Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
8th Edition
ISBN: 9781305387102
Author: Kreith, Frank; Manglik, Raj M.
Publisher: Cengage Learning
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Textbook Question
Chapter 1, Problem 1.17P
The heat transfer rate from hot air by convection at 100°C flowing over one side of a flat plate with dimensions
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A 2-m2 window has a surface temperature of 15° C,
and the outside wind is blowing air at 2° C across it
with a convection heat transfer coefficient of h = 125
W/m2 K. What is the total heat transfer loss?
Solar radiation is incident on the glass cover
of a solar collector at a rate of 700W/m². The
glass of collector absorbs 88 percent of the
incident radiation on it and has an emissivity of
0.9. The entire hot water needs of a family can be
provided by a single collector of 1.2m height and
2m width. The temperature of the glass cover of
the collector is measured to be 35C° on a day
when the surrounding air temperature is 25C° and
the wind is blowing at 30km/h. The effective sky
temperature for radiation exchange between the
glass cover and the open sky is -40C°. Water
enters the tubes which attached to the absorber
plate at a rate of 1kg/min. Assuming the back
surface of the absorber plate to be heavily
insulated and the only heat loss to occur through
the glass cover, determine (a) the total rate of
heat loss from the collector, (b) the collector
efficiency, which is the ratio of the amount of
heat transferred to the water to the solar energy
incident on the collector, and (c) the…
Air is flowing in parallel over the upper surface of a flat plate with a length of 4m. The first half of the plate length, from the leading edge, has a constant surface temperature of 50 degrees Celsius. The second half of the plate length is subjected to a uniform heat flux of 86 W/m2. The air has a free stream velocity and temperature of 2 m/s and 10 degrees Celsius, respectively. Determine the local convection heat transfer coefficients at 1 m and 3 m from the leading edge. Evaluate the air properties at a film temperature of 30 degrees Celsius. Is the film temperature Tf=30 degrees Celsius applicable at x = 3 m?
Chapter 1 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
Ch. 1 - 1.1 On a cold winter day, the outer surface of a...Ch. 1 - 1.2 The weight of the insulation in a spacecraft...Ch. 1 - 1.3 A furnace wall is to be constructed of brick...Ch. 1 - 1.4 To measure thermal conductivity, two similar...Ch. 1 - To determine the thermal conductivity of a...Ch. 1 - A square silicon chip 7mm7mm in size and 0.5-mm...Ch. 1 - A cooling system is to be designed for a food...Ch. 1 - 1.80 Describe and compare the modes of heat loss...Ch. 1 - Heat is transferred at a rate of 0.1 kW through...Ch. 1 - 1.10 A heat flux meter at the outer (cold) wall of...
Ch. 1 - 1.11 Calculate the heat loss through a glass...Ch. 1 - 1.12 A wall with a thickness is made of a...Ch. 1 - 1.13 If the outer air temperature in Problem is...Ch. 1 - Using Table 1.4 as a guide, prepare a similar...Ch. 1 - 1.15 A thermocouple (0.8-mm-diameter wire) used to...Ch. 1 - Water at a temperature of 77C is to be evaporated...Ch. 1 - The heat transfer rate from hot air by convection...Ch. 1 - The heat transfer coefficient for a gas flowing...Ch. 1 - 1.19 A cryogenic fluid is stored in a...Ch. 1 - A high-speed computer is located in a...Ch. 1 - 1.21 In an experimental set up in a laboratory, a...Ch. 1 - 1.22 In order to prevent frostbite to skiers on...Ch. 1 - Using the information in Problem 1.22, estimate...Ch. 1 - Two large parallel plates with surface conditions...Ch. 1 - 1.25 A spherical vessel, 0.3 m in diameter, is...Ch. 1 - 1.26 Repeat Problem 1.25 but assume that the...Ch. 1 - Determine the rate of radiant heat emission in...Ch. 1 - 1.28 The sun has a radius of and approximates a...Ch. 1 - 1.29 A spherical interplanetary probe with a 30-cm...Ch. 1 - A spherical communications satellite, 2 m in...Ch. 1 - A long wire 0.7 mm in diameter with an emissivity...Ch. 1 - Wearing layers of clothing in cold weather is...Ch. 1 - A section of a composite wall with the dimensions...Ch. 1 - A section of a composite wall with the dimensions...Ch. 1 - Repeat Problem 1.35 but assume that instead of...Ch. 1 - 1.37 Mild steel nails were driven through a solid...Ch. 1 - Prob. 1.38PCh. 1 - 1.39 On a cold winter day, the outside wall of a...Ch. 1 - As a designer working for a major electric...Ch. 1 - 1.41 A heat exchanger wall consists of a copper...Ch. 1 - 1.43 A simple solar heater consists of a flat...Ch. 1 - A composite refrigerator wall is composed of 5 cm...Ch. 1 - An electronic device that internally generates 600...Ch. 1 - 1.47 A flat roof is modeled as a flat plate...Ch. 1 - A horizontal, 3-mm-thick flat-copper plate, 1-m...Ch. 1 - 1.49 A small oven with a surface area of is...Ch. 1 - A steam pipe 200 mm in diameter passes through a...Ch. 1 - 1.51 The inner wall of a rocket motor combustion...Ch. 1 - 1.52 A flat roof of a house absorbs a solar...Ch. 1 - Determine the power requirement of a soldering...Ch. 1 - 1.54 The soldering iron tip in Problem 1.53...Ch. 1 - Prob. 1.55PCh. 1 - A pipe carrying superheated steam in a basement at...Ch. 1 - Draw the thermal circuit for heat transfer through...Ch. 1 - 1.60 Two electric resistance heaters with a 20 cm...Ch. 1 - 1.63 Liquid oxygen (LOX) for the space shuttle is...Ch. 1 - The interior wall of a large, commercial walk-in...Ch. 1 - 1.67 In beauty salons and in homes, a ubiquitous...Ch. 1 - The heat transfer coefficient between a surface...Ch. 1 - The thermal conductivity of fibreglass insulation...Ch. 1 - 1.71 The thermal conductivity of silver at 212°F...Ch. 1 - 1.72 An ice chest (see sketch) is to constructed...Ch. 1 - Estimate the R-values for a 5-cm-thick fiberglass...Ch. 1 - A manufacturer in the United States wants to sell...Ch. 1 - Referring to Problem 1.74, how many kilograms of...Ch. 1 - 1.76 Explain a fundamental characteristic that...Ch. 1 - 1.77 Explain each in your own words. (a) What is...Ch. 1 - What are the important modes of heat transfer for...Ch. 1 - 1.79 Consider the cooling of (a) a personal...Ch. 1 - Describe and compare the modes of heat loss...Ch. 1 - A person wearing a heavy parka is standing in a...Ch. 1 - Discuss the modes of heat transfer that determine...
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- what is the convection heat transfer coefficient for ambient air at 43°Carrow_forwardWhen is the heat transfer through a fluid conduction and when is it convection? For which case is the rate of heat transfer higher? How does the convection heat transfer differ from the thermal conductivity of the fluid?arrow_forwardA 6 cm diameter cylinder is initially at a temperature of 10 °C. Later, this cylinder was thrown into water at 80°C. Calculate how long it will take for the center temperature of the cylinder to reach 50 °C by taking the convection heat transfer coefficient as 80W / /m?K. Thermal properties of the cylinder material k=0,587 W/m°C wwww a = 0,13 x10 * m /s attachments Heisler diagrams for cylinder 1.0 F100 50 30 12 0.7 0.5 0.4 0.3 0.2 2.5 3.0 0.1 3 02 B hr 0.07 0.05 0.04 0.03 0,02 0.007 0.005 0.004 0.00 0.002 0.001 ! 2 3 468 101214 16 18 20 22 24 26 28 30 40 50 60 70 B0 90100 115 130 150200 300 kenle)= Fo 1.0 0.2 0.9 0.8 0.4 0.7 0.6 0.6 0.5 0.4 0.3 0.8 0.2 0.9 0.1 1.0 8.01 0.02 0.05 0.1 O.2 0.5 1.0 2 3 5 10 20 CA/hr)- Bi 50 100 T-Tarrow_forward
- The top surface of the passenger car of a train moving at a velocity of 115 km/h is 2.8 m wide and 8 m long. The top surface is absorbing solar radiation at a rate of 380 W/m2 and the temperature of the ambient air is 30°C. Assuming the roof of the car to be perfectly insulated and the radiation heat exchange with the surroundings to be small relative to convection, determine the equilibrium temperature of the top surface of the car. The properties of air at 30°C are (Table A-15) k = 0.02588 W/m⋅°C, v = 1.608 × 10−5 m2/s, and Pr = 0.7282.The equilibrium temperature of the top surface of the car is:arrow_forward(b) A transistor with a height of 0.4 cm and a diameter of 0.6 cm is mounted on a circuit board as shown in Figure 3. The transistor is cooled by air flowing over it with an average heat transfer coefficient of 30 W/m².K. If the air temperature is 55°C and the transistor case temperature is not to exceed 70°C, determine the amount of power this transistor can dissipate safely. Disregard any heat transfer from the transistor base. Air 55°C Power transistor 0.6 cm T, ≤ 70°C -0.4 c 0.4 cm- Figure 3arrow_forwardA long 9 cm-diameter steam pipe whose external surface temperature is 70 0C passes through some open area that is not protected against the winds. Determine the rate of heat loss from the pipe per unit of its length when the air is at 1 atm pressure and 5,6 0C and the wind is blowing across the pipe (pipe is vertical) at a velocity of 50 km/h.arrow_forward
- Air at 20°C with a convection heat transfer coefficient of 25 W/m2-K blows over a horizontal steel hot plate (k = 43 W/m-K). The surface area of the plate is 0.38 m2 with a thickness of 2 cm. The plate surface is maintained at a constant temperature of Ts = 250°C and the plate loses 300 W from its surface by radiation. Calculate the inside plate temperature (Ti). FIGURE P1-96 Air, 20°C T, = 250°C Steel Plate T; = ?arrow_forwardA person extends his uncovered arms into the windy air outside at 54°F and 30 mph in order to feel nature closely as shown in the figure. Initially, the skin temperature of the arm is 84°F. Treating the arm as a 2-ft-long and 3-in-diameter cylinder, determine the rate of heat loss from the arm. It is given that the properties of air at 1 atm and the film temperature of 69°F are (Table A-15E) k = 0.01455 Btu/h-ft.°F, v = 0.1638 × 10¬3 ft2/s, and Pr = 0.7308. Air 54°F, Vmph -84°F The rate of heat loss from the arm is Btu/h.arrow_forwardwhat are the different modes of heat transfer? Explain transfer of heat by convection process?arrow_forward
- A solid plate, with a thickness of 15 cm and a thermal conductivity of 80 W/m-K, is being cooled at the upper surface by air. The air temperature is 10°C, while the temperatures at the upper and lower surfaces of the plate are 50 and 60°C, respectively. Determine the convection heat transfer coefficient of air at the upper surface and discuss whether the value is reasonable or not for force convection of air. Air, T. = 10°C T1 = 50°C T2 = 60°C L = 15 cmarrow_forwardA 6 cm diameter cylinder is initially at a temperature of 10 °C. Later, this cylinder was thrown into water at 80°C. Calculate how long it will take for the center temperature of the cylinder to reach 50 °C by taking the convection heat transfer coefficient as 80W //m?K. Thermal properties of the cylinder material k=0,587 W/m°C a = 0,13x10-m² /sarrow_forwardThe convection heat transfer coefficient between a surface at 40°C and air at 20°C is 20 W⁄m2 − K. Calculate the heat transfer per square meter leaving the surface.arrow_forward
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Heat Transfer – Conduction, Convection and Radiation; Author: NG Science;https://www.youtube.com/watch?v=Me60Ti0E_rY;License: Standard youtube license