Thermal Performance and Analysis of Low Cost Spherical Solar Still With Charcoal Absorber

8/18/2019 Thermal Performance and Analysis of Low Cost Spherical Solar Still With Charcoal Absorber

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INTRODUCTION :

We may not able to separate the two important words, water and the environment. These are

the most essential part of or life !y!le. The world is pollted de to the in!reasin" the poplation and the needs of the hman bein"s. #o the whole environment bein" !ollapsed at the

rapid rate. $bot %&' of the world water is salt water in the o!eans: (' of all fresh water is in"rond water, la)es and rivers, whi!h is spply the most that needed by the hman and animals.

#o every hman and animals were depends on the "rond water sor!e and the rivers. *t thesesor!es are also "ettin" destroyed by the fast "rowin" fa!tories and !hemi!al wastes. The world+s

water !onsmption rate is doblin" every - year, in!reasin" two times the rate of poplation

"rowth. It is proe!ted that by the year -/, water demand will e0!eed spply by /1', de to persistent re"ional dro"hts, shiftin" of the poplation to rban !oastal !ities, and indstrial

"rowth. The spply of fresh water is on the de!reasin" mode, whereas water demand for food,

indstry and people is on the risin" mode. 2a!) of fresh water red!es e!onomi! developmentand lowers livin" standards. There is an important need for !lean and pre drin)in" water in

many developin" !ontries. Often water sor!es are bra!)ish 3i.e. !ontain dissolved salts4 and5or

!ontain harmfl ba!teria, hen!e !annot be sed for drin)in". In addition, there are many !oastallo!ations where seawater is abndant bt potable water is not available. 6re water is also sefl

for batteries, hospitals and s!hools. Distillation is one of many pro!esses that !an be sed for

water prifi!ation. This re7ires an ener"y inpt li)e heat8 solar radiation !an also be a sor!e of

ener"y in this pro!ess. Water "ets evaporated, and separated as water vapor from dissolvedmatter, whi!h is !ondensed as pre water. Desalination powered renewable ener"y sor!es !an

be an ideal soltion for small s!ale !ommnities, where affordable fossil fel spply is not

available 9;. $ solar still is a devi!e by whi!h distilled or portable water !an be prod!ed fromsaline water sor!es li)e s!h as sea water or bra!)ish water. #olar stills are normally sed to

provide small s!ale portable water needed in remote isolated lo!ations 9;. $ review of varios

desi"ns of solar stills was made by <ali) et al., 9(;. The different desi"ns of solar stills 9=; were

stdied by $l>?aye) and *adran. $l>?ssaini and #mith sed va!m te!hnolo"y 9/;, @alo"iro91; desi"ned a paraboli! tro"h solar stills and Al>#ebaii developed triple basin solar stills 9&; for

enhan!in" prod!tivity from the solar stills. In order to improve the performan!e of !onventional

solar stills, several other desi"ns have been developed s!h as the doble basin type 9B;, mlti basin type 9%;, inverted tri!)le 9-; and pyramid type 9;.

The aim of the wor) is to stdy the performan!e of newly desi"ned spheri!al solar still with

and withot !har!oal absorber. The distilled water otpt and effi!ien!y are also !ompared between both stdies.

abri!ation details of the spheri!al solar still :

i". shows the pi!torial view of #pheri!al #olar #till. i". shows the s!hemati! dia"ram of

-.(- m spheri!al solar still. The total hei"ht of the still is abot -.1( m. The still !onsists of!ir!lar basin of diameter -.1- m whi!h is made p of steel. The !ir!lar absorber basin is !oated

with bla!) paint for ma0imm absorption of in!ident solar radiation. The !ir!lar basin is fi0ed

at the middle of the spheri!al alminm rin" li)e a mesh at radial hei"ht of -.B m where saline

water is stored. The stora"e !apa!ity of the basin is arond 1 litres. The basin in the spheri!alsolar still is fitted withot havin" any physi!al !onta!t with the top !over made of low density

polyethylene sheet. The low density polyethylene sheet of thi!)ness -.-& mm is spread over the



spheri!al shaped rin" li)e a mesh. $ "ap of -.-( m is maintained between the !ir!lar basin and

top !over. The oter !over of polyethylene is molded over the still withot any air "ap to prevent

vapor lea). The evaporated water whi!h is !ondensed over the top !over passes between this "apand !reeps down towards the distilled water !olle!tion se"ment. The !alibrated thermo!oples

are sed to measre the temperatre in the basin and also at different pla!es of the still.

A0perimental pro!edre of the spheri!al solar still :

A0perimental measrements are performed to evalate the performan!e of the spheri!al solarstill nder the !lear !limati! !onditions of Coimbatore, India. 3 N latitde4 The basin is filled

with B litres of water. $ layer of !har!oal is allowed to float on the srfa!e of the water. The

e0periment is !ond!ted between %:-- $< to /:-- 6< and its readin"s are re!orded on!e inevery (- mintes. The water temperatre, air temperatre, inner !over temperatre and oter

!over temperatre are re!orded at re"lar intervals of time. $s !har!oal is a!tin" as a "ood

absorber on the srfa!e, it rises the temperatre of the water and so the prod!tivity rate

in!reases to an optimm level. The same stdy is repeated withot !har!oal absorber inside the

spheri!al solar still. The water level in the basin is rapidly de!reases de to more evaporation ofwater in !lear snny days. #o a water tan) is !onne!ted to the still and water level is maintained

at the same level for all stdies. The distillated otpt of spheri!al solar still is fre7entlymeasred by a measrin" ar at re"lar intervals. The measrin" ar is pla!ed at the otlet of the

solar still.

$nalysis :



Reslts and Dis!ssion :

#pheri!al solar still was !onstr!ted and tested e0perimentally. This type of still re!eivesradiation is transmitted from the spheri!al transparent srfa!e. This still has added advanta"e in

evaporatin" the water by floatin" the !har!oal for absorption of radiation. The performan!e of

spheri!al solar still is stdied with two modes of operation, first spheri!al solar still with !har!oalabsorber and then withot !har!oal absorber. i". ( shows the variation of solar radiation with

respe!t to time in both stdies. The solar radiation starts to in!rease in the mornin" and attains

ma0imm at the noon and tends to de!rease in the evenin" time. The variation of solar radiationis re!eived in the ran"e of =/B.B1 W5m to -B1.-- W5m on normal s)y days, where still

performan!e is measred with the !har!oal absorber. #imilarly when the still is stdied withot

!har!oal absorber, the radiation is re!eived in the ran"e of /-&.( W5m to -%.-- W5m. Theavera"e solar radiation re!eived for the spheri!al solar still with !har!oal absorber is B(/.=

W5m similarly the avera"e radiation for withot !har!oal absorber is B=.& W5m. i"s. =>/

show the variation of temperatre with respe!t to time for two e0periments. The rise in water

temperatre ran"es from (%C to 1C, (C to 1-C for air temperatre, %./C to (/./C forroom temperatre, (( to (BC for oter !over temperatre, (.%C to (1C for ambient air

temperatre withot !har!oal absorber. #imilarly the rise in water temperatre ran"es from =-C

to 1BC, (BC to 1C for air temperatre, %./C to (&C for room temperatre, (( to (&C for



oter !over temperatre, ((C to =C for ambient temperatre in spheri!al solar with !har!oal

absorber. These temperatre variations in this stdy show that temperatre of the still with

!har!oal absorber is more than the still withot !har!oal absorber. #in!e the !har!oal absorbsmore radiation and it in!reases the water temperatre to a hi"her vale. i". 1 shows that the

variation of effi!ien!y with respe!t to time in both stdies. The ma0imm effi!ien!y is observed

as B ' for withot !har!oal still and /.(= ' for with !har!oal absorber. i". & shows thevariation water !olle!tion with respe!t to time for both the stdies. The distillates yield arond

.( liters5m5day withot !har!oal absorber and .B liters5 m5day for with !har!oal absorber. i"

.B shows the variation of latent heat with respe!t to time. It is fond in the ran"e of =-1%=% @"> to =--%B/ @"> withot !har!oal absorber inside and ==&% @"> to (%1== @" > is

observed with !har!oal absorber inside the still. i"s. %>- show the variations of Erashof

nmber and Nsselt nmber with respe!t to time for spheri!al with !har!oal absorber. It

!on!ldes that Erashof nmber and Nsselt nmber in!rease with respe!t to time. Erashofnmber is fond as B&-% to (&=1 and the Nsselt nmber fond as (.( to =.11 in the !har!oal

absorber stdy. #imilarly i"s. > show that the variations of Erashof nmber and Nsselt

nmber with respe!t to time for still with withot !har!oal absorber. Erashof nmber is fond as

1=&1 to =/%-= and the Nsselt nmber fond as (.- to =./ for withot the !har!oal absorberstdy. Erashof vale is fond to in!rease steadily drin" warm p period and then it starts to

de!rease with respe!t to de!rease in water temperatre. $fter attainin" the hi"her temperatre,the Nsselt nmber vale maintains a steady state. i" .( shows the variation of satrated vapor

pressre 3N5m4 with respe!t to water temperatre. rom this "raph we !an easily verify the

satrated vapor pressre vales for the water temperatres.

Con!lsion :

The ma0imm effi!ien!y is observed as B ' for withot !har!oal and /.(= ' for with!har!oal absorber. . The distillates yield arond .( liters5m5day for withot !har!oal absorber

and .B liters5 m5day for with !har!oal absorber. The drivin" for!e of the solar distillationte!hni7e is the differen!e between temperatre of water in the still basin and temperatre of the!over 3Tw>T!4. It !an be !on!lded that the spheri!al solar still will be more e!onomi!al on small

s!ale prod!tion to provide drin)in" water in remote areas.

Elossary :

$ $rea 3m4

<w

<ass of Water 3)"4

" $!!eleration de to "ravity 3m5s4

F Wind #peed 3m5se!4

Ta $ir temperatre 3oC4



T ?ot srfa!e temperatre 3oC4

T #rrondin" air temperatre 3oC4

Tw Water temperatre 3oC4

Tf lid avera"e temperatre 3oC4

6 6erimeter of the srfa!e

Tamb $mbient temperatre 3oC4

Ts)y #)y temperatre 3oC4

T! Top Cover Temperatre 3oC4

C pa #pe!ifi! ?eat of $ir at Constant 6ressre 3G5@"o

C4

N Nsselt nmber

6r 6randlt nmber

HT Temperatre differen!e 3oC4

) Thermal !ond!tivity

Greek

Thermal e0pansion !oeffi!ient

ρ 6artial mass density of water vapor 3@"5m(4

J 2atent ?eat 3oC4

σ #tefan>*oltKmann !onstant 3/.11%& 0 ->B W5mo@ =4

τ Elass absorptive

L Dynami! vis!osity of the flid, 6a.s

RAARANCA# :

9; 2. Eran!ia Rodri"eK, Desalination by wind power, Wind An"ineerin". B, 3--=4 =/(.9; Cappelletti E<, $n e0perimental with plasti! solar still, Desalination. = 3--4 >

&.

9(; <ali) <$#, Tiwari EN, @mar $, #odha <#, #olar distillation, a predi!t stdy of a wide



ran"e of solar and optimm desi"n, !onstr!tion and performan!e. New Mor), 6er"amon press,

3%B4.

9=; $l>?aye), *adron OO, The effe!t of sin" different desi"ns of solar stills on waterdesalination, Desalination. 1% 3--=4 >&.

9/; $l> ?ssaini ?, #mith 2@, Anhan!in" of solar still prod!tivity by va!m te!hnolo"y,

Aner"y Conversion <ana"ement, (1 3%%/4 -=&>-//.91; @elo"iros #, Use of paraboli! tro"h solar ener"y !olle!tor for sea water desalination,

$pplied Aner"y, 1- 3%%B4 /B>BB.

9&; Al>sebaii $$, Thermal performan!e of a triple basin solar still, Desalination. &=3--/4(>(&.

9B; $l>@ara"holi $$, $lnaser WA, A0perimental !omparative stdy of the performan!e of

sin"le and doble basin solar still, $pplied Aner"y.&& 3--=4 (&>(/.

9%; Tiwari EN, #in"h #@,*hatna"ra F6, $nalyti!al thermal modelin" of mlti basin solarstill, Aner"y Conversion and <ana"ement. (=34 3%%(4 1>11.

9-; *adron $$, Inverted tri!)le solar still, Affe!t of heat re!overy, Desalination. (( 3--4

1&>&(.

9; @abeel $A, Water prod!tion from air sin" mlti shelves solar lass pyramid system,Renewable Aner"y. ( 3--&4 /&>&.

9; <.$.#. <ali), E.N Tiwari, $. @mar and <.#. #odha, #olar Desalination. 6er"amon6ress, New Mor), %&=.

9(; G.$. Dffie and W.$. *e!)man, %&=. #olar Aner"y Thermal 6ro!ess, Gohn Wiley and

#ons, New Mor).













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Thermal Performance and Analysis of Low Cost Spherical Solar Still With Charcoal Absorber