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HEATING VENTILATING AIR CONDITIONING GUIDE 1943 Table 9. Weight of Saturated and Partly Saturated Air3 Temp FDeg 28.5 Weight or Saturated Air fob Various Barometric and Htgrometric Conditions--Pounds per Cubic Foot Barometric Pressure laches of Mercury 29.0 29.5 30.0 30.5 31.0 Increase la Weight Per 0.1 in. Rise in Barometer Approx. Ateragb Increase in Weight Per Deg Wet-Bulb Depression 30 32 34 ' .36 0.07703 0.07839 0.07671 0.07806 0.07638 0.07772 0.07605 0.07739 0.07974 0.07940 0.07907 0.07873 0.08110 0.08075 0.08041 0.08007 0.08245 0.08210 0.08175 0.08141 0.08381 0.08345 0.08310 0.08274 0.00027 0.00027 0.00027 0.00027 0.000017 0.000017 0.000018 0.000018 38 40 42 44 . 0.07573 0.07706 0.07541 0.07674 0.07509 0.07641 0.07477 0.07609 0.07840 0.07806 0.07773 0.07740 0.07973 0.07939 0.07905 0.07872 0.08106 0.08072 0.08038 0.08004 0.08239 0.08205 0.08170 0.08135 0.00027 0.00027 0.00026 0.00026 0.000019 0.000019 0.000020 0.000020 46 48 50 . 52 0.07445 0.07576 0.07413 0.07544 0.07381 0.07512 0.07350 0.07479 0.07707 0.07674 0.07642 0.07609 0.07838 0.07805 0.07772 0.07739 0.07970 0.07936 0.07902 0.07868 0.08101 0.08066 0.08032 0.07998 0.00026 0.00026 0.00026 0.00026 0.000021 0.000021 0.000022 0.000023 54 0.07318 0.07447 56 0.07287 0.07415 58 . 0.07255 0.07383 60 0.07224 0.07352 0.07576 0.07544 0.07512. 0.07479 0.07706 0.07673 0.07640 0.07607 0.07835 0.07801 0.07768 0.07734 0.07964 0.07930 0.07896 0.07862 0.00026 0.00026 0.00026 0.00026 0.000023 0.000024 0.000025 0.000026 62 0.07193 0.07320 0.07447 0.07574 0.07701 0.07828 0.00026 0.000027 64 0.07161 0.07288 0.07414 0.07541 0.07668 0.07794 0.00026 0.000028 66 0.07130 0.07256 0.07382 0.07508 0.07634 0.07760 0.00026 0.000029 68 0.07098 0.07224 0.07350 0.07475 0.07601 0.07727 0.00026 0.000030 70 0.07067 0.07192 0.07317 0.07442 0.07568 0.07693 0.00026. 0.000031 72 0.07035 0.07160 0.07285 0.07410 0.07534 0.07659 0.00025 0.000032 74 0.07004 0.07128 0.07252 0.07377 0.07501 0.07625 0.00025 0.000033 76 0.06972 0.07096 0.07220 .0.07343 0.07467 0.07591 0.00025 0.000034 78 0.06940 0.07064 0.07187 0.07310 0.07434 0.07557 0.00025 0.000036 80 0.06909 0.07032 0.07155 0.07277 0.07400 0.07523 0.00025. 0.000037 82 0.06877 0.07000 0.07122 0.07244 0.07366 0.07489 0.00024 0.000039 84 0.06845 0.06967 0.07089 0.07211 0.07333 0.07454 0.00024 0.000040 86 88 90 ` 92 0.06812 0.06934 0.06780 0.06901 0.06748 0.06868 0.06715 0.06835 0.07056 0.07022 0.06989 0.06955 0.07177 0.07143 0.07109 0.07075 0.07299 0.07264 0.07230 0.07195 0.07420 0.07385 0.07351 0,07316' 0.00024 0.00024 0.00024 0.00024 0.000042 0.000043 0.000045 0.000047 94 96 98 100 0.06682 0.06801 0.06648 0.06768 0.06615 0.06734 0.06581 0.06700 0.06921 0.06887 0.06853 0.06818 0.07041 0.07006 0.06972 0.06937 0.07161 0.07126 0.07091 0.07055 0.07280 0.07245 0.07209 0.07174 0.00024 0.00024 0.00024 0.00024 0.000049 0.000051 0.000053 0.000055 "Approximate average decrease ia weight per 0.1'F rise in dry-bulb temperature equals 0.000017 lb per cubic foot. 26 CHAPTER 1. THERMODYNAMICS OF AIR AND WATER MIXTURES 32 F; and the relative proportions of the three phases depend upon the location of the state point within the wedge. Below the wedge, tie, mix ture consists of saturated vapor and saturated solid. The curved lines in the single vapor-phase region to the right of the saturation curve are lines of constant per cent saturation; Lines of con stant dew-point are, of course, horizontal straight lines of constant humidity ratio. At point B, for example, the dry-bulb temperature' is 60 F, the thermodynamic wet-bulb is 50 F, the dew-point is 40.8 F, the degree of saturation is 48.6 per cent, the humidity ratio is 0.00536 lb per pound dry air, and the enthalpy is 14.85 + (1000 X 0.00536) = 20.21 Btu per pound dry air. With the aid of the Mollier diagram, it is easy to throw the definition of thermodynamic wet-bulb, Equation 20, into a more familiar form. Consider the three points 1, 2, 3, Fig. 2. Point 3 is located with respect to points 1 and 2 so that W3 = W\ and h = h- Points 1 and 2, being on ' Fig. 2. Diagram Illustrating Thermodynamic Wet:Bulb Temperature a line of constant thermodynamic wet-bulb, satisfy Equation 20; thus, hi -- h, + (W, - Wi) h'Wit = A, - h. where h3 has been subtracted from both sides. Under Dalton's Law, hi -- hz = (W2_-- Wi) h*,i; moreover, hi -- h3 may be replaced by Si {h -- k) where Si is often referred to as mean humid heat and may be calculated with good approximation from s, = 0.240 -f 0.444 Wi (21) Finally, introducing latent heat of vaporization at the wet-bulb tempera ture, namely, (ftfg)2 = (K, -- tij)3, Equation 20 becomes, after omitting the subscript 2, We - Wi = if (22) it being understood that,WB is the saturation humidity ratio and hfg, the latent heat, at the wet-bulb temperature t'. Equation 22 was derived by .Carrier [1]. Example 12. Work Example 10 using Equation 22. Solution. A trial-by-error method is involved. Taking 48 F as a trial value of (80 - 48) `(0.007072 - 0) = 4520; but 1066.7 -h 0.240 = 4440. The trial value must, therefore, be revised upward, the final solution being 48.26 F as in Example 10. > 27