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 between 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. The thermal properties of the fluid and the velocity of flow the fluid over the surface, the temperature difference t and a factor determining 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 the 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 chambers are at different heights, and temperature at each height is different.
4. A group of operation for separating the components of mixture is based on the transfer of material from one homogeneous phase to another. 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 concentration difference 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 characteristic of an individual particle are its composition, its size and its shape. Composition determine such properties 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 iosbuty(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 own 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 vaporization, 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 kerosene, fuel 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 required 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 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 areas of chemical engineering.
