Unlock document.
This document is partially blurred.
Unlock all pages and 1 million more documents.
Get Access
10-81
10-82
10-91 Saturated water vapor at a pressure of 12.4 kPa condenses on a rectangular array of 100 horizontal tubes at 30°C. The
condensation rate per unit length of is to be determined.
Assumptions 1 Steady operating condition exists. 2 The tube surfaces are isothermal.
Properties The properties of water at the saturation temperature of 50°C corresponding to 12.4 kPa are hfg = 2383 kJ/kg and
ρv = 0.0831 kg/m3 (Table A-9). The properties of liquid water at the film temperature of Tf = (Tsat + Ts)/2 = 40°C are, from
KW/m250,11
)008.0)(3050)(10653.0(
)631.0)(102440)(0831.01.992)(1.992)(81.9(
729.0
)(
)(
729.0
2
4/1
3
33
4/1
sat
3
tube1 horiz,
=
−
−
=
−
−
=
−
DTT
khg
h
sl
lfgvll
10-83
10-84
10-85
10-86
10-95 Saturated ammonia vapor is condensed as it flows through a tube. With a given vapor flow rate at the exit, the flow
rate of the vapor at the inlet is to be determined.
Assumptions 1 Steady operating condition exists. 2 The tube surfaces are isothermal. 3 The Reynolds number of the vapor at
kl = 0.5042 W/m·K
Analysis The modified latent heat of vaporization for film condensation inside horizontal tube is
3
)(
8
3
3
sat
−+=
splfgfg TTchh
10-87
10-88
10-97 A copper tube that is used for transporting cold fluid is causing condensation of moist air on its outer surface. The
rate of moisture condensation is to be determined so that a system for removing the condensate can be sized to alleviate the
A-9).
Analysis Since dropwise condensation can occur, and it will have higher rate of heat transfer and therefore higher
condensation rate than film condensation. The system must be able to handle the dropwise condensation rate.
The modified latent heat of vaporization is
J/kg 105063.2K )327)(KJ/kg 4185(68.0J/kg 102438
)(68.0
63
sat
*
=−+=
−+= splfgfg TTchh
kg/s 0.799=
==
J/kg 105063.2
J/s 100036.2
6
6
*
fg
h
Q
m
10-89
10-90
Special Topic: Non-Boiling Two-Phase Flow Heat Transfer
10-99 The flow quality of a non-boiling two-phase flow in a tube with
300/=
gl mm
is to be determined.
10-100 The flow quality and the mass flow rates of the gas and the liquid for a non-boiling two-phase flow, where Vsl = 3Vsg,
are to be determined.
Assumptions 1 Steady operating condition exists. 2 Two-phase flow is non-boiling and it does not involve phase change. 3
Fluid properties are constant.
Properties The densities of the gas and liquid are given to be ρg = 8.5 kg/m3 and ρl = 855 kg/m3, respectively.
10-91
10-92
10-102 Starting with the two-phase non-boiling heat transfer correlation, the expression that is appropriate for the case when
only water is flowing in the tube is to be determined.
( )
−
−
+= 25.0
*
25.0
25.0
4.0
1.0 1
1
55.01 I
Pr
Pr
F
F
x
x
Fhh
g
l
l
g
p
p
pltp
10-93
10-94
10-95
10-96
10-105 Air-water mixture is flowing in a 5° inclined tube with diameter of 25.4 mm, and the mixture superficial gas and
liquid velocities are 1 m/s and 2 m/s, respectively. The two-phase heat transfer coefficient (htp) is to be determined.
0.355×10-3 kg/m·s from Table A-9.
m/s 030.3
33.0
m/s 1 ===
sg
g
V
V
m/s 985.2
33.01
m/s 2
1=
−
=
−
=
sl
l
V
V
The gas and liquid mass flow rates are calculated as
m) 02540(
4
2
3
2−
D
10-97
10-98
10-107 Air-water mixture is flowing in a tube with diameter of 25.4 mm, and the mixture superficial gas and liquid velocities
are 1 m/s and 2 m/s, respectively. The two-phase heat transfer coefficient (htp) for (a) horizontal tubee (θ = 0°) and (b)
0.355×10-3 kg/m·s from Table A-9.
m/s 030.3
33.0
m/s 1 ===
sg
g
V
V
m/s 985.2
33.01
m/s 2
1=
−
=
−
=
sl
l
V
V
The gas and liquid mass flow rates are calculated as
m) 02540(
4
2
3
2−
D
10-99
10-100
