Civil Engineering Reference
In-Depth Information
room and meeting the varying load is controlled via cooling and heating control
valves modulation, or through the steps of the electric heating coil.
The sources of energy consumption in this system are supply fan motor input
power, electric heating strip (if it is used) power requirement, and compressor and
condenser power input. The small energy consumed by low-voltage power provided
for control valves is another source of energy consumption.
8.10
Water Source Heat Pump
In this system an individual constant volume cooling and heating heat pump is
designated to each space, and as the space load varies, unit refrigerant cycle oper-
ates to satisfy the load requirement of the space. Any time the space temperature
moves above the cooling temperature set point, the cooling refrigerant coil will be
energized and fan delivers a constant temperature cooling supply air to cool the
room. Condenser water then absorbs the heat from the refrigeration cycle, and
rejects it to outdoor. In some condition this absorbed heat even may be used to heat
the other parts of the building, which are in need for heating. Heat pumps heat rejec-
tion water loops usually are equipped with heat rejection equipment such as cooling
tower(s), and heat adding equipment such as boiler(s) and of course circulating
pumps. The sources of energy consumption in this type of systems are supply fan
motor input power, electric preheat and reheat coils, compressor power input, pumps
power input and cooling tower fans required power. Duct air leakage, heat transfer
from ducts and pipes, and effi ciency loss in water coils are other sources that can
indirectly increase the energy consumption of the system. Also power required to
run the boiler if necessary could be another source of energy consumption.
The small energy consumed by low-voltage power provided for control valves
and dampers is the other source of energy consumption. There is always electrical
power consumption for heat tracing the water piping outside the heated mechanical
rooms, and protecting the cooling tower basins from freezing (Khazaii
2012
).
8.11
Ground Source Heat Pumps
A typical ground source heat pump is similar to a traditional water source heat
pump system equipped with cooling tower and boiler except that with a ground
source heat pump system there is the opportunity for reducing or eliminating the
need for using cooling tower and boiler. This fact helps the building to consume less
energy by replacing the cooling and heating processes derived from cooling tower
and boiler system, by taking advantage from the fact that the ground stays in an
almost constant temperature as a heat sink and heat source throughout the year.
Ground source heat pumps can be categorized into three major types: (1) ground-
coupled closed heat pump system which uses special high density polyethylene
