Which statement correctly describes adiabatic flow?

• A. Heat is exchanged with surroundings
• B. No heat is exchanged with surroundings
• C. Temperature remains constant
• D. Mass is conserved

Answer: (B)

Adiabatic flow means no heat is exchanged with the surroundings. In this case, all changes in the fluid’s energy come from work done on or by the fluid, not from heat transfer. That’s why the temperature doesn’t have to stay the same—it can rise or fall during compression or expansion even though no heat is crossing the boundary.

So the statement about no heat exchange best captures adiabatic flow. The idea that heat is exchanged would describe a nonadiabatic (or diabatic) process, and the temperature remaining constant would describe an isothermal process, not generally adiabatic. Mass conservation is a separate principle in fluid flow and doesn’t define adiabatic behavior.