 30 CTevap/cond = 20 C
Design I
Design II
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 20 40 60 80 100 120 140 160 180
CO
Pid
eal
Cycle time (min)
FAM-Z02Tdes = 90 CTads = 30 CTevap/cond = 20 C
Design I
Design II
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40
Ideal SCP vs. Actual SCP
𝑆𝐶𝑃Ideal =∆𝜔 × ℎ𝑓𝑔
𝜏𝑐𝑦𝑐𝑙𝑒=
∆𝑚𝑟𝑒𝑓 × ℎ𝑓𝑔
𝑚𝑎𝑑𝑠 × 𝜏𝑐𝑦𝑐𝑙𝑒
𝑆𝐶𝑃Actual =𝑄𝑒𝑣𝑎𝑝
𝑚𝑎𝑑𝑠 × 𝜏𝑐𝑦𝑐𝑙𝑒
𝑁𝑢𝑚𝑒𝑟𝑖𝑐𝑎𝑙 𝑀𝑜𝑑𝑒𝑙𝑖𝑛𝑔
𝑀𝑎𝑠𝑠 𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑚𝑒𝑛𝑡
𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝐸𝑓𝑓𝑒𝑐𝑡 𝑎𝑡 𝐸𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑜𝑟
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Performance of Different Adsorber Bed Designs
41
0
100
200
300
400
500
0
2
4
6
8
10
12
14
1 2 3 4 5 6 7 8 9 10
SC
P (
W/k
g)
Ad
so
rbe
r b
ed
to
ad
so
rbe
nt
ma
ss r
atio
(kg/k
g)
Adsorber bed type [1]
Mass of adsorber bed/adsorbent
SCP
Adsorber bed to adsorbent mass ratio
0
100
200
300
400
500
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1 2 3 4 5 6 7 8 9 10
SC
P (
W/k
g)
CO
P
Adsorber bed type [9]
COP
SCP
1. Spiral plate 2. Shell and tube 3. Hairpin 4. Annulus tube 5. Plate fin 6. Finned tube 7. Plate-tube 8. Simple tube 9. Plate
[9] A. Sharafian, M. Bahrami. Renewable and Sustainable Energy Reviews. 30 (2014) 440–451.
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Single-Bed ACS Equipped with Capillary-Assisted Evaporator
Adsorber bed
Condenser
Evaporator
FAM Z02 in new adsorber bed
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43
Two-Adsorber Bed FAM-Z02-Water ACS
Adsorber bed 2
Condenser
Evaporator
Adsorber bed 1
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44
Modified Test Setup
Tbed, in Tbed, out
Tevap, out
Tevap, in
• Heat transfer fluid flow rate ≈ 4 lit/min
• Evaporator flow rate ≈ 3 lit/min
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Adsorber Bed Designs
45
Parameter Design I Design II
Working pairs AQSOA FAM-Z02/water
Adsorbent particles diameter (m) 0.002
Mass of adsorbent (kg) 0.62 1.50
Metal mass of adsorber bed (kg) 2.80 2.87
Adsorber bed heat transfer surface area, Abed, (m2) 0.235 2.80
Fin spacing (mm) 6.47 (3.5 fins per inch) 2.34 (10 fins per inch)
Fin dimensions 12.7 cm )5”( diameter 43.18×30.48 cm )17”×12”(
Heating fluid mass flow rate to adsorber bed (kg/s) 0.058 (4.1 L/min of silicone oil)
Cooling fluid mass flow rate to adsorber bed (kg/s) 0.062 (4.1 L/min of silicone oil)
Heat capacity of silicone oil (kJ/kgK) 1.8
Heating fluid inlet temperature (°C) 90
Cooling fluid inlet temperature (°C) 30
Evaporation/condensation temperature (°C) 20
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Pressure – 10 fpi, 1500gr
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 10 20 30 40 50 60
Pre
ssu
re (
kPa)
Time (min)
Evaporator Bed
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Pressure - 3 fpi, 620 gr – Cycle time 60 min
47
0
0.5
1
1.5
2
2.5
3
3.5
0 30 60 90 120 150 180
Pre
ssu
re (
kPa)
Time (min)
Bed Evaporator/Condenser
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48
Pressure within Bed and Evaporator – Design II Modified
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 15 30 45 60 75 90
Pre
ssu
re (
kPa)
Time (min)
P Bed
P Evap
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49
SCP – Two different Design Comparison
0
10
20
30
40
50
60
70
80
90
100
30 60 90 120 150
SCP
(W
/kg)
Cycle Time (min)
3 fpi
10 fpi
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Results – effects of silicon oil density change
50
0
20
40
60
80
100
120
0 60 120 180 240 300
Mas
s (g
r)
Time (min)
Total Mass Reading
Oil Mass Reading
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51
Low Pressure Evaporator
• Using the new evaporator (capillary assisted)
• Decreasing cycle time to reach the maximum SCP
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FAM Z02- Equilibrium Uptake
52
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The First Generation
53
50 Bodies 511,000 Cell
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Geometries
54
Flow in Flow in