ANS:B - 1-1 heat exchanger

To reduce the tube side pressure drop for the same flow rate, the recommended heat exchanger configuration is the 1-2 heat exchanger. In a 1-2 heat exchanger configuration, the number "1" represents the number of tube passes on the shell side, and the number "2" represents the number of tube passes on the tube side. This configuration allows for increased tube side velocity and turbulence, leading to lower pressure drop compared to other configurations. Here's why:

• Tube Side Velocity: In a 1-2 heat exchanger, the fluid velocity on the tube side is higher compared to other configurations with fewer tube passes. This increased velocity helps to reduce the boundary layer thickness and enhance heat transfer while minimizing pressure drop.
• Turbulence: Higher tube side velocity promotes turbulence within the tubes, which improves heat transfer efficiency. Turbulent flow also reduces the resistance to flow, resulting in lower pressure drop.
• Pressure Drop: The pressure drop in the tubes is influenced by factors such as fluid velocity, flow distribution, and geometry. By increasing the tube side velocity and promoting turbulence, the 1-2 heat exchanger configuration effectively reduces pressure drop while maintaining the same flow rate.