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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Chapter 1, Problem 1.81P
A person wearing a heavy parka is standing in a cold wind. Describe the modes of heat transfer determining heart loss from the person's body.
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Calculate the thermal resistance due to convection for the following situations:a. w arm water with h = 200 W⁄m2 .Kb. warm air with h = 10 W⁄m2 .Kc. warm moving air (windy situation) h = 30 W⁄m2 .K
Еxample:-
In a warm room, a naked resting person has a skin temperature of 33°C
If the room temperature is 29°C and the body surface area is 1.5m2
.What is the rate of heat loss due to convection if Kc=7.1 watt/m2 .k?
Hi, can you help me to answer this question using the first law of thermodynamics formula to explain this event?
On a hot summer day, a student turns his fan on when he leaves his room in themorning. When he returns in the evening will the room be warmer or cooler than theneighborouing rooms ? Explain your answer using the first law of thermodynamics.Assume ALL doors and windows are kept closed.
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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- Using Table 1.4 as a guide, prepare a similar table showing the orders of magnitude of the thermal resistances of a unit area for convection between a surface and various fluids.arrow_forwardAn electrical transmission line of 1.2-cm diameter carries a current of 200 amps and has a resistance of 310-4 ohm per meter of length. If the air around this line is at v, determine the surface temperature on a windy day, assuming a wind blows across the line at 33 km/h.arrow_forwardH.W1 Consider a person standing in a room. Determine the total rate of heat transfer from this person if the exposed surface area and temperature are 1.6m² and 29°C, respectively. Assume that the convection heat transfer coefficient is 6W/m².K and the emissivity of a person is 0.95. The air temperature in the room is maintained at 22°C at all times of the year. In summer, the wall and ceiling temperatures are observed to be 25°C, while in winter, they are 10°C. Ans: Qrotal =104.4 W In Summer Qrotal =231.3 W In Winterarrow_forward
- Please solve and answer the question correctly please. Thank you!!arrow_forwardDuring hot summer weather, many people put “koozies” around their beverages to keep the drinks cold. In addition to preventing a warm hand from heating the container through conduction, what other mechanisms slow the process of warming beverages?arrow_forwardBriefly discuss the influence of clothing on human comfort. How is the effect of clothing expressed? Why would you expect a mixed group of people in an air conditioned room to have different attitudes to thermal comfort?arrow_forward
- A woman informs an engineer that she frequently feels cooler in the summer when standing in front of an open refrigerator. The engineer tells her that she is only “imagining things” because there is no fan in the refrigerator to blow the cool air over her. A lively argument ensues. Whose side of the argument do you take? Why?arrow_forwardHi, can you help me to answer this question using the first law of thermodynamics? On a hot summer day a student turns his fan on when he leaves his room in themorning. When he returns in the evening will the room be warmer or cooler than theneighborouing rooms ? Explain your answer using the first law of thermodynamics.Assume ALL doors and windows are kept closed.arrow_forwardWhat is the effect of wind shear on thermals?arrow_forward
- Relationship between fluid flow and convection heat transferarrow_forwardQ1. A 6-mm-diameter electrical transmission line carries an electric current of 50 A and has a resistance of 0.002 ohm per meter length. Determine: The surface temperature of the wire during a windy day when the air temperature is 10°C and the wind is blowing across the transmission line at 40 km/h. Wind, 40 km/h 10°C Transmission linesarrow_forwardA camera used for monitoring marine life is placed in water where T.. -5°C and the convection heat transfer coefficient h=1420 W/m²K. The camera is operating, but its battery is experiencing thermal runaway, causing the camera to become very hot, and there is volumetric heat generation, qe inside it. There is no heat generation within the waterproof, protective enclosure surrounding it. 00:08 The camera is already compromised; however, its owner hopes to save the protective case. Each interface (between layers A and B and between layers B and C) must not exceed a temperature of 185°C, or these plastic, protective layers will begin to melt. Approximate the camera and its casing as a composite, rectangular object with flat surfaces. The device's total thickness, L=LA + 2LB +Lc, is much smaller than its area (into the page); therefore, 1-D conduction can be approximated through the layers. On the left surface of layer A, the temperature is measured to be T₁ = 8.0°C, and the temperature on…arrow_forward
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