Document 1QbRJy1b20N7kN7EYyDj4GY1d

HEATING VENTILATING AIR CONDITIONING GUIDE 1941 Table 4. Properties of Carbon Dioxide Sat. Temp. F Ass. Passa La pei% So In. Volume liquid Vapor Heat Contest and Enteoft Taken Feom -40 F Heat Content Liquid Vapor Entropy Liquid Vapor 50 F Superheat 100 F Superheat Ht. Ct Entropy HL Ct 0 2 4 5 6 305-S 315.9 3264 332.0 337.4 0.01570 0.01579 0.01588 0 01592 0.01596 0.29040 0.28030 0.27070 0.26610 0.26140 18.8 19.8 20.8 21.3 21.8 138.9 138.8 138.8 138.8 138.7 0.0418 0.0440 0.0461 0.0472 0.0483 0.3024 0.3014 0.3005 0.3000 0.2994 153.7 153.7 153.7 153.7 153.7 0.3342 0.3330 0.3318 0.3312 0.3306 167.5 167.6 167.7 167.7 167.8 0.3612 0.3600 0.3588 0.3582 0.3576 8 to. 12 14 16 348.7 360.2 371.9 383.9 396.2 0.02605 0.01614 0.01623 0.01632 0.01642 0.2S260 0.24370 0.23540 0.22740 0.21970 22.9 24.0 25.0 26.1 27.2 138.7 138.7 138.6 138.6 138.5 0.0504 0.0526 0.0548 0.0571 0.0S93 0.2982 Q.2970 0.2958 0.2946 0.2933 153.7 153.7 153.7 153.7 153.7 0.3293 0.3281 04270 03259 0.3249 167.9 168,0 168.1 : 168.2 168-3 0.3563 0.3S50 04538 04526 04513 18 20 22 24 26 408.9 421.8 434.0 448.4 462.2 0.01652 0.01663 0.01673 0.01684 0.01695 0.21210 0.20490 0.19790 0.19120 0.18460 28.3 29.4 30.5 31.7 32.9 138.4 138.3 138.2 138.1 138.0 0.0616 0.0638 0.0662 0.0686 0.0710 0.2921 0.2909 0.2897 0.2885 0.2873 153.7 153.7 153.7 153.7 153.7 0J238 0.3227 0.3214 0.3202 0.3189 168.5 168.6 168.7 168.8 168.9 04501 0.3489 04479 04470 04460 2& 30 32 34 36 476.3 490.8 505.5 522.6 536.0 0.01707 001719 0.01731 0.01744 0.01759 0.17830 0.17220 0.16630 0.16030 0.15500 34.1 35.4 36.7 37.9 39.1 137.9 137.8 137.7 137.4 137.2 0.0734 0.0758 0.0781 0.0804 0.0828 0.2861 0.2849 0.2834 0.2820 0.2805 153.7 153.7 153.7 153.7 153.7 0.3177 0.3164 0.3158 0.3151 0.3145 169.0 1694 169.2 169.3 169.4 0.3451 04441 0.3431 0.3421 . 04411 38 39 40 41 42 551.7 559.7 567.8 576.0 584.3 0.01773 0.01780 0.01787 0.01794 0.01801 0.14960 0.14700 0.14440 0.14185 0.13930 40.4 41.0 41.7 424 42.9 136.9 1364 136.7 136.5 136.3 0.0851 0.0862 0.0874 0.0887 0.0899 0.2791 0.2783 0.2776 0.2768 0.2761 153.7 153.7 153.7 153.7 153.7 0.3138 0.3135 0.3132 0.3127 0.3122 169.5 169.5 169.6 169.6 169.7 04401 03*96 04391 04386 04381 44 46 48 50 52 601.1 618.2 635.7 653.6 671.9 0.01817 0.01834 0.01851 0.01868 0.01887 0.13440 0.12970 0.12500 0.12050 0.11610 44.3 . 45.6 47.0 48.4 49.8 136.1 135.7 135.4 135.0 134.5 0.0924 0.0950 0.0975 0.1000 0.1027 0.2745 0.2730 0.2714 0.2699 0.2681 153.7 153.7 153.7 153.7 153.7, 0.3112 0.3101 0-3091 0.3081 0.3069 169.8 - 169.9 170.0 170.1 170.2 04371 04362 04352 04342 04333 54 56 58 60 62 690.6 709.5 728.8 748.6 769.0 0.01906 0.01927 : 0.01948 0.01970 0.01995 0.11170 0.10750 0.10340 0.09940 0.09545 51.2 52.6 54.0 55.5 57.0 133.9 133.4 132.7 132.1 131.3 0.1054 0.1081 0.U08 0.1135 0.1164 0.2663 0.2644 0.2626 0.2608 0.2584 153.7 153.7 153.7 153.7 153.7 0.3057 0.3046 0.3034 0.3022 0.3012 170.3 170.5 170.6 170.7 170.8 04324 04315 04306 04297 04289 64 66 68 70 72 789.4 810.3 8314 853.4 875.8 0.02020 0.02048 0.02079 0.02112 0.02152 0.09180 0.08800 0.08422 0.08040 0.07654 58.6 60.2 61.9 63.7 654 130.6 129.7 128.7 127 .S 126.0 0.1194 0.1223 0.1253 0.1282 0.1321 0.2560 0.2535 0.2511 0.2487 0.2450 153.7 153.7 153.7 153.7 153.7 0.3002 0.2991 0.2981 0.2971 0.2962 170.9 171.0 1714 171.2 1714 04281 04273 04265 04257 04250 74 76 78 80 82 898.2 9214 944.8 968.7 993.0 0.02192 0.02242 0.02300 0.02370 0.02456 0.07269 0.06875 0.06473 0.06064 0.05648- 67j 69.4 71.6 73.9 76.4 1244 122.8 120.9 118.7 116.6 0.1360 0.1398 0A437 0.1476 0.1578 0.2414 0.2377 0.2341 0.2304 0.2195 153.7 153.7 153.7 153.7 153.7 0.2953 0.2945 0.2936 0.2927 0.2920 171.4 1714 171.6 171.7 1734 04242 04235 03227 04220 04215 84 1017.7 0.02553 86 1043.0 0.02686 87.8 1069.9 0.03454 0.05223 0.04789 0.03454 79.4 83.3 97.0 113.9 110.4 97.0 0.1679 0.1781 0.18S0 0.2087 0.1978 0.1880 153.7 153.7 153.7 0.2914 0.2907 0.2901 176.0 178.2 1804 04209 04204 04199 Types of Compressors There are many different types of compressors, using various refrig erants. Each type has its advantages for its particular application, and those generally used for air conditioning are of the following types: 1. Reciprocating compressors (commonly referred to as piston type). 2. Centrifugal compressors. 3. Steam jet. Reciprocating compressors are available in a wide range of sizes and types. Any of a number of refrigerants, including dichlorodifluoromethane 448 CHAPTER 24. REFRIGERATION (Fu), methyl chloride, ammonia, carbon dioxide, and sulphur dioxide jnay be used in reciprocating machines. The first of these is used exten sively in direct expansion systems of comfort air conditioning. Compressors may be classified into two general types, (a) open type, (b) enclosed type. If the driving mechanism is external to the compressor, then the shaft must be brought out through the crankcase and a shaft seal or stuffing box must be used to prevent escape of the refrigerant. This type of compressor is known as an open-type compressor. When the driving mechanism is located within the crankcase of the compressor in such a way as to avoid the necessity of a shaft seal, the compressor is known as the completely enclosed or hermetically sealed type. ' Open type compressors may be further classified as belt driven and directly connected. A great number of direct-driven units are now. being used which generally operate at higher rotational speeds than the beltdriven type. The present tendency is toward forced lubrication of the bearings of compressors by means of an oil pump driven from the crankshaft, although there are many splash lubricated compressors on the market. The chief advantages of the forced lubricated compressor are. that the lubrication system requires less energy for its operation than the splash type, the oil can be easily filtered before it enters the bearings, and less oil is usually required. The compressor capacity must be selected for and matched to the maximum load for the installation on which it is to be used. Air-con ditioning loads, however, vary over a wide range, and a wide fluctuation in air conditions may result during periods of light load if on-and-off control of full compressor capacity is used. To prevent such undesirable fluctuation, several methods are employed to vary the capacity of reciprocating compressors, such as: 1. By-passing one or more cylinders, of a multicylinder compressor, from discharge to suction. 2. Rendering the suction valves of one or more cylinders of a multicylinder compressor inoperative. This is usually accomplished by depressing the suction valves. 3. Varying the speed of the compressor, usually by using variable speed or two-speed electric motors. 4. Using clearance pockets to control the quantity of refrigerant pumped. 5. Restricting the suction inlet to one or more of the cylinders of a multicylinder compressor either by an automatic modulating valve or by an on and off valve. All of these methods, with the exception of variable speed, result in a slightly lowered overall compressor efficiency when in use, since the mechanical losses remain constant whereas the quantity of refrigerant pumped is lowered'. Centrifugal compressors are used with very low pressure refrigerants; usually both evaporator and condenser work below atmospheric pressure. Water and monofluorotrichloromethane (Fu) are the refrigerants com monly used in centrifugal machines. " Compression of the refrigerant is accomplished by means of centrifugal force; therefore, this type of compressor is inherently suitable for large volumes of refrigerant-at low pressure differentials. Two or more stages are usually required and high speeds are necessary to obtain good efficiency. 449