Document 3QEygD8zMYvVOLqLn2YJ5bkva

American Society of Heating and Ventilating Engineers Guide, 1937 The pressure-volume method starts with state point a, whose pressure and specific volume are known. The work of compression is the adiabatic work of compression from Pi to Pi, plus the work of expelling the vapor at constant pressure Pi minus the external work of evaporation of the vapor to volume Vi at pressure Pi. ^= (2) It is frequently helpful to think of the compression of the vapor in terms of head. The head may be likened to a vertical column of vapor in which is located the vapor to be compressed. The compression occurs when the vapor is moved down from a level corresponding to Pi to a new. level corresponding to Pi, in equilibrium with the surrounding vapor. If this process is carried on isentropi'cally, the result will be the same as indicated previously. Then if h is the head in feet, W=h (3) This relationship may easily be seen from the fact that a small difference of head dh divided by the specific volume of the vapor V is equal to the increment' of pressure difference dP. Table 5. Properties of Methyl Chloride Sat. Temp. P Abs Press. Lb per SqIn. Volume liquid Vapor Heat Content and Entropt Taken From -40 F Heat Content Liquid Vapor Entropy 100 F Superheat 200 F Superheat liquid Vapor HtCt. Entropy Ht. Ct Entropy 0 18.73 0.0162 5.0520 14.4 192.4 0.0328 0.4197 215.6 0.467 237.2 0.507 5 20.91 0.0163 4.5630 16.2 194.1 0.0368 0.4195 217.0 0.464 238.5 0.503 10 23.30 0.0164 4.1290 18.1 195.8 0.0407 0.4192 218.5 0.463 240.0 0.500 15 25.89 0.0165 3.7430 19.9 196.9 0.0446 0.4177 219.8 0.461 241.0 0.498 20 28.71 0.0166 3.4030 21.8 198.1 0.0486 0.4152 221.0 0.460 242.5 0.496 25 31.77 0.0167 3.0980 23.6 199.1 0.0525 0.4137 222.1 0.459 244.0 0.494 30 35.07 0.0168 2.8260 25.5 200.1 0.0562 0.4130 223.4 0.457 245.2- 0.493 35 38.63 0.0169 2.5830 27.3 201.1 0.0600 0.4110 224.5 0.454 246.5 0.492 40 42.47 0.0170 2.3650 29.2 202.2 0.0637 0.4099 225.7 0.453 247.7 0.490 45 46.50 0.0171 2.1700 31.0 203.1 0.0675 0.4086 226.8 0.451 249.1 0.488 so 51:03 0.0172 1.9920 32.9 204.1 0.0709 0.4069 227.9 0.449 250.5 0.487 55 55.80 0.0173 1.8320 34.8 204.9 0.0746 0.4052 228.8 0.448 251.7 0.486 60 60.88 0.0174 1.6880 36.7 205.7 0.0784 0.4037 229.6 0.446 253.0 0.484 65 66.32 0.0175 1.5580 38.5 206.4 0.0821 0.4022 230.5 0.443 254.3 0.483 70 72.11 0.0176 1.4390 40.4 207.2 0.0855 0.4004 231.3 0.441 255.5 0.481 75 78.29 0.0177 1.3310 42.2 207.8 0.0891 0.3989 232.2 0.439 256.8 0.479 80 84.86 0.0178 1.2330 44.1 208.5 0.0926 0.3973 233.0 0.437 257.9 0.478 85 91.86 0.0179 1.1440 46.0 209.2 0.0962 0.3959 233.8 0.435 259.2 0.477 90 99.26 0.0180 1.0620 47.8 209.7 0.0994 0.3941 234.5 0.433 260.4 0.476 95 107.10 0.0181 0.9877 49.7 210.3 0.1029 0.3926 235.2 0.432 261.5 0.475 100 115.40 0.0182 0.9193 51.6 210.9 0.1063 0.3910 236.0 0.431 262.4 0.474 105 124.20 0.0183 0.8567 53.5 211.4 0.1097 0.3894 237.0 0.430 263.3 0.473 110 133.40 0.0185 0.7990 55.3 211.8 0.1130 0.3877 237.9 0.428 264.3 0.472 115 143.20 0.0186 0.7461 57.2 212.3 0.1164 0:3861 238.5 0.427 265.0 0.470 120 153.50 0.0187 0.6972 59.1 212.8 0.1198 0.3845 239.0 0.425 265.6 0.468 40 Chapter 2--Refrigeration . 6. (Fu)Table Properties of Monofluorotrichloromethane Sat. Temp. Abs Press. Lb per Sq Ik. Volume Liquid Vapor Heat Content and Entropt Taken From -40 F Heat Content liquid Vapor Entropy 25 F Superheat 50 F Superheat liquid Vapor Ht. Ct Entropy Ht. Ct Entropy 2.59 0.01020 13.700 7.81 90.4 0.0178 0.1975 93.9 0.2049 97.4 0.2120 2.96 0.01024 12.100 8.81 91.2 0.0200 0.1974 94.7 0.2047 98.2 0.2117 10 15 20 25 3.38 0.01028 10.700 3.85 0.01032 9.530 4.36 0.01036 8.490 4.94 0.01040 7.580 9.82 10.80 11.90 12.90 92.0 0.0222 0.1973 92.8 0.0243 0.1971 93.7 0.0264 0.1970 94.5 0.0286 0.1969 95.5 0.2045 99.0 0.2114 96.3 0.2043 99.8 0.2111 97.2 0.2041 100.7 0.2109 98.0 0.2039 101.5 0:2107 30 35 5.57 0.0104S 6.770 13.90 95.3 0.0307 0.1969 98.8 0.2038 102.3 0.2105 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 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 0.0432 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 2.090 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 0.0573 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 1.135 Head is very useful in considering the performance of centrifugal com pressors, which merely substitute a centrifugal for the gravity head. It is'also useful in considering problems of fluid flow. In these problems, the head per degree can be obtained either by direct calculation or approximately by dividing the total head by the temperature difference Tt -- T\. The velocity head loss can then be calculated in degrees, using the customary formula Vs = 2gh. Refrigerating Effect per Pound The refrigerating effect per pound is computed by the same method, regardless of the type of refrigeration system. The solution is indicated on the temperature-entropy diagram of Fig. 2. Assuming that the vapor leaving the evaporator is saturated, the refrigerating effect in Btu per pound is obtained by subtracting from the heat content of the vapor at temperature Tit the heat content of the liquid at Tt, or if the liquid is sub-cooled, the liquid temperature. Thus, the refrigerating effect in Btu per pound is equal to fla - flc = fla - He (4) If the vapor entering the compressor is superheated or supersaturated, a correction in the heat of the vapor is made accordingly. 41