🔍 Key Concepts

• Forced convection vs. natural convection in heat exchangers • Geometry of finned coils and how air typically moves across them • Differences between counter flow, parallel flow, series flow, and cross flow patterns

💭 Think About

• Visualize an air-cooled hydraulic oil cooler: where does the oil flow and from what direction does the air usually pass over the fins? • Which flow pattern describes one fluid moving through tubes while the other moves roughly perpendicular to those tubes? • Which patterns (counter, parallel) usually involve two fluids flowing generally in the same line, and which involve them intersecting?

✅ Before You Answer

• Identify which medium (oil or air) is inside the coil/tubes and which is outside across the fins • Confirm whether the air path is mostly in line with or across the direction of oil flow in the tubes • Match that geometry to the standard textbook definition of each flow pattern: counter, parallel, series, cross