Heat Transfer Flashcards
6 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 6 Heat Transfer flashcards as text
The Prandtl number is defined as the ratio of:
Answer: Momentum diffusivity to thermal diffusivity
Prandtl number Pr = ν/α = momentum diffusivity / thermal diffusivity, indicating the relative thickness of velocity and thermal boundary layers.
In a counter-flow heat exchanger, the maximum possible temperature change of the cold fluid is limited by:
Answer: The hot fluid inlet temperature
In counter-flow, the cold fluid can theoretically be heated up to the inlet temperature of the hot fluid, giving the highest thermodynamic efficiency.
Stefan-Boltzmann law states that radiation heat flux is proportional to:
Answer: T⁴
The Stefan-Boltzmann law states E = εσT⁴, meaning emissive power is proportional to the fourth power of absolute temperature.
The LMTD method for heat exchanger analysis stands for:
Answer: Log Mean Temperature Difference
LMTD (Log Mean Temperature Difference) is the effective driving temperature difference for heat transfer in a heat exchanger.
Which dimensionless number governs natural (free) convection?
Answer: Grashof number
The Grashof number Gr = gβΔTL³/ν² represents the ratio of buoyancy forces to viscous forces and governs natural convection.
For a blackbody, the emissivity (ε) equals:
Answer: 1
A blackbody is an ideal perfect emitter and absorber, defined by emissivity ε = 1; real surfaces have ε < 1.