the Flow of Air through a Pipe. 393 



On doing this,, formula (4), which may be written as 



becomes 

 Writing this as 



1 B»" c P~ n 



(5) 

 (6) 



we get, on taking logarithms, 



log[^^]=»[logj 3M .»„.rf-logB]+logA. (7) 



(3) Experimental Data. 



The experiments examined are tabulated below : — 

 (1) Experiments by Messrs. Kiedler and Guter ninth on 

 the Paris air-mains. These results are taken from values 

 given by Professor Unwin (Proc. Inst. C. E. vol. cv. p. 190). 

 The pipes were of cast iron, llf ins. ('VS ft.) diameter. 

 Owing to allowance having to be made for the effect of 

 numerous draining tanks, traps, and stop-valves on the pipe- 

 line, the values of bp quoted in this table are only approximate. 

 The length of pipes ranges from 10982 ft. to 54270 ft., the 

 mean pressure from 92 to 118 lbs. per sq. in. abs., and the 

 mean velocity from 8'5 to 28*(3 ft. per second. The tempe- 

 rature of the air is unknown, but was probably about 6*5° F. 



Table I. 



Expt. 



1 



2 



3 '.'.'.'.'.'. 



4 



5 



6 



7 



8 



9 



10 



11 



1 

 Pipe. 



Pressure — lbs. per sq. in. (abs.). 



1 



I'm, 

 ft. per see. 



Length 

 ft. 



Diam. 

 ft. 



Pi- ' Pr 



Pm. dp. 



54270 



14460 



10982 

 , 28776 



•98 



» 



106-6 ( 8015 

 1144 97-25 

 1194 105-4 

 1161 109-4 

 114-4 1100 



116-1 112-6 



119-4 1173 

 114-4 107-2 

 119-4 114-3 



[ 



102-9 100-5 

 112-5 109-9 



91-9 

 96-6 



110-0 

 111-6 

 111-6 



1144 

 118-2 

 1099 

 116-3 



101-7 

 110-5 



20-45 



27-15 



14-04 



6-66 



3-98 



345 

 208 

 7-17 

 506 



2-40 

 2-63 



28-62 

 2735 

 19-35 

 13-89 

 8-51 



16-80 

 10-94 

 2406 

 18-30 



20-95 

 13-97 



1 



