[1] During a plant visit, it was noticed that a 12-m-long section of a 10-cm-diameter steam pipe is completely exposedto the ambient air. The temperature measurements indicate that the average temperature of the outer surface of thesteam pipe is 75°C when the ambient temperature is 5°C. There are also light winds in the area at 10 km/h. Theemissivity of the outer surface of the pipe is 0.8, and the average temperature of the surfaces surrounding the pipe,including the sky, is estimated to be 0°C. Determine the amount of heat lost from the steam during a 10-h-long workday. Steam is supplied by a gas-fired steam generator that has an efficiency of 80 percent, and the plant pays$1.05/therm of natural gas. If the pipe is insulated and 90 percent of the heat loss is saved, determine the amount ofmoney this facility will save a year as a result of insulating the steam pipes. Assume the plant operates every day of theyear for 10 h. State your assumptions.T= 0°Csurrɛ = 0.875°C10 cmSteam pipe/////5°C10 km/ha.) Amount of heat lost.A. 2.461x105 kJ/dayB. 4.361x105 kJ/dayC. 3.361x105 kJ/dayD. 2.361x106 kJ/dayb.) Money saved.A. $ 965B. $ 985C. $ 1065D. $ 950

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Answered: 1] During a plant visit, it was noticed…

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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Under conditions for which the same room temperature is maintained by a heating or cooling system, it is not uncommon for a person to feel chilled in the winter but comfortable in the summer. Consider a room whose air temperature is maintained at 16°C throughout the year, while the walls of the room are nominally at 30°C and 14°C in the summer and winter, respectively. The exposed surface of a person in the room may be assumed to be at a temperature of 32°C throughout the year and to have an emissivity of 0.90. The coefficient associated with heat transfer by natural convection between the person and the room air is approximately 2 W/m2.K. Calculate the following. Heat flux due to convection: q'onv W/m? Heat flux due to radiation in the summer: i W/m? Heat flux due to radiation in the winter: qad W/m? i ||
Consider steady, laminar, two-dimensional flow over a hot plate. Does the convective heat transfer coefficient (h) increase, decrease, or remain constant with distance from the leading edge? Explain.
Thick fluids such as asphalt and waxes and the pipes in which they flow are often heated in order to reduce the viscosity of the fluids and thus to reduce the pumping costs. Consider the flow of such a fluid through a 100-m-long pipe of outer diameter 30 cm in calm ambient air at 0oC. The pipe is heated electrically, and a thermostat keeps the outer surface temperature of the pipe constant at 250C. The emissivity of the outer surface of the pipe is 0.8, and the effective sky temperature is-300C. Determine the power rating of the electric resistance heater, in kW, that needs to be used. Also, determine the cost of electricity associated with heating the pipe during a 10-h period under the above conditions if the price of electricity is $0.09/kWh. Properties The properties of air at 1 atm and the film temperature of (Ts+To)/2 = (25+0)/2 = 12.5°C are: k = 0.02458 W/m.oC, v = 1.448x10-5 m2/s, Pr = 0.7330 D=m
Fruit is impeded from ripening when it reaches high temperatures (>32°C). Farmer Joe isworried that Deleware's summer heat wave will affect the ripening of his ground cherries.The spherical fruit (1 cm in diameter) is surrounded by a spherical papery husk (λhusk = 0.3W/m K) with an inner diameter of 2 cm and an outer diameter of 2.1 cm. The air in betweenthe fruit and the husk is stagnant (λair = 0.03 W/m K). On a calm day in July, the delewareair (outside of the husk) is very warm, with a temperature of ~38°C and a heat transfercoefficient of h deleware,calm = 10 W/m 2K. (a) Sketch the system, labeling all temperatures, dimensions, and proportionality constants. (b) sketch the electrical analogy tothis system, labeling all temperatures, resistances, and heat flows (c) what is the overall resistance to heat transfer from the air in Deleware to the fruit?
We assume that air at 40°C passes over a 1.5 m long and 50 cm wide plate with a velocity of 3 m/s, as shown in the figure. Calculate the heat transfer from the air to the plate if the temperature of the plate is 10 °C.
What are the differences between velocity boundary layer and thermal boundary layer? Discuss about both boundary layers including the characteristics, the profiles and factors affecting the boundary layers.
Air is to be heated by passing it over a bank of 4-m-long tubes inside which steam is condensing at 100°C. Air approaches the tube bank in the normal direction at 20°C and 1 atm with a mean velocity of 5.2 m/s. The outer diameter of the tubes is 0.016 m, and the tubes are arranged staggered with longitudinal and transverse pitches of SL = ST = 0.03 m. There are 20 rows in the flow direction with 10 tubes in each row. Assume the air properties at mean temperature of 35°C and 1 atm. The air properties at the assumed mean temperature of 35°C and 1 atm are k = 0.02625 W/m·K, ρ = 1.145 kg/m3, cp = 1.007 kJ/kg·K, Pr = 0.7268, μ = 1.895 × 10−5 kg/m·s, Prs = Pr@Ts = 100°C = 0.7111. Determine the pressure drop across the tube bank

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