Fundamentals of Thermal-Fluid Sciences
5th Edition
ISBN: 9780078027680
Author: Yunus A. Cengel Dr., Robert H. Turner, John M. Cimbala
Publisher: McGraw-Hill Education
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Chapter 17, Problem 56P
To determine
The new thermal resistance of the epoxy board after the modification.
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A counter flow double pipe heat exchanger is being used to cool hot oil from 320°F to 285°F
using cold water. The water, which flows through the inner tube, enters the heat exchanger at 70°F
and leaves at 175°F. The inner tube is ¾-std type L copper. The overall heat transfer coefficient
based on the outside diameter of the inner tube is 140 Btu/hr-ft2-°F. Design conditions call for a
total heat transfer duty (heat transfer rate between the two fluids) of 20,000 Btu/hr. Determine the
required length of this heat exchanger (ft).
!
Required information
A one-shell-pass and eight-tube-passes heat exchanger is used to heat glycerin (cp=0.60 Btu/lbm.°F) from 80°F to 140°F
by hot water (Cp = 1.0 Btu/lbm-°F) that enters the thin-walled 0.5-in-diameter tubes at 175°F and leaves at 120°F. The total
length of the tubes in the heat exchanger is 400 ft. The convection heat transfer coefficient is 4 Btu/h-ft²°F on the glycerin
(shell) side and 70 Btu/h-ft²°F on the water (tube) side.
NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part.
Determine the rate of heat transfer in the heat exchanger before any fouling occurs.
Correction factor F
1.0
10
0.9
0.8
R=4.0 3.0 2.0.15 1.0 0.8.0.6 0.4 0.2
0.7
0.6
R=
T1-T2
12-11
0.5
12-11
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
(a) One-shell pass and 2, 4, 6, etc. (any multiple of 2), tube passes
P=
T₁-11
The rate of heat transfer in the heat exchanger is
Btu/h.
!
Required information
Air at 25°C (cp=1006 J/kg.K) is to be heated to 58°C by hot oil at 80°C (cp = 2150 J/kg.K) in a cross-flow heat exchanger
with air mixed and oil unmixed. The product of heat transfer surface area and the overall heat transfer coefficient is 750
W/K and the mass flow rate of air is twice that of oil.
NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part.
Air
Oil
80°C
Determine the effectiveness of the heat exchanger.
Chapter 17 Solutions
Fundamentals of Thermal-Fluid Sciences
Ch. 17 - Prob. 1PCh. 17 - Consider heat conduction through a plane wall....Ch. 17 - What does the thermal resistance of a medium...Ch. 17 - Can we define the convection resistance for a unit...Ch. 17 - Consider steady heat transfer through the wall of...Ch. 17 - How is the combined heat transfer coefficient...Ch. 17 - Why are the convection and the radiation...Ch. 17 - Consider steady one-dimensional heat transfer...Ch. 17 - Someone comments that a microwave oven can be...Ch. 17 - Consider two cold canned drinks, one wrapped in a...
Ch. 17 - Consider a surface of area A at which the...Ch. 17 - How does the thermal resistance network associated...Ch. 17 - Consider steady one-dimensional heat transfer...Ch. 17 - Consider a window glass consisting of two...Ch. 17 - Prob. 15PCh. 17 - Prob. 16PCh. 17 - Prob. 17PCh. 17 - Prob. 18PCh. 17 - Prob. 19PCh. 17 - Consider a power transistor that dissipates 0.2 W...Ch. 17 - A 1.0 m × 1.5 m double-pane window consists of two...Ch. 17 - Consider a 1.2-m-high and 2-m-wide glass window...Ch. 17 - Prob. 23PCh. 17 - Prob. 24PCh. 17 - Prob. 26PCh. 17 - Prob. 27PCh. 17 - Prob. 28PCh. 17 - Prob. 29PCh. 17 - Prob. 30PCh. 17 - A 2-m × 1.5-m section of wall of an industrial...Ch. 17 - The wall of a refrigerator is constructed of...Ch. 17 - Prob. 34PCh. 17 - Prob. 35PCh. 17 - Prob. 36PCh. 17 - What is thermal contact resistance? How is it...Ch. 17 - Will the thermal contact resistance be greater for...Ch. 17 - Explain how the thermal contact resistance can be...Ch. 17 - A wall consists of two layers of insulation...Ch. 17 - A plate consists of two thin metal layers pressed...Ch. 17 - Consider two surfaces pressed against each other....Ch. 17 - Prob. 43PCh. 17 - Prob. 44PCh. 17 - Prob. 45PCh. 17 - Prob. 46PCh. 17 - Prob. 47PCh. 17 - Prob. 48PCh. 17 - Prob. 49PCh. 17 - Prob. 50PCh. 17 - Prob. 51PCh. 17 - Prob. 52PCh. 17 - Prob. 53PCh. 17 - When plotting the thermal resistance network...Ch. 17 - Prob. 55PCh. 17 - Prob. 56PCh. 17 - Prob. 57PCh. 17 - A typical section of a building wall is shown in...Ch. 17 - Prob. 59PCh. 17 - Prob. 61PCh. 17 - Prob. 62PCh. 17 - Prob. 63PCh. 17 - In an experiment to measure convection heat...Ch. 17 - What is an infinitely long cylinder? When is it...Ch. 17 - Can the thermal resistance concept be used for a...Ch. 17 - Consider a short cylinder whose top and bottom...Ch. 17 - Prob. 68PCh. 17 - 50-m-long section of a steam pipe whose outer...Ch. 17 - Superheated steam at an average temperature 200°C...Ch. 17 - Steam exiting the turbine of a steam power plant...Ch. 17 - Repeat Prob. 17–72E, assuming that a 0.01-in-thick...Ch. 17 - A 2.2-mm-diameter and 10-m-long electric wire is...Ch. 17 - Prob. 76PCh. 17 - Chilled water enters a thin-shelled 5-cm-diameter,...Ch. 17 - Steam at 450°F is flowing through a steel pipe (k...Ch. 17 - Prob. 79PCh. 17 - Prob. 80PCh. 17 - An 8-m-internal-diameter spherical tank made of...Ch. 17 - What is the critical radius of insulation? How is...Ch. 17 - Consider an insulated pipe exposed to the...Ch. 17 - A pipe is insulated to reduce the heat loss from...Ch. 17 - Prob. 86PCh. 17 - Prob. 87PCh. 17 - A 0.083-in-diameter electrical wire at 90°F is...Ch. 17 - Prob. 89PCh. 17 - Prob. 90PCh. 17 - Prob. 92PCh. 17 - What is the reason for the widespread use of fins...Ch. 17 - What is the difference between the fin...Ch. 17 - The fins attached to a surface are determined to...Ch. 17 - Explain how the fins enhance heat transfer from a...Ch. 17 - How does the overall effectiveness of a finned...Ch. 17 - Hot water is to be cooled as it flows through the...Ch. 17 - Consider two finned surfaces that are identical...Ch. 17 - The heat transfer surface area of a fin is equal...Ch. 17 - Prob. 101PCh. 17 - Prob. 102PCh. 17 - Two plate fins of constant rectangular cross...Ch. 17 - Two finned surfaces are identical, except that the...Ch. 17 - A 4-mm-diameter and 10-cm-long aluminum fin (k =...Ch. 17 - Consider a very long rectangular fin attached to a...Ch. 17 - Consider a stainless steel spoon (k = 8.7...Ch. 17 - A DC motor delivers mechanical power to a rotating...Ch. 17 - A plane wall with surface temperature of 350°C is...Ch. 17 - Prob. 111PCh. 17 - Steam in a heating system flows through tubes...Ch. 17 - Prob. 113PCh. 17 - A hot surface at 100°C is to be cooled by...Ch. 17 - Prob. 116PCh. 17 - A 40-W power transistor is to be cooled by...Ch. 17 - Prob. 118PCh. 17 - Prob. 119RQCh. 17 - Cold conditioned air at 12°C is flowing inside a...Ch. 17 - Prob. 121RQCh. 17 - Prob. 122RQCh. 17 - Prob. 123RQCh. 17 - Prob. 124RQCh. 17 - Prob. 125RQCh. 17 - Prob. 126RQCh. 17 - Prob. 127RQCh. 17 - Prob. 128RQCh. 17 - Prob. 129RQCh. 17 - Prob. 130RQCh. 17 - Prob. 131RQ
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