Please answer question 5 Air at 10 degree C dynamic viscosi

Air at - 10 degree C (dynamic viscosity of 1.67 times 10^-5 ns/m^2) is delivered in a straight smooth pipe (D = 80 cm) in a large scale industrial refrigeration facility over a length of 150 m. A fan is used to deliver the required volume flow rate of 3020 m^3/min from the cooling unit (pipe inlet/exit pressure at 75.5 kPa absolute). If the fan is 75% efficient, what is the power requirement for the fan?) A. 537 kW B. 320 kW C. 426 kW D. 569 kW E. None of the above. Which of the following would cause an increase in the power requirements for the fan? A. Bends in the pipe B. Roughness in the pipe C. A higher exit pressure for the pipe D. A and B E. A, B and C

Solution

Answer is E

A. Bends in pipe cause loss of head or pressure and hence more power is reqauired.

B. Roughess in pipe creats frictional resistance to flow which has to be overcome. Hence increases power requirement.

C. If higher output pressure is required , more work is required and hence more power.