Heat and Mass Transfer

An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be_____.

  • A. 25 mm
  • B. 40 mm
  • C. 160 mm
  • D. 800 mm
Answer: Option A.
Explanation:

Critical radius of insulation for cylinder
=k/h.
K= thermal conductivity of cylinder

0.15/6 = .025m = 25mm.

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