Q5A) Consider a composite spherical shell comprising an insulating layer of unknown thermal conductivity sandwiched between two layers of steel (k = 45 W/m. °C). The inner shell has 100 mm inner diameter and wall thickness of 5 mm. The outer shell has 150 mm inner diameter and wall thickness of 2 mm. The inner surface of inner spherical shell was experimentally found 120 °C while outer surface of outer spherical shell was at 67 °C. The ambient air was at 30 °C with heat-transfer coefficient at outer surface 6 W/m². °C. Determine thermal conductivity of insulating material. Then, experiment was repeated on another day when ambient air temperature was 13 °C. The inner surface temperature of inner shell and convection coefficient remained unchanged. Calculate temperature of outer surface of outer shell in this case.

Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
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Q5A) Consider a composite spherical shell comprising an insulating layer of unknown thermal
conductivity sandwiched between two layers of steel (k = 45 W/m. °C). The inner shell has
100 mm inner diameter and wall thickness of 5 mm. The outer shell has 150 mm inner
diameter and wall thickness of 2 mm. The inner surface of inner spherical shell was
experimentally found 120 °C while outer surface of outer spherical shell was at 67 °C. The
ambient air was at 30 °C with heat-transfer coefficient at outer surface 6 W/m². °C. Determine
thermal conductivity of insulating material. Then, experiment was repeated on another day when
ambient air temperature was 13 °C. The inner surface temperature of inner shell and convection
coefficient remained unchanged. Calculate temperature of outer surface of outer shell in this case.
Transcribed Image Text:Q5A) Consider a composite spherical shell comprising an insulating layer of unknown thermal conductivity sandwiched between two layers of steel (k = 45 W/m. °C). The inner shell has 100 mm inner diameter and wall thickness of 5 mm. The outer shell has 150 mm inner diameter and wall thickness of 2 mm. The inner surface of inner spherical shell was experimentally found 120 °C while outer surface of outer spherical shell was at 67 °C. The ambient air was at 30 °C with heat-transfer coefficient at outer surface 6 W/m². °C. Determine thermal conductivity of insulating material. Then, experiment was repeated on another day when ambient air temperature was 13 °C. The inner surface temperature of inner shell and convection coefficient remained unchanged. Calculate temperature of outer surface of outer shell in this case.
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