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American Society of Heating and Ventilating Engineers Guide, 1924-25 investigation the following problems have thus far been studied, at the Research Laboratory and complete reports will be found in the Society's Journal: 1. Critical velocity of risers--one and two-pipe systems; 2. Effect of rounded, reamed and unreamed entrances, to pipe upon the critical velocity; 3. Effect of entrances of pipe cut with single and three-wheel cutters upon the critical velocity; 4. Effect of unions and couplings upon the critical velocity; 5. Critical velocity in horizontal, vertical and inclined pipes; 6. Effect of high pressures, horizontal offsets and valves. Fig. 14 shows the relation between the pressure drop through a 10 ft. vertical pipe and its capacity. N u m ber ?of Riser 3 Dion 4cr. < t^plp Type d# Entrance bottom "Too Koinf AB Viartd Enfant iUiL s. Alit lit A A A dt A r Sr <fl Earned 5p5 a 1 A A A A A a A A A A a IT A 12 At A IS A A A Bounded A A AA _LSnqltllMCtiAr Three . _L j! A r 3 S s Iff 4--E>----- | --o-"-*! ---0 -- ---1> ---- I 1 *-- c 4 h-*--4 r-- K --H ^auAKeo Zhtramcc camcd EWmvcc -----A--! !--A--f twkoco Entrance ^iMGt^rHRteWfcaCurTER ^ ... Fig. 15: ^^ -- BuPKITcTwMoRrMMWpt*e.) p*Tt.?trT.tfa'Lt pgVta wo. Details of Four Types of Entrances Tested The capacity of a vertical pipe is greatly affected by the shape of its entrance. By gently flaring the entrance of the pipe its capacity may be greatly increased. A series of tests were made on 1-in. risers with various shaped entrances as shown in Fig. 15. The maximum capacities obtained in these tests were as follows: Reamed entrances.......... -................... 24.7 lb. per hr. Rounded entrances................. 23.9 lb. per hr. Squared entrances.................................22.2 lb. per hr. Three wheel cutter.............................. 19.2 lb. per hr. Single wheel cutter.,...... .................. 17.6 lb. per hr. 52 Per Cent Decrease 0.0 3.2 10.1 22.2 28.7 American Society of Heating and Ventilating Engineers Guide, 1924-25 TABLE 42. EFFECT OF VARIATION OF SIZE AND SMOOTHNESS OF PIPE Per Cent Difference due to Variation of Pipe Maximum Condensation. Lb. per Hr. 14.00 15.20 8.6 1' 24.89 30.08 20.8 IK' 45.42 52.08 14.7 & 70.50 82.00 16.3 Table 42 shows the variation in capacity of a pipe as affected by varia tion of size and smoothness of pipe generally found on the market. The maximum and minimum results were obtained by picking out very smooth and very rough pipe from the stock room of a large manufacturer. The capacity of risers based upon 18 and 22 ft. velocity is given in Table 43. TABLE 43. CAPACITIES OF ONE PIPE RISERS Allowable Velocity in Feel per Second Dia. op Pipe In. % 1 iK iH 2 18 Cond. Lb. Hr. 8.9 14.5 25.2 34.2 56.5 Sq. Ft. Rad. B.t.u. Loss Hr. Based on 240 B.t.u. 8,640 14,070 24,460 33,190 54,830 36.0 58.6 101.9 138.1 228.4 22 Cond. Lb. Hr. 10.9 17.8 30.8 41.8 69.0 Sq. Ft. Rad. B.t.u. Loss Hr. Based on 240 B.t.u. 10,580 17,270 29,890 40,560 66,960 44.1 72.0 124.5 169.0 279.0 TABLE 44. PITCH REQUIRED IN HORIZONTAL PIPES TO GIVE SAME CAPACITY AND VELOCITY AS GIVEN IN TABLE 43 FOR RISERS OF LIKE SIZE Allowable Velocity in Feet per Second Nominal Diam. op Pipe in In. % 1 IK IK 2' Cond. in Lb. per Hr. 8.9 14.5 25.2 34.2 56.5 18 B.T.U. Loss per Hr. Sq. Ft. Rad. Based on 240 B.t.u. Pitch op Pipe In. per 10 Ft. 8,640 14,070 24,460 33,190 54,830 36.0 58.6 101.9 138.1 228.4 1.00 0.75 0.50 0.50 0.50 Cond. in Lb. per Hr. 10.9 17.8. 30.8 41.8 69.0 22 B.t.u. Loss per Ha. Sq. Ft. Rad. Based on 240 B.t.u. 10,580 17,270 29,890 40,560 66,960 44.1 72.0 124.5 169.0 279.0 Pitch op Pipe In. per 10 Ft. 2.6 to 3.0 1.7 to 2.0 1.00 1.00 . 1.00