Civil Engineering Reference
In-Depth Information
The sources of energy consumption in this type of systems are the air handling
unit supply fan motor input power, return fan motor input power, electric preheat
strip (if it is used for freeze protection instead of hot water coil) in air handling unit
and electric baseboard reheat unit (if it is used for dehumidifi cation or heating
instead of hot water coil). Duct air leakage, heat transfer from ducts connecting air
handling unit to the under fl oor plenum, and effi ciency loss in water coils are other
sources that can indirectly increase the energy consumption of the system. The
small energy consumed by low voltage power provided for control valves and
dampers, and the power input to the variable frequency drives for supply and return
fans that can be factored in supply and return fan consumption itself are the other
sources of energy consumption.
8.13.5
Displacement Ventilation CV
Displacement ventilation originally was invented for industrial purposes such as
using in welding industry in late 1970s. Since then its use has been increased in
other industries and also in commercial and institutional in order to provide good
indoor air quality along with means of saving energy. Utilizing this system similar
to the under fl oor system not only results in saving energy by delivering air with a
higher temperature than what is usually used in traditional cooling systems, but also
creates higher occupant comfort by delivering air where it is most effective. In this
system (Fig.
8.14
) as low velocity air moves across the fl oor and as it gets in touch
with heat sources (people, equipment, etc.) warms up and as a result of this higher
temperature similar to what happens in the under fl oor system moves up by natural
buoyancy and convection. Similar to under fl oor systems, when the room sensible
load decreases the supply air temperature can be increased to even higher than 63 °F
and therefore cooling consumption decreases even more.
Chen and Glicksman in their topic (Chen and Glicksman
2003
) represented the
results of a CFD modeling for displacement ventilation system suitable for the US
weather climate and showed with proper design these units can be utilized for cool-
ing buildings with up to 40 Btu/h ft
2
cooling load.
The sources of energy consumption in this type of systems are the air handling
unit supply fan motor input power, return fan motor input power, electric preheat
strip (if it is used for freeze protection instead of hot water coil) in air handling unit
and electric baseboard reheat unit (if it is used for dehumidifi cation or heating
instead of hot water coil). Duct air leakage, heat transfer from ducts connecting air
handling unit to the sidewall diffuser, and effi ciency loss in water coils are other
sources that can indirectly increase the energy consumption of the system. The
small energy consumed by low-voltage power provided for control valves and
dampers is the other sources of energy consumption.
