Document rpOM7x9jgbv2L4veroqzMbKva

780 CHAPTER 36 Guide 1951 of refrigerant which is present in vapor form. Consider, for example, F-12 with a quality (the percent in vapor form) of 30 percent; the enthalpy of this material would be equal to: where K, = At + 0.30 (ft. - A,) (4) ha = specific enthalpy of the mixture. ftf = specific enthalpy of the liquid. ft. = specific enthalpy of the saturated vapor. Values of hi and A. are obtained from Table 1 for the actual pressure of the mixture. By a reversal of this same procedure the tabular data can be used to determine the state of a mixture leaving an expansion valve. Consider a valve to which saturated liquid at pressure p. is admitted, and a mixture of saturated liquid and vapor at pressure Pd is discharged. The quality of the material at discharge is then determined by making use of the fact that the expansion process is completely irreversible, is a throttling process, and hence, occurs without change in enthalpy. Thus, the enthalpy of the mix ture, hm, is equal to the enthalpy of the saturated liquid at the entrance state, ht,, and can therefore be read from the table. Thus, Ai, = An = Art -- (1 -- x) (Art -- Am) (5) or, where x = (Am -- Am) -s- (Art -- Ah) (6) hi. = enthalpy of saturated liquid at entrance to expansion valve. Am = enthalpy of mixture. Art = enthalpy of saturated vapor at discharge. Am = enthalpy of liquid at discharge. x = proportion of liquid in the mixture, decimal. Vapor Compression Refrigeration Cycle Simple Cycle. The refrigerant cycle is the series of state changes (which occur in the conditioning processes) needed to restore the refrigerant to a condition in which it will possess the ability to extract heat from the space to be cooled. For all compression-type systems the cycle consists of four processes: heat gain in the evaporator; pressure rise in the compressor; heat loss in the condenser; pressure loss in the expansion valve. The com pression process is accomplished at the expense of energy added to the compressor in the form of shaft work, and the expansion process could be carried out, if the economics of the system would permit, in an expanding engine with consequent release of energy as shaft work. In ordinary sys tems, however, the additional first cost and maintenance costs of an expand ing engine so greatly exceed the advantage resulting from the work realized, that such engines are not used, and the pressure reduction is allowed to occur irreversibly in an expansion valve. Basically, then, a refrigeration cycle consists of two heat transfer processes and two pressure change proc esses, no work entering into the heat transfer processes and--in the simple cycle--no heat transfer occurring during the pressure-change processes. Refrigeration 781 Table 2. Propebties op Monochlobodifluobomethanh (F-22) Sat Temp F Acs Press Lb per Sq In. Volume Enthalpy and Entropy Taken from -40 F Enthalpy Entropy 50 Dec Superheat 100 Deg Superheat Liquid Vapor Liquid Vapor Liquid Vapor Enthalpy En tropy Enthalpy En tropy 0 38.79 0.01192 2 40.43 0.01195 4 5 6 42.14 43.02 43.91 0.01198 0.01200 0.01201 8 45.74 0.01205 10 47.63 0.01208 12 49.58 0.01211 14 51.59 0.01215 16 18 53.66 0.01218 55.79 0.01222 20 57.98 0.01225 22 60.23 0.01229 24 62.55 0.01232 26. 64.94 0.01236 28 67.40 0.01239 30 69.93 0.01243 32 72.53 0.01247 34 75.21 0.01250 36 77.97 0.01254 38 80.81 0.01258 40 * 42 44 - 46 48 83.72 86.69 89.74 92.88 96.10. 0.01262 0.01266 0.01270 0.01274 0.01278 50 99.40 0.01282 52 102.8 0.01286 54 106.2 0.01290 56 109.8 0.01294 58 113.5 0.01299 60 117.2 62 121.0 64 124.9 66 128.9 68 133.0 0.01303 0.01307 0.01312 0.01316 0.01320 70 137.2 72 141.5 74 145.9 76 150.4 78 155.0 0.01325 0.01330 0.01334 0.01339 0.01344 80 159.7 82 164.5 84 169.4 86 174.5 88 179.6 0.01349 0.01353 0.01358 0.01363 0.01368 90 184.8 92 T90.1 94 195.6 96 201.2 98 206.8 0.01374 0.01379 0.01384 0.01390 0.01396 100 212.6 102 218.5 104 224.6 106 230.7 108 237.0 0.01402 0.01408 0.01414 0.01420 0.01426 110 243.4 . 0.01433 112 249.9 0.01440 114 256.6 0.01447 116 263.4 0.01454 118 270.3 0.01461 120 277.3 0.014G9 1.373 10.63 105.02 0.0240 0.2293 112.35 0.2446 120.00 0.2590 1.320 1.270 1.246 1.221 1.175 11.17 11.70 11.97 12.23 12.76 105.24 105.45 105.56 105.66 105.87 0.0251 0.0262 0.0268 0.0274 0.0285 0.2289 0.2285 0.2283 0.2280 0.2276 112.59 112.83 112.95 113.07 113.31 0.2442 0.2438 0.2436 0.2434 0.2430 120.20 120.52 120.65 120.78 121.04 0.2586 0.2581 0.2579 0.2577 0.2572 1.130 1.088 1.048 1.009 0.9721 13.29 13.82 14.36 14.90 15.44 106.08 106:29 106.50 106.71 106.92 0.0296 0.0307 0.0319 0.0330 0.0341 0.2272 0.2268 0.2264 0.2260 0.2257 113.55 113.79 114.02 114.25 114.48 0.2426 0.2422 0.2418 0.2414 0.2410 121.30 121.56 121.82 122.08 122.33 0.2568 0.2564 0.2560 0.2556 0.2552 0.9369 0.9032 0.8707 0.8398 0.8100 15.98 16.52 17.06 17.61 18.17 107.13 107.33 107.53 107.73 107.93 0.0352 0.0364 0.0375 0.0379 0.0398 0.2253 0.2249 0.2246 0.2242 0.2239 114.71 114.94 115.17 115.40 115.62 0.2406 0.2402 0.2398 0.2395 0.2391 122.59 122.84 123.10 123.35 123.60 0.2548 0.2544. 0.2540 0.2537 0.2533 0.7816 0.7543 0.7283 0.7032 0.6791 18.74 19.32 19.90 20.49 21.09 108.13 108.33 108.52 10S.71 108.90 0.0409 0.0421 0.0433 0.0445 0.0457 0.2235 0.2232 0.2228 0.2225 0.2222 115.84 116.07 116.29 116.52 116.74 0.2387 0.2383 0.2380 0.2376 Q.2373 123.85 124.10 124.35 124.59 124.84 0.2529 0.2525 0.2522 0.2518 0.2515 0.6559 0.6339 0.6126 0.5922 0.5726 21.70 22.29 22.90 23.50 24.11 109.09 109.27 109.45 109.63 109.80 0.0469 0.0481 0.0493 0.0505 0.0516 0.2218 0.2215 0.2211 0.2208 0.2205 116.96 117.18 117.40 117.61 117.82 0.2369 0.2366 0.2363 0.2359 0.2350 125.08 125.32 125.56 125.80 126.04 0.2511 0.2508 0.2504 0.2501 0.2497 0.5537 U.5355 0.5184 0.5014 0.4849 24.73 25.34 25.95 26.58 27.22 109.98 110.14 110.30 110.47 110.63 0.0528 0.0540 0.0552 0.0564 0.0576 0.2201 0.2198 0.2194 0.2191 0.2188 118.02 118.22 118.42 118.62 118.82 0.2353 T26.27 0.2350 126.50 0.2347 126.73 0.2343 126.96 ,0.2340 127.19 0.2494 0.2491 0.2488 0.2484 0.2481 0.4695 0.4546 0.4403 0.4264 0.4129 27.83 28.46 29.09 29.72 30.35 110.78 110.93 111.08 111.22 111.35 0.0588 0.0600 0.0012 0.0624. 0.0636 0.2185 0.2181 0.2178 0.2175 0.2172 119.01 0.2337 119.21 .0.2331 119.40 0.2331 119.59 0.2327 119.77 0.2324 127.42 127.65 127.87 128.10 128.32 0.2478 0.2475 0.2472 0.2469 0.2466 0.4000 0.3875 0.3754 0.3638 0.3526 30.99 31.65 32.29 32.94 33.61 111.49 111.63 111.75 111.88. 112.01 0.0648 0.0661 0.0673 0.0684 0.0696 0.2168 0.2165 0.2162 0.2158 0.2155 119.96 120.15 120.32 120.50 120.67 0.2321 0.2318 0.2315 0.2312 0.2309 128.54 128.76 128.97 129.19 129.40 0.2463 0.2460 0.2457 0.2455 0.2452 0.3417 0.3313 0.3212 0.3113 0.3019 34.27 34.92 35.60 36.28 36.94 112.13 0.0708 112.24. 0.0720 112.36 0.0732 112.47 0.0744 112.57 0.0756 0.2151 0.2148 0.2144 0.2140 0.2137 120.85 121.02 121.18 121.34 121.50 0.2306 0.2303 0.2300 0.2297 0.2294 129.61 129.82 130.02 130.23 130.43 0.2449 0.2446 0.2443 0.2441 0.2438 0.2928 0.2841 0.2755 0.2672 0.2594 37.61 38.28 38.97 ' 39.65 40.32 112.67 112.76 112.85 112.93 113.00 0.0768 0.0780 0.0792 0.0803 0.0315 0.2133 0.2130 0.2126 0.2122 0.2119 121.6G 121.82 121.97 122.12 122.26 0.2291 0.228S 0.2285 0.2282 0.2279 130.63 130.83' 131.03 131.23 131.42 0.2435 0.2432 0.2429 0.2427 0.2424 0.2517 0.2443 0.2370 0.2301 0.2233 40.98 41.65 42.32 42.98 43.66. 113-06 113.12 113.16 113.20 113.24 0.0827 0.0839 0.0851 0.0862 0.0874 0.2115 0.2111 0.2107 0.2104 0.2100 122.40 122.53 122.66 122.79 122.92 0.2276 0.2273 0.2270 0.2267 0.2264 131.61 131.80 131.99 132.17 132.35 0.2421 0.2418 0.2416 0.2413 0.2411 0.2167 0.2104 0.2043 0.19S3 0.1926 44.35 45.04 45.74 46.44 47.14 113.29 113.34 113.38 113.42 113.46 0.0886 0.0898 0.0909 0.0921 0.0933 0.2096 0.2093 0.2089 0.2085 0.2081 123.04 123.16 123.28 123.40 123.51 0.2261 0.2258 0.2255 0.2253 0.2250 132.53 132.71 132.88 133.05 133.2? 0.2408 0.2405 0.2403 0.2400 0.2398 .0.1871 47.85 113.62 0.0945 0.2078 123.62 0.2247 133.39 0.2395 Data from Kinetic Chemicals,- Inc., 1945