1 Introduction to Solar Energy …
7
to make use of such collectors, in conjunction with other auxiliary heat sources,
for providing heat to power an adsorption chiller, it is imperative to have a proper
mathematical model. This can aid in designing the network and predicting the performance of the whole system, prior to installation. This chapter focuses on the
modelling of a system that incorporates flat plate collectors, evacuated tube collectors and a thermally powered adsorption chiller. Here, mathematical equations to
calculate the efficiency of flat plate and evacuated tube collectors are presented; processes that are involved in a typical two bed adsorption cooling system are explained
in brief, and a mathematical model of an adsorption chiller, that employs mass and
heat recovery schemes is developed. Finally, the simulation results of the model are
presented, and the performance of the chiller is investigated to demonstrate a clear
understanding of its operation.
Chapter 9: Conventional cooling and refrigeration systems already evolved to
efficient design, have higher COP and compact size. However, the compressor part
of such system consumes a tremendous amount of electricity and contribute indirectly
to global warming. The working fluids of these systems are typically HFC or HFC
blends which possess very high global warming potential. A significant percentage
of working fluid is leaked from the high-pressure side of the system and directly
contribute to global warming. The summation of indirect and direct warming impact,
namely, total equivalent warming impact (TEWI) of the vapour compression cooling
systems are significantly high. Adsorption cooling system (ACS) can resolve this
critical issue. In ACS, the mechanical compressor of the traditional cooling system
is replaced by a thermal compressor, namely, a pair of adsorption beds. Highly
porous adsorbent material (silica gel, activated carbon, zeolite and so forth) is the
key component of an adsorption bed. These materials have the capability to capture
and hold certain types of fluid. This phenomenon is known as adsorption. Upon
heating, the adsorbed fluid is liberated from the pores (desorption process) and gets
thermally compressed. Solar thermal energy is the most prospective option for the
desorption process to occur. Since there is no mechanical compressor, electricity
consumption is deficient, which significantly minimizes the indirect warming impact.
Moreover, natural or alternative refrigerants are used as the working fluid, which
has zero/negligible GWP. Hence, the direct warming impact is also shallow. In this
chapter, the working principle and governing equations of a solar energy driven
adsorption cooling system will be elaborated. Besides, TEWI assessment procedure
will be explained and compared for both vapour compression and adsorption cooling
systems.
Chapter 10: The present study focuses on the thermodynamic analysis of
zeolite-water and activated carbon-ethanol based adsorption cooling systems. The
performance of the system depends critically on four operating temperatures namely
maximum desorption temperature, minimum adsorption temperature, condensing
temperature, and evaporating temperature and also on the ratio of specific heat of
structural material and the specific heat of adsorbent. Dubinin-Astakhov equation
is used to estimate the equilibrium uptake of working pairs. A comparative study is
made between these working pairs for the air-conditioning applications.
7
to make use of such collectors, in conjunction with other auxiliary heat sources,
for providing heat to power an adsorption chiller, it is imperative to have a proper
mathematical model. This can aid in designing the network and predicting the performance of the whole system, prior to installation. This chapter focuses on the
modelling of a system that incorporates flat plate collectors, evacuated tube collectors and a thermally powered adsorption chiller. Here, mathematical equations to
calculate the efficiency of flat plate and evacuated tube collectors are presented; processes that are involved in a typical two bed adsorption cooling system are explained
in brief, and a mathematical model of an adsorption chiller, that employs mass and
heat recovery schemes is developed. Finally, the simulation results of the model are
presented, and the performance of the chiller is investigated to demonstrate a clear
understanding of its operation.
Chapter 9: Conventional cooling and refrigeration systems already evolved to
efficient design, have higher COP and compact size. However, the compressor part
of such system consumes a tremendous amount of electricity and contribute indirectly
to global warming. The working fluids of these systems are typically HFC or HFC
blends which possess very high global warming potential. A significant percentage
of working fluid is leaked from the high-pressure side of the system and directly
contribute to global warming. The summation of indirect and direct warming impact,
namely, total equivalent warming impact (TEWI) of the vapour compression cooling
systems are significantly high. Adsorption cooling system (ACS) can resolve this
critical issue. In ACS, the mechanical compressor of the traditional cooling system
is replaced by a thermal compressor, namely, a pair of adsorption beds. Highly
porous adsorbent material (silica gel, activated carbon, zeolite and so forth) is the
key component of an adsorption bed. These materials have the capability to capture
and hold certain types of fluid. This phenomenon is known as adsorption. Upon
heating, the adsorbed fluid is liberated from the pores (desorption process) and gets
thermally compressed. Solar thermal energy is the most prospective option for the
desorption process to occur. Since there is no mechanical compressor, electricity
consumption is deficient, which significantly minimizes the indirect warming impact.
Moreover, natural or alternative refrigerants are used as the working fluid, which
has zero/negligible GWP. Hence, the direct warming impact is also shallow. In this
chapter, the working principle and governing equations of a solar energy driven
adsorption cooling system will be elaborated. Besides, TEWI assessment procedure
will be explained and compared for both vapour compression and adsorption cooling
systems.
Chapter 10: The present study focuses on the thermodynamic analysis of
zeolite-water and activated carbon-ethanol based adsorption cooling systems. The
performance of the system depends critically on four operating temperatures namely
maximum desorption temperature, minimum adsorption temperature, condensing
temperature, and evaporating temperature and also on the ratio of specific heat of
structural material and the specific heat of adsorbent. Dubinin-Astakhov equation
is used to estimate the equilibrium uptake of working pairs. A comparative study is
made between these working pairs for the air-conditioning applications.