Thermodynamics Flashcards
7 cards from real BME practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Thermodynamics flashcards as text
For a steam power plant operating as a Rankine cycle, the purpose of the feedwater pump is to:
Answer: Increase pressure of the liquid condensate
The feedwater pump increases the pressure of the liquid water from condenser pressure to boiler pressure, requiring relatively little work.
Maxwell's relations in thermodynamics are derived from which thermodynamic potentials?
Answer: Internal energy, enthalpy, Helmholtz, and Gibbs functions
Maxwell's relations are derived from the exactness of the differentials of the four thermodynamic potentials: U, H, A, and G.
In a refrigeration system using the vapor-compression cycle, the throttling device (expansion valve) reduces pressure by:
Answer: An irreversible isenthalpic process
The expansion valve is an isenthalpic (constant enthalpy) throttling device where pressure drops irreversibly without work or heat transfer.
The triple point of water is approximately:
Answer: 0.01°C and 611.7 Pa
The triple point of water occurs at approximately 0.01°C (273.16 K) and 611.7 Pa, where all three phases coexist.
For an Otto cycle (ideal spark-ignition engine), thermal efficiency depends on:
Answer: Compression ratio and specific heat ratio γ
Otto cycle efficiency η = 1 - (1/r^(γ-1)), where r is the compression ratio and γ is the specific heat ratio.
Which property is NOT a state function in thermodynamics?
Answer: Heat transfer
Heat transfer (Q) is a path function that depends on the process path, not just initial and final states.
In a real gas, the compressibility factor Z = PV/nRT is less than 1 when:
Answer: Intermolecular attraction dominates
When attractive forces between molecules dominate, Z < 1 because the actual volume is less than the ideal gas prediction.