Answer:
86 mm
Explanation:
From the attached thermal circuit diagram, equation for i-nodes will be
Equation 1
Similarly, the equation for outer node “o” will be
Equation 2
The conventive thermal resistance in i-node will be
Equation 3
The conventive hermal resistance per unit area is
Equation 4
The conductive thermal resistance per unit area is
Equation 5
Since is given as 100, is 40 is 300 is 25
Substituting the values in equations 3,4 and 5 into equations 1 and 2 we obtain
Equation 6
Equation 7
From equation 6 we can substitute wherever there’s with 3000L+40 as seen in equation 7 hence we obtain
The above can be simplified to be
-3000L=1.665-260
Therefore, insulation thickness is 86mm