The exhaust duct from a heater has an inside diameter of 114.3 mm with ceramic walls 6.4 mm thick. The average k =1.52 W/m· K. Outside this wall, an insulation or rock wool 102 mm thick is installed. The thermal conductivity of the rock wool is k = 0.046 + 1.56 × 10+ T°C (W/m · K). The inside surface temperature of the ceramic is T1 = 588.7 K, and the outside surface temperature of the insulation is 311 K. Calculate the heat loss for 1.5 m of duct and the interface temperature T2 between the ceramic and the insulation. [Hint: The correct value of km for the insulation is that evaluated at the mean temperature of (T2 + T3)/2. Hence, for the first trial assume a mean temperature of, say, 448 K. Then calculate the heat loss and T2 Using this new T2, calculate a new mean temperature and proceed as before.]

The exhaust duct from a heater has an inside diameter of 114.3 mm with ceramic walls 6.4 mm thick. The average k =1.52 W/m· K. Outside this wall, an insulation or rock wool 102 mm thick is installed. The thermal conductivity of the rock wool is k = 0.046 + 1.56 × 10+ T°C (W/m · K). The inside surface temperature of the ceramic is T1 = 588.7 K, and the outside surface temperature of the insulation is 311 K. Calculate the heat loss for 1.5 m of duct and the interface temperature T2 between the ceramic and the insulation. [Hint: The correct value of km for the insulation is that evaluated at the mean temperature of (T2 + T3)/2. Hence, for the first trial assume a mean temperature of, say, 448 K. Then calculate the heat loss and T2 Using this new T2, calculate a new mean temperature and proceed as before.]

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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