过程装备与控制工程专业英语第十九课第二篇课文完整翻译

19 Shell-and-Tube Heat Exchangers

壳式和管式热交换器

Shell-and-tube exchangers are made up of a number of tubes in parallel and series through which one fluid travels and enclosed in a shell through which the other fluid is conducted. The shell side is provided with a number of baffles to promote high velocities and largely more efficient cross flow on the outsides of the tubes. The versatility and widespread use of this equipment has given rise to the development of industrywide standards of shich the most widely observed are the TEMA standards. A typical shell-and-tube exchanger is presented on Fig. 4. 3.

壳式和管式热交换器是由一定数量的平行管和一个能够提供液体流过的外壳而组成的。在换热器的外壳里面我们安装了一定数量的隔流挡板，以促进管壳之间的液体流动的湍去程度，从而在很大程度上提高传热的效率。多功能性的换热器设备的广泛使用极大地促进了制造业的高度发展，图4.3是一个典型的管壳式换热器的例子。

Baffle pitch , or distance between baffles, normally is 0. 2~1. 0 times the inside diameter of the shell. Both the heat transfer coefficient and the pressure drop depend on the baffle pitch, so that is selection is part of the optimization of the heat exchanger. The window of segmental baffles commonly is abort 25%, but it also is a parameter in the thermal-hydraulic design of the equipment.

换热器的隔流挡板之间的距离通常是0.2到1倍的壳体内径的大小，隔流挡板的间距不仅影响了换热器的传热效率，还影响着管壳间的液体压降的大小，所以设计或是选择换热器的时候我们要选取最佳方案。窗口节段性挡板流产通常是25 ％，但设备的挡板尺寸通常也要考虑到液体压降的问题。

In order to simplify external piping, exchangers mostly are built with even number of tube passes. Partitioning reduces the number of the tubes that can be accommodated in a shell of a given size. Square tube pitch in comparison with triangular pitch accommodates fewer tubes but is preferable when the shell side must be cleaned by brushing.

为了简化换热器的外部管路系统，大多数的换热器一般都不仅仅是一个管程数，多管程数的换热器减少了单壳壳和管子数，可以使换热器能够适应更多情况下的工作条件，方形管心距排列管子与三角形管子排列对比来说，虽然没有后者排列的管子数多，但却更容易污垢的清洁。

Two shell passes are obtained with a longitudinal baffle. More than two shell passes normally are not provided in a single shell, but a 4~8 arrangement is thermally equivalent to two 2~4 shells in series, and higher combinations is obtainable with shell-and –tube exchangers, in particular: 两壳程的换热器的壳内是一块纵向的挡板，但当换热器的壳程大于二时，通常就不仅仅有一块纵向的挡板了，一般情况来说，一个四到八程的换热器的传热当量相当于两个二到四程的换热器的传热量，较高的组合可与管壳式换热，特别是：

● Single phase, condensation or boiling can be accommodated in either the tubes or the shell, in vertical or horizontal positions.

单相，凝结或沸水等到不同条件下的换热器的管壳设计都是不同的，还有是纵向安置或是垂直安置。

● Pressure range and pressure drop are virtually unlimited, and can be adjusted independently for the two fluids.

压力范围和压降是没有范围限定的，并且是两个可调节的液体。

● Thermal stresses can be accommodated inexpensively.

能够适应一定的热应力范围

● A great variety of materials of construction can be used and may be different for the shell

and tubes.

结构的制造可以使用多种材料，并且换热器的壳和管子也可以是不同材料来制作的。

● Extended surfaces for improved heat transfer can be used on either side.

在换热器的内外都可以通过增加传热面积来提高传热效率。

● A great range of thermal capacities is obtainable.

能够提供相当大的热容量。

● The equipment is readily dismantled for cleaning or repair.

设备是可以拆卸修理和清洗的。

Several considerations may influence which fluid goes on the tube side or the shell side.

The tube side is preferable for the fluid that has the higher pressure, or the higher temperature or is more corrosive. The tube side is less likely to leak expensive or hazardous fluids and is more easily cleaned. Both pressure drop and laminar heat transfer can be predicted more accurately for the tube side. Accordingly, when these factors are critical, the tube side should be selected for that fluid.

下面讨论几个影响液体在管子内和壳层内流动的问题。

首先是，高压，高温或是强腐蚀性的液体更适合在管程内流动。相比来说，管程的使用更经济，更安全，也更容易清洗。这两个层压力降和传热在很大程度上是由管程来决定的，因此，，当这些因素是至关重要的，管子应选择这一流体。

Turbulent flow is obtained at lower Reynolds numbers on the shell side, so that the fluid with he lower mass flow preferably goes on that side. High Reynolds numbers are obtained by multipassing the tube side, but at a price.

壳程流动的液体通常都是流动雷诺数较低那种液体，因此，低湍动程度的流体更适合走壳程。高湍动程度的流体走管程。

A substantial number of parameters is involved in the design of a shell-and –tube heat exchanger for specified thermal and hydraulic conditions and desired economics, including: tube diameter, thickness, length, number of passes, pitch, square or triangular; size of shell, number of shell baffles, baffle type, baffle windows, baffle spacing, and so on. For even a modest sized design program, it is estimated that 40 separate logical designs may need to be made which lead to different paths through the logic. Since such a number is entirely too large for normal computer process, the problem must be simplified with some arbitrary decisions based on as much current practice as possible.

相当多的参数是参与设计的管壳式换热器的指定热和水力条件和理想的经济效益，包括：管直径，厚度，长度，程数，高度，管子排列形状（方形或三角形），外壳的直径，壳程数，隔流挡板数，挡板形状，隔板间距，等等。即使优良的的设计项目，至少需要有四十个独特的设计地方。

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