978-0078027680 Chapter 19 Part 7

subject Type Homework Help
subject Pages 14
subject Words 6206
subject Authors John Cimbala, Robert Turner, Yunus Cengel

Unlock document.

This document is partially blurred.
Unlock all pages and 1 million more documents.
Get Access
page-pf1
19-121
19-122 A spherical tank used to store iced water is subjected to winds. The rate of heat transfer to the iced water and the
amount of ice that melts during a 24-h period are to be determined.
Assumptions 1 Steady operating conditions exist. 2 Thermal resistance of the tank is negligible. 3 Radiation effects are
negligible. 4 Air is an ideal gas with constant properties. 5 The pressure of air is 1 atm.
page-pf2
19-122
19-123 A spherical tank used to store iced water is subjected to winds. The rate of heat transfer to the iced water and the
amount of ice that melts during a 24-h period are to be determined.
Assumptions 1 Steady operating conditions exist. 2 Air is an ideal gas with constant properties. 7 The pressure of air is 1 atm.
Properties The properties of air at 1 atm pressure and the free stream temperature of 30C are (Table A-22)
kg/m.s 10872.1
/sm 10608.1
C W/m.02588.0
5
25-
k
7282.0Pr
kg/m.s 10729.1 5
C0@
,
s
1 cm
Di = 3 m
Ts, out
V = 25 km/h
T = 30C
0C
page-pf3
page-pf4
19-124
19-125 Crude oil is cooled as it flows in a pipe. The rate of heat transfer and the pipe length are to be determined.
Assumptions 1 Steady flow conditions exist. 2 The surface temperature is constant and uniform. 3 The inner surfaces of the
page-pf5
page-pf6
19-126
19-127 Air is flowing through a thin smooth copper tube that is submerged in the nearby lake; the necessary copper tube
length for the air to exit with an outlet mean temperature of 20°C is to be determined.
Assumptions 1 Steady operating conditions exist. 2 Properties are constant. 3 Constant tube surface temperature. 4
Conduction through the copper tube wall is negligible.
Analysis The Reynolds number is
)/sm 10562.1(
)m 1.0)(m/s 5.2(
avg
DV
Since the flow inside the copper tube is turbulent, we can use
The length of the copper tube can be determined using
DLh
page-pf7
19-127
19-128 Liquid mercury flowing through a tube, the tube length is to be determined using (a) the appropriate Nusselt number
relation for liquid metals and (b) the Dittus-Boelter equation. The results of (a) and (b) are to be compared.
Assumptions 1 Steady operating conditions exist. 2 Properties are constant. 3 Constant tube surface temperature. 4 Fully
1.12610−3 kg/m∙s, and Pr = 0.0152; at Ts = 250°C: Prs = 0.0119 (Table A-14).
Analysis The Reynolds number is
)kg/s 6.0(44
m
624.5)0119.0()13570(0156.08.4PrRe0156.08.4Nu 93.085.0
93.0
85.0 s
Hence, length of the tube is
200250
)KJ/kg 1.136)(kg/s 6.0(
es
p
TT
cm
page-pf8
19-128
19-129 The convection heat transfer coefficients for air (a) flowing through and (b) flowing across a thin-walled tube are to
be determined.
Assumptions 1 Steady operating conditions exist. 2 Properties are constant. 3 Constant tube surface temperature. 4 Fully
Hence the convection heat transfer coefficient is
K W/m027350
.
k
Hence the convection heat transfer coefficient is
K W/m027350
.
k
page-pf9
page-pfa
page-pfb
page-pfc
page-pfd
19-133
19-134E Air is flowing through a smooth thin-walled copper tube that is submerged in water; the necessary copper tube
length for the air to exit with an outlet mean temperature of 70°F is to be determined.
Assumptions 1 Steady operating conditions exist. 2 Properties are constant. 3 Constant tube surface temperature. 4
67.51)7336.0()17370(023.0PrRe023.0Nu 3.08.04.08.0
RftBtu/h184.2 2 h
The length of the copper tube can be determined using
DLh
page-pfe
page-pff
19-135
19-136 Hot water enters a copper pipe whose outer surface is exposed to cold air with a specified heat transfer coefficient.
The rate of heat loss from the water and the exit temperature of the water are to be determined.
Assumptions 1 Steady flow conditions exist. 2 The inner surfaces of the pipe are smooth.
96.1Pr
Analysis (a) The mass flow rate of water is
m) (0.04
2
3
Water
90C
1.2 m/s
Di = 4 cm
Do = 4.6 cm
page-pf10
page-pf11
19-137
19-138 Water is heated in a heat exchanger by the condensing geothermal steam. The exit temperature of water and the rate
of condensation of geothermal steam are to be determined.
kJ/kg 5.2066
/sm 1044.3
kg/m 968.1
kg/m.s 10333.0
08.2Pr
CJ/kg. 4201
C W/m.673.0
kg/m 1.968
C165@
27-
3
3
3
fg
p
h
c
k
m/s 6576.0
4
m) 04.0(
)kg/m 1.968(kg/s 8.0 avgavg
2
3
avg VVAVm
465,76
/sm 1044.3
m) m/s)(0.04 (0.6576
Re 27
avg
DV
which is greater than 10,000. Therefore, the flow is turbulent and the entry lengths in this case are roughly
m 0.4=m) 04.0(1010 DLL th
7.248)08.2()465,76(023.0PrRe023.0 4.08.04.08.0 k
hD
Nu
14 m
Water
20C
0.8 kg/s
4 cm
Ts = 165C
page-pf12
19-138
19-139 Cold-air flows through an isothermal pipe. The pipe temperature is to be estimated.
Assumptions 1 Steady operating conditions exist. 2 The inner surface of the duct is smooth. 3 Air is an ideal gas with
page-pf13
19-139
19-140 Crude oil is heated as it flows in the tube-side of a multi-tube heat exchanger. The rate of heat transfer and the tube
length are to be determined.
Assumptions 1 Steady flow conditions exist. 2 The surface temperature is constant and uniform. 3 The inner surfaces of the
 
m/s 4.13
4/m) (0.01)kg/m 950(
kg/s )100/100(
23
c
A
m
V
100 tubes
page-pf14

Trusted by Thousands of
Students

Here are what students say about us.

Copyright ©2022 All rights reserved. | CoursePaper is not sponsored or endorsed by any college or university.