The attached image displays three different drain pipe materials. The vertical pipe is cast iron, the elbow is galvanized steel and the remaining section is PVC. Question; why does the galvanized elbow appear warmer than the other materials? Emissivity?
Was hot water recently run?
Did it absorb, and transfer to its surface, the heat from that more readily?
Warm water was running down the vertical section probably 15 minutes prior to taking the image. The PVC from the kitchen received drain water about 30 minutes earlier.
Steel section appears to have a thermal gradient. This is a good image that shows the thermal characteristics of different materials. The mass of the objects being heated along with the ability to transfer the energy are different for the three materials.
It’s obvious that heavy duty cast iron will not conduct or retain heat like galvanized and PVC material does.
Will this question be on the test?