adsorptive properties of activated charcoal methanol combinations
TRANSCRIPT
7/26/2019 Adsorptive Properties of Activated Charcoal Methanol Combinations
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Renewable Ener tv
Vo[. 3, No.
6/7,
pp. 567-575, 1993 096(~1481/93 $6. 00+ .00
Printed in Grea t Bri tai n (' 1993 Pergamon Press Ltd
ADSORPTIVE PROPERTIES OF ACTIVATED
CHARCOAL/METHANOL COMBINATIONS
HU JING and R. H. B. EXELL
Division of Energy Technology, Asian Institute of Technology, P.O. Box 2754,
Bangkok 10501, Thailand
( R ec e i ved 26 N o v e m b e r 1992;a c c ep ted 17 December 1992)
Abstract---The adsorptive properties of several activated charcoal/methanol combinations were measured
in the laboratory. The Dubinin.-.Astakhov quation is used to analyze the data, and pressure temperature
concentration diagrams are given. From these results the coefficients of performance of ideal adsorption
refrigeration cycles applicable in solar heated adsorption refrigerators are calculated. It was found that
extruded samples from the U.K. and China had similar properties, but the best results were given by
granular samples from Thailand. There is some evidence hat small grain sizes (1 mm) are better than large
grain sizes (5 mm).
I. INTRODUCTION
Among the intermittent solid adsorption cycles for
solar ice-making refrigerators operating in a daily
cycle, the charcoal/methanol combination appears to
have advantages over other combinations. The advan-
tages include chemical stabil ity, better coefficient o f
performance (COP) [1], and relatively inexpensive
materials locally available in developing countries.
The pore structure of adsorptive solids is divided
into three approximate classes: micropores (radii
<a bo ut 15 A), transi tiona l pores (radii 15-200 A.),
and macropores (radii > 200 ~) [2]. The basis of this
classification is the behavior of each type of pore in
the process of vapor adsorption. However, although
meaningful informat ion about pore size distribution
in transitional pores and macropores can be obtained
[2], there is no satisfactory method of estimating the
size distr ibut ion in micropores. The pores in activated
charcoal are in the micropore range. Since it is there-
fore impossible to estimate theoretically the adsorp-
tive properties of the activated charcoal/methanol
combi nation, and since there are big variat ions in the
quality of activated charcoals available from different
sources, it is necessary to measure the adsorptive
properties of methanol on these different charcoals in
order to choose the one that is most suitable for mak-
ing solar refrigerators in particular circumstances.
Such measurements have been made by Passos
e t a l .
in France [3], by determining the isosters, and by
Sridhar in the Asian Institute of Technology (AIT)
[4] by determining the isobars.
In this paper, we describe some new measuremen ts
of the adsorptive properties of activated charcoals from
several different sources with the help of the simple,
but effective, experimental rig developed at AIT. The
results are compared with each other by the Dub inin
Radushkevich (D-R ) and Dubin in Astakhov (D A)
representations. In addition, the pressure-temperature
concentration (P T-X) diagrams derived from the
test results are given for each kind of activated char-
coal in a form that is convenient for specifying and
analyzing adsorption refrigeration cycles. The dia-
grams were used to calculate and compare the COPs
of a number of ideal cycles using these activated
charcoals.
2 . E X P E R I M E N T A L W O R K
The experimental rig for testing the adsorptive
properties of activated charcoal and methanol is
shown in Fig. 1. The charcoal sample (250 g) is con-
tained in the stainless steel cylinder container (A)
immersed in an oil bath with a temperature controller.
Temperature gradients inside the charcoal are reduced
by the central pipe of container A that allows warm
oil to circulate and heat the charcoal from the center.
The temperatures of the charcoal sample and the oil
are measured by the thermocouples. The pressure of
the system is indicated by the vacuum gauge and mer-
cury U-tube. The quick release coupling enables one
to remove container A from the system easily, for
changing the charcoal sample.
The graduated glass cylinder conta iner (B) is used
as a methanol receiver and evaporator ; it is immersed
in a glass water bath whose temperature is held con-
stant by means of flowing tap water or ice. The quan-
567
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568 H. JING and R. H. B. EXELL
V a c u u m
P u m p
V a c u u m g a u g e
V~alve
, ( ~ M e r c u r y U t u b e T e m p e r a t u r e c o n tr o l
Fig. 1. Diagram of experimental rig.
tity (volume) of methanol adsorbed can be read
directly from the graduations, and the temperature
of the methanol is measured by the thermocouple.
Several valves are used to isolate and evacuate parts
of the system when necessary.
After introducing a measured amoun t of the char-
coal sample (about 250 g) into container A and
enough methanol into container B, the tests are car-
ried out according to the following three steps.
(1) The charcoal sample is degassed at 120 C under
vacuum and the air is flushed from container B by
means of the vacuum pump while part o f the methanol
is evaporated.
(2) The two containers are connected, keeping the
methanol in container B at a constant temperature
Tin, while cooling container A with charcoal sample
in ~ 10 ~' steps from an initial temperature of abou t
120°C to a final temperature o f abou t 30°C. A t each
step, a sufficiently long time is allowed for equi librium
to be reached between the charcoal sample and the
methanol. The temperatures of A and B and the level
of methanol in B are recorded in order to obtain the
adsorption isobar at the saturation vapor pressure of
methanol at temperature Tin.
(3) Similar data are taken while reheating the char-
coal sample in steps of 10° back to 120°C to obtain
the desorption i sobar at the same pressure.
Theoretically, the desorption isobar is the same as
the corresponding adsorpt ion isobar. However, in our
experiments only the adsorption isobar was reliable
because during desorption some methano l condensed
in the connecting pipe instead of in container B. For
each sample two isobars were measured by fixing Tm
at tap water temperature (about 30°C) and at iced
water temperature (about 5°C).
The activated charcoal samples measured came
from the U.K., China and Thailand. The descriptions
of the charcoal samples are listed in Table 1.
3. PRESENTATION OF THE TEST DATA
Based on the potential theory, a description of
adsorption in activated charcoal was proposed by
Polyani [5]. Dubinin and Raduskhevich originally
gave the fundamental state equation for the adsorp-
tion (D-R equation) as follows :
W= Woexp[-D TlnPs/P)2],
(1)
where W is the adsorbed volume (liters of methano l
per kilogram of charcoal) at temperature T (K) and
pressure P (bar) ; Ps is the saturated vapor pressure of
the adsorbate at temperature T; Wo is the maximum
volume of the adsorption space ; and D is a constant
for the charcoal sample. Because it is found that there
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Adsorptive properties of activated charcoal/methanol
Table 1. The charcoal samples
569
Charcoal sample Country Description
207 E4* U.K
LSZ-40t China
LSZ-30t China
MD6070~. Thailand
MD5060~: Thailand
Normal charcoal Thailand
Coconut shell based, extruded
Coal based CCL4 > 55%, extruded
Coal based CCL4 > 65%, extruded
Coconut shell based, granular, mesh size = 4 x 8
Coconut shell based, granular, mesh size = 8 x 30
Coal based, not activated
* Sutcliffe Speakman Carbon Ltd, U.K.
t Beijing Beijiao Activated Carbon Manufacturing Co., China.
~. UDP Chemical Co. Ltd, Thailand.
are some deviations from the above D-R expression,
Dubinin and Astakhov [6] have introduced an
improved equation (the D-A equation) to fit the
experimental data better. The D- A equation contains
a third parameter, n :
W = W o e x p [ - D ( T l n P ~ / P ) " ] .
(2)
Although it has been pointed out [7, 8] that the D -
A equation still deviates from the experimental data
near s atura tion [namely, for very small and very large
values of (T In
Ps/P)'],
it is considered to be accurate
enough for comparing the adsorptive properties of
different charcoals and for use as a tool in correlating
adsorpt ion data for engineering purposes.
Figure 2 shows the D R representat ions of the char-
coal we tested in the temperature range 30-120°C
at two different pressures. All the activated charcoal
samples yield a curve that is convex downwards. This
is typical of highly activated charcoal in contrast to
the unactivated charcoal, for which the graph appears
convex upwards. This implies that eqn (1) cannot
express the adsorptive properties of activated char-
coal/methanol well. To analyze the data in terms of
the D-A equation the parameter n is allowed to vary
and the value that gives the best linear correlation
between In W and (TIn
Ps/P)"
is found. Figure 3 shows
the resulting D-A representations of the charcoal
samples. Though there are still some slight deviations
from the straight lines, the D-A presentations of eqn
(2) renders the experimental data with sufficient accu-
racy for use in engineering design.
Table 2 gives the numerical values of the pa rameters
in eqn (2) for each of the combinations studied. The
parameter Wo is an indicator for the degree of acti-
vation, since it gives the volume of micropores (per
unit mass of charcoal) available for adsorption. The
parameter n decreases as the degree of activation
increases, with the exception of charcoal MD5060,
which consists of grains much smaller in size (< 1 mm
diameter) than the grains of the other samples (4-5
mm diameter). The parameter D increases with the
degree of activation, again with the exception of char-
coal MD5060. The exception in the case of MD5060
may be due to the fact that the small spaces between
the grains provide an additional conribution to the
volume available for adsorption, for the observed
value of Wo in MD5060 is approximately twice the
value that would be expected from the relation con-
necting n and D with Wo in the other samples.
From eqn (2) we find that In P and -
1/T
are lin-
early related along an isoster (W = constant) if we
omit the quadratic and higher terms in the expansion
of In P~. Therefore, with the experimentally deter-
mined parameters in eqn (2), we can ob tain an isoster
as a straight line on a In P versus - 1/T plot by con-
necting two corresponding points with the same W.
Figure 4 shows the isosters derived for the charcoal
samples studied, where W has been replaced by the
more familiar symbol X as the concentra tion of meth-
anol adsorbed in the charcoal (kg methanol per kg
charcoal).
4. CYCLE PERFORMANCE WITH THE
CHARCOALS
The In P versus - 1 / T diagram is convenient to
describe the principle of the adsorption refrigeration
cycle. Theoretically, the cycle consists of two isosters
and two isobars (Fig. 5).
The process starts at point 1, where all the adsorbate
(methanol) is adsorbed on the adsorbent (charcoal)
at the ambient temperature, Td, and pressure P~. As
the adsorben t is heated, the temperature and pressure
increase along the isoster while the concentration of
the adsorbate in the adsor bent remains at Xm~,, unti l
point 2 is reached. At point 2 the generation process
starts on the isobar for the saturat ion vapor pressure,
P2,
of the adsorba te at the condenser temperature, T~.
During generation the adsorbate is driven from the
adsorbent and the adsorbent temperature increases
along the isobar to a maxi mum value, Tm~, at point
3. During this process the adsorbate vapor condenses
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5 7 0 H . J 1 N G a n d R . H . B . E X E L L
- 1 ,
C h a r c o a l 2 0 7 E 4
~ 112~k~,~ c2 P = 0.1 96 ba r
-1 "n ~ + P = 0.05 ba r
\
- 2 . 4 t \
- 2 .6 p
-2 .8 F x ~
_ :~E '\
- 3 .4 L + ' x , L
- 3 6 i ~ - ~
X f ~ - ~
o 2 1 ~ ; ~ - ~ 2 5
- - 3 o - -
(T In (Ps /P ) ) ~ , 1 ~
_5
C h a r c o a l L S Z 4 0
-1115 ~
r J P = 0 . 183 ba r
2 1 . X ~ + P = O . O S b a r
i:i \
0 5 1 0 1 1 5 2'0 215 3'0
(T In(P s/P) ) 2 lo- '
3 5
- 1
C h a r c o a l L S Z 3 0
-1.5
-2
-2 .5
- 3 ~
i
- 3 .5 1
I
- 4 ~
-4 .5
P = 0 . 1 9 0 b a r
+ P = 0 . 05 bar
~ - . . &
1 0 - - 1 5 2 '0 2 5 3 0 - - - -
(T In(Ps /P) ) 2 ,o- '
3 5
-0 ,6
-0 ,8
-1
-1 .2
-1 ,4
-1 .6
-1 ,8
-2
-2 .2
-2 .4
-2 .6
-2 .8
-3
-3 .2
-3 .4
-3 .6
-3 .8
- 4 - -
0
C h a r c o a l M D 6 0 7 0
y [3 P = 0 . 157 bar
~ - ~ 0 ; 5 2 0 2'5 3 0
(T In (Ps /P ) ) 2 ~1 ~
3 8
5
- 0 . 6 .
C h a r c o a l M D 5 0 6 0
o : ] ~ \ = P = o , , 3 b a r
- 1 2 P b
, : 4 t \ o = o o 5 ~,
- I
.6 ~ " ~
- 2 . 2 i - ~ .
- 2 . 4 i
" , ,
-2.6F N
- 3 .2 ~ " q
o T s Y o ~ 1 5 2 0 2 ; £
( m h ' l ( P ~ t P ) ) 2 ~ i o 5
35
Unac t i v a ted c h a rc oa l
, ~
-2"1
- 2 "2 ~ - " ~ o = P = 0 . 1 6 0 b a r
-2.6
-2.7
-2.8
- 2 .
-3.2
-3.3
-3.4
-3.5
-3.6
-3.7
-3.8
-3-~L
1'0 115 2'0 215 3'0
( T I n ( P s /P ) ) 2 , l ~
F i g . 2. D R r e p r e s e n t a t i o n o f s i x c h a r c o a l s a m p l e s . - - , B e s t fi t p a r a b o l i c r e g r e s s i o n c u r v e s .
3 5
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A d s o r p t i v e p r o p e r t i e s o f a c t i v a te d c h a r c o a l / m e t h a n o l 5 71
5
C h a r c o a l 2 0 7 E 4
- 0 . 5 . . . . . . .
-I I~)'~. n = 1 . 3 4
1 5 t ~ , ~ {3 P : 0 . t 9 6 b a r
- 2 . 5
- 3 ~ ~ \
- 3 . s '
I
-4 .5 ~ r ~ i - ' ~ - ~ - 4
0 0 .02 0 .04 0 .060 .0% .0 . % .; 4 0 .% .1 8 0 . 2 0 .~ 2 0 . 2 4
(T In( Ps/P ))~, l o ~
C h a r c o a l L S Z 4 0
- 1 °
_ ~ P = 0 . 1 8 3 b a r
-2.5.3 -- "
-3 .5
-4
-4.5
- 5 i i i b i i . l l i i
o o ? ° & o ~ ° & o ~ & o g ° & o # • o .1 7 1 ~ 4 • ~
(T In (PsJP ) )*, o "
C h a r c o a l L S Z 3 0
-1 I -
- 1 . 5 n = 1 . 26
- 2 ' k n p = 0 . 1 9 0 b a r
- 2 .5 L
- 3 . 5
- 4 j
- 4 . 5
5 ~ o o O y ~ ; ~ o ~ ~ o 1 1 O ~ 3
(T In(Ps/P )) , 1~,
C h a r c o a l M D 6 0 7 0
-0 .6
- 0 .8 t r 3 ~ + ~ i 1
- 1 = 1 . 1 2
- 1 . 2
- 1 . 4 E l P = 0 , 1 5 7 b a r
- 1 .6 + ~ . . + P = 0 . 0 5 b a r
- 1 . 8
-2
- 2 . 2
- 2 . 4 I
- 2 . 6 L
- 2 , 8 ~ 1
-3
- 3 . 4
-3 .61 '~ .
. 3 .8 k \ ' L
4 F - q
o o ~ . . . . ~ 1 . . . . . . T - -
5 0 . 0 1 5 0 . 0 2 5 0 . 0 3 5 0 . 0 4 5
0 .01 0 .02 0 ,03 0 .04
(T In (P s /P) ) " , o ,
-0.5
C h a r c o a l M D 5 0 6 0
-1
-1 .5
-2
. 2 . 5
-3
- 3 . 5
. 4
- 4 . 5
u • o + n
1 . 5 0
Q P
=
0 . 1 4 3 b a r
0 1 0 : 2 0 3 0 : 4 0 5 o : 6 0 7 -
T In (P s /P) ) " , ~o
F i g . 3. D - A r e p r e s e n t a t i o n o f a c t i v e c h a r c o a l s a m p l e s . , B e s t f it l i n e a r r e g r e s s i o n c u r v e s .
0 .8
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572
H . J I N 6 and R. H. B. EXELL
i n t h e c o n d e n s e r a n d i s c o l l e c t e d i n a re c e i ve r , a n d
t h e c o n c e n t r a t i o n o f t h e a d s o r b a t e i n t h e a d s o r b e n t
d e c r ea s e s t o i ts m i n i m u m X , , . . T h e r e ce i v er is t h e n
i s o l at e d f r o m t h e a d s o r b e n t , a n d t h e a d s o r b e n t is
c o o l e d a l o n g t h e i s o s t e r a t c o n s t a n t c o n c e n t r a t i o n ,
X m ~,, t o p o i n t 4 w h e r e t h e p r e s s u r e i s a g a i n P , . A t t h i s
p o i n t t h e r e c e iv e r is c o n n e c t e d a g a i n t o t h e a d s o r b e n t
t o a l lo w t h e a d s o r p t i o n p r o c e s s t o s ta r t . D u r i n g t h i s
p r o c e s s t h e l i q u i d a d s o r b a t e c o l l e c t e d i n t h e r e c e i v e r
e v a p o r a t e s a n d a b s o r b s h e a t a t t h e r e f r i g e r a ti o n t e m -
p e r a t u r e , T ~ ,. , o f t h e e v a p o r a t o r w h i l e t h e c o n -
c e n t r a t i o n o f t h e a d s o r b a t e i n t h e a d s o r b e n t i n c r e as e s
0 . 2
0 :1
0 . 0 9
0 . 0 8
o.gz.
0 . 0 6
.I.
o o ~
~ , _ - -
0 . 0 4 .
o . Q _ ~ .
o 9?
harcoal 2 0 7 E 4
[ I
' , /
_ _ . _ , / _ .
-
7 - - ~
- - -
- - - ' H - ' - 4 ~
___ _
_ I i
' i 1
/ I I i
I ° , c I = ° > I ° ' c I
- 3 . 7 - 3 . 5 - & 3 - 3 .1
I
I ' I
I j
I
i I , -
L
I I
I I
I I
I I
- 2 . 9 - 2 . 7 - 2 - 5
- I / T x l O 3 ( K - I }
0 . 2
0 . 1 5
9.A ___
o
_ 9 _
o.9_8
o _ o
o . _ o _ s
o.o_5
o .2 _
o . _ o ~ _ _7
0 . 0 2
- & 7
harcoal L S Z 4 0
/ / / / / / / / / I
- I--- -I- l- -
- - T N i T T i - T T - r i - q - -
I I
I I
I I
I I
- & 5 - 3 . 5 - & l - 2 . 9 - 2 . 7 - 2 . 5
3 - I
- I / T x l 0 ( K )
0 . 2
0 . 1 9
0 , 1 5
o-9P_
0 . 0 8
o #
0 . 0 6
~. o _
o 4_
0 . 0 ~ _
0 . 0 2
harcoal L S Z 3 0
I
I
I
I
I
- 3 . 5
I
2 - - i -
' I - -
I I
I I
I I
I I
I I
- & 3 - :5 .1 - 2 . 9 - 2 . 7 - 2 . 5
. l I T x 1 0 3 ( K - i l
harcoal M D 6 0 7 0
0 . 2
° i
o.osq_ ,_ d _ p _ ,___l.f lH ¢t_f_7_~_~L__
-~ o . o ~ _ _ + # _ + _ ' ~ _ ~l / _ k / _ l _ d _ _
- ~ o o , I @ / i
; _ f lY J ~ J _ Y _ _ _
oo-q--]7-7-
L_
"- - -1 - - Z ~ ,- q / I / i l l / ~ I
0 . 0 4 / { ;
J I J J I I2 L L _ _ L L _ _
I i I i i i I
/ i I i I
/ I I i I
o._o_2t i i I ~ I i
- 3 . 6 - 3 . 4 - 3 . 2 - 3 . 0 - 2 . 8 - 2 . 6 - 2 . 4
- I / T x 1 0 3 ( K - I~
F ig . 4 . Expe r im enta l i sos te r s on a In P ver sus - 1 /T p lo t . Va lues of X a re 0 .02 , 0 .04 . . . . 0 .18 , 0 .20 .
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A d s o r p t i v e p r o p e r ti e s o f a c t i v a t ed c h a r c o a l / m e t h a n o l
573
0 . 2
0 . 1 5
0_._1_
0 . 0 9
o.o_8_
o . o L
o.9_6_
0 9 _ _
o _ o _ 4 _
o ._o~
0 0 2
C h a r c o a l M D 5 0 6 0
, t /
I / ' 1
V
I , / i I ,
I / I I ~ = o z /
- - - ~ - - r e - - - r - ' : - ~
i / I I
/ / /
- -
I I
- - W t J
- -
1 1
o : I c l o 9 ° ° e l
- 3 . 6 - 3 . 4 - 3 . 2 - 3 D - 2 . 8 - 2 . 6 - 2 . 4
3 - I
- I / T x l O K )
Fig. 4.
(continued)
t o X ~ ,,~ a t p o i n t 1. A t t h e s a m e t i m e , t h e a d s o r b e n t
c o o l s t o 7-..,b y r e j e c t i n g t h e s e n s i b le h e a t a n d t h e h e a t
o f a d s o r p t i o n .
I n o u r s i m u l a t i o n c a l c u l a t i o n t o c o m p a r e t h e s y s t em
p e r f o r m a n c e s w i t h d i ff e r e n t c h a r c o a l s w e a s s u m e d t h e
h e a t c a p a c i t y o f t h e m e t a l c h a r c o a l c o n t a i n e r t o b e
1 .0 1 k J / K p e r k g c h a r c o a l a n d t h e f in a l a d s o r p t i o n
t e m p e r a t u r e t o b e 3 0~ C . T h e p h y s i c a l p r o p e r t i e s ( d e n -
s i ty , s p e c if i c h e a t c a p a c i t y , e t c . ) o f c h a r c o a l s a r e
a s s u m e d t o b e th e s a m e . T h e D - A e q u a t i o n ( 2)
w a s u s e d a s t h e s t a te e q u a t i o n w i t h t h e p a r a m e t e r s i n
T a b l e 2 .
I n P
P 2
P1
J
. . . . . . . . . .
:
3
|
Y e v T a T C T m a x - 1F T
Fig . 5 . P T X d iag ram o f th e s imp le ad so rp t io n cy c le . T~ ,
ev ap o ra to r t emp era tu re ; T , , amb ien t t emp era tu re , T~ ,
c o n d e n s e r t e m p e r a t u r e ; T ~ ,, ~, m a x i m u m t e m p e r a t u r e o f
ch arco a l .
T h e c o e f fi c i e nt o f p e r f o r m a n c e ( C O P ) i s d e f i n e d a s :
C O P = L / ( Q ~e , + Qde~)
w h e r e L i s t h e u s e f u l h e a t o f r e f r i g e r a t i o n e x t r a c t e d a t
t h e e v a p o r a t o r t e m p e r a t u r e , T o , ; Q ~ e , i s t h e s e n s i b l e
h e a t n e e d e d t o h e a t t h e m e t a l c o n t a i n e r a n d t h e c h a r -
c o a l t o t h e t e m p e r a t u r e , T m ,x ; a n d Q a ,~ i s t h e h e a t o f
d e s o r p t i o n .
T h e c a s e s i n v e s t i g a t e d i n c l u d e e v a p o r a t o r t e m -
p e r a t u r e s o f 0 a n d - 1 0 C , w h i c h a r e t y p i c a l f o r c o o l
s t o r a g e a n d i c e - m a k i n g , r e s p e c ti v e ly . T h e c o n d e n s e r
t e m p e r a t u r e s , T o, a r e 25 , 35 a n d 5 O C c o r r e s p o n d i n g
t o a c o n d e n s e r i n c i r c u l a t i n g w a t e r , a c o n d e n s e r i n
s t a ti c w a t e r a n d a n a i r - c o o l e d c o n d e n s e r , r e s p e c t i v e ly .
T h e s i m u l a t i o n r e s u lt s a r e s h o w n i n F i g s 6 a n d 7 .
C h a r c o a l M D 6 0 7 0 h a s t h e b es t p e r f o r m a n c e i n a ll
c a se s , f o l l o w e d b y c h a r c o a l M D 5 0 6 0 . T h e s e t w o c h a r -
c o a l s a re g r a n u l a r w i t h o u t e x t r u s i o n a n d h a v e a W,,
m u c h h i g h e r t h a n t h e o t h e r s a m p l e s ( se e T a b l e 2 ) .
T h e t w o c h a r c o a l s L S Z 3 0 a n d L S Z 4 0 h a v e s i m i l a r
p e r f o r m a n c e s i n a ll c a s e s b e c a u s e t h e n u m e r i c a l v a l u e s
o f t h e p a r a m e t e r s W o , D a n d n i n e q n ( 2) a r e s i m i l a r .
T h e c h a r c o a l 2 0 7 E 4 f r o m t h e U . K . h a s a s im i l a r p er -
f o r m a n c e w h e n T ¢, = 0 ' C , b u t i s b e t t e r w h e n
T ~,. = - 1 0 ° C a n d h i g h e r v a l u e s o f T m , x a r e a t t a i n e d .
F r o m t h e r es u lt s o f t h e C O P c o m p u t a t i o n s w e fi nd
t h a t l a r g e r v a l u e s o f W o n o r m a l l y g i v e b e t t e r C O P s .
H o w e v e r , t h e C O P i s i n f l u e nc e d b y th e o p e r a t i n g t e m -
p e r a t u r e s . T h e s m a l l e r v a l u e s o f D a n d l a r g e r v a lu e s
o f n g i v e s m a l l e r v a r i a t i o n s o f th e C O P a s t h e p e a k
t e m p e r a t u r e T m ,x i n c re a s e s, s o f o r s o m e c h a r c o a l s w i t h
c l o s e v a l u e s o f W o , n a n d D i t i s n o t a l w a y s t r u e t h a t
l a r g e v a l u e s o f W 0 g i v e b e t t e r v a l u e s o f t h e C O P .
5 . C O N C L U S I O N
T h e a d s o r p t i v e p r o p e r t i e s o f s e v e ra l c h a r c o a l /
m e t h a n o l c o m b i n a t i o n s ( T a b l e 2 ) h a v e b e e n d e t e r -
m i n e d e x p e r i m e n t a l l y . T h e c o r r e s p o n d i n g D A p re -
s e n t a t i o n s a n d t h e P T - X d i a g r a m s t h a t a re n e c e s s a ry
t o d e s i g n a s o l a r r e f r i g e r a t i o n c y c l e a r e a l s o g i v e n .
S i m p l e p e r f o r m a n c e s i m u l a t i o ns s h o w e d t h a t t h e
Tab le 2 . Nu m er ica l v a lu es o f p a ramete r s in eqn (2)
W,, Temperature
Ch arco al (1 /kg) n D x l0 s range ( 'C)
207E4 0 .365 1 .3 4 14 .962 30~1 I0
LSZ40 0.384 1 .28 28.814 30 110
LSZ3 0 0 .405 1 .1 6 31 . 972 30-- 110
MD 6070 0 .989 1 .12 88 .9 82 30 120
M D 5 0 6 0 0 .5 3 5 1 .5 0 4 .5 8 95 3 0 , 1 20
No rm al 0 .1 5 6 9 2 .0 0 .1 9 82 3 0 -1 1 0
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5 7 4 H . J 1 N G a n d R . H . B . E X EL L
( T o = 2 5 " C )
0 5 . . . . . . . . . . . . . . . ~
0 4 . . . . . . . I I I . . ~
0 2
0.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
070 1~0 1
0 g o 1 0 0 1 ~ 'o 1 3 0 1 4 0 1 5 0
Tm~ ~)
0 . 6 [ f r c = 3 5 C )
O 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
O 4 . . . . . . . . . . . . . . . . . . . . . . . . . . .
~ 0 3
O 2 . . . . . . . . . . . . . . . . . . . . . . . . . .
0 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Q
7 0 8 0 9 0 1 0 0 1 1 0
1 2 0 1 3 0 1 4 0 1 5 0
T m a x ( ° C )
0 5 I ( T c = 2 5 C )
0 4 . . . . . . . . . . . . . . . . .
0 3 . . . . . . . . .
0 2 . . . . . . . . . . . .
0 1
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0
7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0
"fma× (~C)
O3
0 2
( T c = 3 5 " C ) 1
0
7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0
T m a x ( " C )
0 4
0 3
0 2
0 . 1
( T o = 5 0 C }
0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0
T m ax (~C)
F i g . 6 . C O P a s a f u n c t i o n o f m a x i m u m c h a r c o a l t e m p e r a t u r e ,
w h e n T, .v 0 C . - - , U n a c t i v a t e d c h a r c o a l ; ÷ , M D 6 0 7 0 :
A , M D 5 0 6 0 ; I I , 2 0 7 E 4 ; × , L S Z 3 0 ; V , L S Z4 0 .
f r C 5 0 C )
0 3
0 2 5
0 2
0 1 5
0 1
0 0 5
0 7 0 8 0 9 0 l O G 1 1 0 1 2 0 1 3 G 1 4 0 , 5 0
Tmax ( ° C )
F i g . 7. C O P a s a fu n c t i o n o f m a x i m u m c h a r c o a l t e m p e r a t u r e ,
w h e n T ~,. - - 1 0 ~ C. , U n a c t i v a t e d c h a r c o a l ; + , M D 6 0 7 0 ;
A , M D 5 0 6 0 ; I I , 2 07 E 4 ; x , L S Z 3 0 ; ~ ' , L S Z 4 0.
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A d s o r p t i v e p r o p e r t ie s o f a c t i v a te d c h a r c o a l / m e t h a n o l
575
g r a n u l a r a c t i v a t e d c h a r c o a l g i v es a b e t t e r p e r-
f o r m a n c e t h a n e x t r u d e d a c t i v a t e d c h a rc o a l . T h e T h a i
c o c o n u t s h e ll b a s e d M D 6 0 7 0 g r a n u l a r a c t i v a t e d c h a r -
c o a l g a v e t h e b e s t p e r f o r m a n c e i n t h e s a m p l e s t e s t e d .
T h e r e i s a n i n d i c a t i o n i n t h e o t h e r T h a i s a m p l e
( M D 5 0 6 0 ) t h a t a s m a l l e r g r a i n si ze (1 m m ) i s b e t t e r
t h a n a l a r g e r g r a i n s i z e ( 5 m m ) . A g e n e r a l r e s u l t i s
t h a t t h e U . K . a n d C h i n e s e s o u r c e s p r o v i d e a c t i v a t e d
c h a r c o a l s o f e q u a l q u a l i t y , a n d t h e T h a i s o u r c e p r o -
v i d e s e v e n b e t t e r a c t i v a t e d c h a r c o a l f o r u s e i n a d s o r p -
t i o n r e f r i g e r a ti o n . T h i s i s o f i n t e r e s t t o A s i a n c o u n t r i e s
i n t e r e st e d i n th e f u t u r e d e v e l o p m e n t a n d l o c a l p r o -
d u c t i o n o f s o l a r a d s o r p t i o n r e f r i g e ra t o r s .
R E F E R E N C E S
I . M . Po n s an d J . J . Gu i l l em in o t , Des ig n o f an ex p er ime n ta l
so la r p o wered so l id ad so rp t io n i ce mak er . J. Solar Enerqy
Enq.
108. 332 (1986).
2 . H . M arsh , Th e ch arac te r iz a t io n o f m ic ro p o ro u s ca rb o n s
b y m e a n s o f t h e D u b i n in R a d u s h k e v i c h e q u a t i o n . J. Col-
lo idlnter face Sc i . 33, 101 (1970).
3 . E . Passo s , F . M eu n ie r an d J . C . Gian o la , Th erm o d y n a m ic
p e r f o r m a n c e i m p r o v e m e n t o f a n i n t e rm i t t e n t s o l a r p o w -
ered r e f r ig e ra t io n cy cle u s in g ad so rp t io n o f me th an o l o n
ac t iv a ted ca rb o n . Heat R ec oveo , Sy s ems 6, 258 (1986).
4 . K . S r id h ar , S tu d y o f ac t iv a ted ca rb o n /m eth an o l p a ir s
with relevance to ice ma king . Thesis No . ET-87-2, A sian
In s t i tu e o f Tech n o lo g y , B an g k o k (1 98 7 ).
5 . M. Po lyani , In : M. Sm isek and S. Cerney , Act ive Carbon
Mam~[acture, Properties and Application (edited by M.
Smisek and S. Cerney ), pp . 17 161 . Elsev ier . Am sterd am
(1970).
6 . M . M . D u b in in an d V . A. As tak h o v , Adv. Chem.Ser. 102,
69 (1970).
7 . M . Po n s an d Ph . Gren ie r , A p h en o men o lo g ica l ad so rp -
t io n equ i l ib r iu m law ex t r ac ted f ro m ex p er imen ta l an d
th eo re t i ca l co n s id era t io n s ap p l i ed to th e ac t iv a ted ca rb o n
an d me th an o l p a i r. A ccep ted b y Carbon (1986).
8 . Z . Lav an an d W . M . W o rek , Per so n a l co mmu n ica t io n
(1986).