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systems are the fans and the chiller unit. In this study, the energy
consumption of the ACS was determined by the following proce-
dure. Firstly, part load ratio of the chiller unit (PLRchil) was found
using:
PLRchil ¼ Qcoil part=Qcoil full
ð1Þ
where Qcoil_full indicates the full load of the chiller unit and is ob-
tained from the manufacturer’s data for all bin data (time shift
and interval temperature). Qcoil_part indicates the instantaneous load
removed by the ACS from interior of building. It was obtained using
psychometric analysis for all bin data. Qcoil_part is the sum of the
cooling load of the building and the fresh air load due to the mixing
air supplied to room.
Secondly, coefficient of performance at part load (COPpart) was
calculated by the following equation [30]:
COPpart ¼ðCOPfull PLRchilÞ=ð0:16 þ 0:32PLRchil þ 0:52PLR2
chil
Þð2Þ
in which, COPfull indicates the coefficient of performance of the chil-
ler at full load. It was obtained from the manufacturer’s data for all
bin data.
Thirdly, the power consumption of the compressor in the chiller
unit for part load (Wchil_part) was determined using:room. For the CAV system, mass-flow rate is constant through the
operation of the system; therefore even for the part-load conditions
the fans consume the maximum power. Under peak-cooling condi-
tions, the VAV system operates identically to a CAV system with
AHU operating at maximum flow (Mfan_full) and maximum cooling
coil capacity (Qcoil_full). However, at reduced cooling load, the air-
flow is reduced by the combined action of the closing of the zonal
VAV box dampers and the fan speed controller. The power con-
sumption of the fan under the real operating conditions (Wfan_part)
was calculated by the following equation [19]:
Wfan part ¼ Wfan fullPLR3
fan ð5Þ
in which,Wfan_full indicates the power consumption of the fan at full
load.
Finally, total energy consumption of the compressor in the chil-
ler unit and the fans under real operating conditions (Epart) was ob-
tained multiplying BIN data (Nbin) with the power consumption of
the chiller unit and the fans:
Epart ¼ NbinðWchil part þWfan partÞð6Þ
Energy cost of the system (Ocost), can be determined using the en-
ergy consumption of the system (Epart) and price of electricity (T),
which is currently about 0.11 $/kWh in Turkey:
Ocost ¼ EpartT ð7Þ
Using the procedure given above, operating costs of the chiller, the
fans and the total operating cost were calculated and the results are
given in Table 10 for a cooling season.
Seasonal operating cost of the ACS with VAV was determined to
be $6967 for the no insulation building. In the case of Buildings A, B
and C, seasonal operating cost is about 25% less than that of the no
insulation building. Similar results were obtained with CAV air dis-
tribution system. In this case, seasonal operating cost for Buildings
A, B and C is about 33% less than that of the no insulation building.
5. Economic analyses
An economic analysis was carried out in order to determine
influence of the thermal insulation on the initial and operating
costs of the ACS. Present-worth cost (PWC) method, which is one
of the analyses methods of the life-cycle cost, was used for evalu-
ating the ACS in case of different thermal insulations [19,27,31,32].
Results of the LCC analysis are directly affected by the economic
measures. Therefore, in the analyses, an annual interest rate of14% and inflation rate of 8% were selected considering the present
economic conditions of Turkey. The system life of the ACS was ta-