10 Thermodynamic Analysis of Activated Carbon–Ethanol …
183
and it is observed that the COP of zeolite–water system is 0.10 having collector area of 20 m
2 and mass of adsorbent is 360 kg. The COP of activated
carbon–methanol system (Pons and Guilleminot 1986) was found out to be
0.12–0.14 having collector area of 6 m
2 and mass of adsorbent is 20–24 kg/m
2 .
Sumathy et al., studied an activated carbon–methanol system driven by solar
energy, and observed that output of the system is 4–5 kg of ice per day and the
COP is about 0.1–0.2 with collector area of 0.92 m
2 (Sumathy and Zhongfu
1999). Li et al., at Guangzhou Institute of Energy Conversion and Tan at South
China University of Technology developed a refrigeration system powered by
solar energy having similar performance to the system developed by Sumathy
(Wang et al. 2014).
To enhance the energy efficiency a compound refrigerator and water heater
system based on solar energy was developed by SJTU (Wang et al. 2000) and in
2004, SJTU also developed a solar energy based adsorption chiller which uses
silica gel–water as working pair for building and grain storage hall.
El-Sharkawy et al. (2008) worked on activated carbon–ethanol based solar powered adsorption system. Ideal COP of the system is 0.8 at an evaporator temperature of 15
◦ C and desorption temperature of 80
◦ C.
10.4 Adsorption Process and Selection Criteria
for Working Pairs
Adsorption is a surface phenomenon in which molecules of one substance adheres
to the surface of another. This results in an increase in concentration at the interface. The solid which adsorbs the molecules called adsorbent and the liquid or gas
which is getting adsorbed is called adsorbate. Adsorption is of mainly two types,
physical adsorption (Ponec et al. 1974) and chemisorption (Wang 2005). Driving
force in case of physisorption is weak wander wall force of attraction whereas in
case of chemisorption adsorbent and adsorbate undergo a chemical reaction (Gasser
and Ehrlich 1987). Chemisorption is an endothermic process and is not reversible.
Physisorption is an exothermic process and the heat released during this process is
known as adsorption heat. This process is reversible in nature, means desorption
occurs when heat is supplied to the adsorbent and this heat can be acquired using
solar energy and waste heat from automobiles or any other sources.
Basic requirements for the selection of adsorbent are as follows:
1. Should desorb large amount of adsorbate over a given range of temperature.
2. Should have low specific heat.
3. Should have high conductivity.
4. Should be stable with adsorbate/refrigerant used.
5. Should be easily available and have low cost.
183
and it is observed that the COP of zeolite–water system is 0.10 having collector area of 20 m
2 and mass of adsorbent is 360 kg. The COP of activated
carbon–methanol system (Pons and Guilleminot 1986) was found out to be
0.12–0.14 having collector area of 6 m
2 and mass of adsorbent is 20–24 kg/m
2 .
Sumathy et al., studied an activated carbon–methanol system driven by solar
energy, and observed that output of the system is 4–5 kg of ice per day and the
COP is about 0.1–0.2 with collector area of 0.92 m
2 (Sumathy and Zhongfu
1999). Li et al., at Guangzhou Institute of Energy Conversion and Tan at South
China University of Technology developed a refrigeration system powered by
solar energy having similar performance to the system developed by Sumathy
(Wang et al. 2014).
To enhance the energy efficiency a compound refrigerator and water heater
system based on solar energy was developed by SJTU (Wang et al. 2000) and in
2004, SJTU also developed a solar energy based adsorption chiller which uses
silica gel–water as working pair for building and grain storage hall.
El-Sharkawy et al. (2008) worked on activated carbon–ethanol based solar powered adsorption system. Ideal COP of the system is 0.8 at an evaporator temperature of 15
◦ C and desorption temperature of 80
◦ C.
10.4 Adsorption Process and Selection Criteria
for Working Pairs
Adsorption is a surface phenomenon in which molecules of one substance adheres
to the surface of another. This results in an increase in concentration at the interface. The solid which adsorbs the molecules called adsorbent and the liquid or gas
which is getting adsorbed is called adsorbate. Adsorption is of mainly two types,
physical adsorption (Ponec et al. 1974) and chemisorption (Wang 2005). Driving
force in case of physisorption is weak wander wall force of attraction whereas in
case of chemisorption adsorbent and adsorbate undergo a chemical reaction (Gasser
and Ehrlich 1987). Chemisorption is an endothermic process and is not reversible.
Physisorption is an exothermic process and the heat released during this process is
known as adsorption heat. This process is reversible in nature, means desorption
occurs when heat is supplied to the adsorbent and this heat can be acquired using
solar energy and waste heat from automobiles or any other sources.
Basic requirements for the selection of adsorbent are as follows:
1. Should desorb large amount of adsorbate over a given range of temperature.
2. Should have low specific heat.
3. Should have high conductivity.
4. Should be stable with adsorbate/refrigerant used.
5. Should be easily available and have low cost.