For a fan the specific speed is independent of size and is a function of the flow and head coefficients (see 'notes' bel
Posted: Thu May 05, 2022 5:41 pm
- For A Fan The Specific Speed Is Independent Of Size And Is A Function Of The Flow And Head Coefficients See Notes Bel 1 (58.12 KiB) Viewed 45 times
Show calculations and your answers should match
these
b) 1.19 kg/m³
c) 3.137 rad
d) 2831 rev/min
e) 1287 W
For a fan the specific speed is independent of size and is a function of the flow and head coefficients (see 'notes' below for definitions). It is calculated at the conditions of N, Q and AP that give the maximum efficiency. a) Show that the specific speed for a fan (in radians) is: (7 marks) Ns = NO (gH) A 2 stage axial fan is tested and the following optimum design conditions are found when the inlet conditions are 1 bar, 20°C. N=2700 rev/min, Q = 100 m³/min, AP= 676 N/m², W = 1758 W b) Calculate the inlet air density (3 marks) c) Calculate the specific speed of the fan (in radians). (3 marks) The fan is required to circulate hot air in a curing oven at a flow rate of 90 m³/min with a pressure rise of 550 N/m². The inlet pressure and temperature are to be 1.1 bar and 120°C respectively. d) Calculate the speed that the fan should be run at to meet the duty at its optimum efficiency. (4 marks) e) Calculate the power required to drive the fan at the required duty (4 marks) Briefly comment on the effect on the fan of reducing the circulating air temperature to 20° (4 marks) f)