Document OJ1jJxQ9OJa21e0YyNGO7x4ov

*9 HEATING VENTILATING AIR CONDITIONING GUIDE 1941 Table 7. Pressure Losses in Dichlorodifluoromethane Discharge or Hot Gas Lines4 Capacitt Bto per Hour 10,000 15,000 20,000 .. 25,000 . 30,000 40,000 50,000 60,000 70,000 80,000 90,000 100,000 125,000 150,000 175,000 200,000 250,000 300,000 400,000 500,000 600,000 800,000 1,000,000 1,250,000 1,500,000 2,000,000- Pressure Drop in Pounds per Square Inch per 100 Ft*> Line Sizes, Inches K H K m IK IK 2K 2K m 3K 2.3 1.0 0.6 4.9 2.0 1.0 8.5 3.4 1.7 0.6 5.3 2.6 0.9 7.5 3.6 1.2 0.5 6.4 2.1 0.7 9.8 3.1 1.0 0.5 4.4 1.3 0.7 6.0 1.9 0.9 8:0 2.5 1.1 10.2 3.1 1.4 3.8 1.7 0.5 ' 6.0 2.6 0:7 8.5 3.8 1.0 11.6 5.1 1.3 6.7 10.4 1.7 2.6 3.7 6.7 10.5 0.6 0.9 1-2 2.2 3.5 5.0 0.5 0.9 1.5 2.1 0.7 1.0 9.0 3.8 5.8 9.5 1.8 2.9 4.4 6.4 11.3 . *Soft annealed copper tubing up to and including l/i in. outside diameter. Hard copper pipe Ji in. outside diameter and larger. bLehgth of tubing includes the average number of fittings. control and regulating valves must be added to the other pipe losses to determine the total drop. All copper pipe referred to in these tables are of type L wall thickness and are designated by outside diameter. The effect of the sizes of refrigerant lines on the system may be studied by referring to the preceding discussion on Characteristics of Compression Systems. It will be noted that any lowering of the suction pressure at the compressor lowers the capacity. Therefore, excessive pressure drop through the suction piping should be avoided. On the other hand, the suction line must riot be made too large when using refrigerants which are soluble in oil, because under such circumstances the velocity of the returnirig refrigerant may become too low to carry back the entrained oil, Pressure drop in the discharge line also lowers the capacity of the system 462 CHAPTER 24! REFRIGERATION . Table 8. . Pressure Losses in Dichlorodifluoromethane Liquid Refrigerant Lines, Capacitt Btu per Hour 100,000 125,000 150,000 175,000 200,000 225,000 250,000 275,000 300,000 325,000 350,000 375,000 400,000 450,000 500.000 550,000 600,000 700,000 800,000 900,000 1,000,000 1,200,000 1,400,000 1,600,000 1,800,000 2,000,000 2,200,000 Pressure Drop in Pounds' per Square Inch per 100 Ft* Pipe Sizes, Inches .K 0.6 0.9 1.3 1.8 2.3 2.9 3.6 4.3 5.1 5.9 6.9 7.9 9.0 IK IK 0.6 0.8 1.0 1.2 1.4 . 1.6 1.8 2.1 2.3 2.9 3.5 4.3 5.0 6.7 8.7 0.8 1.0 1.3 1.5 1.8 2.4 3.1 3.9 4.7 6.7 9.0 IK 0.7 0.8 1.1 1.4 1.7 2.1 3.0 4.0 5.1 6.3 7.9 9.2 ^Length of tubing includes the average number of fittings. but not to the same extent as does the pressure drop in the suction line. The velocities of the refrigerant in either suction or discharge lines must not be excessive or noise will result. Velocities of 1000 to 2000 fpm are common in suction lines, and from 2000 to 3500 fpm are used in discharge lines. Velocities in the discharge lines as high as 5000-fpm can only be used where the fittings and bends are all stream-lined as noise will other wise result. - The pressure drop in the liquid line affects the capacity of the expansion valve as the pressure drop across the valve is reduced by the amount of the pipe line drop. If the liquid line drop is sufficient to cause flashing (i.e. vaporizing) of someof the liquid refrigerant, a hissing noise in the lines and valves usually develops. 463 !