传热(APS审核课程准备)

Learned different ways of heat transfer, including heat conduction, heat convection and heat radiation

因为过程设备中经常涉及到热量传递

Because heat transfer is often involved in process equipment

●热传导heat conduction

定义：由于物体各部分之间不发生运动，仅依靠分子的热运动而产生的热能传递

Because there is no movement between the parts of the object, only the heat energy generated by the thermal movement of molecules is transferred

傅里叶导热定律导热速率的大小与该处的温度梯度、导热面积成正比，负号表示其方向与温度梯度的方向相反。Q热传导速率（单位时间传导的热量）W，λ为热导率（传热系数，表示物体导热能力的大小）W/（m·℃），S导热面积m²，温度梯度。

●分类

稳态导热Steady heat conduction Temperature does not change with time

非稳态导热Transient conduction Temperature change with time

毕渥数：Bi=h(V/A)/λ，反映物体内部温度的分布规律。h表面传热系数

It reflects the distribution law of the internal temperature of the object. H surface heat transfer coefficient

●热对流Thermal convection 是指存在温差时，流体宏观流动引起的冷、热流体相互掺

混所导致的热量迁移It refers to the heat transfer caused by the mixing of cold and hot fluids in the presence of temperature difference

定律（公式）牛顿冷却定律：单位面积的换热量与壁面和流体之间的温度差成正比Newton's cooling law: the heat exchange per unit area is directly proportional to the temperature difference between the wall and the fluid

Φ=h·A·Δt Φ为总传热速率，W ；h为表面传热系数，W/（m²·℃）；A为总传热面积，m²

●热辐射Thermal radiation

●定义：物体具有热量，向外辐射电磁波，从而进行传热. Definition: the object has heat

and radiates electromagnetic wave to carry out heat transfer

太阳向地球传热，真空中唯一的传热方式

Heat transfer from the sun to the earth, the only way of heat transfer in vacuum 热量传递不需要介质：真空中唯一的传热方式物体的固有属性：任何物体的温度只要大于绝对零度，都会向外辐射热量绝对零度0K=-273.15℃ 存在能量形式的转化：热能和电磁波之间。在物体内部，热量以内能形式存在，物体之间时，以电磁波为载体传递辐射能

绝对零度0K=-273.15℃

热辐射到物体上发生吸收、反射、透射Absorption, reflection and transmission of heat radiation to objects

黑体辐射定律：斯蒂芬—玻尔兹曼定律：确定黑体辐射力（单位时间内从物体的单位面积上发出的辐射能）

Blackbody radiation law: Stephen Boltzmann's Law: determining blackbody radiation force (radiation energy per unit area of an object per unit time)

吸收率=1：黑体

反射率=1：白体Absorptivity = 1: blackbody

Reflectivity = 1: white body