This input determines the acceptable deviation from the median number of tubes per pass. This value is used in the tubesheet layout subroutine to determine the maximum number of tubes.
Ideally, it is desirable to have the same number of tubes in each pass when there is no change of phase on the tube side. However, for most layouts of more than two passes, this would require removing tubes which would otherwise fit within the outer tube limit. Since it is preferable to maximize the surface area within a given shell and minimize the possible shell side bypassing, a reasonable deviation in tubes per pass is usually acceptable.
It is recommended that you avoid large deviations since this gives significantly different velocities in some passes and wastefully increases the pressure drop due to additional expansion and contraction losses. Since the Aspen Hetran program bases the tube side
calculations on an average number of tubes per pass, such aberrations are not reflected in the thermal design. Default: 5 %
（d）Number of tie rods拉杆数
拉杆保持间隔，持有弓形折流板的地方。这种输入没有 在网格挡板的指（杆和带挡板）。
特马已转向横拉杆的最小数目的建议，这是一个函数 壳直径。额外的拉杆，有时希望阻止绕过沿通 划分车道或更好地锚的两倍或三倍的弓形折流板。 杨hetran程序将首先定位拉杆使他们不能取代任何
管。如果这是不可能的，它将取代管是必要的。程序只会 定位杆周围的维管束周围，不在bundle中。 默认值：TEMA标准
The tie rods hold the spacers, which hold segmental baffles in place. This input has no meaning in the case of grid baffles (rod and strip baffles).
TEMA has recommendations for a minimum number of tie rods, which is a function of the shell diameter. Additional tie rods are sometimes desirable to block bypassing along pass partition lanes or to better anchor double or triple segmental baffles.
The Aspen Hetran program will first try to locate the tie rods so that they do not displace any tubes. If this is not possible, it will then displace tubes as necessary. The program will only locate tie rods around the periphery of the bundle, not in the middle of the bundle. Default: TEMA Standards
（e）Number of sealing strip pairs密封条对数
密封条是用来减少在壳体内侧和最外侧的换热管之间的流体绕过壳体侧。在固定管板（L, M, & N rear heads，L, M, & N的后端结构）和U型管式换热器中，其壳体内侧和最外侧的换热管之间的间隙有一定的限制。因此密封条很少用于该类换热器。在内浮头（(S & T rear heads，钩圈式浮头和可抽式浮头的后端结构），外包装浮头（P rear head填料函式浮头后端结构）和浮头固定管板（(W rear head带套环填料函式浮头后端结构）热交换器中，在壳体内侧和最外侧的换热管之间的流体绕过壳体侧的潜力更大。在种情况下，需安装密封条。
默认值：没有为L，M，N，U，和W型后端结构不需密封条；S，T，P型后端结构每5排管需配置1对密封条。
Sealing strips are used to reduce bypassing of the shell side flow around the bundle between the shell ID and the outer most tubes. In fixed tubesheet (L, M, & N rear heads) and U-tube heat exchangers the clearance between shell ID and the outer tube limit is comparatively small. Therefore sealing strips are seldom used for these types. In inside floating head (S & T rear heads), outside packed floating head (P rear head), and floating tubesheet (W rear head) heat exchangers, the potential for bypassing is much greater. In these cases sealing strips should always be installed.
The thermal design calculations in Aspen Hetran assume that sealing strips are always present in P, S, T, & W type heat exchangers. Default: none for L, M, N, U, & W types 1 pair per 5 tube rows for S, T, & P types
（f）Minimum u-bend diameterU型管最小的直径
这是从中心管中心管，U型管可弯曲的最小距离。的 程序缺陷的管子外径的真正最小三次，一般最低安全 是一个功能的材料，管壁厚度，和弯曲过程。
这对热设计的一个重要的作用，因为它决定了管子的数目
在一个U型布局。
您也可以使用此输入力的程序来模拟一个U型布局的地方 内心的U型管安装在非正常的垂直平面角度（2次） 或水平面（4或更多）。然而，在这样做时，程序会高估 每经过一管数。 默认值：三倍管外径
This is the minimum distance from tube center to tube center that a U-tube can be bent. The program defaults to a generally safe minimum of three times the tube O.D. The true minimum is a function of the material, the tube wall thickness, and the bending process.
This has a significant effect on the thermal design, because it determines the number of tubes in a U-tube layout.
You can also use this input to force the program to simulate a U-tube layout where the
innermost U-tubes are installed at an angle other than the normal vertical plane (for 2 passes) or horizontal plane (for 4 or more passes). However, when doing this, the program will overpredict
the number of tubes by one for each pass. Default: three times the tube outside diameter
(g)Pass partition lane width隔板间距
通过划分车道之间的开放，通过从最外侧边缘的测量 一通中未来通管的最外层管。这种必要的距离
这是通过隔板的厚度的函数，在U形管的情况下，该 最小的直径。
程序默认为隔板厚度加3毫米或0.125。 该隔板的厚度是根据TEMA标准确定。 默认值：隔板厚度+ 3毫米或0.125。
The pass partition lane is the opening between passes as measured from the outermost edge of the tube of one pass to the outermost edge of a tube in the next pass. This necessary distance is a function of the thickness of the pass partition plate and, in the case of U-tubes, the minimum U-bend diameter.
The program default equals the thickness of the pass partition plate plus 3 mm or 0.125 in. The thickness of the pass partition plate is determined according to the TEMA standards. Default: pass partition plate thickness + 3 mm or 0.125 in.
(h)Location of center tube in 1st row第一排管中心位置
你可以选择管的位置排在第一位的是在中心线或中心。如果设置为 程序，管位将被设置在布管数最大化。 默认值：程序优化
You can select the tube position in the first row to be on the center line or off center. If set to program, the tube position will be set to maximize the number of tubes in the layout. Default: program will optimize
（i）Outer tube limit diameter布管限定圆直径（设计过程无用）
不管限定圆，只在优化模型中使用。
外管的极限（OTL）是圆的，没有超出部分的管的直径
将放。这只适用于额定输入模式。 在设计模式中，程序会忽略该项。
控制采用的一种方式，在评价和设计模式是 指定“壳ID挡板OD”和“挡板，外管直径限制” 在间隙/选项屏幕间隙。 默认值：程序将计算
The outer tube limit (OTL) is the diameter of the circle beyond which no portion of a tube will be placed. This input only applies to rating mode. In design mode, the program ignores this entry. An alternative means of controlling the OTL, in both rating and design mode is to specify the \Clearances in the Clearances/Options Screen. Default: program will calculate
（4）Layout Limits布置的限定
（a）Open space between shell ID and outermost tube壳体内径与最外侧换热管的间距
At top, S1最上端的间距 At bottom, S2最下端的间距 At sides, S3两侧的间距
可以指定外侧换热管与壳体的距离，也可以指定与壳体直径的百分比。 默认值：由最外侧管决定
You can control where the program will place tubes by specifying limits at the top of the bundle, bottom of the bundle, and/or both sides of the bundle.