川大884化工原理电子版本课件双语problem

1、Problem on dryingEdited by Zhonghai LiuIn wet seasons, air is almost saturated with water vapor. As we know, a saturated gas can not be used as a drying agent. Thus, somebody thinks that we have to stop drying operation. what do you think? The wet bulb temperature, tw is_. A the gas temperature when

2、 heat transfer rate of gas/liquid equals to the heat absorb rate of liquid evaporation. B the temperature of gas and liquid when they are heat and mass transfer equilibrated. C the liquid temperature when conductive and radiation heat transfer rate of gas/liquid equals to the heat absorb rate of liq

3、uid evaporation. D the liquid temperature when convective heat transfer rate of gas/liquid equals to the heat absorb rate of liquid evaporation.3 In air-water system, usually, t _ td _ tas _ tw; when = _, we have t = tw.4 If a saturated air is cooled at constant total pressure, its relative humidity

4、 will_, humidity will_, wet bulb temperature will_, dew point will_.5 Somebody says that if a pure water vapor is heated to above 373.94C at atmospheric pressure, it can be used as a drying agent. Do you agree?6 The gas temperature leaving a dryer, t2 can not be lower than _of the gas, otherwise the

5、 product will be wet again. 7 It is given that the total mass of feed is G1 and absolute dry mass is Gc, then the moisture content, w=_, X=_.8 In the definitions of H and X，the common place is they are based on_.In drying, most of the heat is consumed by_, others by _and _.10 There are three gas/sol

6、id contacting forms in convective drying : _, _ and_. The most effective of them is_.11 In convective drying process, the direction of heat transfer is from_ through _ to_; the direction of mass transfer is from_ through _ to_.12 the sufficient condition to ideal drying process is A heat loss in dry

7、er is zero. B drying is in constant rate period. C material surface temperature equals wet bulb temperature. D all heat released from gas is for moisture evaporation.13 There is no supplement heating in dryer, if the entering gas temperature, t1 is increased ，the heat efficiency of the dryer will be

8、 _.14 When a material of X Xh contacts with unsaturated air，it will be_; when a fully wet material contacts with saturated air，it will be_. 15 Free moisture is the moisture which _ in drying process and it can be divided as _ and _.16 If material is given, the equilibrium moisture content, X* is rel

9、ated with _ and _of contacted gas; if the humidity of gas decreases, X* will _.In falling rate drying period, the material surface temperature, ti _ tw, surface vapor pressure, pi_ pw (vapor pressure of pure water); here the drying rate is controlled by_.18 Which is correct ? A Combined moisture con

10、tent of material equals Xc. B Combined moisture content of material equals Xh.19 if the required product moisture content is higher than the critical moisture content at same operation condition, the drying is in _period; if the initial moisture content is lower than the critical content, there is only _period.20 For timber and wood powders of same material under same drying condition, their critical moisture content is_, the equilibrium moisture content is_.21When a drying process at its critical point, the Xh is the _ moisture at_; Xc is the _ moisture at, thus Xc _Xh.2