A pipe of 25 mm outer diameter carries steam.The heat transfer coefficient between the cylinderand surroundings is 5 W/m2K. It is proposed toreduce the heat loss from the pipe by addinginsulation having a thermal conductivity of 0.05W/mK. Which one of the following statements isTRUE?(a) The outer radius of the pipe is equal to thecritical radius.(b) The outer radius of the pipe is less than thecritical radius.(c) Adding the insulation will reduce the heat loss.(d) Adding the insulation will increase the heatloss.

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Answered: ansfer coeffic ndings is 5 e heat loss

Engineering

Mechanical Engineering

ansfer coeffic ndings is 5 e heat loss

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter7: Forced Convection Inside Tubes And Ducts

Section: Chapter Questions

Problem 7.17P: Determine the rate of heat transfer per meter length to a light oil flowing through a 2.5-cm-ID,...

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Determine the rate of heat transfer per meter length to a light oil flowing through a 2.5-cm-ID, 60-cm-long copper tube at a velocity of 0.03 m/s. The oil enters the tube at 16C, and the tube is heated by steam condensing on its outer surface at atmospheric pressure with a heat transfer coefficient of 11.3 kW/m K. The properties of the oil at various temperatures are listed in the following table: Temperature, T(C) 15 30 40 65 100 (kg/m3) 912 912 896 880 864 c(kJ/kgK) 1.80 1.84 1.925 2.0 2.135 k(W/mK) 0.133 0.133 0.131 0.129 0.128 (kg/ms) 0.089 0.0414 0.023 0.00786 0.0033 Pr 1204 573 338 122 55
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Steam in a heating system flows through tubes whose outer diameter is 5 cm and whose walls are maintained at a temperature of 180°C. Circular aluminum alloy 2024-T6 fins (k = 186 W/m · °C) of outer diameter 6 cm and constant thickness 1 mm are attached to the tube. The space between the fins is 3 mm, and thus there are 250 fins per meter length of the tube. Heat is transferred to the surrounding air at T= 25°C, with a heat transfer coefficient of 40 W/m2 · °C. Determine the increase in heat transfer from the tube per meter of its length as a result of adding fins.