Heat and Mass Transfer: Fundamentals and Applications
5th Edition
ISBN: 9780073398181
Author: Yunus A. Cengel Dr., Afshin J. Ghajar
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 3, Problem 100CP
A pipe is insulated such that the outer radius of the insulation is less than the critical radius. Now the insulation is taken off. Will the rate of heat transfer from the pipe increase or decrease for the same pipe surface temperature?
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A steam pipe, made of copper, has an inside diameter of 5 cm and an outside diameter of 6.2 cm. To reduce thermal loss to the surroundings, the pipe is insulated with 2.55 cm thick fiberglass. An aluminum foil of a thickness of 0.2 mm covers the insulation. Find the rate of heat loss from the pipe using the following data: hi = 142 W/m K, Ti = 150 C, ho = 68 W/m K, To = 27C, Lpipe = 98.5 m. [Ans.: 0.43 kW].
A metal furnace with a 1.25 m x 0.75 m metal door is placed in a room and set to 400K. A 0.3 m x 0.3 m glass window is located in the furnace door. The thickness of the metal alloy and the glass window are 3 mm and 2 mm, respectively. The glass window has a thermal conductivity (k) of 0.7 W/m .K and the metal door has a thermal conductivity (k) of 3.5 W/m.K. The convective heat coefficient hi and ho on each site of the furnace door is estimated as 10W/m2.K. Assuming the room temperature is held constant at 297 K, calculate the total heat loss from the furnace door.
P.S Could you write the solution clearly to better understanding? Step by step using formulas. Another page with detailed steps would be better. Thanks in advance.
(b) A hydrogen gas cylinder is situated in the cylinder cage. The cylinder wall is
constructed from 15.5 mm carbon fiber (kcp = 0.75 W mK-¹). The outside of the
cylinder is lagged with an inner 10 mm layer of ceramic insulation (kc =
0.08 W mK-¹) and an outer 80 mm layer of fiberglass insulation (kp = 0.15 W mK-¹).
The temperature on the hydrogen gas is 150 °C and the temperature of the cylinder
cage is 45 °C. Given that the walls of the cylinder can be assumed to be flat and
neglecting the contribution of radiation, calculate:
(i) the heat flux per square meter of the gas cylinder wall
(ii) the temperature at the interface between the fibreglass and the ceramic
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1.1
Chapter 3 Solutions
Heat and Mass Transfer: Fundamentals and Applications
Ch. 3 - Consider heat conduction through a wall of...Ch. 3 - Consider heat conduction through a plane wall....Ch. 3 - What does the thermal resistance of a medium...Ch. 3 - Can we defme the convection resistance for a unit...Ch. 3 - Consider steady heat transfer through the wall of...Ch. 3 - How is the combined heat transfer coefficient...Ch. 3 - Why are the convection and the radiation...Ch. 3 - Consider steady one-dimensional heat transfer...Ch. 3 - Someone comments that a microwave oven can be...Ch. 3 - Consider two cold canned drinks, one wrapped in a...
Ch. 3 - The bottom of a pan is made of a 4-mm-thick...Ch. 3 - Consider a surface of area A at which the...Ch. 3 - How does the thermal resistance network associated...Ch. 3 - Consider steady one-dimensional heat transfer...Ch. 3 - Consider a window glass consisting of two...Ch. 3 - Prob. 16PCh. 3 - Consider a person standing in a room at 20C with...Ch. 3 - Consider an electrically heated brick house...Ch. 3 - A12-cm18-cm circuit board houses on its surface...Ch. 3 - Water is boiling in a 25-cm-diameter aluminum pan...Ch. 3 - A cylindrical resistor element on a circuit board...Ch. 3 - Prob. 22PCh. 3 - A1.0m1.5m double-pane window consists of two...Ch. 3 - Prob. 24PCh. 3 - Prob. 25PCh. 3 - Prob. 26PCh. 3 - Prob. 27PCh. 3 - Prob. 28EPCh. 3 - To defog the rear window of an automobile, a very...Ch. 3 - A transparent film is to be bonded onto the top...Ch. 3 - To defrost ice accumulated on the outer surface of...Ch. 3 - Prob. 32PCh. 3 - Prob. 33PCh. 3 - Prob. 34PCh. 3 - Prob. 35PCh. 3 - Prob. 36PCh. 3 - Heat is to be conducted along a circuit board that...Ch. 3 - Prob. 38EPCh. 3 - Consider a house that has a 10m20-m base and a...Ch. 3 - Prob. 40EPCh. 3 - Prob. 41PCh. 3 - Prob. 42PCh. 3 - What is thermal contact resistance? 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A and B, with the same surface...Ch. 3 - Prob. 206PCh. 3 - A room at 20C air temperature is losing heat to...Ch. 3 - Prob. 208PCh. 3 - A 1-cm-diameter, 30cm-long fin made of aluminum...Ch. 3 - A hot surface at 80C in air at 20C is to be cooled...Ch. 3 - A cylindrical pin fin of diameter 0.6 cm and...Ch. 3 - A 3-cm-long. 2-nuti x 2-mm rectangular...Ch. 3 - Two finned surfaces with long fins are identical,...Ch. 3 - A 20-cm-diameter hot sphere at 120C is buried in...Ch. 3 - A 25-cm-diameter, 2.4-rn-long vertical cylinder...Ch. 3 - Prob. 216PCh. 3 - The walls of a food storage facility are made of a...Ch. 3 - The equivalent thermal resistance for the thermal...Ch. 3 - Prob. 219PCh. 3 - Prob. 220PCh. 3 - Prob. 221PCh. 3 - The fin efficiency is defined as the ratio of the...Ch. 3 - Prob. 223PCh. 3 - In the United States, building insulation is...Ch. 3 - Prob. 225PCh. 3 - A plane brick wall (k=0.7W/m.K) and is 10 cm...Ch. 3 - The temperature in deep space is close to absolute...Ch. 3 - In the design of electronic components, it is...Ch. 3 - Using cylindrical samples of the same material,...Ch. 3 - Find out about the wall construction of the cabins...Ch. 3 - Prob. 231PCh. 3 - A house with 200-m2 floor space is to be heated...
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