四川大学化工考研884复试面试英语题库翻译原文

1、1. when a fluid flows through a duct or over a surface, the velocity over a place at right angles to the stream is not normally uniform. the variation of velocity can be shown by the use of streamlines which are lines so drawn that the velocity vector is always tangential to them. the flow rate betw

2、een any two streamlines is always the same. constant velocity over a cross-section is shown by equidistant streamlines and increase in velocity by closer spacing of streamlines.2. it is found the heat transfer rate per unit area q is dependent on those physical properties which affect flow pattern.

3、the thermal properties of the fluid and the velocity of flow the fluid over the surface, the temperature difference t and a factor deternming the natural circulation effect cause by expansion of the fluid on heating.3. the oil distilled in a very large steel tower, the technical names of which is th

4、e fractionating tower. the tower is thirty to fifty meters tall and its diameter is one to three meters. it is divided into chambers, each of which contains a layer of trays. there are holes in the trays. the chanbers are at different heights, and temperature at each height is different.4. a group o

5、f operation for separating the components of mixture is based on the transfer of material from one homogeneous phase to anther. unlike purely mechanical separation, these methods utilize differences in vapor pressure or solubility, not density or particle size. the driving force for transfer is a co

6、noantration differce to or a concentration gradient, much as a temperature difference or a temperature gradient provides the driving force heat transfer.5. the three most important characteristics of an individual particle are its composition, its size and its shape. composition determine such prope

7、rties as density and conductivity， provided that the particle is completely uniform. a particle shape may be regular such as spherical or cubic, or it may be irregular as, for example, with a piece of broken glass.6. homogeneous catalysis is the industrical oxo process for manufacturing normal iosob

8、uty(异丁醛)。 a homogeneous catalysis press involve more than one phase， usually the catalyst is a solid and the reactants and products are in liquid or gaseous form.7. when the vapors rise into the cooler part of the fractionating tower, they lose heat, the vapors rise until they are just below their o

9、wn boiling temperature . then they condense on a tray and turn into a liquid again. the liquid on each tray flows into a separate small tower where the liquid breaks down into smaller fractions. the separation of the hydrocarbons is more accurate.8. the function of distillation is to separate , by v

10、aporization, a liquid mixture of miscible, and volaule substances into individual components or , in some cases, into groups of components, the separation of a mixture of alcohol and water into its component of liquid nitrogen, oxygen and argon, and of crude petroleum into gasoline, kerosence, fuel

11、oil, and lubrication stock are examples of distillation.9. for the pumping of liquids or gases from one vessel to another or through long pipes, some from of mechanical pump is usually employed. the energy require by the pump will depend on the height through which the liquids raised, the pressure r

12、equired at delivery point, the length and diameter of the pipe, the rate of flow, together with the physical properties of the liquid, particularly its viscosity and density.10. in the majority of chemical processes, heat is either given out or absorbed, and fluids must often be heated or coole in a

13、 wide range of plant, such as furnaces, evaporates, distillation units, dryers ,and reaction vessels where one of the major problems is that of transferring heat at the desired rate. in addition, it may be necessary to prevent the loss of heat at the desires rate forms one of the most important area

14、s of chemical engineering.11. membrane science has reached maturity, and the separation processes, which are based on the technologies that it has spawned, are now commonplace. they cover such wide ranging application as microfiltration, reserve osmosis, gas separation, the artificial kidney and con

15、trolled-release pharmaceuticals, and they are used extensively in industry, medicine and to protect the environment.12. the removal of one or more selected components from a mixture of gases by absorption into a suitable liquid is the second major operation of chemical engineering that is based on i

16、nterphase mass transfer controlled largely by rates of diffusion. thus , acetone can be recoverd from an acetone-air mixture bt passing the gas stream into water in which the acetone dissolves while the air passes out.13. evaporation is achieved by adding heat to the solution to vaporise the solvent

17、. the heat is supplied principally to provide the latent heat of vaporization, and ,by adopting methods for recovery of heat from the vepor, it has been possible to achieve great economy in heat utilization. whilst the normal heating medium is generally low pressure exhaust steam from turbines, spec

18、ial heat transfer fluids or flue gases are also used.14. many organic liquid are purified by crystallization rather than by distillation since enthapies of crystallization are generally much lower than enthalpies of vaporization and caystallization may be carrie out closer to ambient temperature the

19、reby reducing energy requirements. against this, crastallization is rarely the last stage in a process and solvent separation, washing and drying stages are usually required.15. the separation of liquid mixture into their various component is one of the major operations in the process industries, an

20、d distillation, the most widely used method of achieving this end, is the key operating in and oil refinery. in processing, the demand for purer product, coupled with the need for greater effiency, has promoted continued research into the techniques of distillation.16. this is the classic reator use

21、d by organic chemists. the typical volume in glassware is a few hundred milliliters. reactants are charges to the system, rapidly mixed, and repidly brought up to temperature so that reaction conditions are well defined. heating is carried out with an oil bath or an electric heating mantle. mixing i

22、s carried out with a magnetic stirrer or a small mechanical agitator. temperature is controlled by regulation the temperature or by allowing a solvent to reflux.17. in a batch reator all molecules enter and leave together. if the systems is oinermal, reaction yields depend only on the elapsed time a

23、nd on the initial composition, the situation in flow system is more complicate but not impossibly so. the counterpart of the batch reaction time is the age of a molecule. aging begins when a molecule enters the reactor and ceses when it leaves, the total time spent within the boundaries of the react

24、ion is known as the exit age, or residence time.18. several possible mechanisms have been suggested as the cause of crystal nucleation from a supersaturated solution. three recognized nucleation processes are(1)homogeneous nucleation , which occurs spontaneously and does not require the presence of

25、surfaces of any kind;(2)heterogeneous nuclestion, usually prompted by the presence of a crystalline phase of the solute material.19. enzymes are natures catalysts. for the moment it is sufficient to consider an enzyme as a large protein, the structure of which results in a very shape-specific active

26、 site. having shape that are optimally suited to guide reactant molecules(usually referred to as substrates)in the optimum configuration for reaction, enzymes are highlt special and efficient catalysts.20. environmental catalysis is projected to grow faster than any other segment of the catalyst mar

27、ket in the next 20 years. this growth will come both from traditional areas, such as emissions treatment, and from new areas that range from the automotive industry to pharmaceuticals. to sustain this growth and to meet more stringent environment demands, researchers will require ever-increasing con

28、trol and understanding of catalytic material and processes at the molecular level.21. process engineering design is the appllication of chemical, mechanical, petroleum, gas and other engineering talents to the process-related development, planning, designs and decisions requires for economical and e

29、ffective completion of a process project. althought process design engineers are organizationally located in research, technical service, wconomic evaluation, the usual arrangement is to have them available to the engineering groups concerned with developing the engineering details of a project.22.

30、compressors are used for providing gas pressure required to transort gas with pipelines and to lift oil in gas-lift operations. the compressors used in todays natural gas production industy fall into two distinct types: reciprocating and rotary compressors. reciprocating compressors are most commonl

31、y used in the natural gas industry. they are built for practically all pressures and volumetric capacities.23. hydrocarbons constitute the essential components of petroleum, their molecules contain only carbon and hydrogen; they are grouped into many chemical families accoring to their structure. all structure are bas