诚信应考,考试作弊将带来严重后果！ 华南理工大学期末考试 《mass transfer and separation process 》试卷 A 注意事项：1. 考前请将密封线内填写清楚； 2. 所有答案请直接答在试卷上(或答题纸上)； 3．考试形式：开（闭）卷；
1. (40 points) Fill in the blanks or choose the correct answer (1) The diffusivities of gases are proportional to ( 1.5 ) power of absolute temperature and are ( inversely proportional to ) pressure of the system. (2) The relation between the flux and the driving force of mass transfer for the equimolar diffusion is ( )(21c c D N --=δ ) (3) Rising the pressure in an absorption process of gas, the Henry ’s constant m will ( decrease ), and the rate of absorption will ( increase ) (4)For a separation process in which relative volatility α =1, the compositions of component A would be ( the same ) in both phases, separation is ( not possible ) when this occurs. (5) At the azeotropic point,both the vapor and the liquid in equilibrium have ( the same ) composition. It is ( not possible ) to separate the azeotropic mixtures by using ordinary distillation. (6) The definition of ideal stage is: (the vapor stream and liquid stream leaving the stage are in equilibrium ) (7) The separations of binary mixtures by a distillation operation are based on differences in vapor- and liquid-phase compositions arising from the ( partial vaporization ) of a liquid mixture or the ( partial condensation ) of a vapor mixture. (8)The difference between the actual plate and the ideal plate is corrected by ( plate efficiency ) (9) In general, the liquid rate for the absorber should be ( D ) times the minimum
rate, too high a value requires ( A ) and the ( E ) of recovering, a small value results in ( F)
A) a large-diameter tower B) 1 C) 2.5 D) 1.1-2.0 E) cost F) a high tower
(10)“G as phase is controlling” means that the major resistance through both the gas and liquid phases is in the ( D), and the solute A in a gas phase is ( A )
A) very insoluble in the liquid B) very soluble in the liquid C) can’t make sure D) gas phase E) liquid phase F) the gas and liquid phases
(11) Flash distillation is used most for separating components that boil at ( very large ) different temperatures
(12) A single total condenser is used, the concentrations of the vapor from the top plate, of the reflux to the top plate, and of the overhead product are ( the same), replacing it by a partial condenser, then, the concentration of overhead is ( larger than) that of reflux.
(13) The stream relationships for the various thermal conditions of feed
•Cold feed ( C,D,G )
•Feed at bubble point ( B, E)
•Feed partly vapor (C,D,I )
•Feed at dew point ( F, A )
•Feed is a superheated vapor (C,D,H)
A) L=L′B)V=V′ C) L′=L+ q F D) V=V′+(1-q)F
E) L′=L+F F)V=V′+F G) q>1 H)q<0 I) 0(14) When the rates of feed and of both the overhead and bottom products are ( 0), called total reflux and the slopes of both operating lines are ( 1 ). (15)Optimum reflux ratio is the point of ( most economical ), and ( not) much larger than the minimum reflux ratio.
(16)The approach of azeotropic distillation, choosing an entrainer to cause ( an new azeotropic mixture )
(17) A significant entrainment will ( reduce ) the plate efficiency.
(18) In the constant-rate drying period, the rate of evaporation is ( A ) of
the solid, and is ( B ) of the properties and flow type of air.
A) independent B) dependent C) uncertain
(19) The relationship among dry-bulb temperature t, wet-bulb temperature t w, dew-point t d of unsaturated moist air is( t> t w > t d)
