Page 74 - HVAC Pump Handbook

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Piping System Friction
Piping System Friction 71

TABLE 3.16 PVC and CPVC Plastic Pipe: Inside Diameters (in)

Schedule 40 Schedule 80
1 ⁄ 2 − 0.622 3 − 3.068 1 ⁄ 2 − 0.546 3 − 2.900
3 3
⁄ 4 − 0.824 4 − 4.026 ⁄ 4 − 0.742 4 − 3.826
1 − 1.049 6 − 6.065 1 − 0.957 6 − 5.761
1 1
1 ⁄ 4 − 1.380 8 − 7.981 1 ⁄ 4 − 1.278 8 − 7.625
1 1
1 ⁄ 2 − 1.610 10 − 10.020 1 ⁄ 2 − 1.500 10 − 9.564
2 − 2.067 12 − 11.938 2 − 1.939 12 − 11.376
1 1
2 ⁄ 2 − 2.469 14 − 13.124 2 ⁄ 2 − 2.323 14 − 12.500
16 − 15.000 16 − 14.314

Hydraulic shock and ambient temperature are factors that must be
considered with plastic pipe; greater care must be exerted with plastic
pipe than while designing with steel pipe of equivalent sizes.
Like other types of piping, the inside diameter of the pipe under
consideration must be checked before consulting a pipe friction table.
Table 3.16 provides the inside pipe diameters for the Schedules 40
and 80 PVC and CPVC pipe. Friction losses for Schedule 40 PVC and
CPVC pipe can be determined from Fig. 3.10 and Schedule 80 PVC
and CPVC pipe from Fig. 3.11.

3.6 Copper Pipe and Tubing
Copper pipe is not used extensively in HVAC systems like steel pipe.
It is of value on HVAC equipment assemblies, and tables for friction
of water in it up to 2 in size are included in Table 3.17. The friction
losses in copper fittings should be evaluated as has been done for
plastic pipe; ASHRAE has under consideration the testing of the
flow of water in the smaller copper fittings. Questions about friction
of refrigerant flow in copper pipe should be referred to the refriger-
ant manufacturers.

3.7 Glycol Solutions
Few special liquids are used in the HVAC industry, but both ethylene
glycol and propylene glycol are found in these water systems. The
friction for ethylene glycol–based, heat transfer solutions can be com-
puted using Fig. 2.4, which shows the variation in viscosity for vari-
ous temperatures and percent of solution. Once the viscosity is
known, the Reynolds number can be determined, and then the f fac-
tor can be computed for the Darcy Weisbach equation. The pump

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