Document e56weg480e2ZjOZny8MnRjO9m

764 CHAPTER 36 ...Guide 1950 of refrigerant which is present in vapor fonn. Consider, for exainple, F-I2 with a quality (the per cent in vapor form) 'of 30 Ter cent j the enthalpy., of this material would be equal to: where Af + 0.30 (hr'-- hi) -........ - ha = specific enthalpy of the mixture. x ! ht -- specifics enthalpy of the liquid. . .' hr = specific enthalpy. of the saturated vapor. - : ,- j - Values of ht and h, are obtained from Table 1 for the: actual ipressure of the mixture. ~ - | - i -- By a reversal of this same procedure the tabular datai'can ^be usedltx) 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, Tim, is equal to the enthalpy, of the saturated liquid at the entrance state, A,,, and can therefore be read from the table. Thus, . ' All ; A,, -- hrd' -- (1 "" x'j (Aid -- Afd) (5) r, ; . ; X (An, -- hid) -3- (Ard --. Afd) (6) where ht. = enthalpy of saturated liquid at entrance to expansion valve. ' Am = enthalpy of mixture. Ad = enthalpy of saturated vapor at discharge. hid = 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 ah 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 allowed1 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--rno heat' transfer occurring during the pressure-change processes;1' Refrigeration 765 Tabus 2. Pbopebties op Monochlobodifluorosethane'(F-22): , - Sat Temp F. Ads Press Lb per Sq In. Volume Enthalpy and Entropy Taken from -40 F; Enthalpy Entropy 50 Deg Superheat 100 Deg Superheat Liquid ; Vapor Liquid Vapor. Liquid Vapor Enthalpy En tropy En- i Enthalpy tropy ; 0 38.79 0.01192 1.373 10.63. 105i02 0.0240 0.2293 112.35 0.2446 120.00 0.2590 40.43 0.01195 1.320 11.17 105.24 0.0251 0.22S9 112.59 0.2442 120.26 0.2586 42.14 0.01198 1.270 11.70 105.45 0.0262 0.2285 112.83 0.2438 120.52 0.2581 * 43.02 0.01200 1.246 .11.97 105.56 0.0268 0.2283 112.95 0.2438 120.65 0.2579 ; 6 43.91 0.01201 1.221 12.23 105.66 0.0274 0.2280 113.07 0.2434 120.78 0.2577 . 8 45.74 0.01205 1.175 22.76 105.87 0.0285 0.2276 213.31 0.2430 121.04 0.2572 10 47.63 0.01208 1.130 13.29 106.08 0.0296. 0.2272 113.55 0.2426 121.30 0.2568 12 49.58 0.01211 1.088 13.82 106.29 0.0307 0.2263 113.79 0.2422 121.56 0.2564 14 51.59 . 0.01215 1.048 * '14.36 106.50 0.0319 0.2204 114.02 0.2418 121.82 0.2560 16 53.66 0.01218 1.009 14.90 106.71 0.0330 0.22G0 114.25 0.2414 122.08 0.2556 18 55.79 0.01222 0.9721 15.44 106.92 0.0341 0.2257 114.48 0.2410 122.33 0.2552 20 57.98 0.01225 0.9369 15^98 107.13 0.0352 0.2253 114.71 0.2406 122.59 0.2548 22 60.23 0.01229 - 0.9032 16.52 107.33 0.0364 0.2249 114.94 0.2402 122.84 0.2544 24. 62.55. 0.01232 0.8707 17.06 107.53 0.0375 0.2246 115.17 0.2398 123.10 0.2540 26 64.94 0.01236 0.8398 17.61 107.73 0.0379 0.2242 115.40 0.2395 123.35 0.2537 28 67.40 0.01239 0.8100 18.17 107.93 0.0398 0.2239 115.62 0.2391 123.60 0.2533 30 69.93 0.01243 0.7816 18.74 108.13 0.0409 0.2235 115.S4 0.2387 123.85 0.2529 32 72.53 0.01247 0.7543 19.32 108.33 0.0421 0.2232 116.07 0.2383 124.10 0.2525 34 75.21 0.01250 0.7283 19.90 108.52 0.0433 0.2228 116.29 0.2380 124.35 0.2522 36 77.97 0.01254 0.7032 20.49 108.71 0.0445 0.2225 116.52 0.2376 124.59 0.2518 38 80.81 0.01258 0.6791 21.09 108.90 0.0457 0.2222 116.74 Q.2373 124.84 0.2515 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 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 116.96 117.18 117.40 117.61s 117.82 0.2369 0.2366 0.2363 0.2359 0.235C 125.08 125.32 125.56 125.80 126.01 0.2511 0.2508 0.2504 0.2501 0.2497 0 99.40 0.01282 0.5537 24.73 109.98 0.0528 0.2201 118.02' 0.2353 T26.27 0.2494 52 102.8 0.01286 0.5355 25.34 110.14- 0.0540 0.2198 118.22 0.2350 126.50 0.2491 54 106.2 0.01290 0.5184 25.95 110.30 0.0552 0.2194 118.42 0.2347 126.73 0.2488 56 109.8 0.01294 0.5014 20.58 110.47 0.0564 0.2191 118.62 0.2343 126.96 0.2484 58 113.5 0.01299 0.4849 27.22 110.63 0.0576 0.2188 118.82 0.2340 .127.19 0.2481 60 62 64 66 68 117.2 121.0 124.9 128.9 133.0 0.01303 0.01307 0.01312 0.01316 0.01320 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 0.0612 0.0624. 0.0636 0.2185 0.2181 0.2178 0.2175 0.2172 119.01 119.21 119.40 119.59 119.77 0.2337 0.2334 0.2331 0.2327 0.2324 127.42 127.65 127.87 128.10 128.32 0.2478 0.2475 0.2472 0.2469 0.2460 70 72 . 74 . 76 , 78 137.2 141.5 145.9 150.4 .155.0 0.01325 0.01330 0.01334 0.01339 - 0.01344 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 , 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 0.3417 0.3313 0.3212 0.3113 0.3019 34.27 34.92 35.60 36.28 36.94 112.13 112.24 112.36 112.47 112.57 0.0708 0.0720 0.0732 0.0744 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 Q.2294 129.61 129.82 130.02 130.23 130.43 0.2449 0.2446 0.2443 0.244r 0.2438. 90 92 > '94. 96-. 98 184.8 190.1 195.6 201.2 206.8 . 0.01374 . 0.01379 0.01384 0.01390 0.01396 ; 0.2928 0.2841 0.2755 0.2672 0.2504 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 .0.0815 0.2133 0.2130 0.2126 0.2122 0.2119 121.60 121.82 121.97 122.12 122.26 0.2291 0.2288 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:. 100 -102 ' 104 106 108 212.6 218.5 224.6 230.7 237.0 0.01402 0.01408 0.01414 0.01420 0.01426 0.2517 0.2443 0.2370 0.2301 0.2233 40.98 41.65 42.32 42.93 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 1 0.2416 ,, 0.2413) 0.2411', 110 112 114 116 ' 118 243.4 249.9 256.6 263.4 270.3 0.01433 0.01440 0.01447 0.01454 0.01461 0.2167 0.2104 0.2043 0.1983 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 0.2098 0.2003 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 132.53 132.71 132.88 133.05 133.28 0.2408 * 0.2405 0.2403 ' 0.2400 . 0.2398 i 120.. - 277.3 . . 0.01469 0.1871 . 47.S5 113.52 0.0945 0.2078 123.62. 0.2247 133.39 0.2395>j . Datafrom KineticChemjcalarlnc-;'1945^ / -i-t