Question

A solid wire of inside radius 7 mm from which heat is being generated by passing electric current. An insulating material having thermal conductivity 0.09 W/m Khas been wrapped to reduce the heat transfer from the wire to the surrounding. Determine the thickness of the insulation at which heat transfer start reducing. Take the heat transfer coefficient as 10 W/m²K. Answer Choices: a. 1.5 mm b. 3 mm 2 mm C. d. None of the above

​

Answer 1

The thickness of the insulation at which heat transfer starts reducing is approximately 1.43 mm.

Step-by-step explanation:

To determine the thickness of the insulation at which heat transfer starts reducing, we need to calculate the critical radius. The critical radius is the radius at which the heat transfer from the wire to the surrounding becomes equal to the heat transfer coefficient of the insulation material.

The formula for calculating the critical radius is:

rc = k / (h * 2 * π)

Where:

• rc is the critical radius
• k is the thermal conductivity of the insulation material
• h is the heat transfer coefficient

Substituting the given values:

rc = 0.09 / (10 * 2 * 3.14)

Simplifying the expression:

rc = 0.00143 m = 1.43 mm

Therefore, the thickness of the insulation at which heat transfer starts reducing is approximately 1.43 mm.