The air-conditioning of a building employs three centrifugal chillers of identical capacity (3000 kW). One of them is a variable speed chiller and the other two are constant speed chillers. Figure Q6 shows the performance (COP) curves of constant speed and variable speed chillers respectively. Where, PLR is the part load ratio of chillers. Their polynomial regression equations are also displayed in the Figure Q6. 6-a) Determine the best combination and load sharing of the operating chillers at the following cooling loads respectively: 900 kW, 2700 kW, 3600 kW and 5100 kW. 6-b) Determine the energy savings of the chiller plant at the above loads compared with the cases when three constant speed chillers are employed. 6-c) Determine the energy savings of the chiller plant at the above loads compared with the cases when three variable speed chillers are employed. 6-d) Comment on what attentions engineers should pay to ensure that the cooling load is shared equally among the operating chillers and suggest a method to properly control the sharing of loads among operating chillers if the expected loads on different chillers are different. COP 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 0 y=-2.75x +4.5256x +3.7417 1 0.1 1 1 1 0.2 0.3 y=-6.3258x + 10.831x + 1.1883 0.4 0.5 PLR Figure Q6 0.6 0.7 0.8 0.9 Ti - VSD CSD