Document wjOnN1DD73Z4mJJGxdw7pwyQ

r HEATINC VENTILATING AIR CONDITIONING GUIDE 1941 800000 CHAPTER 31. AIR DUCT DESIGN the coefficient of friction based on the rule that the coefficient of friction varies inversely as the 2/7 power of the diameter, and inversely as the 1/7 power of the velocity. The chart in Fig. 2 is based on a loss of one velocity head (at a velocity of 2000 fpm) in a length equal to 50 diameters .06 .10 .20 .40 .60 1.0 2.0 FRICTION IN INCHES OF WATER PER 100 FEET Fig. 2. Friction of Air in Pipes 574 of 24 in. round galvanized iron duct of the usual construction. Although this chart is laid out for a value of C equivalent to 50, it may be used for other values of C by varying the friction inversely as this constant.. For example, if a rougher pipe is used with 40 as the value of C, the friction loss as read from the chart should be multiplied by 50 -f- 40. 575