Coal-Mine Ventilation Factors Page: 79
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79
PRESSURE LOSSES CAUSED BY RIGHT-ANGLE BENDS
TABLE 29.-Pressure-loss tests with Veniuri bendsAVERAGE BASE CONDITION, WITH SQUARE CORNERS
Pressure loss, inch Ratio of
Air of water Equiva-
Date, velocity, bendloss lent feet
Test No. 1923 feet per to of clear
minute Mean Loss due velocity entry
total loss to bend pressure
-------------------........ 300 0.0095 0.0078 1.40 233
---------- -............. ............................ 500 .0264 .0218 1. 40 243
--------------............................ 700 .0513 .0427 1.40 250
------------------------............................ 900 .0848 .0707 1.40 257
No. 1 VENTURI BEND
800...............---------------------------------. Aug. 22 300 0.0078 0.0061 1.09 182
799 -...----------------------------- ---do... ,500 .0202 .0157 1.01 176
798---- ------------------------------do700 .0390 .0304 100 178
797.--------------------------------do... 900 .0616 .0476 .94 171
No. 2 VENTURI BEND
832 --... -------------------------------Aug. 26 300 0. 0056 0. 0039 0.70 116
831 ..... ...--------------------------------do.... 500 .0157 .0112 .72 125
830 ------------------------------ do-- --- 700 .0302 .0216 .71 127
829................--------------------------------do--.. 900 .0504 .0364 .72 131
860.................... -------------------------------Sept. 5 300 .0059 .0042 .75 125
859 --------------------------------................do.... 00 .0149 .0104 .67 -116
858 --------------------------------do- 700 .0279 .0193 .63 113
857 - --------------------------------do .. 900 .0457 .0317 .63 114Direction of air flow
-'
FIoURE 39.-Second type of Venturi used on right-angle bends in pressure-loss tests
The ratio of bend loss to velocity pressure with No. 1 Venturi was
0.94 at the highest velocity, a decrease of 33 per cent from base con-
ditions. With No. 2 Venturi the similar ratio was 0.63 in the second
group of tests, a decrease of 55 per cent. This, however, was no
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Greenwald, H. P. & McElroy, G. E. Coal-Mine Ventilation Factors, report, 1929; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc12463/m1/85/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.