1. A fan unit in a flour mill warehouse has a system resistance of 0.4 inches W.G. at 2,000 CFM, 0.8 inches at 3,000 CFM, 1.4 inches at 4,000 CFM, 2.4 inches at 5,000 CFM, and 3.0 inches at 5,500 CFM. Using the figure below, sketch in the system resistance curve, and determine the fan capacity and the brake horsepower at the operating point. (The operating point indicated is an example, not the operating point for this system)

2. Given the same fan and system as given above, what rpm would be required to move 15% more air (115% of the system curve volume)? What is the corresponding static pressure and BHP?

3. An axial flow fan is used to ventilate a inspection lab in a factory. The outlet is rectangular 20” x 24”. The volumetric flow rate of the fan is 15,000 cfm at a static pressure of 4 inches (density – 4.34 x 10-5 lb/in3). It requires a unit providing at least 7.5 HP. Determine the total pressure, total efficiency, and static efficiency.

4. What would the operating conditions be if 4 fans like the one in problem 3 were operating at the same rpm and connected in parallel? In series?

5. What would the overall sound power level be for the fans in problem 4 if each fan has a sound level of 90.5 dB?

Fan Design HomeworkBAE2023 Spring 2012Due March 16th

BHPStatic Pressure,Inches W.G.