Performance Analysis of Single Slope Solar Still

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

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Performance Analysis of Single Slope Solar Still Dinesh Kumar

1, Patel Himanshu

2, Zameer Ahmad

3

M.Tech Student, Alternate Hydro Energy Centre, Indian Institute of Technology, Roorkee

Uttarakhand- 247667

Abstract-- This paper presents evaluation of performance of

solar water distillation using solar still. Solar distillation

represents a most attractive and simple technique among

other distillation processes, and it is especially suited to small-

scale units at locations where solar energy is considerable. in

this we have calculated internal heat transfer coefficient and

the mass output hourly basis. The effect of depth of water and

inclination of tilted glass on water output is also evaluated.

The performance analysis is carried out by developing Matlab

Simulink based model and result obtained is verified by

experimental setup.

Keywards-- Solar still, internal heat transfer coefficient,

Matlab/ Simulink, distillation, inclination of tilted glass

I. INTRODUCTION

The fresh water crisis is already evident in many parts of

India, varying in scale and intensity at different times of the

year. The fresh water crisis is not the result of natural

factors, but has been caused by human actions. India’s

rapidly rising population and changing lifestyles also

increases the need for fresh water. Widespread pollution of

surface and groundwater is reducing the quality of fresh

water resources. Most of the conventional Water

distillation processes are highly energy consuming and

require fossil fuels as well as electric power for their

operation. A solar still, however, employs a comparably

shallow water basin located inside a fully closed,

greenhouse like structure. Water vapour generated inside

the still condenses at the inner side of its transparent cover,

which is convectively cooled from the outside by natural

airflow. Dunkle [1] who derived a widely used as well as

analyzed, semi empirical relation for evaluating the internal

heat and mass transfer within solar distillation units. This

empirical relation is popularly known as Dunkle’s relation.

Malik et al. [2] then summarized a historical review on

solar distillation systems, Tiwari and Lawrence [3]

attempted to incorporate the effect of inclination of the

condensing surface using the same values of C and n as

proposed by Dunkle. Kumar and Tiwari [4] developed a

thermal correlation for outdoor conditions based on linear

regression analysis to determine convective mass transfer

for a varying range of Grashof numbers.

Tripathi and Tiwari [5] thereafter applied the correlation

of Kumar and Tiwari [4] to evaluate the internal heat and

mass transfer correlations for active solar distillation for a

very small inclination of condensing cover in winter

climatic conditions.[6] Anil Kr. Tiwari and G. N. Tiwari

evaluated Effect of Cover Inclination and Water Depth on

Performance of a Solar Still.

This paper comprises of six section. in section two we

discussed mathematical model and in section three Matlab

block diagram is discussed. Experimental setup is

discussed in section four. While simulation result,

experimental result, and conclusion are presented in section

five and six respectively.

II. MATHEMATICAL MODEL OF SOLAR STILL

These are the following equations which are presenting

the solar still system.

Temperature dependent physical properties of vapor

Cp =999.2+0.1434 x Tv + 1.101 x 10-4

x Tv2-6.7581x 10

-8x

Tv3 (1)

ρ =353.44/(Tv x 273.15) (2)

k=0.0244 x 0.7673 x 10-4

x Tv (3)

μ=10718 x 10-5

+ 4.620 x 10-8

xTv (4)

L=3.1615x106x[1-(7.616x10

-4xTv)]; (5)

Pci=exp[25.317 – 5144/(Tci + 273)] (6)

Pw =exp[25.317 – 5144/(Tw + 273)] (7)

β=1/(Tv + 273.15) (8)

Thus the heat transfer per unit area per unit time

evaporation from the water surface to glass cover

qew = hew (Tw-Tci) (9)

The relation between evaporative heat transfer

coefficient and convective heat transfer coefficient

hew = 0.016273*hcw*(Pw-Pci / Tw-Tci) (10)

hew = 0.016273*[(k/a)c(Gr.Pr)n*(Pw-Pci/ Tw-Tci)] (11)

qew= 0.016273*[(k/d)c(Gr.Pr)n*(Pw-Pci / Tw-

Tci)*(Tw-Tci)] (12)



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It can also be written as

qew = hew (Tw-Tci) (13)

The rate of mass transfer mew is given by

me = qew/L (14)

mw=.0163(Pw-Pci)(k/d)c(Gr.Pr)n*(3600/L)*Aw (15)

III. MATLAB SIMULINK MODEL

The above system equations (1)-(15) are implemented

in Matlab simulink bloc diagram shown in figure 1 and its

sub system block diagram are shown in figure 2.

Fig.1.bloc diagram of solar still

Fig.2. sub system solar still

IV. EXPERIMENTAL SETUP

The installed experimental setup is shown in Fig.3

Experiments are performed for both stills with different

depth of water to three consecutive days and the following

data are observed as temperatures at water surface, inner &

outer surface of glass and ambient condition, global and

diffuse radiation and yield are recorded hourly basis round

the clock.

Fig.3.Experimental setup of solar distillation with two different

inclination of glass cover

Fig.4.Instruments used

V. RESULT AND DISCUSSION

These figures 5 and 6 indicate that the internal heat

transfer coefficients decrease with the increase of water

depth in the basin due to decrease in the temperature

difference between the glass and water temperature.

Further it is important to note that the fluctuation in internal

convective heat transfer coefficient decreases with the

increase of water depth due to storage effect presents the

theoretical and experimental results of the hourly yield for

the studied water depths in the basin. From it is observed

that there is a fair agreement between the experimental and

theoretical results for 0.05 m water depth in the basin.

However, for higher depths (0.10 m and 0.15 m), the

fluctuation between the experimental and theoretical results

is large.



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Fig.5.Variation of convective heat transfer coefficient(hc) from Tiwari

model vs time

Fig.6.Explanation given for solar still with inclination angle of 30

degree is same as in this case also.

A. Comparison Of Ig For Both Still

The global radiation for both the still varies with almost

same characteristics and it is found higher during time

interval 11am to 2 pm in this interval the global radiation is

almost 1000 to 1050W/m2. And the comparison of the Ig

for same depth of water separately for both still is also

illustrated in fig as this varies almost similar way there is

no more deviation found.

Fig.7.global radiation vs time at 30 degree

Fig.8. global radiation vs time at 23 degree

B. Comparison Of Id For Both Still

The diffused radiation for both still at different water

level as illustrated below and it is found that the higher

value is found in case of 15cm depth of water for both still

at different angle of inclination. the higher value is found

during time interval 12noon to 1pm and its value is reach

up to179W/m2 for both still.The graph of defused radiation

for both still at different level of water separately is also

shown and it also varies with similar way and higher value

is found at 15cm depth of water for both still.

Fig.9. diffuse radiation vs time at 23 degree

Fig.10.diffuse radiation vs time at 30 degree



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C. Comparision Of Tw For Both Still

The variation of temprature of water for both still at

different water level is illustrated and is found its value

higher when the depth of water is minimum and its value is

approximately 54 degree in all cases either seperately at

different level or combined for both the still. And its value

is higher during time 1to 2 pm and water temprature varies

similarly for different depth at difffrent angle of

onclination.

Fig.11.Water temp vs time at 30 degree

Fig.12.Water temp vs time at 23 degree

D. Comparision Of Tgi For Both Still

The variation of temprature of inner glass surface with

different glass cover inclination at difrent depth of water is

illustrated its variation is similar for both still and higher

value is also same for all depth of watereither seperately or

combined and its value is approximately equal to52 degree

centigrate and it is found during 1pm to 2pm.

Fig.13.inner glass temp vs time at 30 degree

Fig.14.inner glass temp vs time at 23 degree

E. Comparision Of Tgo For Both Still

The variation of temprature of outer glass surface with

different glass cover inclination at difrent depth of water is

illustrated its variation is similar for both still and higher

value is also same for all depth of watereither seperately or

combined and its value is approximately equal to51 degree

centigrate and it is found during 1pm to 2pm.

Fig.15.outer glass temp vs time at 30 degree



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Fig.16.outer glass temp vs time at 23 degree

F. Comparision Of Yeild For Both Still

The variation of yield with different angle of inclination

of different depth of water is illustrated bellow . the value

of yeild is found higher at 5cm depth of water for both the

still during 3pm to 4pm but when the grapf is ploted

seperately at same depth of water and different angle of

inlination is also shown.the higher value is found in 30

degree angle of inclination for all the depth of water

seperately and it is found during same time intervalas

above for combined graph.

0 2 4 6 8 10 12 14 16 18 20 22 240

10

20

30

40

50

60

70

80Yield (ml) VS Time (hr) at 30 deg inclination

TIME (hr)

YIE

LD

(m

l)

5 cm depth

15 cm depth

10 cm depth

Fig.17.Yield vs time at 30 degree by simulation

Fig.18.Yield vs time at 30 degree by experiment

0 2 4 6 8 10 12 14 16 18 20 22 240

20

40

60

80

100

120Yield (ml) vs Time (hr) at 23 deg inclination

TIME (hr)

YIE

LD

(m

l)

5 cm depth

10 cm depth

15 cm depth

Fig.19.Yield vs time at 23 degree by simulation

Fig.20.Yield vs. time at 23 degree by experiment



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G. Comparision Of Efficiency For Both Still

The variation of efficiency with different angle of

inclination of different depth of water is illustrated bellow .

the value of efficiency is found higher at 5cm depth of

water for both the still during 3pm to 4pm but when the

grapf is ploted seperately at same depth of water and

different angle of inlination is also shown.the higher value

is found in 30 degree angle of inclination for all the depth

of water seperately and it is found during same time

intervalas above for combined graph.

5 6 7 8 9 10 11 12 13 14 150

5

10

15

20

25

30efficiency vs water depth

depth of water(cm)

Eff

icie

ncy(%

)

30 degree inclination

23 degree inclination

Fig.21.Efficiency vs. depth of water by simulation

Fig.22.Efficiency vs. depth of water by experiment

VI. CONCLUSION

The performance analysis of solar still is carried out by

developing Matlab model and result obtained is verified by

experimental setup.Dynamic system simulation studies

demonstrate the effectiveness of the proposed single slope

solar still.

The investigation is carried out for 30 degree and 23

degree inclination, based on this investigation it is

concluded that 30 degree inclination of solar still is more

efficient and effective for all point of view as heat transfer

coefficients, yield, global radiation diffused radiation for

the month of April.

Nomenclature

Cp = Specific heat

ρ = Density

k =Thermal conductivity

μ =Viscosity

L =Latent heat of Vaporization of water

Pci=Partial saturated Vapor pressure at condensing cover

temperature

Pw=Partial saturated vapor pressure at water

temperature

β=Expansion factor

hew= evaporative heat transfer coefficient

hcw= convective heat transfer coefficient.

Tw=water surface temperatue

Tci=glass inner temperature,

Tv=vapor temperature

qew= heat transfer per unit area per unit time

mew= rate of mass transfer, kg/s

Pr = Prandtl number

Gr= Grashoff’s number

d=depth of water in cm

Aw =evaporative surface area, m2

REFERENCES

[1 ] Dunkle, R. V., 1961, “Solar Water Distillation: The Roof Type Still and a Multiple Effect Diffusion Still,” Proceedings of the

International Development in Heat Transfer, ASME, University of

Colorado, Pt. V, p. 895.

[2 ] Malik, M. A. S., Tiwari, G. N., Kumar, A.,and Sodha, M. S., 1982,

Solar Distillation, Pergamon, London.

[3 ] Tiwari, G. N., and Lawrence, S. A., 1999, “New Heat and Mass

Transfer Relations for a Still,” Energy Convers. Manage., 31, pp.

201–203.

[4 ] Kumar, S., and Tiwari, G. N., 1996, “Estimation of Convective Mass

Transfer in Solar Distillation System,” Sol. Energy, 57, pp. 459–464.

[5 ] Tripathi, R., and Tiwari, G. N., 2005, “Effect of Water Depth on

Internal Heat and Mass Transfer for Active Solar Distillation,”

Desalination, 173, pp. 73–88

[6 ] Anil Kr. Tiwari and G. N. Tiwari”Effect of Cover Inclination and

Water Depth on Performance of a Solar Still for Indian Climatic Conditions” Journal of Solar Energy Engineering, MAY 2008, Vol.

130 / 024502-1

[7 ] Tiwari, A. Kr., and Tiwari, G. N., 2006, “Effect of Water Depth on Heat and Mass Transfer in a Passive Solar Still: In Summer,”

Desalination, 195, pp. 78–94.



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[8 ] Tiwari, G. N., 2002, Solar Energy, 1st ed., Narosa, New Delhi/CRC,

New York, p. 506.

[9 ] Anil Kumar, G.N. Tiwari, “Thermal modeling of a natural convection greenhouse drying system for jaggery: An experimental

validation,” Solar Energy 80 (2006) 1135–1144.

[10 ] Rajesh Tripathi and G.N. Tiwari, Thermal modeling of passive and

active solar stills for different depths by using concept of solar

fraction, solar energy., 80 (2006) 956-967.

[11 ] Bala, B.K., Mondol, M.R.A., Biswas, B.K., Das Chowdury, B.L.,

Janjai, S., 2003. Solar drying of pineapple using solar tunnel drier.

Renewable Energy 28 (2), 183–190.

Documents

Performance Analysis of Single Slope Solar Still