課程名稱︰單元操作三
課程性質︰必修
課程教師︰劉懷勝
開課學院：工學院
開課系所︰化工系
考試日期（年月日）︰102/4/20
考試時限（分鐘）：120
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
Closed book:
1. (10%) Please draw the concentration profiles near the gas-liquid interface
during the mass transfer of an extremely insoluble component from air
into water, for example the mass transfer of oxygen from air into
water. ( The solubility of oxygen in water is roughly 8mg/L only.)
Please also explain it briefly
2. (15%) Please derive Fenske's equation for distillation as below and specity
all the notations and assumptions.
n + 1 = log[(Xa/Xb)d * (Xb/Xa)s ] / log αav
3. (25%) The figure shows a simplified schematic diagram of a rotating packed
bed that consists of a rotor and a stationary housing. Liquid flows
outward from the outer edge of the packed bed by the pressure driven
force. Please derive a design equation for this rotating packed bed
carrying out removing ethanol from a liquid phase to a gas phase. The
design equation can be derived ising the mass balance and the concept
of transfer unit. Where Gm is the molar flow rate of gas; Pt is the
total pressure in the system; z is the axial height of the packing;
KGa is the product mass transfer coefficient and interfacial area;
Hc is the Henry;s law constant expressed as the ratio of mole fraction
of ethanol in gas phase to that in liquid phase. And Y1 and Y2 are the
mole fraction if ethanol in outlet and inlet air streams,respectively.
X2 is the mole fraction of ethanol in the outlet water stream; r1 and
r2 are the inner radius and outer radius if packing respectively. S is
the so called stripping factor that you need to define when you derive
the design equation. Be sure to identify all other notations if needed
//
Open book
1. (25%) A 50% solution of solute C in solvent A is extracted with a second
solvent B in a counter-current mutiple contact extraction units. The
mass of B is 25% that of the feed solution, and the equilibrium data
are as given in the diagram. Determine the number of ideal stages
required, and the mass concentration of the first extract if the final
raffinate has 20% of solute C.
2. (5% ) In a design of distillation, please draw two arbitary tie lines in the
enthalpy-composition chart with the aid of x-y chart.
(20%) Also, please sketch the operating lines perhaps curves in x-y chart
with the aid of the the enthalpy-composition data. Then, draw the
stage wise operations of this distillation in the x-y chart. You need
clearly indicate how you ontain at least two points for each operating
lines and the intersection point as well.
///
Figure : http://ppt.cc/o~t~
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