Status of Humidification Dehumidification Desalinationweb.mit.edu/lienhard/www/IDA_Perth_Presentation_2011.pdf · Status of Humidification Dehumidification Desalination Prakash Narayan

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


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


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


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


� 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


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.


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


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.


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


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


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


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


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


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


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


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


HDH FOR LARGER SCALE SYSTEMS

HDH hybridized with RO

18


HDH system hybridized with RO

19Narayan G.P., 2011. Submitted for publication to Energy


Performance of HDH-RO

At reasonable efficiency, most

water is produced in the RO

section

20


21


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.


INNOVATIONS TO REDUCE

DEHUMIDIFIER SIZE

1. Helium as carrier gas

2. HDH with direct contact dehumidifier

23

2. HDH with direct contact dehumidifier


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


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


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


Thanks

Prakash: [email protected]

Professor Lienhard: [email protected] Lienhard: [email protected]

Ronan McGovern: [email protected]

Syed Zubair: [email protected]

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Documents

Status of Humidification Dehumidification Desalinationweb.mit.edu/lienhard/www/IDA_Perth_Presentation_2011.pdf · Status of Humidification Dehumidification Desalination Prakash Narayan