# 2 - CHE 378 Heat and Mass Transfer Spring 2008 Homework 2...

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CHE 378: Heat and Mass Transfer Spring 2008 Homework 2 Due: Friday, January 25, 2008 at the beginning of lecture 1. A spherical shell with inner radius r 1 and outer radius r 2 has surface temperatures T 1 and T 2 , respectively, where T 1 > T 2 . Determine the temperature distribution and rate of heat loss assuming steady-state one-dimensional conduction with constant properties. Sketch the temperature distribution versus radius. Also, derive an expression for the thermal resistance of the spherical shell. 2. Clothing made of several thin layers of fabric with trapped air in between, often called ski clothing, is commonly used in cold climates because it is light, fashionable, and a very effective thermal insulator. So it is no surprise that such clothing has largely replaced thick and heavy old-fashioned coats. Consider a jacket made of five layers of 0.1 mm thick synthetic fabric ( k = 0.13 W/(m*°C)) with 1.5-mm-thick air space ( k = 0.026 W/(m*°C)) between the layers.

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