Microsoft Word - Cengel and Boles TOC _2-03-05_.doc

Chapter 1 | 49

Air

Oil Water 30 in

FIGURE P1–112E

1–112E Consider a U-tube whose arms are open to the
atmosphere. Now equal volumes of water and light oil (r
49.3 lbm/ft^3 ) are poured from different arms. A person blows
from the oil side of the U-tube until the contact surface of the
two fluids moves to the bottom of the U-tube, and thus the
liquid levels in the two arms are the same. If the fluid height
in each arm is 30 in, determine the gage pressure the person
exerts on the oil by blowing.

1–115 Repeat Prob. 1–114 for a pressure gage reading of

180 kPa.

1–116E A water pipe is connected to a double-U manome-

ter as shown in Fig. P1–116E at a location where the local

atmospheric pressure is 14.2 psia. Determine the absolute

pressure at the center of the pipe.

1–117 It is well-known that the temperature of the atmo-

sphere varies with altitude. In the troposphere, which extends

to an altitude of 11 km, for example, the variation of temper-

ature can be approximated by TT 0 
bz, where T 0 is the

temperature at sea level, which can be taken to be 288.15 K,

and b0.0065 K/m. The gravitational acceleration also

changes with altitude as g(z) g 0 /(1 z/6,370,320)^2 where

g 0 9.807 m/s^2 and zis the elevation from sea level in m.

Obtain a relation for the variation of pressure in the tropo-

sphere (a) by ignoring and (b) by considering the variation of

gwith altitude.

1–118 The variation of pressure with density in a thick gas

layer is given by PCrn, where Cand nare constants.

Noting that the pressure change across a differential fluid

layer of thickness dzin the vertical z-direction is given as

dP
rgdz, obtain a relation for pressure as a function of

1.2 m

Patm

IV bottle

FIGURE P1–113

45 cm

10 cm

50 cm 22 cm

Mercury

SG = 13.6

Gasoline SG = 0.70

Water

Air

Oil SG = 0.79

Pgage = 370 kPa

Pipe

FIGURE P1–114

Mercury

SG = 13.6

Oil SG = 0.80

Oil SG = 0.80

Water

pipe

15 in

60 in 40 in

35 in

FIGURE P1–116E

1–113 Intravenous infusions are usually driven by gravity
by hanging the fluid bottle at sufficient height to counteract
the blood pressure in the vein and to force the fluid into the
body. The higher the bottle is raised, the higher the flow rate
of the fluid will be. (a) If it is observed that the fluid and the
blood pressures balance each other when the bottle is 1.2 m
above the arm level, determine the gage pressure of the
blood. (b) If the gage pressure of the fluid at the arm level
needs to be 20 kPa for sufficient flow rate, determine how
high the bottle must be placed. Take the density of the fluid
to be 1020 kg/m^3.

1–114 A gasoline line is connected to a pressure gage
through a double-U manometer, as shown in Fig. P1–114. If
the reading of the pressure gage is 370 kPa, determine the
gage pressure of the gasoline line.