🔍 Key Concepts

• Heat exchanger flow arrangements (counterflow vs. parallel flow) • Temperature gradient and how it affects heat transfer efficiency • How maximum outlet temperature is limited by inlet temperatures in different flow types

💭 Think About

• In a parallel flow heater, how do the oil and steam temperatures change as they move in the same direction? What limit does that place on the maximum oil outlet temperature? • In a counterflow heater, the hot and cold fluids move in opposite directions. How does this affect the average temperature difference (driving force for heat transfer) across the length of the heater? • Do wall thickness or heater size automatically change just because the flow is counterflow instead of parallel flow, or is that a separate design choice?

✅ Before You Answer

• Compare the maximum possible oil outlet temperature in parallel flow vs. counterflow for the same steam inlet temperature. • Decide whether flow direction alone guarantees larger heat transfer area or thinner tube walls, or if those are independent design parameters. • Consider whether changing to counterflow by itself would prevent coking when overheated, or if coking depends mainly on oil temperature and cleanliness, not just flow pattern.