🔍 Key Concepts

• Modes of heat transfer in a fuel oil heater (conduction, convection, radiation) • Effect of fouling/carbon deposits on heat transfer surfaces • Relative thermal conductivity of clean metal vs. carbon/solid contaminants

💭 Think About

• Think about how a clean metal heating surface transfers heat to fuel oil compared to one covered with a carbon layer. What changes physically at the surface? • Which mode of heat transfer is dominant inside a typical fuel oil heater: conduction through solids, convection in fluids, or radiation? How would a solid layer affect that? • If you put an insulating layer on a hot metal surface, what happens to the rate of heat flow to the fluid on the other side?

✅ Before You Answer

• Identify which choice refers to thermal conductivity (how well heat passes through a solid layer). • Decide whether carbon/solid contaminants are more like a good conductor or a thermal insulator compared to steel or copper. • Check which options talk about phenomena that are actually dominant in a typical shell-and-tube or coil-type fuel oil heater (mostly conduction/convection, limited radiation).