A stainless-steel cylindrical flask has an external radius of and height

PHYSICS · Subjective · CBSE · Physics · Thermal Properties of Matter · Thermal Properties of Matter

Problem

A stainless-steel cylindrical flask has an external radius of 4.0 cm4.0\,\text{cm} and height 20 cm20\,\text{cm}. The steel wall is 0.50 mm0.50\,\text{mm} thick (thermal conductivity 15 W m−1 K−115\,\text{W}\,\text{m}^{-1}\,\text{K}^{-1}). A layer of polyurethane foam (thermal conductivity 0.03 W m−1 K−10.03\,\text{W}\,\text{m}^{-1}\,\text{K}^{-1}) is to be added outside the steel so that the rate of heat conduction through the cylindrical surface falls to one-tenth of its present value. Neglect heat flow through the ends. Calculate the required foam thickness.

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