Chapter 1: Problem 5
What is the importance of modeling in engineering? How are the mathematical models for engineering processes prepared?
Chapter 1: Problem 5
What is the importance of modeling in engineering? How are the mathematical models for engineering processes prepared?
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Get started for freeA \(200-\mathrm{ft}\)-long section of a steam pipe whose outer diameter is 4 in passes through an open space at \(50^{\circ} \mathrm{F}\). The average temperature of the outer surface of the pipe is measured to be $280^{\circ} \mathrm{F}$, and the average heat transfer coefficient on that surface is determined to be $6 \mathrm{Btu} / \mathrm{h} \cdot \mathrm{ft}^{2},{ }^{\circ} \mathrm{F}\(. Determine \)(a)$ the rate of heat loss from the steam pipe and \((b)\) the annual cost of this energy loss if steam is generated in a natural gas furnace having an efficiency of 86 percent and the price of natural gas is \(\$ 1.10 /\) therm (1 therm \(=100,000\) Btu).
A series of ASME SA-193 carbon steel bolts are bolted to the upper surface of a metal plate. The bottom surface of the plate is subjected to a uniform heat flux of \(5 \mathrm{~kW} / \mathrm{m}^{2}\). The upper surface of the plate is exposed to ambient air with a temperature of \(30^{\circ} \mathrm{C}\) and a convection heat transfer coefficient of \(10 \mathrm{~W} / \mathrm{m}^{2}\). K. The ASME Boiler and Pressure Vessel Code (ASME BPVC.IV-2015, HF-300) limits the maximum allowable use temperature to \(260^{\circ} \mathrm{C}\) for the SA-193 bolts. Determine whether the use of these SA-193 bolts complies with the ASME code under these conditions. If the temperature of the bolts exceeds the maximum allowable use temperature of the ASME code, discuss a possible solution to lower the temperature of the bolts.
Water enters a pipe at \(20^{\circ} \mathrm{C}\) at a rate of $0.25 \mathrm{~kg} / \mathrm{s}\( and is heated to \)60^{\circ} \mathrm{C}$. The rate of heat transfer to the water is (a) \(10 \mathrm{~kW}\) (b) \(20.9 \mathrm{~kW}\) (c) \(41.8 \mathrm{~kW}\) (d) \(62.7 \mathrm{~kW}\) (e) \(167.2 \mathrm{~kW}\)
A thin metal plate is insulated on the back and exposed to solar radiation on the front surface. The exposed surface of the plate has an absorptivity of \(0.7\) for solar radiation. If solar radiation is incident on the plate at a rate of \(550 \mathrm{~W} / \mathrm{m}^{2}\) and the surrounding air temperature is \(10^{\circ} \mathrm{C}\), determine the surface temperature of the plate when the heat loss by convection equals the solar energy absorbed by the plate. Take the convection heat transfer coefficient to be $25 \mathrm{~W} / \mathrm{m}^{2} \cdot \mathrm{K}$, and disregard any heat loss by radiation.
Consider a 3-m \(\times 3-\mathrm{m} \times 3-\mathrm{m}\) cubical furnace whose top and side surfaces closely approximate black surfaces at a temperature of \(1200 \mathrm{~K}\). The base surface has an emissivity of \(\varepsilon=0.7\), and is maintained at \(800 \mathrm{~K}\). Determine the net rate of radiation heat transfer to the base surface from the top and side surfaces.
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