Heat exchanger cooling control is influenced by which factors?

• A. Volume of airflow across the exchanger
• B. Speed of the air flowing across the exchanger
• C. Temperature of ambient air
• D. All of the above

Answer: (D)

Cooling the heat exchanger depends on how effectively air can absorb and carry away heat. The amount of air moving across the exchanger—the volume of airflow—determines how much heat with a given temperature can be transported away. The speed of that air across the exchanger influences the convective heat transfer; faster air generally improves heat transfer by disrupting the boundary layer and increasing the rate at which heat is carried away. The ambient air temperature sets the inlet temperature of the cooling air, which affects the temperature difference driving heat transfer; colder ambient air increases this difference and boosts cooling, while warmer ambient air reduces it. Because each of these factors changes the rate of heat removal, all of them influence heat exchanger cooling control.