Document x53eR5VnqagdB9Xbg3VvVamvm

HEATING VENTILATINC AIR CONDITIONING CUIDE 1940 Table 5. Properties of Monofluorotrichlorombthane (Fn) 8at. Temp. F Abs. La per So In. Volume Liquid Vapor Heat Content and Entropy Taken From -40 F Heat Content Entropy 25 F Superheat 50 F Superheat Liquid Vapor- liquid Vapor EtCt Entropy Ht Ct Entropy 0 2.59 0.01020 13.700 7.81 90.4 0.0178 0.1975 93.9 0.2049 97.4 0.2120 5 2.96 0.01024 12.100 8.81 91.2 0.0200 0.1974 94.7 0.2047 98.2 0.2117 10 3.38 0.01028 10.700 9.82 92.0 0.0222 0.1973 95.5 0.2045 99.0 0.2114 15 3.85 0.01032 9.530 10.80 92.8 0.0243 0.1971 96.3 0.2043 99.8 0.2111 20 4.36 0.01036 8.490 11.90 93.7 0.0264 0.1970 97.2 0.2041 100.7 0.2109 25 4.94 0.01040 7.580 12.90 94.5 0.0286 0.1969 98.0 0.2039 101.5 0.2107 30 5.57 0.01045 6.770 13.90 95.3 0.0307 0.1969 98.8 0.2038 102.3 0.2105 35 6.27 0.01049 6.080 14.90 96.1 0.0328 0.1968 99.6 0.2037 103.1 0.2103 40 7.03 0.01053 5.460 16.00 96.8 0.0349 0.1968 100.3 0.2036 103.8 0.2101 45 7.88 0.01057 4.920 17.00 97.6 0.0370 0.1967 101.1 0.2035 104.6 0.2099 50 8.79 0.01062 4.440 18.10 98.4 0.0391 0.1967 101.9 0.2034 105.4 0.2098 55 9.80 0.01066 4.020 19.10 99.2 0.0412 0.1967 102.7 0.2033 106.2 0.2097 60 10.90 0.01071 3.640 20.20 100.0 XK0432 0.1967 103.5 0.2033 107.0 0.2096 65 12.10 0.01076 3.300 21.30 100.8 0.0453 0.1967 104.3 0.2032 107.8 0.2094 70 13.40 0.01081 3.000 22.40 101.5 0^0473 0.1967 105.0 0.2032 108.5 0.2093 75 14.80 0.01086 2.740 23.50 102.2 0.0493 0.1967 105.7 0.2031 109.2 0.2092 80 16.30 0.01091 2.500 24.50 102.9 0.0513 0.1966 106.4 0.2030 109.9 0.2090 85 17.90 0.01096 2.280 25.60 103.6 0.0533 0.1966 107.1 0.2029 110.6 0.2089 90 19.70 0.01101 21090 26.70 104.4 0.0553 0.1966 107.9 0.2028 111.4 0.2088 95 21.60 0.01106 1.918 27.80 105.1 1L0573 0.1966 108.6 0.2028 112.1 0.2087 100 23.60 0.01111 1.761 28.90 105.7 0.0593 0.1965 109.2 0.2027 112.7 0.2085 105 25.90 0.01116 1.620 30.10 106.4 0.0613 0.1965 109.9 0.2026 113.4 0.2084 Example 1. What is the heat content above --40 F of 2.5 lb of ammonia when under a pressure of 92.9 lb per square inch gage and a temperature of 160 F? Solution. First determine the condition of the ammonia at the stated temperature and pressure. Do this by finding the absolute pressure which in this case is 92.9 lb gage plus 14.7 or 107.6 lb per square inch absolute. From Table 1 note that the satu ration temperature at this pressure is 60 F. Therefore, the ammonia is superheated 100 F, and the total heat per pound can be read directly from the Table as 689.9 Btu. In the 2.5 lb of ammonia there are 2.5 X 689.9, or 1724.75 Btu. Example 2. What volume is necessary to accommodate 0.27 lb of saturated Fu vapor when compressed to 99.6 lb gage? Solution. The absolute pressure is 99.6 plus 14.7 or 114.3 lb. In Table 2 find that one pound of Fa vapor saturated occupies 0.368 cu ft. Then the 0.27 lb would occupy 0.27 X 0.368, or 0.099 cu ft. Example 3. How much heat would be removed from air passing over a coil through which 2 lb of methyl chloride per minute is forced? The coil is under a gage pressure of 64 lb per square inch and the liquid refrigerant is completely vaporized in passing through the coil. Solution. Find that the absolute pressure is 64 plus 14.7 or 78.7 lb per square inch. From Table 3 note that the saturation temperature at this pressure is 75 F (nearly) and that the heat content per pound of the vapor is 207.8 Btu. Also that the heat content of the liquid is 42.2 Btu per pound. Subtract 42.2 from 207.8 and 165.6 Btu per pound is the heat necessary to change the liquid refrigerant to a vapor (latent heat). As the heat to accomplish this change comes from the air around the coil, the heat removed from the air is 165.6 Btu per pound of methyl chloride evaporated in the coil. When the refrigerant is circulated at 2 lb per minute, 2 X 165.6, or 331.2 Btu per minute are removed from the air, or refrigerating effect is produced at the rate of 331.2 -r 200, or 1.65 tons. AIR DRYINC AGENTS Moisture may be removed from air, thus accomplishing dehumidi fication, by the use of any one of a number of substances if the moist air 36 CHAPTER 2. REFRICERANTS AND AIR DRYING AGENTS and these substances are brought together under suitable circumstances. One class of these substances are solids at ordinary conditions and have the power of adsorbing the moisture from the air. Another class of air drying agents are liquids under ordinary conditions and absorb the mois ture from the air.. Nearly all the drying agents in frequent commercial use in air conditioning installations are of one or the other of these two classes. Adsorbents These substances are characterized by a physical structure containing a great number of extremely small pores but still retaining sufficient mechanical strength to resist whatever wear and handling to which they are subjected. To be suitable for air drying purposes they must be widely available at economical cost, durable in use, stable in form and properties, and capable of withstanding the re-activation processes by which they are made ready for repeated use. They must also possess capacity for adsorbing and holding so sufficient a quantity of moisture that _ the dimensions of the beds necessary to a.ccommodate them will be practical. Aluminum Oxide, (Alumina), in a porous, amorphous form is a solid adsorbent frequendy called by the common name activated alumina, and containing small amounts of hydrated aluminum oxide, and very, small amounts of soda, and various metallic oxides. A good grade of activated alumina will show 92 per cent of AkO3, and its soda content will be com bined with silica and alumina into an insoluble compound. This substance also has the property of adsorbing certain gases and certain vapors other than water vapor--a property which is sometimes useful in air condi tioning installations. It is available commercially in granules ranging from a fine powder to pieces approximately 1.5 in. in diameter. It has Table 6. Properties op Water Temp. F Is PER Sq In. liquid Vapor Heat Contest and Entropy Taken From +32 F Heat Content liquid Vapor Entropy 50 F Superheat 100 F Superheat liquid Vapor Ht Ct Entropy Ht. Ct. Entropy 32 0.0887 0.01602 3296.0 0.00 1073.0 0.0000 2.1826 1096.9 2.2277 1120.8 2.2688 35 0.1000 0.01602 2941.0 3.02 1074.4 0.0062 2.1724 1098.3 2.2172 1122.2 2.2581 40 0.1217 0.01602 2441.0 8.05 1076.8 0.0163 2.1555 1100.6 2.2000 1124.5 2.2406 45 0.1475 0.01602 2034.0 13.07 1079.2 0.0262 2.1390 1102.9 2.1832 1126.7 2.2234 50 0.1780 0.01602 1702.0 18.08 1081.5 0.0361 2.1230 1105.2 2.1667 1129.0 2.2066 55 0.2140 0.01603 1430.0 23.08 1083.9 0.0459 2.1073 1107.5 2.1506 1131.3 2.1902 60 0.2561 0.01603 1206.0 28.08 1086.2 0.0556 2.0920 1109.8 2.1349 1133.5 2.1742 65 0.3054 0.01604 1021.0 33.08 1088.6 0.0652 2.0771 1112.2 2.1196 1135.8 2.1585 70 0.3628 0.01605 868.0 38.07 1090.9 0.0746 2.0625 1114.5 2.1046 1138.1 2.1432 75 0.4295 0.01606 740.0 43.06 1093.2 0.0840 2.0483 1116.7 2.0900 1140.3 2.1283 80 0.507 0.01607 632.9 48.05 1095.5 0.0933 2.0344 1119.0 2.0758 1142.5 2.1138 85 0.596 0.01609 543.3 53.04 1097.8 0.1025 2.0208 1121.2 210619 1144.7 2.0996 90 0.698 0.01610 467.9 58.03 1100.0 0.1116 2.0075 1123.4 2.0483 1146.8 2.0857 95 0.815 0.01612 404.2 63.01 1102.3 0.1206 1.9946 1125.6 2.0350 1148.9 2.0721 100 0.949 0.01613 350.3 68.00 1104.6 0.1296 1.9819 1127.9 2.0220 1151.1 2.0588 105 1.101 0.01615 304.4 72.98 1106.8 0.1384 1.9695 1130.2 2.0093 1153.2 2.0458 For properties of steam at high temperatures, see Page 27. 37