Critical Radius of Insulation

• Heat loss increases initially when one adds insulation (why?)

• Maximum heat loss at critical radius of insulation that rcritical =kinsul/houtside

• In the present case, rcritical=0.5/20=0.025

• Its criticasl thickness is t=0.025-0.0125=0.0125(m)

Critical thickness

Note: similar derivation can be made for a spherical container. The critical radius for a spherical shell is rcritical=2k/h

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