status of humidification dehumidification...
TRANSCRIPT
Status of Humidification Dehumidification Status of Humidification Dehumidification
Desalination
Prakash Narayan Govindan
For Lienhard Research Group
Massachusetts Institute of Technology
email: [email protected]
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Layout of presentation
1. The problem
2. Matrix for ideal solution
3. HDH system
4. Features of HDH system
5. Innovations in HDH system
– For reducing energy consumption– For reducing energy consumption
– HDH for larger scale water production
– For reducing dehumidifier size/cost
6. Potential niche for various HDH
technologies
Banswara district, Rajasthan, India.http://photos.merinews.com/
2
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
The problem
3
Ref: CK Prahlad & Al Hammond, HBR
• “Global” water scarcity – a major portion of it is in low-income countries;
• There is a large market opportunity in water purification and desalination in these countries;
• The poor currently pay a very blotted price for safe water;
World water scarcity map
Source: UNEP
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Matrix for ideal solution
(ca
n i
t b
e ta
ken
to
a m
illi
on
peo
ple
?)
Community level water
supplyTransport Bottled water: high
specific cost
Standalone Reverse Osmosis–
resource intensive
Sca
lab
ilit
y (c
an
it
be
tak
en t
o a
mil
lio
n p
eop
le?
)
Implement-ability (related to cost and resource)
Water cone –specific cost very
high
resource intensive
Lifesaver – only for certain
types of water purification
PuR – not scalable
4
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
HDH systemCarrier gas
(humidified)
Packed bed
Th
Carrier gas
(humidified)
Packed bed
Th
Humidifier Dehumidifier
Solar Heater
Sea water
in, ṁw,i ,To
Pure water, ṁpw
Carrier gas
Packed bed
Brine, ṁb
Humidifier Dehumidifier
Solar Heater
Sea water
in, ṁw,i ,To
Pure water, ṁpw
Carrier gas
Packed bed
Brine, ṁb5
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
� GOR is the thermal efficiency of the system.2
3
4
5G
ain
ed
-ou
tpu
t-ra
tio
4.5
Performance benchmark
� GOR is the thermal efficiency of the system.
� Used for MSF and MED.
0
1
2
Al-Hallaj et al. 1998.
Ben Bacha et al., 2003.
Farid et al., 1996
Nawayseh et al., 1999
Muller-Holst et al., 2007
Klausner & Mei., 2005
Ga
ine
d
Narayan G.P. et al., 2010. Renewable and Sustainable Energy Reviews,
doi:10.1016/j.rser.2009.11.0146
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Features of the HDH system
Demerits:
1. Low water vapor content in carrier gas
2. Extra thermal resistance to heat transfer (esp. in dehumidifier)
3. Low energy recovery compared to MSF/MED
� GOR existing systems = 0.2 to 4.5
� GORMSF= 8 to 12*� GORMSF= 8 to 12
� GORMED=12 to 16*
Merit:
1. Simple and low-cost construction
2. Low maintenance requirements
* Awerbuch L., Seminar at MIT, Feb, 2009.
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
INNOVATIONS IN HDH TO
REDUCE ENERGY
CONSUMPTION
SECTION 2
CONSUMPTION
8
1. Multi stage air heated HDH
2. Mechanical compression HDH
3. Thermally balanced HDH
4. HDH with a common heat transfer wall
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Multi stage air heated cycle
9
Psychrometeric chart Schematic of the experimental setup
1. Invented by Chafik1
2. Vapor content at the exit of the humidifier is increased to 9.5% in 4 stages
(corresponds to saturated air at 51.5ºC)
3. The increase in humidity/ water production comes with an increase in energy input
in the heaters and hence, the energy consumption of these cycles is not reduced
greatly.
1 Chafik. E., 2003. A new type of seawater desalination plants using solar energy. Desalination
156, 333-348.
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Pressure as a parameter in HDH
Humidity ratio:
P=100 kPa
P=70 kPa
P=50 kPa
P is total pressure;
PW is partial pressure
of water vapor;
φ is relative humidity;
ω↑ as P↓10
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Pressure as a parameter in HDH
Narayan, G.P., Sharqawy, M.H., Lienhard V, J.H. and Zubair, S.M. , 2009.
Water separation under varied pressure. US Patent application, USSN 12/573,221.11
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Mechanical compression driven HDH
Seawater
Pure water
Carrier gas
HumidifierCompressor
Ẇin
Dehumidifier
ηc
εDεH
PDPH
Brine
Humidifier
Expander
Ẇout
Dehumidifier
Tsw,in
ṁpw ṁsw,in
ṁda
ηE
εDεH
PD-∆PD PH+∆PH
12
… Proceedings of AJTEC 2011; ASME/JSME 8th Thermal Engineering Joint conference:
Hawaii. 2011
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Mechanical compression driven HDH
Technologies Thermal
energy
consumed
(kJ/kg)
Electrical energy
consumed
(kJ/kg)
Overall
equivalent
GOR
Water heated HDH 950 5-18 2
Mechanical compression HDH - <160 >6
13
ηPP = 40%
Higher equivalent GOR than traditional HDH systems
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Thermally balanced HDH
• HDH cycle performance can be
improved upon by thermally
balancing the system for minimum
entropy generation
• By vary the mass flow rate ratio, the
temperature and humidity profiles are
adjusted for minimum entropy
heater
adjusted for minimum entropy
generation
• Natural* and forced♀ convection
based systems have both been studied
for balancing by researchers
elsewhere previously. GOR of upto
4.5 was reported.
H D
seawater air Pure water
*Müller-Holst , PhD Dissertation, Technical
University Munich, 2002.♀Thomas Brendel, German Patent, DE 10215079A1
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Minimum entropy generation in
a humidifier/dehumidifier
Dehumidifier
Tw,o
ṁw,o
Ta,i ,ωi
ṁda
Water stream
Tpw, ṁpw
Tw,i =20 ºC; Ta,i =70 ºC; φi=φo=1; ε=80%
15
Narayan, G.P. et al., 2010. IJTS, 49(10), Pages 2057-2066.
Narayan, G.P. et al., 2010. FHMT, 1 - 023001.
Tw,i
ṁw,i
Ta,o ,ωo
ṁda
Humid air stream
Tpw, ṁpw
Condensed water
stream
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
HDH with common heat transfer
wallProcess
• Moist air enters the dehumidifier and condenses along
the common wall, releasing heat to the evaporator
through the wall
Advantages
• Common wall enhances heat recovery between the
16
• Common wall enhances heat recovery between the
two sides of the system, giving high theoretical GOR
of 9.5
• Experimental systems constructed from cheap
materials.
Disadvantages
• Poor flow distribution along both sides of the wall
resulted in a lower experimental GOR of 4.5
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Section Summary • Mechanical compression driven HDH has potential because the capital and
maintenance cost of the system itself is expected to be very low. It also
gives the option of dual heat or electric operation
Niche: Diesel generator and biomass driven decentralized system
• Currently, two companies from Germany (Magewater Management GmbH
and Terra Water GmbH) are trying to commercialize (single pressure) HDH and Terra Water GmbH) are trying to commercialize (single pressure) HDH
systems with thermodynamic balancing.
Niche: Small scale, renewable energy based, decentralized system
• The HDH systems with a common heat transfer wall is a commercial
product which is patented and produced by two companies - Altela Inc
in the US and Three Millenium Water Technologies in France.
Niche: Small scale, renewable energy based, decentralized system
17
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
HDH FOR LARGER SCALE SYSTEMS
HDH hybridized with RO
18
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
HDH system hybridized with RO
19Narayan G.P., 2011. Submitted for publication to Energy
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Performance of HDH-RO
At reasonable efficiency, most
water is produced in the RO
section
20
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
21
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Ejector Research
Define Performance
Metrics
Understand
Fundamentals 10%
15%
20%
Eff
icie
ncy
Fundamentals
Investigate Novel
Designs
0%
5%
10%
0 0.2 0.4 0.6 0.8
Eff
icie
ncy
Entrained to Motive Mass Ratio
Turbine-Compressor
Exergetic
Entrainment
Data from Eames, 1995. Internat. Journal of Refrig.
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
INNOVATIONS TO REDUCE
DEHUMIDIFIER SIZE
1. Helium as carrier gas
2. HDH with direct contact dehumidifier
23
2. HDH with direct contact dehumidifier
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
HDH with Helium as the carrier gasTw,i =30 ºC; Tht,i =90 ºC; εH=60%; εD=90%
24
1. The thermodynamic performance (GOR) of the water heated HDH system is not affected by
changing the carrier gas.
2. However, the reduction of pressure drop will reduce the auxiliary electricity consumption by 5 to 8
times and increase in dehumidifier heat transfer coefficient by 5 to 6 will reduce dehumidifier size
greatly.
Narayan G.P., Paper accepted for presentation at ASME IMECE 2011, Denver
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
HDH with direct contact
dehumidifier*
25
• The heat transfer coefficients are higher for the direct contact
dehumidifier than for the other HDH systems. Hence, the heat
exchanger size and cost are relatively low.
• Because the heat from the humidified air is not recovered directly to
preheat seawater, the system heat recovery is low and the energy
consumption is high.
*James Klausner., University of Florida
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Overall Conclusions
• Simple HDH technology with a GOR of 2 and low CAPEX and
maintenance requirements is appropriate for community level
water purification and can play a role in solving the global
water problem
• New embodiments of HDH are under development and can • New embodiments of HDH are under development and can
potentially improve upon on the simple HDH technology
• Further research (not mentioned in this paper) is under
progress at MIT & other institutions to make HDH a low cost
desalination system
26
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPTEMBER 4-9, 2011INTERNATIONAL DESALINATION ASSOCIATION
Thanks
Prakash: [email protected]
Professor Lienhard: [email protected] Lienhard: [email protected]
Ronan McGovern: [email protected]
Syed Zubair: [email protected]
27