Page 34 - Fluid mechanics, heat transfer, and mass transfer

FLUID STATICS 11

TABLE 1.2 Viscosity Conversions
Saybolt Viscosity Redwood Viscosity (s)
Kinematic Engler
Viscosity (cSt) Universal (SSU) Furol (SSF) No. 1 No. 2 Viscosity (s)

1 31 – 29 – 1
2 32.6 – 30.2 – 1.1
3 36 – 32.9 – 1.2
4 39.2 – 35.5 – 1.3
5 42.4 – 38.6 5.28 1.37
6 45.6 – 41.8 5.51 1.43
7 46.8 – 43.1 5.6 1.48
8 52.1 – 46 6.03 1.64
9 55.4 – 48.6 6.34 1.74
10 58.8 – 51.3 6.6 1.83
20.52 100 – 85.6 10.12 3.02
42.95 200 – 170 18.9 5.92
108 500 52.3 423 46.2 14.6
215.8 1000 102.1 846 92.3 29.2
431.7 2000 204 1693 185 58.4
1078.8 5000 509 4230 461 146
1510.3 7000 712 5922 646 204
2157.6 10,000 1018 8461 922 292
3236.5 15,000 1526 12,692 – 438
4315.3 20,000 2035 16,923 – 584

& Barometer is used for measuring the pressure of the . What is the working principle of an aneroid barometer?
air, due to the weight of the column of air above it. As What are its plus points?
the Earth’s atmosphere gets thinner with increasing & An aneroid is a flexible metal bellows that has been
height, it follows that at higher altitudes above sea tightly sealed after having some of the air removed.
level, the weight of air will decrease. In other words, Higher atmospheric pressures squeeze the metal
pressure decreases. bellows while lower pressures allow it to expand.
& Barometer consists of a long glass tube closed at one & Aneroid barometer has certain advantages over a
end and filled with a liquid, usually mercury, and mercury barometer because it is much smaller and
inverted upside down in an open container having compact and can also record a week’s worth of data.
the same liquid, taking care that no air is entrapped in
the tube. Pressure of air acting on the liquid in the
container forces the liquid up the tube. Height of the
liquid column in the tube above the liquid surface in
the container indicates atmospheric pressure at the
place. The space above the liquid column is not
absolute vacuum as it contains vapors of the liquid
used as barometric fluid, exerting its vapor pressure,
which is a function of temperature.
& Figure 1.8 shows a barometer setup.
& At sea level, height of mercury column will be
760 mm. Mercury is normally used as the barometric
liquid as its vapor pressure is very low.
. If water is used as a barometric fluid instead of mercury,
what will be height of the water column at sea level?
& The height of the water column above sea level,
corrected to vapor pressure exerted above the col-
umn, is 10.33 m. FIGURE 1.8 Mercury barometer.