BME Thermodynamics 5

Question 1

Entropy generation during an irreversible process is always:

Accepted Answer

Positive

Answer

The Second Law requires that entropy generation S_gen > 0 for any irreversible process; it is zero only for reversible processes.

Question 2

In a regenerative Rankine cycle, the regenerator (feedwater heater) is used to:

Accepted Answer

Preheat feedwater using extracted steam, improving efficiency

Answer

Extracted steam from the turbine preheats feedwater before the boiler, reducing the heat input needed and increasing overall cycle efficiency.

Question 3

The Clapeyron equation relates the slope of the saturation curve (dP/dT) to:

Accepted Answer

Latent heat, temperature, and specific volume change between phases

Answer

The Clapeyron equation dP/dT = h_fg / (T·v_fg) relates the saturation pressure slope to enthalpy of phase change, temperature, and volume change.

Question 4

Which dimensionless number represents the ratio of inertial forces to viscous forces in fluid flow, and is often relevant to heat transfer analysis?

Accepted Answer

Reynolds number

Answer

The Reynolds number Re = ρVL/μ represents the ratio of inertial to viscous forces and determines whether flow is laminar or turbulent.

Question 5

For a reversible adiabatic compression of an ideal gas from V1 to V2, the work done ON the gas is:

Accepted Answer

W = nCv(T2 - T1)

Answer

For a reversible adiabatic process, Q = 0, so by the first law, W_in = ΔU = nCv(T2 - T1).

BME - Bachelor of Mechanical Engineering Practice Test