Document a1pqEmR4y6BgeYk7rvx713xea

HEATING VENTILATING AIR CONDITIONING GUIDE 1943 Table 4. Properties of Carbon Dioxide Sat. Tkvp. P 0 2 4 5 6 8 10 12 14 16 18 20 22 24 . 26 28 30 32 34 36 38 39 40 41 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74' 76 78 80 82 84 86 87.8 Ab& Press. La per Sq In. VOLUME liquid Vapor 305-5 0.01570 315.9 . 0.01579 326-5 . 0.01588 332.0 0 01592 337.4 0.01596 0.29040 0.28030 0.27070 0.26610 0.26140 348.7 0.01605 360.2 0.01614 371.9 0.01623 383.9 0.01632 396.2 0.01642 0.25260 0.24370 0.23540 0.22740 0.21970 408.9 421-8 434.0 448.4 4623 0.01652 0.01663 0.01673 0.01684' 0.01695 0.21210 0.20490 0.19790 0.19120 0.18460 476.3 0.01707 0.17830 490.8 0.01719 0.17220 505.5 0.01731 0.16630 522.6 0.01744 0.16030 536.0 0.01759 0.15500 551.7 S59.7 567.8 576.0 5843 0.01773 0.01780 0.01787 0.01794 0.01801 0.14960 0.14700 0.14440 0.14185 0.13930 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 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 789.4 810-3 831.6 853.4. 875.8 0.02020 0.02048 0.02079 0.02112 0.02152 0.09180 0.08800 0.08422 0.08040 0.07654 898.2 921.3 944.8 968.7 993.0 0.02192 0.02242 0.02300 0.02370 0.02456 0.07269 0.06875 0.06473 0.06064 0.05648 1017.7 0.02553 0.05223 1043.0 0.02686 0.04789 1069.9 0.03454 0.03454 -40 FHeat Content and Entbopt Taken Fbou - Heat Content Entropy 50 F Superheat 100 F Superheat liquid . Vapor liquid Vapor Ht Ct Entropy Ht Ct Entropy 18.8 138.9 0.0418 0.3024 153.7 0.3342 167-5 03612 19.8 138.8 0.0440 0-3014 153.7 0.3330 167.6 0.3600 20.8 138.8 0.0461 0-3005 153.7 0.3318 167.7 0.3588 213 138.8 0.0472 0.3000 153.7 0.3312 167.7 03582 21.8 138.7 0.0483 0.2994 153.7 0.3306 167.8 0.3576 22.9 138.7 0.0504 0.2982 1S3.7 0-3293 167.9 03563 24.0 138.7 0.0526 0.2970 153.7 0-3281 168.0 03550 25.0 138.6 0.0548 0.2958 153.7 0-3270 168.1 03538 26.1 138.6 0.0571 0.2946 153.7 0-3259 168.2 03526 27.2 138.5 0.0593 0.2933 153.7. 0.3249 1683 03513 28.3 138.4 0.0616 0.2921 153.7 0.3238 168.5 03501 29.4 138.3 0.0638 0.2909 153.7 0.3227 168.6 0.3489 30.5 138.2 0.0662 0.2897 153.7 0.3214 168.7 0.3479 31.7 138.1 0.0686 0.2885 153.7 0.3202 168.8 03470 32.9 138.0 0.0710 0.2873 153.7 0.3189 168.9 03460 34.1 137.9 0.0734 0.2861 153.7 03177 169.0 0.3451 35.4 . 137.8 0.0758 0.2849 153.7 0.3164 169.1 03441 36.7 137.7 0.0781 0.2834 153.7 0.3158 169.2 0.3431 37.9 137.4 0.0804 0.2820 153.7 0.3151 169.3 03421 39.1 137.2 0.0828 0.2805 153.7 0.3145 169.4 03411 40.4 136.9 0.0851 0.2791 153.7 0.3138 169.5 0.3401 41.0 136.8 0.0862 03783 153.7 0.3135 169.5 03396 41.7 136.7 0.0874 0.2776 153.7 0.3132 169.6 0.3391 42.3 136.5 0.0887 0.2768 153.7 0.3127 169.6 03386 42.9 136.3 0:0899 0.2761 153.7 0.3122 169.7 03381 44.3 136.1 0.0924 0.2745 153.7 ` 0-3112 169.8 0.3371 45.6 135.7 0.0950 0.2730 153.7 03101 169.9 0.3362 47.0 135.4 0.0975 0.2714 153.7 0.3091 170.0 03352 48.4 135.0 0.1000 0.2699 153.7 0.3081 170.1 0.3342 49.8 134.5 0.1027 0.2681 153.7 0-3069 170.2 0.3333 51.2 133.9 0.1054 0.2663 153.7 0.3057 170.3 03324 52.6 133.4 0.1081 0.2644 153.7 0.3046 170.5 03315 54.0 132.7 0.1108 0.2626 153.7 0.3034 170.6 03306 55.5 132.1 0.1135 0.2608 153.7 0.3022 170.7 0.3297 57.0 131.3 0.1164 0.2584 153.7 0.3012 170.8 03289 58.6 130.6 0.1194 0.2560 153.7 03002 170.9 0.3281 60.2 129.7 0.1223 0.2535 153.7 0.2991 171.0 03273 61.9 128.7 0.1253 0.2511 153.7 0.2981 171.1 0326S 63.7 127-5 0.1282 0.2487 153.7 0.2971 171.2 03257 65-5 126.0 0.1321 0.2450 153.7 0.2962 1713 03250 ' 67.3 69.4 71.6 73.9 76.4 124-5 0.1360 0.2414 153.7 0.2953 171.4 03242 122.8 0.1398 0.2377 153.7 0.2945 1713 03235 120.9 0.1437 0.2341 153.7 0.2936 171.6 0.3227 118.7 0.1476 0.2304 153.7 0.2927 171.7 0.3220 116.6 0.1578 0.2195 1S3.7 0.2920 173.8 03215 79.4 113.9 0.1679^ 0.2087 153.7 0.2914 176.0 03209 83.3 110.4 0.1781 0.1978 153.7 0.2907 178.2 0.3204 97.0 97.0 0.1880 0.1880 153.7 0.2901 180.1 0.3199 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 refer.ed 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 480 CHAPTER 25. REFRIGERATION (Fu), methyl chloride, ammonia, carbon dioxide, and sulphur dioxide may 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 belt- driven 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 muiti-cylinder compressor, from discharge to suction. 2. Rendering the suction valves of one or more cylinders of a multi-cylinder 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 multi-cylinder 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. 481