Introduction to Heat Transfer
6th Edition
ISBN: 9780470501962
Author: Frank P. Incropera, David P. DeWitt, Theodore L. Bergman, Adrienne S. Lavine
Publisher: Wiley, John & Sons, Incorporated
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Chapter 1, Problem 1.79P
(a)
To determine
Rate of heat loss from the duct.
(b)
To determine
The outlet temperature of heated air.
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A pipe 30 m long with an outer diameter of 75 mm is used to deliver steam at a rate of 1500 kg / hour. The vapor pressure is 198.53 kPa entering the pipe with a quality of 98%. The pipe needs to be insulated with a thermal conductivity of 0.2 W / (m K) so that the quality of the steam will only slightly decrease to 95%. The outer surface temperature of the insulation is assumed to be 25 ° C. Ignore resistance conductive of the pipe material and it is assumed that there is no pressure drop in the pipe.
a. Determine the enthalpy of incoming vapor = Answer
kJ / kg.
b. Determine the enthalpy of steam coming out = Answer
kJ / kg.
c. Determine the vapor heat change / loss along the flow = Answer
watt.
d. Specify the minimum required insulation thickness = Answer
cm.
Determine the rate of heat loss per unit length (q′), in W/m, and outer surface temperature Ts,2, in K, for the steam pipe with the inner surface temperature fixed at Ts,1=800 K, inner radius r1=0.06 m, and outer radius r2= 0.12. The outer surface is exposed to an airflow (∞T∞=25°C) that maintains a convection coefficient of h=25 W/m2·K and to large surroundings for which ∞Tsur=T∞=25°C. The surface emissivity of calcium silicate is approximately 0.8.
Consider a wall of 6-m x 2.8-m constructed by the following threelayers: plaster with a thickness of 1 cm (k = 0.36 W⁄m ∙ °C),brick with a thickness of 20 cm (k = 0.72 W⁄m ∙ °C) and wallcovering with a thickness of 2 cm (k = 1.4 W⁄m ∙ °C). Disregardthe effect of convection in the inner surface of the wall and considerthe inner temperature of the wall to be 23 °C. Consider thetemperature of the surroundings to be 8 °C. The heat transfer ratein this wall must be reduced by 90% by the installation of a layerof insulation. If heat transfer between the outer surface of the walland the surroundings is by natural convection (12 W m2 ⁄ ∙ °C)and radiation, and considering the outer wall to be black with atemperature of 9 °C, determine:a) The heat transfer rate without insulation.b) The thickness of the insulation if the material of the layer is polyurethane foam (k =0.025 W⁄m ∙ °C)c) The thickness of the insulation if the material of the layer is fiber glass (k = 0.036 W⁄m ∙ °C)
Chapter 1 Solutions
Introduction to Heat Transfer
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Ch. 1 - The heat flux that is applied to one face of a...Ch. 1 - Prob. 1.12PCh. 1 - Prob. 1.13PCh. 1 - Prob. 1.14PCh. 1 - The 5-mm-thick bottom of a 200-mm-diameter pan may...Ch. 1 - Prob. 1.16PCh. 1 - For a boiling process such as shown in Figure...Ch. 1 - You've experienced convection cooling if you've...Ch. 1 - Prob. 1.19PCh. 1 - A wall has inner and outer surface temperatures of...Ch. 1 - An electric resistance heater is embedded in a...Ch. 1 - Prob. 1.22PCh. 1 - A transmission case measures W=0.30m on a side and...Ch. 1 - Prob. 1.24PCh. 1 - A common procedure for measuring the velocity of...Ch. 1 - Prob. 1.26PCh. 1 - Prob. 1.27PCh. 1 - Prob. 1.28PCh. 1 - Prob. 1.29PCh. 1 - Prob. 1.30PCh. 1 - Prob. 1.31PCh. 1 - Prob. 1.32PCh. 1 - Prob. 1.33PCh. 1 - Prob. 1.34PCh. 1 - An electrical resistor is connected to a battery,...Ch. 1 - Pressurized water pin=10bar,Tin=110C enters the...Ch. 1 - Consider the tube and inlet conditions of Problem...Ch. 1 - An internally reversible refrigerator has a...Ch. 1 - A household refrigerator operates with cold- and...Ch. 1 - Chips of width L=15mm on a side are mounted to a...Ch. 1 - Consider the transmission case of Problem 1.23,...Ch. 1 - One method for growing thin silicon sheets for...Ch. 1 - Heat is transferred by radiation and convection...Ch. 1 - Radioactive wastes are packed in a long,...Ch. 1 - An aluminum plate 4 mm thick is mounted in a...Ch. 1 - A blood warmer is to be used during the...Ch. 1 - Consider a carton of milk that is refrigerated at...Ch. 1 - The energy consumption associated with a home...Ch. 1 - Liquid oxygen, which hems a boiling point of 90 K...Ch. 1 - The emissivity of galvanized steel sheet, a common...Ch. 1 - Three electric resistance heaters of length...Ch. 1 - A hair dryer may be idealized as a circular duct...Ch. 1 - In one stage of an annealing process, 304...Ch. 1 - Convection ovens operate on the principle of...Ch. 1 - Annealing, an important step in semiconductor...Ch. 1 - In the thermal processing of semiconductor...Ch. 1 - A furnace for processing semiconductor materials...Ch. 1 - Single fuel cells such as the one of Example 1.5...Ch. 1 - Prob. 1.59PCh. 1 - Prob. 1.60PCh. 1 - Prob. 1.61PCh. 1 - A small sphere of reference-grade iron with a...Ch. 1 - A 50mm45mm20mm cell phone charger has a surface...Ch. 1 - A spherical, stainless steel (AISI 302) canister...Ch. 1 - Prob. 1.65PCh. 1 - Prob. 1.66PCh. 1 - A photovoltaic panel of dimension 2m4m is...Ch. 1 - Following the hot vacuum forming of a paper-pulp...Ch. 1 - Prob. 1.69PCh. 1 - Prob. 1.70PCh. 1 - Prob. 1.71PCh. 1 - The roof of a car in a parking lot absorbs a solar...Ch. 1 - Prob. 1.73PCh. 1 - Prob. 1.74PCh. 1 - Consider Problem 1.1. If the exposed cold surface...Ch. 1 - Prob. 1.76PCh. 1 - Prob. 1.77PCh. 1 - A thin electrical heating element provides a...Ch. 1 - Prob. 1.79PCh. 1 - Prob. 1.80PCh. 1 - Prob. 1.81PCh. 1 - The curing process of Example 1.9 involves...Ch. 1 - The diameter and surface emissivity of an...Ch. 1 - Bus bars proposed for use in a power transmission...Ch. 1 - A solar flux of 700W/m2 is incident on a...Ch. 1 - In considering the following problems involving...
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- A pipe 30 m long with an outer diameter of 75 mm is used to deliver steam at a rate of 1500 kg / hour. The steam pressure is 198.53 kPa entering the pipe with a quality of 98%. The pipe that needs to be insulated with a thermal conductivity of 0.2 W / (m K) so that the quality of the steam only decreases slightly to 95%. The temperature of the outer surface of the insulation is assumed to be 25 ° C. The conductive of the pipe material and the situation of no pressure drop in the pipe. A. Determine the enthalpy of incoming vapor = Answer kJ / kg. b. Determine the enthalpy of steam that comes out = Answer kJ / kg. c. Determine the change / loss of steam heat along the flow = Answer watt. d. Determine the minimum required insulation thickness = Answer cm.arrow_forwardA composite wall constructed of 2.5cm of steel (k-60.5 W/m-K) and 5.0 cm of aluminum (k177W/m-K) separates two liquids. The liquid on the steel side has a film coefficient of 15W/m²-K and a temperature of 400degC. The liquid on the steel side has a film coefficient of 30W/m² and a temperature of 100degC. Assume steady state conditions, what is the temperature at the steel-aluminum interface in deg Carrow_forwardOn a cold winter day, you decide to keep the outside surface windshield temperature at +2°C to prevent ice formation on the outside of your car's windshield. a. Use the following information to calculate the rate of energy loss through the window in Watts. Windshield area = 0.5 m2 ● Outside convection heat transfer coefficient is 250 W/(m2K) Outside "bulk" air temperature = -15°C. b. Using your answer from part a, find what temperature you need to keep the inside of the windshield in °C. ● Windshield thickness = 5 mm Glass k= 1.25 W/(m K) ●arrow_forward
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