Figure 1: System architecture of a water-cooled chilled water plant.
For conventional Water-Cooled Chilled Water
Systems, the total chiller capacity must meet the
building space peak load. The building space peak
load has to be estimated to provide the basis for
selecting the plant equipment. Thus, the design
flow for a chilled water system can be divided into
two phases, i.e. (i) cooling load estimation and (ii)
selection of plant equipment. The main steps in
each phase are shown in Figure 2.
Common Design Issues
Generally, during the design of an air conditioning
system, the design concerns include the cooling
load required for the building space, the physical
size of the equipment, energy consumption,
maintenance, capital investment and operating
costs.
During the cooling load estimation phase, the
main concern is heat load over-conservatism,
i.e. over estimation. A poor estimate may result
in the selection of the wrong equipment, causing
Plant System over sizing and may eventually lead
to challenges in meeting the objectives of energy
efficiency, environmental stewardship, operating
costs and maintainability.
Over sizing is a critical engineering design issue
for ACMV systems in Malaysia. Typical challenges
faced by mechanical engineers during the design
of an ACMV system include:
Malaysia's climate is equatorial, hot and
humid throughout the year. Owners of
buildings do not want to receive comfort
complaints from the occupants and then
have to call back the contractors to solve
the complaints.
● ●
M&E consultants do not have control over
the building envelope and it is challenging
to accurately estimate how much infiltration
a large building allows.
● ●
Frequent last minute design changes are
often received from the architect or client.
● ●
Buildings are rarely built to detailed design
specifications.
System over sizing issues should not be
taken lightly because they may cause numerous
disadvantages to all parties, including the owner
of the building and its occupants, for example:
● ●
High investment costs.
● ●
High energy consumption.
● ●
High operating costs, in term of higher
electricity bills for the operator.
● ●
High carbon dioxide footprint.
● ●
Shorter lifespan of equipment due to
frequent chiller start/stop modes.
● ●
High humidity in cooling space resulting in
the formation of mould and fungus growth.
● ●
Poor Indoor Air Quality due to high humidity
in cooling space. The energy efficiency
of ACMV systems is interrelated with the
over sizing issue. The Green Building Index
● ●
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