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.
Chapter7: Forced Convection Inside Tubes And Ducts
Section: Chapter Questions
Problem 7.5P
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![3. 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.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F747eb112-7c3d-4e37-b293-572e18446c56%2F080e144e-68bb-4273-8374-89c0c6c6f610%2Fuxzwzyq_processed.png&w=3840&q=75)
Transcribed Image Text:3. 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.
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