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3.4. The chiller can operate down to about 10% of its rated full load capacity via a modulating slide valve in the compressor. The design air flow rate and the electric power input of variable speed cooling tower fan at maximum air flow rate are 29000 m3/h and 1.5 kW respectively. The design air flow rate of the air handling unit with variable air volume fan is 37500 m3/h and its rated power input is 12.8 kW. The design water flow rate and electric power of each chilled water pump is 41m3/h and 1.7 kW respectively. The design water flow of each con-denser water pump is 50 m3/h and their electric power is 2.3 kW. All circulator pumps operate at constant speed.The simulation information flow diagram for all mentioned components is shown in Fig. 3. 4 Results and Conclusion TRNSYS is run to obtain component-wise energy analysis and the indoor comfort conditions throughout the summer. The proposed algorithm determines the different configuration designs for the cooling coil which are shown in Table 1. 4.1 Energy Analysis Fig.4 shows the simulation results for energy consumption of each cooling coil geo-metry and compares it with monitored energy consumption of the central cooling plant in summer. According to the results, as the number of rows increase, the chiller and supply fan power increase. The influence of the number of rows on cooling tower fan is relatively very small. Meanwhile, a lower number of fins albeit resulting less plant energy consumption in the system reduces cooling coil capacity which causes a higher supply air temperature leaving the cooling coil. Therefore, the supply fan must work with higher air flow rate, in turn increase fan power consumption. The optimal configuration exists when the summation of power consumption for both the chiller and supply fan is minimal. As a result, considering the number of rows as the only parameter will consume more electrical energy in the whole system. Also results show that the reduction of the number of tubes in a row does contribute to lowering the cooling coil capacity while the system power saving increases.
The influence of the number of tubes on the system power consumption is more than fins number and thus the balance between system power and cooling coil capacity can be occurred by increasing the fin number while number of tubes are decreased. Further benefits can be obtained when the reduction in tubes number is coupled with a reduced coil aspect ratio. This is evident from the simulation results that system power consumption drops from 3% to 8% when the tube number in a row is reduced from 52 to 34 while the fin numbers are increased from 8 to 14 to keep the cooling coil capacity. The investigation of current coil geometry on CCP performance showed that by re-ducing the effective number of operating coil rows from a 6-row to a 4-row configu-ration, the cooling coil capacity is reduced to the building cooling load demand and thus the cooling coil efficiency is increased.However, the potential of energy saving for configuration 1, 2, 3, 4 and 5 in summer are respectively 8.1%, 9.3%, 3.2%, 6.4% and 4.8% which are significant enough to consider. The simulation is performed in the same conditions such as tube diameter, tube and fin material, tube spacing, and fin thickness for each case. 4.2 Thermal Comfort Thermal comfort is all about human satisfaction with a thermal environment. The design and calculation of air conditioning systems to control the thermal environment to achieve standard air quality and health inside a building should comply with the ASHRAE standard 55-2010. To predict the thermal comfort condition, an index called predicted mean vote (PMV) which indicates mean thermal sensation vote on a standard scale for a large group of people is used in this paper. PMV is defined by six thermal variables from human condition and indoor air, namely air temperature, air humidity, air velocity, mean radiant temperature, clothing insulation and human activ-ity. The PMV index predicts the mean value of the votes on the seven point thermal sensation scale +3: hot, +2: warm, +1: slightly warm, 0: neutral, -1: slightly cool, -2: cool, -3: cold. According to ISO 7730 standard the values of PMV between -1 and 1 are in the range that 75% people are satisfied while between -0.5 and 0.5 is the range that 90% people will be satisfied. It is of interest to see how the resulting PMV ap-pears with each control scenarios. The resulting PMV fluctuates between 0.15 and 0.94 for hottest day in July for configuration 2 as most effective configuration discussed in the last section. The PMV for all configurations is shown in Fig. 5.