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109年 - 109 國立臺灣大學_碩士班招生考試_化學工程學研究所:輸送現象及單元操作#106060

科目：台大◆化工◆輸送現象及單元操作 | 年份：109年 | 選擇題數：0 | 申論題數：19

試卷資訊

所屬科目：台大◆化工◆輸送現象及單元操作

選擇題 (0)

申論題 (19)

Problem 1 (39 points)
 (1) (10 points) Please give the SI units of the following physical quantities: (a) rate of strain (b)thermal diffusivity (c) NPSH (d)Fanning friction factor (e) Reynolds stress
(a) For a steady velocity field, which term(s) in the above equation can be neglected? (I point)
(b) For a flow with very small Reynolds number, which term(s) in the above equation can be neglected? (2 points)
(c) For an ideal flow, which term(s) in the above equation can be neglected? (2 points)
(d) Can the Navier-Stokes cquation be used to describe the flow of compressible fluid? (2 points)
(e) Can the Navier-Stokes equation be used to describe the turbulent flow of water? (2 points)

(3)(6 points)
 The fish concentration distribution in a lake is given by C-5t+3x+2y+z, where C represents the fish concentration (number of fish per cubic meter), t the time (min), and x,y;z the spatial coordinates (m). What is the 62022eee8af86.jpgfor an observer fixed on a boat travelling on the lake with a velocity of Vx=5 (m/min), Vy=2 (m/min) and Vz=0.
(a) Give the definition of the "selectivity ratio" and "distribution coefficient' in extraction? (6 points)
(b) Which property in distillation has the same significance as the distribution coefficient? (2 points)

(5) (6 points) The following figure shows the relationship between the pressure drop and the gas velocity in a packed column where the liquid flows down wards and the gas stream goes upwards. What are the names and the meanings of point X and Y?
62022f9c742c3.jpg
(1) Derive the Fick's first law for the absolute molar flux NA. (6 points)

(2) Show62022ffdd90fc.jpg. (5 points)
(3) If B is stagnant, show that the absolute molar flux Na is always pointing from higher CA to lower CA. (5 points)
(1) Please explain the working principle of this cooler. (5 water out points)
(2) A psychometric chart can be used to estimate the maxinum temperature drop of the air obtainable with such cooler. Sketch the chart with the marks on important properties (8 points) and describe how to estimate the maximum temperature drop using the chart. (4 points).
(3) Is this type of cooler suitable for uise in Taiwan? Why? (3 points)
(1) Find T1(the temperature at t=Rc) without solving any differential equations. (8 points) (Hint: overall heat balance may help)
(2) Write down the differential equation and the boundary conditions needed to solve Tc, the temperature in the cladding. Find T0-T1, the temperature drop across the cladding. You are asked to find the answer without solving Tr, the temperature in the sphere of fissionable material. (10 points)

(3) Write down the differential equation and the boundary conditions needed to solve TF, the temperature in the sphere of fissionable material. Find 620230e5b76c0.jpg, the maximum temperature in the sphere. (7 points)