qra - khon kaen universitythis paper presented an experimental study in order to increase the...

170

The International Conference on Sustainable Community Development27-29 January 2011

Increase of performance in ethanol distillation for the basin solar still with fin

Rattanapol Panomwan Na Ayuthaya*1, Pichai Namprakai1 and Wirut Ampun2

1Division of Energy Technology, School of Energy Environment and Materials, King Mongkut’s University of Technology Thonburi,

Thungkhru, Bangkok 10140, Thailand 2Agricultural Research Technology Institute, Rajamangala University of Technology Lanna, Lampang 52000, Thailand.

*Corresponding author: [email protected]; [email protected]

Abstract This paper presented an experimental study in order to increase the performance of the ethanol solar still of basin type by using fin. The 0.7 x 0.7 x 1 m constructed stainless-steel still had a horizontal evaporating surface and the condensing surface inclined 14o to a horizontal, which was suggested to be the optimum for the transmission of an incident solar radiation and could prevent the condensate from dropping back to the basin. The 0.7 x 0.7 x 0.04 m fin was attached to the basin of the still. The concentrations of the solution input to the still were 10%v/v measured by alcoholmeter. The distillation temperatures varied from 40 to 70oC. The temperature measurements were made both at the evaporating and condensing surfaces of the still by type-K thermocouples. This experiment was carried out at outdoor conditions. It was found that 32.69% efficiency of the solar still with fin was achieved, compared to 28.28% efficiency of the solar still without fin. The predicted output by the model was found to agree fairly well with results of the experiments.

Keywords: Basin solar still, Ethanol distillation, Fin, Sustainable energy

1. Introduction The distillation of ethanol by solar energy is a method to use free energy to increase the alcohol concentration. The basin solar still can be developed as an effective devise for a ethanol distillation [1, 2]. But the yield of the single basin solar still is not high enough. To augment the productivity of the solar still, several research works were carried out. Badran et al. [3] and Tiris et al. [4] integrated a flat plate collector with a single basin solar still. Hijileh et al. [5] used sponge cubes in the saline water to improve the evaporation rate. Nafey et al. [6] used the black rubber. Moreover, Velmurugan et al. [7, 8] used fins for increasing productivity of liquid waste still. The objective of this work is to increase the performance of the solar still integrated with fin at the basin plate. The ethanol solution is of 10% concentration as a feed. The studied result showed a comparison between the test and

the model.

2. Experimental setup An experimental still is shown in Fig. 1. The basin

solar still of 0.70 m x 0.70 m area with a glass cover of 14o

inclination and the average height of 10.3 cm on a 100 cm

stand was constructed. A fin size is 0.7 x 0.7 x 0.04 m in Fig. 2

that is acting as an extended surface for increasing the solution

temperature and hence productivity rate. This fin can decrease

the preheating time required for evaporation in the still basin.

It could increase the area of the absorber plate that transfers

heat to the basin water. Consequently, it increases temperature

of the ethanol solution. Thus, the temperature difference between

solution and glass cover increases hence productivities increase.

The ethanol solution temperature was within the range of

40-70oC. The ethanol solution input with known concentration of

10%v/v was fed continuously to keep the solution concentration

constant during the test period.

Fig. 1 Basin solar still

The experiments were carried out under outdoor

condition. The temperatures of the evaporating and condensing

surfaces were monitored by a set of K-type thermocouples and

concentration of products was read by the alcoholmeter. The

production rate was read directly by a measuring cylinder.

Fig. 2 Fin

Increase of performance in ethanol distillation for the basin solar still with fin

Rattanapol Panomwan Na Ayuthaya*1, Pichai Namprakai1 and Wirut Ampun2

1Division of Energy Technology, School of Energy Environment and Materials, King Mongkut’s University of Technology Thonburi, Thungkhru, Bangkok 10140, Thailand

2Agricultural Research Technology Institute, Rajamangala University of Technology Lanna, Lampang 52000, Thailand.

*Corresponding author: [email protected]; [email protected]

Abstract

This paper presented an experimental study in order to increase the performance of the ethanol solar still of basin type by using fin. The 0.7 x 0.7 x 1 m constructed stainless-steel still had a horizontal evaporating surface and the condensing surface inclined 14o to a horizontal, which was suggested to be the optimum for the transmission of an incident solar radiation and could prevent the condensate from dropping back to the basin. The 0.7 x 0.7 x 0.04 m fin was attached to the basin of the still. The concentrations of the solution input to the still were 10%v/v measured by alcoholmeter. The distillation temperatures varied from 40 to 70oC. The temperature measurements were made both at the evaporating and condensing surfaces of the still by type-K thermocouples. This experiment was carried out at outdoor conditions. It was found that 32.69% efficiency of the solar still with fin was achieved, compared to 28.28% efficiency of the solar still without fin. The predicted output by the model was found to agree fairly well with results of the experiments. Keywords: Basin solar still, Ethanol distillation, Fin, Sustainable energy 1. Introduction The distillation of ethanol by solar energy is a method to use free energy to increase the alcohol concentration. The basin solar still can be developed as an effective devise for a ethanol distillation [1, 2]. But the yield of the single basin solar still is not high enough. To augment the productivity of the solar still, several research works were carried out. Badran et al. [3] and Tiris et al. [4] integrated a flat plate collector with a single basin solar still. Hijileh et al. [5] used sponge cubes in the saline water to improve the evaporation rate. Nafey et al. [6] used the black rubber. Moreover, Velmurugan et al. [7, 8] used fins for increasing productivity of liquid waste still.

The objective of this work is to increase the performance of the solar still integrated with fin at the basin plate. The ethanol solution is of 10% concentration as a feed. The studied result showed a comparison between the test and the model.

2. Experimental setup An experimental still is shown in Fig. 1. The basin solar still of 0.70 m x 0.70 m area with a glass cover of 14o inclination and the average height of 10.3 cm on a 100 cm stand was constructed. A fin size is 0.7 x 0.7 x 0.04 m in Fig. 2 that is acting as an extended surface for increasing the solution temperature and hence productivity rate. This fin can decrease the preheating time required for evaporation in the still basin. It could increase the area of the absorber plate that transfers heat to the basin water. Consequently, it increases temperature of the ethanol solution. Thus, the temperature difference between solution and glass cover increases hence productivities increase. The ethanol solution temperature was within the range of 40-70oC. The ethanol solution input with known concentration of 10%v/v was fed continuously to keep the solution concentration constant during the test period.

Fig. 1 Basin solar still The experiments were carried out under outdoor condition. The temperatures of the evaporating and condensing surfaces were monitored by a set of K-type thermocouples and concentration of products was read by the alcoholmeter. The production rate was read directly by a measuring cylinder.

Fig. 2 Fin

3. Theoretical analysis Assumption and descriptions used in the mathematical model of the still are as follows:

1. Ethanol solution, basin wall and absorber are at the same temperature.

2. Total pressure in the vapor phrase around 1 atm.

3. The movement of the vapors from the evaporating surface to the condensing surface is under the effect of the buoyancy force only.

The energy balance in the basin solar still

was shown in Fig.3. The solar energy absorbed (Fig. 3) by the ethanol solution, the basin wall and the absorber is equal to the energy used for evaporation, energy transfer by convection and radiation to the cover plus heat losses through the still walls to the surroundings and energy stored in the ethanol solution, the basin wall and the absorber. [9, 10]

Fig. 3 Heat streams in the solar still

dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar

energy absorbed by the ethanol solution, the basin wall and the absorber and A is the absorber area. The solar energy absorbed by the cover plus energy transfer by evaporation, convection and radiation from the ethanol solution to the cover is equal to the energy stored by the cover plus heat convection by wind and thermal radiation to the surrounding.

raqcaqdtgdT

gpmcrqcqeq sAHg

(2) Heat transfer by evaporation of the ethanol solution may be calculated based on the Spalding’s work. [11, 12]

Ahmq fgiiie

"2

1. (3)

The ethanol and water mass transfer rated in the still can be calculated from eq. (4):

B1lngm" (4) Where B is the driving force obtained from eq. (5).

Ti,mMi,mMi,mGi,mB (5)

Mass transfer conductance (g) in the solar still is experimentally obtained from the indoor experiment with 10%v/v ethanol solution (eq.6).

0.9615(Gr.Sc)5-10DgL ρ (6)

Where is density of the ethanol, water and air mixture. D is diffusivity of the ethanol, water and air mixture. Heat convection within the still can calculated from eq. (7)

gMcc TTAhq (7) The radiative heat transfer between glass and sky was given by eq. (8)

44 273273 skyggra TTAq (8) Where the sky temperature is calculated from eq. (9) [13]:

2732730552.0 5.1 asky TT (9) The energy losses by wind to surroundings are estimated from eq. (10)

agcaca TTAhq (10) Where Vhca 38.2 . V is wind speed in m/s.

HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

171


3. Theoretical analysis Assumption and descriptions used in the mathematical

model of the still are as follows:

1. Ethanol solution, basin wall and absorber are at

the same temperature.


3. The movement of the vapors from the evaporating

surface to the condensing surface is under the

effect of the buoyancy force only.

The energy balance in the basin solar still was shown

in Fig.3. The solar energy absorbed (Fig. 3) by the ethanol

solution, the basin wall and the absorber is equal to the energy

used for evaporation, energy transfer by convection and

radiation to the cover plus heat losses through the still walls to

the surroundings and energy stored in the ethanol solution, the

basin wall and the absorber. [9, 10]


(1)

Where

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

is the solar energy

absorbed by the ethanol solution, the basin wall and the

absorber and A is the absorber area. The solar energy absorbed

by the cover plus energy transfer by evaporation, convection and

radiation from the ethanol solution to the cover is equal to the

energy stored by the cover plus heat convection by wind and

thermal radiation to the surrounding.

(2)

Heat transfer by evaporation of the ethanol solution may be

calculated based on the Spalding’s work. [11, 12]

(3)

The ethanol and water mass transfer rated in the still can be

calculated from eq. (4):

(4)

Where B is the driving force obtained from eq. (5).

(5)

Mass transfer conductance (g) in the solar still is experimen-

tally obtained from the indoor experiment with 10%v/v ethanol

solution (eq.6).

(6)

Where W is density of the ethanol, water and air mixture. D is

diffusivity of the ethanol, water and air mixture. Heat convection

within the still can calculated from eq. (7)

(7)

The radiative heat transfer between glass and sky was given

by eq. (8)

(8)

Where the sky temperature is calculated from eq. (9) [13]:

(9)

The energy losses by wind to surroundings are estimated from

eq. (10)

(10)

Where

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

. V is wind speed in m/s.

The energy losses from the ethanol solution through the still

wall to surroundings is

(11)

Where

The energy losses from the ethanol solution through the still wall to surroundings is

aMs TTUAq (11) Where U is the overall loss coefficient obtained

from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is

the material thickness and ki is the thermal conductivity which are the still wall properties.

Vhca 8.37.5' (12) Where '

cah combines the effect of wind and thermal radiation [13] The daily efficiency, ( i ) is obtained by summing up the hourly condensate product (alcohol, water) m, multiplied by the latent heat of vaporization fgh and

divided by the daily solar radiation tI .

tIwfghwmalcfghalcm

i

,,

(13)

4. Results and discussion After addition of fin to the bottom of the still, the fin plate could absorb the solar radiation as the increase of the area plate absorber of 0.128 m2 and the decrease of preheating time in the ethanol solution. It was found that when the fin is used at the bottom of the still, the daily efficiency of distillation unit was increased to 32.7% as shown in Fig. 4.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2

ExperimentalTheoretical

Fig. 4 Effect of the fin in the basin solar still

The experimental result was relevant to the theoretical model of distillation rate. When the absorber area was 0.49 m2, the 28.3% daily efficiency of distillation was obtained. (Fig. 5)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2

ExperimentalTheoret ical

Fig. 5 Effect of no fin in the basin solar still

5. Conclusion The basin solar still with fin could increase productivity. Adding fin to the basin could decrease the preheating time required for evaporating in the still basin as an extended fin surface could increase the absorbing area and the solution temperature including the productivity rate. The experimental results showed that the daily production was higher when fin was integrated in the still. The experimental productivity agreed well with the calculation. 6. References [1] Kiatsiriroat T, Bhattacharaya SC and Wibulsawas P. (1968) Prediction of mass transfer in solar still. Energy 11: 881-886. [2] Namprakai P and Hirunlabh J. (2007) Theoretical and Experimental Studies of an Ethanol Basin Solar Still. Energy 32: 2376-2384. [3] Badran AA, Al-Hallaq AA, Eyal Salman IA and Odat MZ. (2005) A solar still augmented with a flat plate collector. Desalination 172: 227-234. [4] Tiris C, Tiris M, Erdalli Y and Sohmen M (1998) Experimental studied on a solar still coupled with a flat-plate collector and a single basin still. Energy Convers Manage 39: 853-856. [5] Abu-Hijileh Bassam A/K and Rababa’h Himzeh M. (2003) Experimental study of a solar still with sponge cubes in basin. Energy Convers Manage 44: 1411-1418. [6] Nafey AS, Abdelkader M, Abdelmotalip A and Mabrouk A.A. (2001) Solar still productivity enhancement. Energy Convers Manage 42: 1401-1408. [7] Velmurugan V, Gopalakrishnan M, Raghu R and Srithar K. (2008) Single basin solar still with fin for enhancing productivity. Energy Convers Manage 49: 2602-2608. [8] Velmurugan V, Deenadayalan CK, Vinod H and Srithar K. (2008) Desalination of effluent using fin type solar still. Energy 33: 1719-1727. [9] Zurigat YH and Abu-Arabi MK (2004) Modeling and performance analysis of a regenerative solar desalination unit. Appl Thermal Eng 24: 1061-1072.

is the overall loss coefficient obtained from



from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




, w h e n



from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




i s t h e

material thickness and ki is the thermal conductivity which are

the still wall properties.

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta



from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

Fig. 2 Fin








dtMdT

Sq

rqcqeqSAHMM

ApmCMpmC

gAg

(1)

Where SAHMM

gAg is the solar


raqcaqdtgdT

gpmcrqcqeq sAHg


Ahmq fgiiie

"2

1. (3)





0.9615(Gr.Sc)5-10DgL ρ (6)






HS

qS

qr qe qc

Tw

Tg

ethanol

Ta

172


(12)

Where



from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




combines the effect of wind and thermal radiation

[13]

The daily efficiency,



from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




is obtained by summing up the

hourly condensate product (alcohol, water) m, multiplied by the

latent heat of vaporization



from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




and divided by the daily solar

radiation



from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




.

(13)

4. Results and discussion After addition of fin to the bottom of the still, the fin

plate could absorb the solar radiation as the increase of the area

plate absorber of 0.128 m2 and the decrease of preheating time

in the ethanol solution. It was found that when the fin is used at

the bottom of the still, the daily efficiency of distillation unit was

increased to 32.7% as shown in Fig. 4.


The experimental result was relevant to the theoretical model of

distillation rate. When the absorber area was 0.49 m2, the 28.3%

daily efficiency of distillation was obtained. (Fig. 5)


5. Conclusion The basin solar still with fin could increase productivity.

Adding fin to the basin could decrease the preheating time

required for evaporating in the still basin as an extended fin

surface could increase the absorbing area and the solution

temperature including the productivity rate. The experimental

results showed that the daily production was higher when fin

was integrated in the still. The experimental productivity agreed

well with the calculation.

6. References[1] Kiatsiriroat T, Bhattacharaya SC and Wibulsawas P.

(1968) Prediction of mass transfer in solar still. Energy 11:

881-886.

[2] Namprakai P and Hirunlabh J. (2007) Theoretical and

Experimental Studies of an Ethanol Basin Solar Still. Energy

32: 2376-2384.

[3] Badran AA, Al-Hallaq AA, Eyal Salman IA and Odat MZ.

(2005) A solar still augmented with a flat plate collector.

Desalination 172: 227-234.

[4] Tiris C, Tiris M, Erdalli Y and Sohmen M (1998) Experimental

studied on a solar still coupled with a flat-plate collector and

a single basin still. Energy Convers Manage 39: 853-856.

[5] Abu-Hijileh Bassam A/K and Rababa’h Himzeh M. (2003)

Experimental study of a solar still with sponge cubes in

basin. Energy Convers Manage 44: 1411-1418.

[6] Nafey AS, Abdelkader M, Abdelmotalip A and Mabrouk

A.A. (2001) Solar still productivity enhancement. Energy

Convers Manage 42: 1401-1408.

[7] Velmurugan V, Gopalakrishnan M, Raghu R and Srithar

K. (2008) Single basin solar still with fin for enhancing

productivity. Energy Convers Manage 49: 2602-2608.

[8] Velmurugan V, Deenadayalan CK, Vinod H and Srithar

K. (2008) Desalination of effluent using fin type solar still.

Energy 33: 1719-1727.

[9] Zurigat YH and Abu-Arabi MK (2004) Modeling and

performance analysis of a regenerative solar desalination

unit. Appl Thermal Eng 24: 1061-1072.

[10] ElSherbiny SM and Fath HES. (1993) Solar distillation under

climatic conditions of Egypt. Renewable Energy 3(1): 61-65.

[11] Splading DB. (1963) Convective mass transfer. London:

Edward Arnold.

[12] Namprakai P, Hirunlabh J and Kiatsiriroat T. (1997) Ethyl

alcohol distillation in a basin solar still. Renewable Energy

11(2): 169-175.

[13] Duffie JA and Beckman WA. (1991) Solar engineering of

thermal processes. New York: John Wiley & Sons Inc.

NomenclatureA area of the absorber or the glass cover, m2

B driving force

Cp specific heat, J/kg K

Gr Grashof number, L3Δρg/ρν2



from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2






from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2






from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2






from

'1

111

cahUU, when

i

ii kx

U1

1 , xi is


Vhca 8.37.5' (12) Where '



tIwfghwmalcfghalcm

i

,,

(13)


0.0

0.1

0.2

0.3

0.4

0.5

0.6

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

8 9 10 11 12 13 14 15 16 17 18

Time, h

Prod

uctiv

ity, k

g/m2 /h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Sola

r in

tens

ity, k

W/m

2




173


g mass transfer conductance, kg/m2 s

g acceleration of gravity, 9.806 m/s2

Hs total solar radiation on horizontal surface, W/m2

hfg latent heat, J/kg

hc convective heat transfer coefficient,W/m2 K

hca convective heat transfer coefficient from the cover to

the surroundings, W/m2 K

h’ca heat loss coefficient which combines both convection

and radiation effects at the outside walls of the still,

W/m2 K

L mean still height, m

m mass, kg

mi mass fraction of a component i

miT transfer mass fraction of a component i

m” total mass transfer rate, kg/m2 s

m”i mass transfer rate of a component i, kg/m2 s

qc heat stream by convection from the ethanol solution

to the glass cover, W

qca heat loss by convection from the cover to the

surroundings, W

qe heat of evaporation from the ethanol solution, W

qr heat stream by radiation from the ethanol solution to

the glass cover, W

qra heat loss by radiation from the cover to the sky, W

qS total heat loss from the ethanol solution, the basin wall

and the absorber through the bottom and the walls of

the still to the surroundings, W

Sc Schmidt number

T temperature, oC

Ta ambient temperature, oC

Tg temperature of glass cover, oC

TM temperature of ethanol solution, absorber and basin

wall, oC

Tsky

sky temperature, oC

t time, s

U overall loss coefficient from the bottom and the wall

of the still to the surroundings, W/m2 K

V wind speed, m/s

V diffusion volumes, cm3/g-mole

x wall material thickness, m

Greek symbols

α absorptivity

ε emissivity

ρ density, kg/m3

ν kinematic viscosity, m2/s

τ transmissivity

σ Stefan-Boltzmann constant, 5.67 x 10-8 W/m2K4

%v/v percent by volume of ethanol

Subscripts

A the absorber and the basin wall

G condensing surface

g glass cover

i,j,k ethanol water and air, respectively

M ethanol solution

S evaporating surface

T transfer

qra - khon kaen universitythis paper presented an experimental study in order to increase the...

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