An industrial freezer is designed to operate with an internal air temperature of - 20°C when the external air temperature is 27°C, and the internal and external heat transfer coefficients are 8 W/m²-K and 12 W/m²-K, respectively. The walls of the freezer are composite construction, comprising an inner layer of plastic (k = 0.33 W/m-K, and thickness of 10 mm), and an outer layer of stainless steel (k = 15 W/m- K, and thickness of 3 mm). Sandwiched between these two layers is a layer of insulation material with k = 0.07 W/m-K. Find the width (mm) of the insulation that is required to reduce the convective heat loss to 60 W/m².

An industrial freezer is designed to operate with an internal air temperature of - 20°C when the external air temperature is 27°C, and the internal and external heat transfer coefficients are 8 W/m²-K and 12 W/m²-K, respectively. The walls of the freezer are composite construction, comprising an inner layer of plastic (k = 0.33 W/m-K, and thickness of 10 mm), and an outer layer of stainless steel (k = 15 W/m- K, and thickness of 3 mm). Sandwiched between these two layers is a layer of insulation material with k = 0.07 W/m-K. Find the width (mm) of the insulation that is required to reduce the convective heat loss to 60 W/m².

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.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.39P

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