Experimental and theoretical studies on adsorption chillers driven by waste heat and propane

EXPERIMENTAL AND THEORETICAL STUDIES ON
ADSORPTION CHILLERS DRIVEN BY
WASTE HEAT AND PROPANE



AZHAR BIN ISMAIL
(B.Eng, National University of Singapore, Singapore)





A THESIS SUBMITTED
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
DEPARTMENT OF MECHANICAL ENGINEERING
NATIONAL UNIVERSITY OF SINGAPORE
2013
Declaration


i

DECLARATION



I hereby declare that this thesis is my original work and it has been written by
me in its entirety. I have duly acknowledged all the sources of information
which have been used in the thesis.

This thesis has also not been submitted for any degree in any university
previously.


………………
Azhar Bin Ismail
20 December 2013


Acknowledgements



ii

ACKNOWLEDGEMENTS
BismiLLAHI-arRahman-arRaheem Alhamdu-LILLAH was-solatu wassalamu
‘alaa rosuliLLAH wa ‘alaa aalihi wa sohbihi wa man walaah. I sincerely
praise and express my gratitude to Allah, the Most Gracious, the Most Loving
for His abundant blessings and strength that I am able to write and work on
this thesis.
I am truly grateful to my supervisor, Professor Ng Kim Choon who has taught
me, both at a conscious and sub-conscious level, how good experimental
thermodynamics is done. I am truly blessed by all the valuable ideas, funding
and time, which positively enhanced my PhD experience, making it both
enriching and stimulating. The enthusiasm he has for research was a personal
motivation and inspiration for me. I would like to express my sincere thanks to
Professor Bidyut Baran Saha of Kyushu University and Professor Kandadai
Srinivasan for their insights and being a role model of high quality research

excellence. I will forever be thankful to my mentor cum teacher, Dr Kyaw Thu
from the National University of Singapore for his inspiration and motivation
without which it was not possible for me to hover the toughest times of my
candidature. I am also indebted to Dr Loh Wai Soong who has taught me the
fundamental aspects of adsorption and the experimental techniques and
advised much on the path of this thesis. I would also like to thank Mr
Sacadevan Raghavan of air conditioning laboratory for all the technical skills
he imparted me and the support. I would like to express my special thanks to
Dr Kazi Afzalurrahman from Chittagong University of Engineering &
Technology, Dr Fillian Arbriyani and Dr Aung Myat from A STAR.
Acknowledgements



iii

Most importantly, I am most grateful to all my beloved family and friends for
their prayers, unwavering support and motivation. I would like to especially
thank my beloved mum, Ummi Rosnah Bte Bajuri, my maternal grandmother,
Jaddati Halipah Bte Sadeli, my dad, Abi Ismail Bin Talib and my best friend
for their love and support. I dedicate this thesis to them. I have to especially
thank my closest lab pals, Wakil Shahzad, Li Ang and Muhammad Burhan
who had been great buddies who helped and supported me throughout my
entire Phd journey.
Azhar Bin Ismail
20 December 2013
List of Journal Publications

iv

List of Journal Publications
1. Ismail, Azhar Bin, Ang Li, Kyaw Thu, K. C. Ng, and Wongee Chun.
"On the Thermodynamics of Refrigerant+ Heterogeneous Solid
Surfaces Adsorption." Langmuir 29, no. 47 (2013): 14494-14502.

2. Loh, Wai Soong, Ismail, Azhar Bin, Baojuan Xi, Kim Choon Ng, and
Won Gee Chun. "Adsorption Isotherms and Isosteric Enthalpy of
Adsorption for Assorted Refrigerants on Activated Carbons." Journal
of Chemical & Engineering Data 57, no. 10 (2012): 2766-2773.

3. Ismail, Azhar Bin, Wai Soong Loh, Kyaw Thu, and Kim Choon Ng.
"A Study on the Kinetics of Propane-Activated Carbon: Theory and
Experiments." Applied Mechanics and Materials 388 (2013): 76-82.

4. Wai Soong Loh, Ismail, Azhar Bin, Kim Choon Ng and Won Gee
Chun. “Experimental Performance Rating of a Miniaturized
Pressurized Adsorption Chiller”, Journal of Heat Transfer Research
(Accepted)

5. Ismail, Azhar Bin, Ang Li, Kyaw Thu, Kim Choon Ng, and Wongee
Chun. "Pressurized Adsorption Cooling Cycles Driven by Solar/Waste
Heat." Applied Thermal Engineering (2014).

6. Li, Ang, Ismail, Azhar Bin, Kyaw Thu, Kim Choon Ng, and Wai
Soong Loh. "Performance evaluation of a zeolite–water adsorption
List of Journal Publications

v

chiller with entropy analysis of thermodynamic insight." Applied
Energy (2014).

7. Ismail, Azhar Bin, Ang Li, Kyaw Thu, Kandadai Srinivasan, Kim
Choon Ng. “Adsorption Kinetics Of Propane On Energetically
Heterogenous Activated Carbon”, (Submitted to Applied Thermal
Engineering)

List of Conferences

1. Ismail, Azhar Bin, Kyaw Thu, Kandadai Srinivasan, and K.C. Ng.
"Adsorption Kinetics Of Propane On Energetically Heterogenous
Activated Carbon" International Symposium on Innovative Materials
for Processes in Energy Systems 2013, Fukuoka, Japan, 4-6 Sep. 2013.

2. Ismail, Azhar Bin, Ang Li, W.S. Loh, Kyaw Thu, Kandadai
Srinivasan, and K.C. Ng. "Dynamic Behavior and Performance
Evaluation of a Two-Bed Activated Carbon Powder + Propane
Adsorption Prototype" The 6th International Meeting of Advances in
Thermofluids, Singapore, 18-19 Nov. 2013.

3. Muhammad Idrus Alhamid, Nasruddin, Bambang Suryawan, Awaludin
Martin, Loh Wai Soong, Ismail, Azhar Bin, Chun Won Gee, Ng Kim
Choon. "High Pressure Adsorption Isotherms of Carbon Dioxide and
Methane on Activated Carbon from Low-grade Coal of Indonesia" The
List of Journal Publications

vi

6th International Meeting of Advances in Thermofluids, Singapore, 18-
19 Nov. 2013.

4. Ang Li, Ismail, Azhar Bin, Kyaw Thu, Muhammad Wakil Shahzad,
Kim Choon Ng. " Dynamic Modeling of a Low Grade Heat Driven
Zeolite – Water Adsorption Chiller" The 6th International Meeting of
Advances in Thermofluids, Singapore, 18-19 Nov. 2013.

5. Kyaw Thu, Young-deuk Kim, Ismail, Azhar Bin, Kim Choon Ng.
"Adsorption Characteristics of Water Vapor on Mesoporous Silica
Gels" The 6th International Meeting of Advances in Thermofluids,
Singapore, 18-19 Nov. 2013.

6. Ismail, Azhar Bin; Wai Soong Loh; Kyaw Thu; Kim Choon Ng
Kinetics Of Propane Adsorption On Maxsorb III Activated Carbon.
The 5th International Meeting in Advanced Thermofluids, Bintan,
Indonesia, 12-13 Nov. 2012.

7. Kyaw Thu, Young-Deuk Kim, Baojuan Xi, Ismail, Azhar Bin, Kim
Choon Ng Thermophysical Properties of Novel Zeolite Materials for
Sorption Cycles. The 5th International Meeting in Advanced
Thermofluids, Bintan, Indonesia, 12-13 Nov. 2012.


8. Muhammad Wakil Shahzad, Kyaw Thu, Won Gee Chun , Ismail,
Azhar Bin and Kim Choon Ng, An Experimental Test on a 3-Stage

List of Journal Publications



vii

Multi Effect Distillation System. The 5th International Conference on
Applied Energy, Pretoria, South Africa 1-4 July 2013.

9. Ang Li, Kyaw Thu, Wai Soong Loh Ismail, Azhar Bin and Kim
Choon Ng, Performance evaluation of a zeolite water adsorption chiller
with entropy analysis of thermodynamic insight. . The 5th
International Conference on Applied Energy, Pretoria, 1-4 July 2013.
Table of Contents



viii

Table of Contents

Declaration i
Acknowledgements ii
List of Publications iv
Table of Contents viii
Summary xiii
List of Tables xvi
List of Figures xviii
Nomenclature xxvii
Chapter 1 Introduction 1

1.1 Background 1
1.1.1 Heat Sorption Systems and Global Concerns on the Environment and Ecology. 1
1.1.2 Limitations of Adsorption Chillers 2
1.1.3 Propane Refrigerant as an Adsorbate 4
1.1.4 Review of Previous Studies on Adsorption Pairs 9
1.2 Objectives and Scope 12
1.3 Thesis Outline 15

Chapter 2 Physical Adsorption 19
2.1 Background 19
2.1.1 The adsorption phenomena from a Statistical Rate Approach 19
2.1.2 Entropy change of an isothermal system during adsorption/desorption 22
2.1.3 Chemical potential of the adsorbed phase 24
2.1.4 Average energy of a single molecule and the molecular partition function 25
2.1.5 Energy of N interacting molecules and the canonical partition function 29
2.1.6 The canonical partition function of an adsorbent+adsorbate system 33
2.2 Review of the Derivation of Adsorption Isotherms 36
2.2.1 Langmuir Model 36
2.2.2 Langmuir-Freundlich Model 38
2.2.3 Dubinin-Astakhov Model 43
2.2.4 Toth Model 45


Table of Contents



ix

2.3 Review of Adsorbents for the Adsorption Chiller System 46

2.3.1 Microporous Adsorbents 48
2.3.2 Activated Carbons 50
2.3.3 Preparation of Activated Carbons 51
2.3.4 Activated Carbon Properties in Adsorption Chillers 53
2.3.5 Types of Activated Carbon 54
2.3.6 Metal Organic Framework (MOFs) 54
2.4 Summary 55

Chapter 3 Adsorption Equilibria of Propane Vapor on Activated Carbon
56
3.1 Background 56
3.1.1 Adsorption Equilibria 57
3.2 Experimental Adsorption Measurement for Surface Characteristics 58
3.2.1 Materials 58
3.2.2 Nitrogen adsorption and desorption 61
3.2.3 BET Surface Area and Pore Size Distribution 64
3.2.4 Density measurements of carbon based adsorbent samples 64
3.3 Experimental Adsorption Isotherm of Propane on Activated Carbon 67
3.3.1 Materials 67
3.3.2 Apparatus and Procedure 67
3.3.3 Data Reduction 72
3.3.4 Results and Discussions 75
3.3.5 Correlation of Isotherms 77
3.3.6 Improvements to the Dubinin-Astakhov Model 81
3.4 Analysis of Isotherm Data for Practical Applications 85
3.4.1 BET Surface Area and Increased Uptake 85
3.5 Isosteric Heat of Adsorption 88
3.6 Summary 93

Table of Contents



x

Chapter 4 Adsorption Thermodynamics of Activated Carbon
+Refrigerant Systems 95
4.1 Background 95
4.2 Adsorption Thermodynamics 96
4.2.1 Gibbs Free Energy 96
4.2.2 Adsorbed Phase Entropy (s
a
) 97
4.2.3 Adsorbed Phase Enthalpy (h
a
) 99
4.2.4 Specific Heat Capacity (C
p,a
) 102
4.3 Results and Discussion 113
4.3.1 Adsorbed Phase Specific Volume (v
a
) 113
4.3.2 Heat of Adsorption (H
ads
) 115
4.3.3 Adsorbed Phase Specific Heat Capacity (C
p,a
) 119

4.3.4 Adsorbed Phase Entropy (s
a
) and Enthalpy (h
a
) 122
4.4 Summary 125

Chapter 5 Equilibrium Analysis of the Pressurized Adsorption
Cooling Cycle 126
5.1 Background 126
5.2 Temperature – Enthalpy/Entropy Diagram (T-h,T-s) 130
5.2.1 Adsorption Stage 134
5.2.2 Isosteric Pre-Heating Stage 135
5.2.3 Desorption Stage 135
5.3 Specific Cooling Effect and COP of highly porous activated carbon
powder of type Maxsorb III + Propane Cycle 137
5.3 Cycle Analysis of Assorted Alternative Adsorption Pairs 141
5.3.1 Uptake Efficiency 144
5.4 Summary 150


Table of Contents



xi

Chapter 6 Adsorption Kinetics of Propane Vapor on Activated Carbon
152
6.1 Background 152

6.2 Adsorption Kinetics Model 154
6.2.1 General rate Expression for Langmuir model of Adsorption 157
6.2.2 Non-Isothermal Linear Driving Force Model 160
6.3 Experimental Method for Kinetics Measurement 163
6.3.1 Materials 165
6.4 Determination of the Particle-Phase Transfer Coefficient 167
6.4.1 Buoyancy Corrections 167
6.5 Results and Discussion 169
6.5.1 Blank Measurements and Buoyancy Corrections 169
6.5.2 Adsorption Measurements of Propane on Activated Carbon 170
6.5.3 Deviation of Equilibrium Uptakes with Constant Volume Isotherm Experiment
177
6.5.4 Non-Isothermal Kinetics Analysis 178
6.6 Summary 182

Chapter 7 Dynamic Behavior And Performance Evaluation of a Two-Bed
Activated Carbon Powder + Propane Adsorption Prototype 184
7.1 Background 184
7.1.1 Advanced Adsorption Chiller Cycle 185
7.1.2 Adsorption Chiller Mass Recovery Scheme 186
7.2 Theoretical Modeling of the Pressurized Bed Adsorption Chiller 189
7.3 Experimental Test Rig 196
7.3.1 Description of Test Facility 196
7.3.2 Experimental Procedure 200
7.4 Results and Discussion 207
7.4.1 Experimental Heat Leak Test 207
7.4.2 Experimental Pressure and Temperature Profiles 208
7.4.3 Experimental and Ideal Dühring Diagram with Pressure Equalization 212
7.4.4 Effect of Cycle Time on the Evaporator Temperature 215
7.4.5 Validation of Simulation Results 217

7.5 Summary 221

Table of Contents



xii

Chapter 8 Conclusion 222
References 228
Appendices 248
Appendix A: Isotherms and Isosteric Heats of Adsorption, Assorted
Refrigerants 248
Appendix B: Measurement Considerations, Magnetic Suspension Balance
251
Appendix C: Wiring Diagram for Pressure Controller 254
Appendix D: Refrigerant Mass Required in Adsorption and Desorption Beds
256
Appendix E: Sample Time-Dependent Kinetics Data 259

Summary



xiii

SUMMARY


The increasing concerns related to the environment and ecology of recent years

have brought about escalating interests in utilizing heat sorption systems for
cooling applications. This is due to its capability of directly utilizing low grade
thermal energy, including heat from solar hot water, industrial waste heat and
geothermal sources. The aim of the current is to investigate, both theoretically
and experimentally the utilization of alternative adsorbent + adsorbate pairs
specifically those in the moderate pressure ranges in a single-stage pressurized
bed adsorption chiller arrangement. A chiller operating at these pressure ranges
eliminates the need of high-maintenance vacuum considerations that exist in
current adsorbent + water systems. Furthermore, the differential uptake as the
pressure increases in general also becomes higher.
Experimental data containing isotherm information for refrigerants in these
moderate pressure regions are first collated and fitted to an improved model that
takes into account the adsorbed phase volume correction. Necessary data with
regard to the adsorption characteristics of activated carbon + propane pairs, which
are currently lacking are then experimentally collected and analyzed namely, its
equilibria uptake characteristics.
A theoretical framework for the study of the pressurized bed adsorption chiller is
also developed. Thermodynamic relations are derived from the rigor of adsorption
thermodynamic incorporating statistical mechanics considerations and the degree
Summary



xiv

of freedom of a translational adsorbed particle motion. The proposed expressions
are relatively convenient to be utilized for the analysis of adsorption systems for
all pressure ranges. The model also incorporates the adsorbed phase volume
corrections and the non-idealities of the gaseous phase
Together with the parameters from the experimental data, the adsorption pairs,

specifically that of highly porous activated carbon powder of type Maxsorb III
with propane, n-butane, HFC-134a, R507a and R-32 are then analyzed to compare
their cooling capacities under various conditions namely the (i) regeneration, (ii)
ambient and (iii) required cooling temperatures. It was found that the activated
carbon + propane pair is the most feasible option when the ambient temperature is
high and the required cooling is low. Furthermore, hydrocarbons are naturally
available working fluids with a low ozone depleting potential (ODP) and global
warming potential (GWP). It also has a high latent heat of vaporization making it
an excellent refrigerant, gaining acceptance in conventional mechanical
compression chillers. It is also capable of cooling below 0°C in comparison to
water systems.
Critical data with regard to the time-dependent kinetics characteristics between
activated carbon and propane have therefore been collected and analyzed. These
data has been regressed to an improved model derived from statistical mechanics.
Further non-isothermal considerations were also studied and the parameters which
may be utilized for numerical analysis are obtained. The adsorption chiller is
finally modeled taking into account the heat and mass transfer as well as pressure
equalization effects in the respective components and verified experimentally
Summary



xv

with a fabricated batch operated single-stage adsorption chiller. This model which
fits the experimental data very well could be used to describe any working
adsorption pair for further studies.

List of Tables



xvi

List of Tables

Table 1.1 Adsorbent-adsorbate pairs found in the literature for adsorption
refrigeration cycles

Table 2.1 Summary of site energy distribution term for corresponding
isotherm models
Table 2.2 Materials used as pre-cursors for activated carbon synthesis

Table 3.1 The thermo-physical properties of the activated carbon samples
Table 3.2 Isotherm data and results for propane on highly porous activated
carbon powder of type Maxsorb III
Table 3.3 Isotherm equations
Table 3.4 Numerical value of the parameters 

,, , 

, 

and  for
both Toth and DA model that have been regressed from the
experimental data
Table 3.5 Numerical values of the parameters for the Improved DA
parameters

Table 3.6 Comparison of regressed values of 

,  and  with works on
highly porous activated carbon powder of type Maxsorb III +
Hydrocarbon pairs in the Dubinin-Astakhov equation

Table 4.1 Summary of assumptions in previous works in deriving the
expression for the change in enthalpy
Table 4.2 The expressions for specific heat capacity from Langmuir and DA
equation
Table 4.3 Comparative study of the thermodynamic framework of this thesis,
that of Kazi (2011) and Chakraborty et al (2009)

Table 5.1 Fitted parameters of the modified DA equation for the assorted
refrigerants

Table 6.1 Regressed values for the K
gs
term of equation (6.23)
List of Tables



xvii

Table 6.2 Parameters of non-isothermal kinetics rate of adsorption

Table 7.1 Summary of modeling equations
Table 7.2 Control schedule of the pressurized bed adsorption chiller for the
two cycles

Table 7.3 Parameters used in simulation program

List of Figures



xviii

List of Figures

Figure 1.1 Saturation pressures of various adsorbates for typical working
temperatures between the evaporator and condenser
Figure 1.2 Heat transfer configuration for ideal adsorption chiller operation
Figure 1.3 Latent heat of vaporization of assorted adsorbates working in the
pressurized saturation region for common working temperatures of
evaporator and condenser

Figure 2.1(a) The definition of a system configuration in an adsorption or
desorption event
Figure 2.1(b) Accompanying transition energy levels for a change in system
configuration
Figure 2.2 Isothermal system model considered where a reservoir ensures that
heat evolved is dissipated
Figure 2.3 System with independent, non-interacting molecules
Figure 2.4 System configuration combinations and the most probable state
Figure 2.5 The canonical partition function describing a system with
interacting molecules
Figure 2.6 The canonical distribution and a system in thermal contact
Figure 2.7 Allowable systems of a system of interacting molecules
Figure 2.8 A system of adsorbent-adsorbate model and defining the canonical

partition function
Figure 2.9 Many localized adsorption sites (1-5) given by its adsorption
energy 


Figure 2.10 Graph of equation (2.70) for different T and 

= 0
Figure 2.11 Gaussian function 
(

)
centered at 

= 0 , dispersion c for c =
10, 20 and 30
Figure 2.12 Asymmetrical Gaussian function 
(

)
of equation (3.21) centered
for r =1, 3 and 5
List of Figures



xix

Figure 2.13 Adsorption equilibria of KC type Silica Gel (BET surface area
850m

2
/g) with propane at temperatures of (278-◊, 293-□ and 303-
∆) K
Figure 2.14 Adsorptione of Linde S-115 silicalite type Zeolite (BET Surface
Area 380m
2
/g) with propane at temperatures of (275-◊, 300-□,
325-∆ and 350-○) K

Figure 3.1 Two adsorption isotherms q = f(P
e
) for given steady state
temperatures T
a
and T
b

Figure 3.2 Specimens of carbon based adsorbents: (a) ACF (A-15) (b) ACF
(A-20) (c) highly porous activated carbon powder of type Maxsorb
III (d) granular activated carbon type Chemviron
Figure 3.3 Scanning electron micrographs (FE-SEM) photos of highly porous
activated carbon powder of type Maxsorb III (left), ACF (A-20)
(right) at magnifications 2000
Figure 3.4 Scanning electron micrographs (FE-SEM) photos of ACF (A-15)
(left), Chemviron (right) at lower magnifications of 950 and 90
respectively
Figure 3.5 Schematic diagram of AUTOSORB-1 apparatus
Figure 3.6(a) Nitrogen adsorption isotherm at 77.4K for the full pressure range
Figure 3.6(b) Nitrogen adsorption isotherm at 77.4K up to Pr = 0.005
Figure 3.7 Surface Area determined by the multi-point BET curve for highly

porous activated carbon powder of type Maxsorb III sample
Figure 3.8 Cumulative and incremental pore volume determined by QSDFT
for the highly porous activated carbon powder of type Maxsorb III
sample
Figure 3.9 Typical pressure and temperature profiles for the highly porous
activated carbon powder of type Maxsorb III + propane pair
Figure 3.10 Schematics diagram of the adsorption isotherm apparatus
Figure 3.11 Pictorial views of the adsorption equilibria apparatus and its
components
Figure 3.12 Isotherm characteristics of activated carbons (a) ACF (A-15) (b)
ACF (A-20) (c) Chemviron and (d) Maxsorb III + propane
List of Figures



xx

Figure 3.13 Raw experimental data of propane uptake on highly porous
activated carbon powder of type Maxsorb III at temperatures from
5~75
o
C
Figure 3.14 Experimental data on highly porous activated carbon powder of
type Maxsorb III regressed with the Toth equation (Left) and DA
equation (Right). The regressions agree to within 5% of
experimental data. Table 3.3 shows the numerical value of the
parameters that have been regressed from the experimental data
Figure 3.15 Final regression of the experimental adsorption isotherm data of
propane on highly porous activated carbon powder of type
Maxsorb III regressed with the improved D-A equation with

adsorbed phase volume correction (Dotted Lines are from
Dubinin’s adsorbed phase volume model, full lines are from
Srinivasan’s adsorbed phase volume model)
Figure 3.16 Comparison of adsorption uptake deviations between experimental
uptake and predicted values using the various models
Figure 3.17 Deviation plots for propane excess adsorption on highly porous
activated carbon powder of type Maxsorb III specimen of activated
carbon
Figure 3.18 Comparison of isotherm data for highly porous activated carbon
powder of type Maxsorb III + propane and different activated
carbons + propane systems
Figure 3.19 Comparison of isotherm data for ACP(highly porous activated
carbon powder of type Maxsorb III) + hydrocarbon for Methane
[28] (∆), propane (◊) and n-butane (□)
Figure 3.20 SEM photos of highly porous activated carbon of type Maxsorb
III at high magnification of 19,000 (left) and 200,000 (right)
Figure 3.21(a) Heat of adsorption as a function of uptake for highly porous
activated carbon powder of type Maxsorb III + propane System.
Colored lines represent a fit with a logarithmic equation
Figure 3.21(b) Limiting Heat of adsorption for highly porous activated carbon
powder of type Maxsorb III + propane system as a function of
temperature for assorted isotherms
Figure 3.22 Relation between k
H
and h
st0


Figure 4.1 Temperature dependence of the adsorbed phase specific volume
(v

a
) in the present model obtained from the experimental data
List of Figures



xxi

points (∆) with the full red line representing the best isotherm fit
obtained from the modified DA equation
Figure 4.2 Isosteric heat of adsorption as a function of surface coverage of a
CaCl
2
-in-silica gel + water system for various temperatures
Figure 4.3 Heat of adsorption (H
ads
) for highly porous activated carbon
powder of type Maxsorb III + propane pair drawn against the
adsorbate loading qv
a
/W
o
at the measured isotherm temperatures

List of Figures



xxii

Figure 4.4 Heat of adsorption (H
ads
) plots for for highly porous activated
carbon powder of type Maxsorb III + propane pair drawn against
the temperature (T). The full black line represents the heat of
vaporization (h
fg
) for propane over temperatures 220K to 370K
Figure 4.5 Heat of adsorption (H
ads
) plots for different refrigerants on
activated carbon powder (highly porous activated carbon powder
of type Maxsorb III) at temperature (T) of 298K
Figure 4.6 Specific heat capacity of the adsorbed phase (c
p,a
) of highly porous
activated carbon powder of type Maxsorb III + propane pair for
temperatures between 270K to 370K and pressures up to 8 bars.
The red lines represent the gaseous phase specific heat capacities at
the same temperatures and pressures
Figure 4.7 Isobaric specific heat capacity of the adsorbed phase (cp,a) of
highly porous activated carbon powder of type Maxsorb III +
refrigerant pairs for temperatures between 270K to 350K.
Pressures correspond to saturated pressures of the refrigerants at
0°C
Figure 4.8 Entropy plots of the adsorbed phase (s
a
) of highly porous activated
carbon powder of type Maxsorb III + propane pair for temperatures
between 230K to 370K and pressures up to 8 bars. The black, red

dotted and full red lines represent the saturated liquid, adsorbed
and gaseous phase respectively
Figure 4.9 Enthalpy of the adsorbed phase (h
a
) of highly porous activated
carbon powder of type Maxsorb III + propane pair for temperatures
between 230K to 370K and pressures up to 8 bars. The black, red
dotted and full red lines represent the saturated liquid, adsorbed
and gaseous phase respectively
Figure 4.10 Degrees of freedom for translational particle motion in (a) solid (b)
liquid (c) gas and (d) adsorbed phases. The fundamental difference
between the adsorbed phase and the liquid phase is the y-
directional forces are Van der Waals instead of intermolecular

Figure 5.1 Process diagram of a thermally driven adsorption chiller
Figure 5.2 Dühring diagram from the regressed D-A equation (ABCD
represents a refrigeration cycle for a given evaporator/condenser
pressure) for an adsorption cycle running with propane and highly
porous activated carbon powder of type Maxsorb III
List of Figures



xxiii

Figure 5.3 The thermodynamic process of the adsorption highly porous
activated carbon powder of type Maxsorb III + propane adsorption
cycle
Figure 5.4(a) Schematic of the basic adsorption cycle (adsorption mode)
Figure 5.4(b) Schematic of the basic adsorption cycle (desorption mode)

Figure 5.5(a) Enthalpy-Temperature (h-T) diagram of the highly porous
activated carbon powder of type Maxsorb III + propane adsorption
cycle
Figure 5.5(b) Entropy-Temperature (s-T) Diagram of the highly porous activated
carbon powder of type Maxsorb III + propane adsorption cycle. 136
Figure 5.6 Dühring diagram from the regressed D-A equation (ABCD
represents a refrigeration cycle for the given evaporator/condenser
Pressure) for an adsorption cycle running with propane as
adsorbate and highly porous activated carbon powder of type
Maxsorb III as adsorbent.
Figure 5.7 COP and SCE plotted as a function of temperature for
hydrocarbons propane and n-butane
Figure 5.8 Schematic of the maximum enthalpy change of working fluid in
the evaporator for a condenser temperature of 40°C and an
evaporator temperature of 5°C
Figure 5.9 Operating profiles for propane, R-507A, R32 and R134a with
adsorbent highly porous activated carbon powder of type Maxsorb
III at 5°C evaporator temperature and 40°C (5.9(a)), 20°C (5.9(b))
and -5°C (5.9(c)) condenser temperature regenerating at 90°C and
adsorbing at 30°C
Figure 5.10 Effect of cooling water temperatures on the cooling (kJ) per kg of
adsorbent of the refrigerants for cooling water temperatures
30°C(5.10(a)), 40°C(5.10(b)) and 50°C (5.10(c)) respectively,
regeneration temperature of 90°C
Figure 5.11 Effect of regeneration water temperatures on the cooling (kJ) per
kg of adsorbent of the refrigerants for temperatures
100°C(5.11(a)), 90°C(5.11(b)) and 80°C(5.11(c)) respectively,
cooling water temperature of 40°C
Figure 5.12 Refrigerant selection chart for a given regenerating temperature
(between 80°C and 100°C), minimum evaporator temperature of -

20°C and cooling water temperatures of 30°C(5.12(a)) ,
40°C(5.12(b)) and 50°C(5.12(c)) respectively
List of Figures



xxiv

Figure 5.13 Description of the cooling load provided by the refrigerant pairs at
various operating conditions. Each line represents the specific
regeneration temperature, 5°C difference

Figure 6.1 Schematics Diagram for Rubotherm unit (MessPro)
Figure 6.2 Pictorial views of the adsorption kinetics apparatus and its
components
Figure 6.3 Blank measurements of the empty cylinder with nitrogen Gas
Figure 6.4 Buoyancy measurements of the empty cylinder with helium gas at
high temperature of 120°C
Figure 6.5 Adsorption cell cressure (kPa) and temperature (°C) against Time
(s) during a typical adsorption process in the kinetics experiment
Figure 6.6 Uptake versus time for the highly porous activated carbon powder
of type Maxsorb III + propane pair, for temperatures 283.16K and
303.16K, denotes the fitted curves from the regression made on
the experimental results in logarithmic scale (top) and normal scale
(bottom)
Figure 6.7 Uptake versus time for the highly porous activated carbon powder
of type Maxsorb III + propane pair for 323.16K, denotes the
fitted curves from the regression made on the experimental results
in logarithmic scale (top) and normal scale (bottom)
Figure 6.8 Uptake versus time for the highly porous activated carbon powder

of type Maxsorb III +p pair for 343K, denotes the fitted curves
from the regression made on the experimental results in
logarithmic scale (top) and normal scale (bottom)
Figure 6.9 K
gs
·P values for the various adsorption processes plotted against
temperature. Equation (5.24×10
-5
) T is valid for temperatures from
283K to 343K where the kinetics experimental data is obtained
Figure 6.10 Deviation plots between current equilibrium uptake and those
obtained from previous work utilizing CVVP apparatus
Figure 6.11 Temperature curves of highly porous activated carbon powder of
type Maxsorb III + propane: experimental data at ●- T
o
=10.96°C,
P
∞
=497 kPa, experimental data at ▲- T
o
=9.15°C, P
∞
=192kPa
Figure 6.12 Temperature curves of highly porous activated carbon powder of
type Maxsorb III + propane: experimental data at ♦- T
o
=28.60°C,
P
∞
=700 kPa, experimental data at ●- T

o
=28.89°C, P
∞
=497 kPa, ▲-
T
o
=29.27°C, P
∞
=195kPa