Document EqK896meN3MkKv4K7vaQ8G3Gb

Ounces Inches 1 .0 i.2 1653 2338 2864 3307 3698 4051 4375 4677 4960 5229 5485 5725 5960 6186 6404 6614 7017 7395 7755 8099 8429 8748 9057 1667 2358 2888 3335 3729 4085 4412 4716 5002 5273 5531 5774 6011 6238 6457 6670 7076 7457 7820 8168 8500 8822 9134 150 1788 2530 3098 3578 4000 4382 4733 5059 5366 5656 5933 6194 6448 6692 6928 7155 7591 8000 8462 8762 9118 9464 9798 1860 2632 3223 3722 4162 4559 4924 5263 5582 5884 6172 6443 6708 6962 7207 7444 7897 8322 9845 10193 1996 2824 .3458 3994 4466 4892 5283 5647 5990 6314 6623 6914 7987 8473 8930 9364 9781 10179 10564 10938 2244 3174 3887 4489 5019 6498 7098 7444 7772 8090 8396 8692 8977 9524 10037 10525 10995 11440 11873 12293 2410 3405 4175 4850 5395 5900 6380 6820 7260 7625 8000 8350 8700 9020 9346 9660 10220 10780 11300 11800 12280 12760 13200 17.4 Am. Soc. of Heat.-Vent. Engineers Guide, 1922 Uft) 3 c* D fr < U a S u H Q Z. < t/3 tU * 3 CtoO . . Uctf CL QL c*o <c* >< h" <2 c*r h JS (Im 8 fr 4> o 2 3 s 4a) OE H 100 e O ift oo oe- c* n 80" 2 S ao j u > za 5 . zo CL 2 O' cotf o2 3 s Im CL oo IN b <0- o Ift .1734 .3468 .5202 .6936 .8670 1.0400 1.2140 1.3870 1.5605 1.7340 1.9073 2.0808 2.2540 2.4275 2.6010 2,7742 3.1210 3.4680 3.8145 4.1615 4.6080 1635 2313 2833 1683 1714 2380 1 2424 2915 2969 3272 3658 4007 3367 3765 4124 3428 3833 4199 oob-CO COIN ooIoncCoO b-b-|N b-tOeO 0dIn0~^CG^ GkOoOr-)cCoO 8038 8396 8737 6179 6412 6638 5420 5685 5935 4535 4848 5142 7894 8245 8581 6734 7143 7528 6068 6297 6520 5323 5584 5828 4454 4761 5050 7672 8012 8338 6543 6942 7315 5896 6120 6335 5172 5426 5664. 4329 4626 4907 . In oo o< tftytift go 88 a?(N 00 8654 8960 8906 9220 9068 9388 Am. Soc, of Heat.-Vent. Engineers Guide, 1922 175 (25) or where we wish to correct for both temperature and barometer u__\t /460 + t w /bo v-v'\m+ix Vr . (26) In the above formulae V represents the velocity of the air at temperature t degrees Fahr. and barometer b, while V. is the corresponding velocity at temperature t. and barometer bo. Relation of Altitude to the Properties of Air The diagram, Fig 2, shows graphically the effect of different altitudes on the properties of air, and the two lines of relative air velocity and of air pressure and density are especially convenient in fan calculation. As an illustration of the use of this diagram assume a case where a fan is to handle 150,000 A. P. M. at 0.5 inch static pressure at an altitude of 5000 feet. We must determine what sea level conditions correspond to these conditions at the given altitude and so be able to select a fan of the required capacity. From the chart we find the relative pressure at this altitude is 0.825, so that sea level pressure corresponding to. 0.5 inch at 5,000 feet altitude will be 0.5 H- 0.825 -- 0 6 inch. The horsepower required to operate this fan will be 82.5 per cent, of the rated horsepower as given in the fan tables for the corresponding pressure of 0.6 inch static. Any given amount of air as commonly specified will be increased in volume by this same ratio when we consider an altitude of say 5000 feet. Thus if we ordinarily require a definite quantity of air for a certain purpose this volume should be divided by 0.825 to determine the capacity required if the apparatus is to be installed at an altitude of 5000 feet, and a fan selected to handle this greater volume. Effect of Temperature on the Volume of Air Air at constant pressure changes its volume almost exactly in proportion to its absolute temperature (460 + temperature deg. Fahr.). The table No. 1 gives the relative volume of a given quantity of air at various temperatures as compared to the volume at 70. For instance, the volume at 160 will be 1.17 times the volume at 70. Expressed as a formula for use with other tempera tures than those given in the table we will have, where Q is the volume at temperature t and Q. the volume at to Q=-(-St) ;2,> The effect of temperature on the various properties of air is shown graphically by the diagram, Fig. 3. As air at 70 is commonly used as a standard, these curves give the various relationships relative to air at 70. Inasmuch as fan tables are usually based on air at 70 F., the upper curve of this diagram is especially applicable to fan calculations. Thus we see that if the air to be handled, by a fan is at 140, the velocity and fan speed would have to be increased to 106.5 per cent, of that given in the tables. Or if the velocity remains the same, the pressure and weight of air handled at 140 will be only 88 per cent, of the rated capacity. Effect of Humidity on Velocity It may be noted that the tables herein given, consider the various properties of dry air at the standard temperature and barometric pressure. But as a matter of fact, atmospheric air is not dry, so that a correction is necessary in order to reduce the actual observed velocity to the standard condition of dry air. This may be accomplished by means of the following relation, the cubic feet per pound of air being determined from the Psychrometric Chaits, Figs. 6 and 7. Actual vel. Vel. Dry AUir ________ ______________________ 1Cu. ft. per lb. air as observed Cu. ft. per lb. dry air (28)