11.9 A duct system has branch sections to threetdifferent zones as shown in Problem 11.9 Figure. The volume flow rate and duct lengths are shown on the figure. The ducts

are circular with right angle tees, diffusers with a loss coefficient of 0.2, and a sum of the loss coefficients for the fittings in each section of22. Assume a friction factor of 0.018 for each section and standard temperature and pressure.Determine the duct die a. Determine the duct diameters and pressure drops using the equal friction method. b. Determine the pressure in each zone. Using the generalized fan curve of Figure11.10, select a fan, and determine the fanpower required. d. Determine the fan power required for the same system when the total flow is reduced to 20,000 cfm with the same proportion of the flow to each zone and a variable speed fan employed. e. Draw some conclusions from your results.