Q.5 (a) Explain the purpose of having two fan-duct systems connected in the following ways: (i) (ii) in series; and in parallel. (b) State the functions of the following curves: (i) system curve; and (ii) fan curve. (5 marks) (4 marks) (c) An air-conditioning system employs two identical fans connected in parallel with a flow resistance. The pressure-volume characteristics of each fan are listed in Table Q.5. Table Q.5 Flow rate, m/s Fan total pressure, Pa Fan power input, kW 0.5 0.75 1.0 1.25 1.5 1.75 2.0 800 780 735 680 600 500 360 0.75 0.91 1.02 1.11 1.15 1.14 1.10 If the total pressure loss of this air-conditioning system is known to be 500 Pa at an air flow rate of 1.85 m/s, calculate: (i) the operating point, the corresponding air flow rate, and the total pressure when both fans are operating; (10 marks) (ii) the operating point, the corresponding air flow rate, and the total pressure loss when only one fan is operating, assuming that the air damper after the other fan is closed; and (2 marks) (iii) the fan total efficiency when only one fan is operating. (4 marks)