Proceedings of International Forum for Green Asia 2017
Special issue of Evergreen - Joint Journal of Novel Carbon Resource Sciences & Green Asia StrategyP-11

Effect of adsorbent layer height on instantaneous adsorption capacity
Animesh Pal1,2, Kyaw Thu1,2, Bidyut Baran Saha2,3
1Kyushu University Program for Leading Graduate School, Green Asia Education Center,
Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Japan
2
International Institute for Carbon-Neutral Energy Research, Kyushu University, Japan3
Mechanical Engineering Department, Kyushu University, Japan

Abstract
This study experimentally investigates the effect of adsorbent layer height on adsorption
capacity rate of ethanol onto activated carbon (AC) based consolidated adsorbents.
Consolidated adsorbents have been prepared using polyvinyl alcohol (PVA) (10 wt%) and 90
wt% Maxsorb III (AC). Apparent packing density of consolidated AC adsorbents is kept nearly
constant by changing the height and mass percentages of AC and PVA. Two different heights
adsorbent have been prepared to investigate the instantaneous adsorption capacity variation.
Instantaneous adsorption experiment are conducted at various evaporator pressures andadsorption temperature at 30°C using magnetic suspension adsorption measurement unit. It isfound that there is no significant difference in equilibrium adsorption capacity. However,significant difference of instantaneous adsorption capacity between two different heights ofsame composition consolidated AC has been observed.
consolidated
adsorbents.
Instantaneousadsorption
capacity
aremeasured
gravimetrically at various evaporator pressuresand adsorption temperature at 30°C using
magnetic suspension adsorption measurementunit.

1. Introduction
Consolidated composite adsorbents haveattracted great attention as next generation
adsorbents in adsorption heat pump (AHP)
application because of their some salientfeatures, such as improved uptake to volume
ratio and high thermal conductivity [1].
Distinguished researchers have been employed anumber of binding material such as expandedgraphite [2], polyvinyl alcohol (PVA) [1],[3],polytetrafluoroethylene(PTFE)
polyvinylpyrrolidone (PVP) [4] to synthesis
composites with good thermal conductivity andhigh volumetric adsorption capacity. However,literatures review indicated that still compositeadsorbents are not much efficient as expected
and there is a dearth of accurate data on theadsorption characteristics of refrigerant onto
consolidated composite adsorbents. Among
various characteristics, instantaneous adsorption
capacity is one of key characteristics ofadsorbent, which is necessary to know the actual
cycle performance of AHP system.
Consequently, the motivation of this study
is to investigate the effect of adsorbent layerheight on instantaneous adsorption capacity of
ethanol onto activated carbon (AC) based

2. Experiments
2.1. Synthesis of consolidated AC
Consolidated AC adsorbents have been
prepared by mixing of Maxsorb III (AC) andbinder (PVA)-water solution with certain ratios.
The process can be explained as follows; firstly,Maxsorb III are dried in the oven at 120 °C.
Secondly, granular type polyvinyl alcohol(PVA) used as a binding material put into thewater for 1 hour to make solution. After thatdried Maxsorb III is added to the water-binder
solution and compressed using pressing
machine at 10 MPa. Finally, the samples aredried in the oven at temperature of 120 °C about
several hours to remove water. Two samples
have been prepared with 90 wt% Maxsorb III +10 wt% PVA and nearly same packing density(316 ± 4 kgm-3). However, sample height are
different (1.4 mm and 5.2 mm) with 17 mm
diameter.

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Proceedings of International Forum for Green Asia 2017
Special issue of Evergreen - Joint Journal of Novel Carbon Resource Sciences & Green Asia Strategy

P-11
2.2. Adsorption characteristics experimentInstantaneous adsorption characteristics ofethanol as a refrigerant onto two studied sample
have been measured gravimetrically using
magnetic suspension adsorption measurement
unit. The system executes the whole experimentautomatically by following the instruction givenin the software. It can be mentioned thatbuoyancy effect on the measurements is
considered automatically by the system.
Experiments have been conducted at adsorption
temperature 30°C with various evaporator
pressures. Figure 1 shows the schematic diagramof sample with ethanol vapor entrance direction
inside the adsorption cell of measurement unit.

Equilibrium adsorption capacity [kg kg-1]

1.210.8
1.4 mm-Consolidated AC
5.2 mm-Consolidated AC

0.6

0.4

0.200246Pressure [kPa]81012Figure 2. Equilibrium adsorption capacity of
ethanol onto 1.4 mm and 5.2 mm height ofconsolidated AC.
1.2Tadsorption : 30 C
Pevaporator : 2.62 kPa

1.4 mm-Consolidated AC
5.2 mm-Consolidated AC

1.0Ethanol vapor entrance direction

0.6

0.5

0.6

Normalized uptake [-]Normalized uptake [-]

0.8

0.4

0.4
1.4 mm-Consolidated AC
5.2 mm-Consolidated AC
0.3

0.2

0.1

Adsorption celltime constant= 448 sec

0.2time constant= 1400 sec

0.00200400600800Time [sec]

1000

1200

1400

0.00

D: 23.5mm

D: 17 mm

H: 1.4 mm

H: 5.2 mm

1000

2000

3000

4000
Time [sec]

5000

6000

7000

8000

Figure 3. Instantaneous adsorption capacity ofethanol onto 1.4 mm and 5.2 mm height ofconsolidated AC.

Consolidated AC

4. Conclusions
The consolidated adsorbents have been
prepared using polyvinyl alcohol (PVA) (10wt%) and 90 wt% Maxsorb III (AC) with height
1.4 mm and 5.2 mm. Apparent packing densityof consolidated AC adsorbents is (316 ± 4 kgm3). It is found that there is no significant
difference in equilibrium adsorption capacity.
However, significant difference of instantaneousadsorption capacity between two different
heights of same sample has been observed. To
reach 63% of maximum value, 1.4 mm heightsample takes 448 sec whilst 1400 sec is for 5.2mm height consolidated AC.

Figure 1. Schematic representation of sample withethanol vapor entrance direction inside theadsorption cell of measurement unit.

3. Results and discussion
Two different heights (1.4 mm and 5.2 mm)
at fixed packing density consolidated AC (90wt% Maxsorb III+ 10 wt% PVA) have preparedby changing the mass ratio with applying thesame pressure. Instantaneous adsorption
experiments are conducted at various evaporator
pressures and adsorption temperature at 30°Cusing
magnetic
suspension
adsorption
measurement unit. Both samples show similarequilibrium adsorption capacity (Figure 2), as it
was expected because of same compositions.
However, instantaneous adsorption capacity
varies for different heights sample with same
packing density. This is due to increasing thevapor diffusion resistance with increasing theheight of same sample. It is observed that time
constant for 1.4 mm height sample is 448 sec
whereas 1400 sec is for 5.2 mm heightconsolidated AC (Figure 3).

References[1] I. I. El-Sharkawy, A. Pal, T. Miyazaki, B. B.
Saha, S. Koyama, Appl. Therm. Eng. 2016, 98,1214–1220.
[2] L. W. Wang, Z. Tamainot-Telto, R. Thorpe, R.
E. Critoph, S. J. Metcalf, R. Z. Wang, Renew.
Energy 2011, 36, 2062–2066.
[3] G. Cacciola, G. Restuccia, L. Mercadante,Carbon N. Y. 1995, 33, 1205–1210.
[4] A. Sharafian, K. Fayazmanesh, C. McCague,
M. Bahrami, Int. J. Heat Mass Transf. 2014,
79, 64–71.

Email: animesh@kyudai.jp

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