The positive and negative issues of the pulling force between the heat exchange tube and the tube sheet
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When the pull-out force q value for the connection between the heat exchange tube and the tube sheet is positive, does it indicate that the force exerted by the tube sheet on the heat exchange tube is a pulling force or a compressive force?
It seems that pulling force is an absolute value, with no concept of positive or negative. If one must discuss positive and negative values, it is necessary to consider whether the axial stress on the heat exchange tubes is positive or negative under various operating conditions, in order to determine the non-absolute value of the pulling force.
I believe tensile force is a shear stress, and it is neither necessary nor appropriate to define whether it is positive or negative.
The shell side temperature is high, causing the tubes to be in tension; otherwise, they are under compression. However, I don’t have any other information available at the moment, so it’s difficult for me to answer the original poster’s question.
This post was last edited by onion1986 on 2009-8-24 at 16:51. 2# Wen Bing: As mentioned in the third comment, the calculation method used for 151 can yield positive or negative values; however, when comparing it with the allowable stress, the absolute value is used. This positive and negative issue is really troublesome; it happens in many places. And what we’ve calculated are the conditions under various operating scenarios. Sister, if you have any advice, please share it.
5# onion1986 Isn’t this much easier? Whether positive or negative, all adjustments just need to be made toward zero. The sign of the pulling force should be the same as the sign of the axial stress in the heat exchange tube, and the axial stress also takes positive or negative values under different conditions
6# Wen Bing: Then please tell me, when the axial force is positive, does it mean that the heat exchange tube expands or contracts relative to the tube sheet?