liquid-air transpired solar collector (latsc): model development, validation and optimization-thesis...

8/11/2019 Liquid-Air Transpired Solar Collector (LATSC): Model Development, Validation and Optimization-Thesis defense

1/61

Liquid-Air Transpired Solar Collector(LATSC): Model Development,Validation and Optimization

By: Abdul Qadir

Advisor: Dr Peter ArmstrongRSC members: Dr Tariq Shamim, Dr Afshin Afshari

1


2/61

OutlineMotivation

ResearchObjectives

LATSC

Experimental Numerical

Sensitivity Analysis

LDR

Numerical

CombinedLATSC-LDR

Model

Sensitivity Analysis Optimization

LATSC -Liquid Air TranspiredSolar Collector

LDR - LiquidDesiccantRegenerator

2


3/61

MotivationIncreased use of solar thermal collectors forcooling and desalinationConventional flat plate collectors have a high

capital costUnglazed collectors have high convection lossesUse of polymer materials in glazed collectors

causes degradation of material at stagnation A supply temperature between 50-70 oC required

3


4/61

Liquid Desiccant Cooling

4


5/61

Humidification-Dehumidification(HDH) Desalination

5


6/61

Motivation

ResearchObjectives

LATSC



LDR

Numerical

CombinedLATSC-LDR

Model


6


7/61

Research objectivesDevelop through first principles, amathematical/numerical model of the LATSCExperimentally validate the LATSC model

Build a numerical model of a liquid desiccantregenerator(LDR) and couple the model with theLATSC

Optimize the combined system for typical AbuDhabi conditions.

7


8/61

Motivation

ResearchObjectives

LATSC



LDR

Numerical

CombinedLATSC-LDR

Model


8


9/61

Concept

Flat platecollector

TranspiredCollector

LATSC

Water heating

Efficient atdesired heating

temperature

Air heating Convectionsuppression

Low cost9


10/61

The DifferenceFlat Plate w/o suction Flat Plate with suction

10


11/61

Motivation

ResearchObjectives

LATSC



LDR

Numerical

CombinedLATSC-LDR

Model


11


12/61

AssumptionsUniform flow of water in the tubesUniform flow of air through perforationsUniform distribution of perforationsNegligible starting length of boundary layerFlat plateNo leakage

12


13/61

Heat flows from absorber plate

13


14/61

Energy balance on differentialelement

14


15/61


16/61

Coupling of heat transfer at the back of the plate

Air is also heated inthe back channel

Results in coupledheating throughholes and at theback of upper plateand lower plate.

16


17/61

Change in ODE for air heating

Efficiency:

17


18/61

Motivation

ResearchObjectives

LATSC



LDR

Numerical

CombinedLATSC-LDR

Model


18


19/61

Constant Parameters for First andSecond Analysis

Property Value Solar radiation (S) 800W/m 2

Wind speed(V w) 3 m/s

Air temperature(T amb ) 25 oC

Air density( a) 1.184kg/m 3

Air Viscosity ( a) 1.849*10 -5 Ns/m 2

Air C p (c pa ) 1.007kJ/kgK

Water C p 4.183kJ/kgK

Water Density 997 kg/m 3

Length of collector (L) 2m

Width of collector (W) 1m

Plenum depth (D) 0.1m Perimeter of plenum cross

section 2.2m

Plate absorptivity 0.9

Hole pitch (triangular pattern) 0.025m

Plate emissivity 0.9

Hole diameter 0.00159m

Property Value

19

Total thermal capacitance rate:

Air capacitance rate fraction:


20/61

Effect of varying ( c p)total and R c p

Uncoupled Model Coupled Model

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.2 0.4 0.6 0.8 1

E f f i c i e n c y ,

(

- )

Air capacitance rate fraction ,Rmcp (-)

mdotcptot=25W/m2K mdotcptot=20W/m2K mdotcptot=15W/m2K

mdotcptot=10W/m2K mdotcptot=5W/m2K

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.2 0.4 0.6 0.8 1

E f f i c

i e n c y ,

( - )




20


21/61

Effect of varying ( c p)total and R c p

Uncoupled Model Coupled Model

0

10

20

30

40

50

60

70

0 0.2 0.4 0.6 0.8 1

T w o u

t ( o C )




0

10

20

30

40

50

60

70

0 0.2 0.4 0.6 0.8 1

T w o u

t ( o C )




21


22/61

Effect of varying T in at Rc p =0.1,mCp(tot)=15W/m 2K

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0 0.02 0.04 0.06 0.08 0.1 0.12 E

f f i c i e

n c y

,

( -

)

Collector Loss Potential, (Tin-Tamb)/G, (K-m 2/W)

e=0.1(C) e=0.5(C) e=0.9(C) e=0.1(UC) e=0.5(UC) e=0.9(UC)

22


23/61

Effect of varying T in at Rc p =0.5

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.02 0.04 0.06 0.08 0.1 0.12

E f f

i c i e n c y

, (

- )



23


24/61

Effect of varying T in at Rc p =0.9

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.02 0.04 0.06 0.08 0.1 0.12

E f f

i c i e n c y

,

( - )



24


25/61

Parameters Varied for Third AnalysisParameter Values

Air temperature(T amb ) 25,35,45(oC)

Water inlet temperature(T wi) 25-115 (

oC) with 10

oC

intervals Air to total thermal capacitance

fraction( Rc p) 0.1, 0.5

Solar radiation (G) 300, 500, 800 (W/m2)

Wind speed(V w) 0, 3, 5 (m/s)

Plate emissivity ( ) 0.9

25


26/61

Rc p =0.1, (c p)total =15W/m 2K

26

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07

E f f

i c i e n c y

,

( -

)


Vw=5m/s Vw=3m/s Vw=0m/s


27/61


28/61

At ASHRAE 93 standard test flow rate

Wind Speed (m/s) Optimum air thermalcapacitance rate (W/m 2K) Rmcp

1 2.5 0.029

3 5 0.0565 6.5 0.072

Parameter Value

Water flow rate 0.02kg/s-m 2= 83.66W/m 2K

28


29/61

Wind Speed=3m/s

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

0 0.02 0.04 0.06 0.08 0.1 0.12 E f f i c i e n c y

,

( -

)


e=0.1(C) e=0.5(C) e=0.9(C)

29

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

0 0.02 0.04 0.06 0.08 0.1 0.12 E f f i c i e n c y

,

( -

)


e=0.1(C) e=0.5(C) e=0.9(C) Flat Plate Collector


30/61

Motivation

ResearchObjectives

LATSC



LDR

Numerical

CombinedLATSC-LDR

Model


30


31/61

Experimental Setup

Flowmeter

Pumpvalve

Wateroutlet

collector

Outletwatertank

Inlet watertank

Waterinlet 31


32/61

y = -7.126x + 0.6491

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

-0.01 0.01 0.03 0.05 0.07 0.09

E f f i c i e n c y

(Ti-Ta)/G

Flat Plate Collector Testing

32


33/61


34/61

Calibration of flow meter

Flowmeter

Inletwatersupply

Outlet pipewithinserted TC

WatercollectingBucket

Precisionweighingscale

34


35/61

Side View

35


36/61

Front View

36


37/61

Flowmeter Pump

Collectoroutlet

Collector

Water tank

Collectorinlet

LoggerBox

Flange Assembly

Air outlet

Pyranometer

37


38/61

Same Wind Speed (3-4m/s)

y = xR = 1

y = 1.039x - 0.191R = 0.972

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.2 0.3 0.4 0.5 0.6 0.7 0.8

E x p e r i m e n t a

l E f f i c i e n c y

Predicted Efficiency

Predicted vs. Experimental Results

Model

Experiment

38


39/61

Same Air Flow Rate

y = xR = 1 y = 1.1295x - 0.2298

R = 0.9792

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.2 0.3 0.4 0.5 0.6 0.7 0.8

E x p e r i m e n t a

l E f f i c i e n c y

Predicted Efficiency

Predicted vs. Experimental Results

Model

Experiment

Lower windspeed

39


40/61

Model Actual Steady State Transience mainly due to erratic wind speed

Uniform distribution of holes Slightly non-uniform hole distribution with largegaps in between patches near tubes

Flat plate Plate has waviness near top due to soldering

faults

Negligible starting length forboundary layer

Large starting length depending on the windspeed and air suction velocity. For some casesup to full collector length in starting region.

Uniform parallel flow of air

behind absorber plate

Non uniform flow with streamlines crossing due

to pressure drop in across plenum

No leakage in collector shell Finite leakage in setup

Uniform absorptivity of collectorplate surface across the solarspectrum.

Non uniform deposition of paint on the absorberplate and specular reflectance of absorber plate.

40


41/61

Motivation

ResearchObjectives

LATSC



LDR

Numerical

CombinedLATSC-LDR

Model


41


42/61

Liquid Desiccant Regenerator (LDR)Falling film typeCounter flow configurationMany parallel plates

42


43/61

Mass and Energy Balance

43


44/61

Solving Method

44


45/61

Motivation

ResearchObjectives

LATSC



LDR

Numerical

CombinedLATSC-LDR

Model


45


46/61

Combined Model

46


47/61

Solution Procedure

47


48/61

Motivation

ResearchObjectives

LATSC



LDR

Numerical

CombinedLATSC-LDR

Model


48


49/61


50/61

Regenerator Efficiency =

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

R e g e n e r a t i o n E f

f i c i e n c y

R cp

Regeneration Efficiency vs. Rmcp

( cp)total=5 W/m2K

( cp)total=10 W/m2K

( cp)total=15 W/m2K

( cp)total=20 W/m2K

( cp)total=25 W/m2K

50


51/61

Overall Efficiency=

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

O v e r a

l l E f

f i c i e n c y

R cp

Overall Efficiency vs. Rmcp

( cp)total=5 W/m2K

( cp)total=10 W/m2K

( cp)total=15 W/m2K

( cp)total=20 W/m2K

( cp)total=25 W/m2K

51


52/61

Motivation

ResearchObjectives

LATSC



LDR

Numerical

CombinedLATSC-LDR

Model


52


53/61

Optimization Air flow rate, water flow rate and desiccant flowrate required for optimum performance ofcombined LATSC-LDR system

Typical Abu Dhabi conditions to be modeled.

Parameter Value

Solar Radiation 850 W/m 2

Wind Speed 4 m/sHumidity 0.02 kg w/kg daTemperature 27.5 oC

53


54/61

Objective FunctionMaximize desiccant flow rateDesiccant outlet concentration =0.4 kg d/kg w

Genetic Algorithm used to minimize function

54


55/61

Results

Parameter Value

Water thermal capacitance rate 176.0257 W/m 2K

Air thermal capacitance rate 22.7955 W/m 2K

Desiccant flow rate 0.0001172 kg/s

55

Parameter Value

Water thermal capacitance rate 123.0850 W/m 2K

Air thermal capacitance rate 51.7855 W/m 2K

Desiccant flow rate 0.00013771 kg/s

Plate Width =0.5m

Plate Width =1m

Increase in Efficiency= 17.5%


56/61

Conclusion

LATSC Numerical model Sensitivity Analysis shows that optimum R mcp

decreases with increasing mc p(tot) Decreasing emissivity and wind speed increasesefficiency Increasing temperature and solar radiation increases

efficiency

LATSC model partly verified Large discrepancies between model and experiment Experimental conditions deviate from assumptions

56


57/61

Conclusion

Combined LATSC-LDR model Optimum Rmcp decreases with increased

mc p(tot) Regenerator prefers hot water over hot air Role of air to suppress convection

Combined system optimization System optimized for typical Abu Dhabi

conditions57


58/61

Further Work

Retesting of collector with area at least 5m 2

Wind tunnel testing for heat exchange effectiveness of plate in starting region AND/OR CFD Analysis

Changes in numerical model to account for starting region

Optimize the height, width and number of plates in the regenerator

Experimental validation of LATSC-LDR combined system

Numerical model and experimental validation of LATSC-HDH Desalinationsystem

58


59/61

AchievementsInvention DisclosureJournal Publication:

Qadir, A. and P. Armstrong. Liquid-Air Transpired Solar Collector: ModelDevelopment and Sensitivity Analysis . ASME Journal of Solar Energy

Engineering. Under second review

Conference Paper:Qadir, A. and P. Armstrong. Hybrid Liquid-Air Transpired Solar Collector: ModelDevelopment and Sensitivity Analysis in ASME 2010 International MechanicalEngineering Congress & Exposition . 2010. Vancouver, Canada: ASME.

Potential/Upcoming Publications:Experimental validation of LATSCLATSC-LDR modeling and optimization for hot humid climatesLATSC-HDH Desalination modeling and optimization

59


60/61

AcknowledgementsDr Peter ArmstrongRSC membersDr Matteo ChiesaLENS group:

Steven MeyersMarwan MokhtarMuhammad Tauha Ali

Irene RubalcabaDr Pawan Singh

All my kith and kin for providing moral and physicalsupport

60


61/61

THANK YOU!

liquid-air transpired solar collector (latsc): model development, validation and optimization-thesis...

Documents