Lesson 4.1 Heat Transter

1. Lesson 4.1 Heat Transter

2. words 1 Expressions and Technical Terms 2 Text 3 content

3. 热量传递 其他 transfer[træns`fә:] n./v. 调动，转移，迁移 operation [͵ɔpә`reiʃən] n. 操作 thermal [`Ѳә:ml] adj. 热的，热量的，温热的；由热造成的 conduction [`kɔndʌkʃən] n. 传导 convection [kən`rekʃən] n. 对流 radiation [͵reidi`eiʃən] n. 辐射 mechanism [`mekənitəm] n. 机理，原理 momentum [mə`mentəm] n. 【物理学】动量 electricity [i͵lek`trisiti] n. 电流，静电，电荷 conductor [kən`dʌktə] n. 【物理学】导体；导管，导线 opaque [əu`peik] adj. 不透明的; (对电、热等)不传导性的 random [`rændəm] adj. 随机的；【物理学】无规则的 furnace [`fə:nis] n. 炉子；熔炉；高炉 Words

4. Expressions and Technical Terms • chemical engineering 化学工程 • temperature gradient 温度梯度 • results from 由…而造成[产生] • unbound electron 自由电子 • thermal conductivity 热传导系数 • electrical conductivity 导电性 • buoyancy force 浮力 • in turn 反过来 • natural convection 自然对流

5. text • . Heat, as a form of energy, cannot be created or destroyed. Heat can be transferred from one substance to another. • 热能作为能量的一种形式既不能产生也不能被破坏,热只能从一种物质转移到另一个物质中. • . Practically all the operations that are carried out by the chemical engineering involve the production or absorption of energy in the form of heat The laws governing the transfer of heat and the types of apparatus that have for their main object the control of flow are therefore of great important. • 实际上化学工程中所有的操作过程都涉及到能量以热的形式的产生和吸收,因此决定传热的定律和为了传热而控制流动的设备的类型是相当重要的.

6. text • . When two objects at different temperatures are brought into thermal contact, heat flows from the object at the higher temperature to that at the lower temperature. The net flow is always in the direction of the temperature decrease. The mechanisms by which the heat may flow are three: conduction, convection, and radiation • 当处于不同温度的两种物体进行热交换时,热总是从温度高的物体转移到温度低的物体中,传热的方向总是向着温度较低的方向进行.传热的基理主要有三种:热传导,对流,辐射。

7. text • . If a temperature gradient exists in a continuous substance, heat can flow unaccompanied by any observable motion of matter. Heat flow of this kind is calledconduction. • 如果温度梯度在一个连续性无之中存在时,热交换就可以进行,并且在热交换中不会发生任何可观察到的物质运动的交换状况

8. text • . In metallic solid, thermal conduction results from the motion of unbound electrons, and there is close correspondence between thermal conductivity and electrical conductivity. • 在金属固体中热传导会使金属中的自由电子发生运动,因此金属的热传导系数和导电性之间有很密切的联系. • . In solids which are poor conductors of electricity, and in most liquids, thermal conduction results from the transport of momentum of individual molecules along the temperature gradient. • 在电的不良导体的固体中,在大多数液体中热传导会导致单个分子沿着温度梯度的动量的传递.

9. text • . In gases conduction occurs by the random motion of molecules, so that heat is “diffused” from hotter regions to colder ones. The most common examples of conduction is heat flow in opaque solids, as in the brick wall of a furnace or the metal wall of a tube. • 在气体中热传导可通过分子的自由运动来实现,因此热总是从高温区向低温区扩散,热传导最普通的例子就是热在不透明固体中的传递,如:在炉内砖墙的热传导或管子中金属面的传导.

10. text • . Simple example of conduction is shown in Fig 12. In Fig 12a, a flat-walled insulated tank contains a refrigerant at perhaps -11ºC, while the air outside the tank is at 27 ºC. • 传导中简单的例子在图12中得以体现,在图12(a)中,一个扁平的绝缘墙中装有制冷剂,可使墙内温度达到-11℃,而墙外空气的温度为27℃.

11. text • . The temperature falls linearly with distance across the layer of insulation as heat flows from the air to the refrigerant. Fig 12b shows a similar tank containing boiling water at 100 ºC, losing heat to air at 20 ºC. • 当热量从空气层传到制冷层时温度沿着绝缘层的距离直线下降,图12(b)表明,装有沸水的类似的墙,墙内的温度可达100℃,墙内的沸水向空气传递热量,可使空气的温度达到20℃.

12. Fig 12 Temperature gradient outside insulated tanks (a) heat flow into the tank; (2) heat flow from the tank

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