Page 20 - HVAC Pump Handbook

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Physical Data for HVAC System Design

Physical Data for HVAC System Design 17

TABLE 2.2 Viscosity of Water

Temperature Absolute Kinematic
2
of water, °F viscosity, cP viscosity, ft /s
32 1.79 1.93
10 5
40 1.55 1.67
10 5
50 1.31 1.41
10 5
60 1.12 1.21
10 5
70 0.98 1.06
10 5
80 0.86 0.93
10 5
90 0.77 0.83
10 5
100 0.68 0.74
10 5
120 0.56 0.61
10 5
140 0.47 0.51
10 5
160 0.40 0.44
10 5
180 0.35 0.39
10 5
200 0.30 0.34
10 5
212 0.28 0.32
10 5
250 0.23 0.27
10 5
300 0.19 0.22
10 5
350 0.15 0.18
10 5
400 0.13 0.16
10 5
450 0.12 0.16
10 5
SOURCE: Engineering Data Book, Hydraulic Institute,
Parsippany, NJ, 1990, p. 19; and Systems and Equipment
Handbook, ASHRAE, Atlanta, Ga., p. 14.3; used with per-
mission.

Operations with water at temperatures above 85°F must take into
consideration both the specific gravity and viscosity. Tables 2.2, 2.3,
and 2.4 provide these data for water from 32 to 450°F.

2.4.1 Viscosity of water
There are two basic types of viscosity: dynamic or absolute, and kine-
matic. Dynamic viscosity is expressed in force-time per square length
terms and in the metric system usually as centipoise (cP). In most
cases, the viscosity of water will be stated as kinematic viscosity in
centistokes (cSt) in the metric system and in square feet per second in
the English system. If the viscosity of a liquid is expressed as an ab-
solute viscosity in centipoise, the conversion formula to kinematic vis-
cosity in square feet per second is
6.7197 10 4
(2.2)

2
where kinematic viscosity, ft /s
absolute viscosity, cP
specific weight, lb/ft 3

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