NCEES Thermodynamics 5

Question 1

The Joule-Thomson coefficient μ_JT is defined as (∂T/∂P)_h. For an ideal gas, μ_JT equals:

Accepted Answer

0

Answer

For an ideal gas, enthalpy depends only on temperature, so throttling (constant h) causes no temperature change; thus μ_JT = 0.

Question 2

Which statement about entropy is CORRECT?

Accepted Answer

Entropy change for a reversible adiabatic process is zero

Answer

A reversible adiabatic (isentropic) process has ΔS = 0 because δQ = 0 and there is no irreversibility.

Question 3

For a steady-flow device, neglecting kinetic and potential energy changes, the energy balance simplifies to:

Accepted Answer

Q̇ − Ẇ = ṁ(h2 − h1)

Answer

The steady-flow energy equation reduces to Q̇ − Ẇ = ṁ(h2 − h1) when kinetic and potential energy terms are negligible.

Question 4

The reduced pressure and reduced temperature used in the generalized compressibility chart are defined as:

Accepted Answer

PR = P/Pc and TR = T/Tc

Answer

Reduced properties are dimensionless ratios: PR = P/Pc and TR = T/Tc, where Pc and Tc are critical point values.

Question 5

A heat pump has a COP of 4.5 and consumes 2 kW of power. How much heat does it deliver to the heated space?

Accepted Answer

9.0 kW

Answer

COP_HP = Q̇_H / Ẇ → Q̇_H = COP × Ẇ = 4.5 × 2 kW = 9.0 kW.

NCEES Practice Test