Two insulating materials of thermal conductivity K and 2K are available for lagging a pipe carrying a hot fluid. If the radial thickness of each material is the same.
- A. Material with higher thermal conductivity should be used for the inner layer...
- B. Material with lower thermal conductivity should be used for the inner layer...
- C. It is immaterial in which sequence the insulating materials are used
- D. It is not possible to judge unless numerical values of dimensions are given.
Explanation: To minimize heat loss (maximize resistance), the material with lower k should be at the inner layer where the area for heat transfer is smaller. Resistance of cylindrical shell ln(r2/r1)/k. Inner layer has smaller radius, so putting lower k there has more impact?