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 1.33P
Wearing layers of clothing in cold weather is often recommended because dead-air spaces between the layers keep the body warm. The explanation for this is that the heat loss from the body is less. Compare the rate of heat loss for a single 2-cm-thick layer of wool
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A wall is constructed of a section of stainless steel [k=16 W/m. C] 4.0 mm thick with identical layers of plastic on both sides of the steel. The overall heat-transfer coefficient, considering convection on both sides of the plastic, is 120W / (m ^ 2) * 9 If the overall temperature difference across the arrangement is 60 degrees * C , calculate temperature difference across the stainless steel.
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An electric furmace is a composite wall consisting of a brick with 0.2 m refractory brick (k=2), 0.15 m insulation (k =0.15) and 0.15 m (k= 1.5) references
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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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- 1.2 The weight of the insulation in a spacecraft may be more important than the space required. Show analytically that the lightest insulation for a plane wall with a specified thermal resistance is the insulation that has the smallest product of density times thermal conductivity.arrow_forwardUsing 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_forwardA 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.arrow_forward
- As a designer working for a major electric appliance manufacturer, you are required to estimate the amount of fiberglass insulation packing (k = 0.035 W/m K) that is needed for a kitchen oven shown in the figure below. The fiberglass layer is to be sandwiched between a 2-mm-thick aluminum cladding plate on the outside and a 5-mm-thick stainless steel plate on the inside that forms the core of the oven. The insulation thickness is such that the outside cladding temperature does not exceed 40C when the temperature at the inside surface of the oven is 300C. Also, the air temperature in the kitchen varies from 15Cto33C, and the average heat transfer coefficient between the outer surface of the oven and air is estimated to be 12.0W/m2K. Determine the thickness of the fiberglass insulation that is required for these conditions. What would be the outer surface temperature when the inside surface of the oven is at 475C?arrow_forward1.4 To measure thermal conductivity, two similar 1-cm-thick specimens are placed in the apparatus shown in the accompanying sketch. Electric current is supplied to the guard heater, and a wattmeter shows that the power dissipation is 10 W. Thermocouples attached to the warmer and to the cooler surfaces show temperatures of 322 and 300 K, respectively. Calculate the thermal conductivity of the material at the mean temperature in W/m K. Problem 1.4arrow_forward1. Consider a 5-m-high, 8-m-long, and 0.22-m-thick wall whose representative cross section is as given in the Fig. The thermal conductivities of various materials used, in W/m-°C, are k = kr = 2, KB = 8,kc=20, KD = 15, and k = 35. The left and right surfaces of the wall are maintained at uniform temperatures of 300 °C and 100 °C, respectively. Assuming heat transfer through the wall to be one-dimensional, determine: (a) the rate of heat transfer through the wall; (b) the temperature at the point where the sections B, D, and E meet; and (c) the temperature drop across the section F. Disregard any contact resistances at the interfaces. 300°C 1 cm C A 4 cm B 4 cm 4 cm D C 6 cm 5 cm 6 cm E| F 10 cm 6 cm 100°C 8 marrow_forward
- Please answer question 1 please show me step by step.arrow_forwardA plane wall of an oven with an insulation coating is attached to an insulated wall. The thermal conductivity and thickness of the insulation coating are 0.1 W/(m K) and 1 mm, respectively. The material of the plane wall is stainless steel 304. The density, thermal conductivity, and specific heat capacity of the stainless steel 304 are 7900 kg/m³, 74.9 W/(mK), and 477 J/(kg K), respectively. The wall thickness of the stainless steel 304 is 15 mm. The temperature of the plane wall with the insulated coating is initially maintained at 30 °C. Suddenly, hot gas with a temperature of 1000 °C enters the oven. The convection heat transfer coefficient at the insulation coating surface is 70 W/(m²K). Insulation Coating Stainless Steel 304 Oven Gas Perfectly Insulated Wall 3-1) What is the overall heat transfer coefficient per unit area from the gas to the surface of the stainless steel? The answer should be given in the unit of W/(m²K). 3-2) What is the value of the Biot number?arrow_forwardA furnace of 50x50x60-cm outside dimensions is constructed of materials having different thermal conductivities. The thermal conductivity of the top and the bottom walls is [k=6 W/m K] whereas the thermal conductivity of the other sides is [k=12 W/m K]. The wall thickness is 10 cm. The inner surface temperatures is 300°C and the outer temperature is 50°C. Calculate the heat loss through the furnace walls. Please solve this question using a piece of paper, not a text A area of wall L= wall thickness D = length of edge Swall === L Sedge=0.54D Scomer = 0.15Larrow_forward
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