热能与动力工程专业英语翻译2.6.docx

Every free surface emits energy in the form of electromagnetic waves; the amount of energy is a function of the surface temperature. This emitted energy is known as radiant thermal energy. The nature of this radiant energy is not completely understood, but laws have been formulated that describe its behavior. It is recognized that, as with other forms of radiant energy , radiant heat energy is transmitted in the form of electromagnetic waves. The complete formulation of the laws governing radiant heat energy must consider that this energy is quantized, that is, the energy is transferred in quanta. In contrast with other modes of heat transfer, no medium is required to transmit radiant energy. In fact some gases, for instance, carbon dioxide and water vapor, absorb some of the radiant energy passing through them.每一个自由表面都会以电磁波的形式发射能量，能量的量是表面温度的函数。这种发射的能量被称为辐射热能。这种辐射能的性质是不完全理解的，但已经制定了法律，描述其行为。这是公认的，与其他形式的辐射能，辐射热能以电磁波形式传播。控制辐射能的法律的制定必须考虑到这种能量是量子化的，即，能量转移量子。与其他模式相比，传热，无需介质传输辐射能。事实上，例如，二氧化碳和水蒸气，吸收一些辐射能通过它们。 For a fixed set of conditions, any free surface emits radiant energy of varying wavelengths. The frequency of vibration (v) of radiant waves is dependent solely on the source of radiation and is independent of the medium through which they pass. The velocity of radiant waves is a function solely of the medium through which they pass. Thus, the wavelength is a function of both the source and the medium.对于一个固定的条件，任何自由表面发射的辐射能的不同波长。辐射波的振动频率是完全依赖于辐射源，是独立的介质，通过它们传递。辐射波的速度是一个函数的介质，通过它们传递。因此，波长是源和介质的函数。 All free surfaces receive radiant energy from all other surfaces that they can “see,” that is , surfaces in direct line of sight. Most problems in radiant deal with the net radiant energy exchanged between a given surface and those that surround it. In common parlance, the term ”heat exchanged by radiation” is used. It must be emphasized, however, that radiation is not heat. Heat is conducted to a surface. By virtue of the temperature of a surface, electromagnetic waves transmit energy from the surface. When these strike another surface, part of the energy will be absorbed, tending to increase the temperature of the surface struck by them, and part will be reflected. When the object is transparent, or partially so, to radiant waves, some of all of the radiant energy received by the surface will pass into the object . The transparency of an object to radiant energy is a function of the wavelength of the radiant waves. these statements relating to the radiant energy received by a surface may be put in equation from as follows:所有的自由表面都会得到所有其他表面的辐射能，即它们能“看见”，即直接在视线中的表面。在一个给定的表面和周围的人之间的净辐射能量交换的最问题。在共同的说法，“辐射热交换”的使用。但是，必须强调的是，辐射是不热的。热传导到表面。借助于表面的温度，电磁波从表面发射能量。当这些撞击到另一个表面时，部分能量会被吸收，倾向于增加表面的温度，并且部分将被反射。当对象是透明的，或部分如此，辐射波，部分的辐射能接收到的表面，将传递到对象。一个物体的透明度是辐射波的波长的函数。这些与表面接收到的辐射能有关的陈述可以从如下的方程中被放置：Where a=absorptivity, or the portion of the radiant energy that is absorbed;P=reflectivity , or the portion of the radiant energy that is reflected;T=transmissivity, or the portion of the radiant energy that is transmitted.=吸收，或是吸收的辐射能量的一部分；=反射率，或反射的辐射能的一部分； =透射率，或是发射的辐射能量的一部分。 A black surface has an absorptivity close to unity. For this reason the term blackbody has been used to designate an imaginary object whose surface has an absorptivity of unity. Since no known surface completely absorbs radiant energy ,the term blackbody refers to an ideal surface. kirchhoff conceived a method of completely absorbing radiant energy. Assume that a hollow sphere contains a very small opening , an is indicated in fig2.4 Radiation entering this opening will be received by the back wall of the sphere. Here it will be partially absorbed and partially reflected to other parts of the walls of the sphere. The reflected waves are , in turn ,partially reflected , so that each reflected portion is a progressively smaller portion of the energy entering the sphere until ultimately all of it is absorbed. Strictly speaking , some of the reflected radiant energy will pass out through the hole. However ,the surface area of the sphere is .Hence , when the diameter of the sphere is chosen to be 50 times that of the opening, the inside surface area is 10000 times that of the opening, and it may be assumed that the hollow sphere absorbs all of the radiant energy.黑色表面的吸收率接近于1。为此，该词已被用来指定黑体的一个虚构的物体表面有一个统一的吸收率。因为没有已知的表面完全吸收辐射能，术语黑体是一种理想的表面。基尔霍夫设想了一种完全吸收辐射能的方法。假定一个空心球体包含一个非常小的开放，一个是fig2.4辐射进入这个开放将由球体的后墙送达。在这里，它将部分地被吸收，部分地反映到球体的其他部分。反射波，反过来，部分反射，因此，每个反射部分是一个逐渐变小的部分的能量进入球体，直到最终所有的它被吸收。严格地说，一些反射的辐射能通过这个孔。然而，球体的表面积是，因此，当球体的直径被选择为50倍，开口，内部的表面积是开放的10000倍，并且它可以假定，中空球体吸收所有的辐射能。 The amount of radiant energy emitted by a surface is a function of the nature of the surface and its temperature. The term blackbody is also used to denote a surface that emits the maximum conceivable amount of radiant energy at any given temperature. There is no actual surface that is a perfect emitter, but the hollow-sphere concept may be used to establish a standard. The process of emission from the inner surface of the sphere is the reverse of that of absorption.由表面发射的辐射能的量是表面的性质和温度的函数。该术语也用于表示黑体表面放射出最大数量的辐射能可能在任何给定的温度。没有实际的表面，这是一个完美的发射器，但空心球概念可以用来建立一个标准。从球体内表面发射的过程是吸收的反向。 The total radiant energy emitted in a unit time by a unit area is known as the total