2025 09 12 ENG

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Exam of Multiphase Systems and Technologies – a.y. 2024-25 1st call of the Fall session – September 12th, 2025 – Energy Engineering programme Surname Name Person code Correct answers Score Mark the correct answer(s), if any, in the dedicated space Question 1 For a vapour bubble in thermodynamic equilibrium with the surrounding liquid: Answer a The vapour pressure is lower than the liquid pressure b The vapour pressure is higher than the liquid pressure X c The vapour pressure is the same as the liquid pressure d The vapour pressure is independent of the temperature Question 2 Regarding the onset of nucleate boiling, a rough surface usually requires: Answer a A lower superheating than a smoother surface X b A higher superheating than a smoother surface c The same superheating as a smoother surface d No superheating at all Question 3 Which statement is correct? Answer a Mass quality is the same as volume quality for homogeneous flows b Mass quality is the same as void fraction for homogeneous flows c Void fraction is lower than volume quality for slip ratio larger than one X d Void fraction and volume quality can never be equal to each other Question 4 The superficial velocity of a phase: Answer a Is the velocity of the phase flowing with the total volume flow rate b Is the velocity of the phase flowing with the total mass flow rate c Is the ratio of the volume flow rate of the phase to the cross-section area occupied by the phase d Is the product of the volume fraction of the phase times the mixture velocity X Question 5 What are the characteristic parameters of the drift-flux model? Answer a The slip ratio and the drift-flux b The distribution parameter and the slip ratio c The distribution parameter and the drift-velocity X d The drift-velocity and the slip ratio…