Civil Engineering Reference
In-Depth Information
conditioning systems. Invention of the heat pumps was an advancement that created
the ability of the space cooling when cooling is required and ability of space heat-
ing when heating is required with the same unit while utilizing reverse cycles
(Khazaii
2012
).
8.2
New Era and Attention Towards Energy Effi ciency
The defi nition of effi ciency for different equipment is generally referred to the ratio
of the effective or useful output to the required total input of the equipment. The Air
Conditioning and Refrigeration Institute (ARI (also known as AHRI)) is an institute
that regulates how the manufacturers have to perform performance tests and how to
publish the effi ciency of their products based on the outcome of those tests. Of
course the published values shall describe the effi ciency of the equipment under full
and part load conditions. As it was noted earlier, the effi ciency of different equip-
ment shall be defi ned by the ratio of effective to implied energy. For example the
effi ciency of a fan should be stated as ratio of power transferred to the airfl ow and
the power used by the fan.
Different reference resources have categorized HVAC systems in different ways,
but two most universally accepted methods to categorize these systems that are also
in-line with ASHRAE systems handbook (ASHRAE
2012
) defi nition are dividing
them into either centralized and decentralized systems, or all air, air-water, and all
water systems.
To ensure receiving high performances from the HVAC systems, different refer-
ence topics have offered different prescriptive guidance, e.g. higher workmanship
for construction materials, advance control strategies and of course higher equip-
ment effi ciency. Some of these sources have also suggested performing simulations
(energy modeling) in order to ensure achieving a minimum acceptable performance
for the whole building including its HVAC system.
One of the methods that is regularly used in practice for energy effi ciency evalu-
ation is structured in ANSI/IESNA/ASHRAE Standard 90.1-2013 (ASHRAE
2013
)
which in order to specify the energy effi ciency of the building demands performing
either a prescriptive based analysis or running a simulation based modeling for the
targeted building. The simulation-based method further requires comparing the
simulation results with the results of another simulation for an imaginary equivalent
building that its structure is described and known as the baseline building in
ASHRAE standard 90.1 (ASHRAE
2013
). The amount of saved energy (cost) in
design building compared to the imaginary building will be represented as the
degree of energy effi ciency of the design building (Khazaii
2012
).
Simulation software basically provides yearly energy consumption output for the
specifi c building in a specifi c climate under full and part load condition of the HVAC
system based on various building and system inputs. But there are some other major
considerations that can affect the overall effi ciency of a system as well. These
considerations cannot be translated into quantitative measures easily and almost all
of the simulation software packages lack the capacity to include these parameters in
