核心动力的英文力翻译力英语怎么说

外语更新时间:2025-02-23 12:10:21

播放的英文译语怎么说-i will be there

2023年4月18日发(作者：启发)2.5 Natural Convection
11Heat transfer involving motion in a fluid caused by the difference in density and the action of gravity is called
natural or free convection.
2Heat transfer coefficients for natural convection are generally much lower than for forced convection, and it is
therefore important not to ignore radiation in calculating the total heat loss or gain.
3Radiant transfer may be of the same order of magnitude as natural convection, even at room temperatures, since
wall temperatures in a room can affect human comfort.
24Natural convection is important in a variety of heating and refrigeration equipment:（1）gravity coils used in high
humidity cold storage rooms and in roof-mounted refrigerant condensers,(2)the evaporator and condenser of
household refrigerators, (3) baseboard radiators and convectors for space heating and(4)cooling 《凉州词》唐王翰翻译 panels for air
conditioning.
5Natural convection is also involved in heat loss or gain to equipment casings and interconnecting ducts and pipes.
36Consider heat transfer by natural convection between a cold fluid and a hot surface.
7The fluid in immediate contact with the surface is heated by conduction, because lighter and rises because of the
difference in density of the adjacent fluid.
8The motion is resisted by the viscosity of the fluid.
9The heat transfer is influenced by:(1) gravitational force due to thermal expansion,(2) viscous drag and (3)thermal
2.5自然对流
11传热流体密度和重力的作用的差异所造成的议案被称为自然
或自由对流。
2自然对流换热系数一般比强制对流低得多，因此，它是重要的不
能忽视，在计算总热量损失或增益的辐射。
3顺序相同数量级的自然对流，辐射传输可能，即使在室温下，因
为在一个房间的墙壁温度会影响人体舒适度。
24自然对流是很重要的各种供暖和制冷设备：（1）重力线圈用
在高湿度的冷藏室，并在屋顶安装制冷剂冷凝器，（2）家用电冰
箱蒸发器和冷凝器，（3）基板散热器和空间加热和对流（4）空调
冷却板。
5也参与了自然对流热损失或增益设备的外壳和连接管道和管道。
36考虑之间的冷流体和热表面的自然对流换热。
7传导被加热流体在表面直接接触，因为更轻，因为在相邻流体的
密度差异升起。
8该议案被抵抗流体的粘度。
9传热的影响：（1）由于热膨胀，（2）粘性阻力和（3）热扩散
diffusion.
10It may be expected to depend on the gravitational acceleration g, the coefficient of thermal expansion , the
kinematic viscosity (=/) ,and the thermal diffusivity =(/c).
p
11These variables can be expressed in terms of dimensionless numbers: the Nusselt number, Nu, is a function of the
product of the Prandtl number，Pr，and Grashof number，Gr， which，when combined，depend on the fluid properties，
the temperature difference between the surface and the fluid，t，and the characteristic length of the surface，L.
12The constant c and exponent n depend on the physical configuration and nature of flow.
413The entire 中国诗词大会2020 process of natural convection cannot三年级下册语文期末试卷及答案 be represented by a single value of exponent n, but can be
divided into three regions: (1) turbulent natural convection for which n equals 0.33, (2) laminar natural convection,
for which n equals 0.25 and (3) a region that has ( GrPr) less than for laminar convection, for which the exponent
n gradually diminishes from 0.25 to lower values.
14Note that, for wires, the (GrPr) is likely to be very small, so that the exponent n is 0.1.
515To calculate the natural convection heat transfer coefficient, determine (GrPr) to find whether the boundary
layer is laminar or turbulent, then apply the appropriate equation.
16The correct characteristic length indicated must be used.
17Since the exponent n is 0.33 for a turbulent boundary layer, the characteristic length cancels out, and the heat
transfer coefficient is independent of the characteristic length.
18Turbulence occurs when length or temperature difference is large.
19Since the length of a pipe is generally greater than its diameter, the heat transfer coefficient for vertical pipes is
larger than for horizontal pipes.
620Convection from horizontal plates facing downward when heated (or upward when cooled) is a specia关于端午节的传说 l case.
21Since the hot air is above the colder air, there is no theoretical reason for convection.
22Some convection is caused, however, by secondary influences such as temperature differences on the edges of
the plate.
23 As an approximation, a coefficient of somewhat less than half of the coefficient for a heated horizontal plate
facing upward can be used.
724Since air is often the heat transport fluid, simplified equations for air are given.
25Other information on natural convection is available in the general heat transfer reference.
826Observed differences in the comparisons of recent experimental and numerical results with existing correlations
for natural convective heat transfer coefficients indicate that caution should be taken when applying coefficients for
(isolated) vertical plates recommended by 桃花源记是鬼故事 ASHRAE for situations with vertical surfaces in enclosed spaces
(buildings).
27Improved correlations for calculating natural convective heat transfer from vertical surfaces in rooms under
certain temperature boundary conditions have been developed.
928Natural convection can affect the heat transfer coefficient in the presence of weak forced convection.
29As the forced convection effect强项令原文拼音 , i.e. , the Reynolds number, increases, the “mixed convection”(superimposed
forced-on-free convection) gives way to the pure forced convection regime.
30Since the heat transfer coefficient in the mixed convection calculation alone, attention is called to references on
combined free and forced convection heat transfer.
31The reference given before summarizes natural, mixed, and forced convection regimes for vertical and horizontal
tubes.
32Local conditions influence the values of the convection coefficient in a mixed convection regime, but the
references permit locating the pertinent regime and approximating the convection coefficient.

的引力。
10它可以依靠的重力加速度g，热膨胀系数，运动粘度（=/
），热扩散系数=（/cp）的。
11这些变量可以量纲数表示：努塞尔数，怒族，是普朗特数，镨，
格拉雪夫数，GR，其中，合并时，取决于流体性质，温度差的产品
的功能之间的表面和流体，T，表面特征长度，L。
12常数C和指数n取决于物理配置和流动的性质。
413整个自然对流过程不能代表1指数n的单值，但可划分为三
个区域：（1）动荡的天然对流而列印等于0.33，（2）层流自然对
流，而列印等于0.25和（3）有（GR•PR）小于层对流的一个区域，
其中指数n逐渐减退从0.25至较低的值。
14请注意，电线，（GR PR）可能是非常小的，这样的指数n为0.1。
515计算的自然对流换热系数，确定（GR•PR）寻找是否层流或湍
流边界层，然后应用相应的方程。
16必须使用正确的特征长度表示。
17由于指数n为0.33湍流边界层特征长度取消，其传热系数是独
立的特征长度。
18动荡发生时长或温差大。
19自管的长度一般是大于它的直径比水平管道，垂直管道的传热
系数较大。
620从横板朝下时，加热（或向上冷却时）对流是一种特殊情况。
21由于热空气冷空气以上，有没有对流的理论原因。
22然而，一些对流引起的，中学的影响，如板边缘上的温度差异。

23作为一种近似，有些超过一半了激烈的横板朝上系数系数都可
以使用。
724由于空气往往是热传输流体，空气简化方程。
25自然对流的其他信息是在一般的传热参考。
826在最近的实验和数值模拟结果与现有的自然对流换热系数的
相关性比较观察到的差异表明，申请在封闭的空间（建筑物）的垂
直表面的情况下由ASHRAE推荐的垂直板（隔离）系数时，应采取
谨慎。
27从房间中的垂直表面一定的温度边界条件下的自然对流换热计
算改进的相关性已经制定出来。
928自然对流的影响存在薄弱强制对流的传热系数。
29由于强制对流效果，即雷诺数的增加，“混合对流”（叠加被
迫自由对流）让位给纯强制对流制度。
30由于在混合对流单独计算的传热系数，注意力被称为联合自由
和强迫对流换热的参考。
31前参考总结了垂直和水平管自然，混合，和强迫对流制度。

32当地条件的影响在对流换热系数混合对流政权的价值，但引用
允许定位的有关制度和近似对流系数。