Handbook of air conditioning and refrigeration / Shan K

REFRIGERATION SYSTEMS: RECIPROCATING, ROTARY, SCROLL, AND SCREW 11.19
TABLE 11.4 Minimum Refrigeration Load for Oil Entrainment up Suction Risers of Type L Copper Tubing, in Tons
1. From Table 11.1, for a suction temperature of 45°F (7.2°C) and a condensing temperature of
115°F (46.1°C), Fsuc,s is 1.10 and Fsuc,c � 0.93. The corrected refrigeration load Qrl for the suction
line is therefore 20/(1.1 � 0.93) � 19.6 tons (68.7 kW).
2. Assume an equivalent length of the suction line Leq of 90 ft (27 m). From Fig. 11.10, for a
refrigeration load of 19.7 tons and Leq � 90 ft (27 m), the next-higher value of the tentative outside
diameter of the suction line is in. (54 mm), a nominal diameter of 2 in. (50 mm).
3. Recalculate the equivalent length, based on a copper tubing outside diameter of 2 in. (54 mm).
The pressure drops of the refrigerant piping fittings and the accessories expressed as equivalent
length of pipe are listed in Table 11.2. The calculated total equivalent length Leq is
1 2
�8 1�8 10 short radius elbows 10 � 5 � 50 ft (15 m)
1 angle valve 1 � 24 � 24 ft (7.2 m)
Measured length of pipe 30 ft (9 m)
Total 104 ft (31.2 m)
Pipe OD, in.
Suction
0.500 0.625 0.750 0.875 1.123 1.375 1.625 2.125 2.625 3.125 3.625 4.125
Saturated gas Area, in. 2
temperature, temperature,
Refrigerant °F °F 0.146 0.233 0.348 0.484 0.825 1.256 1.780 3.094 4.770 6.812 9.213 11.970
HCFC-22 �40.0 �30.0 0.067 0.119 0.197 0.298 0.580 0.981 1.52 3.03 5.20 8.12 11.8 16.4
�10.0 0.065 0.117 0.194 0.292 0.570 0.963 1.49 2.97 5.11 7.97 11.6 16.1
10.0 0.066 0.118 0.195 0.295 0.575 0.972 1.50 3.00 5.15 8.04 11.7 16.3
�20.0 �10.0 0.087 0.156 0.258 0.389 0.758 1.28 1.98 3.96 6.80 10.6 15.5 21.5
10.0 0.085 0.153 0.253 0.362 0.744 1.26 1.95 3.88 6.67 10.4 15.2 21.1
30.0 0.086 0.154 0.254 0.383 0.747 1.26 1.95 3.90 6.69 10.4 15.2 21.1
0.0 10.0 0.111 0.199 0.328 0.496 0.986 1.63 2.53 5.04 8.66 13.5 19.7 27.4
30.0 0.108 0.194 0.320 0.484 0.942 1.59 2.46 4.92 8.45 13.2 19.2 26.7
50.0 0.109 0.195 0.322 0.486 0.946 1.60 2.47 4.94 8.48 13.2 19.3 26.8
20.0 30.0 0.136 0.244 0.403 0.608 1.18 2.00 3.10 6.18 10.6 16.6 24.2 33.5
50.0 0.135 0.242 0.399 0.603 1.17 1.99 3.07 6.13 10.5 16.4 24.0 33.3
70.0 0.135 0.242 0.400 0.605 1.18 1.99 3.08 6.15 10.6 16.5 24.0 33.3
40.0 50.0 0.167 0.300 0.495 0.748 1.46 2.46 3.81 7.60 13.1 20.4 29.7 41.3
70.0 0.165 0.296 0.488 0.737 1.44 2.43 3.75 7.49 12.9 20.1 29.3 40.7
90.0 0.165 0.296 0.488 0.738 1.44 2.43 3.76 7.50 12.9 20.1 29.3 40.7
Note: The capacity in tons is based on 90°F liquid temperature and superheat as indicated by the listed temperatures. For other liquid line temperatures,
use correction factors in the table below.
Liquid temperature, °F
Refrigerant 50 60 70 80 100 110 120 130 140
HCFC-22 1.17 1.14 1.10 1.06 0.98 0.94 0.89 0.85 0.80
Source: ASHRAE Handbook 1998, Refrigeration Systems and Applications.
Reprinted with permission.
4. From the capacity-Leq chart, at Qrl � 19.7 tons (68.7 kW) and Leq � 104 ft (31.2 m), the diameter
of copper tubing is the same as the tentative diameter in. (54 mm). Consequently, 2 in.
(54 mm) should be the size of the suction line.
1 2 �8 1�8