Seeking help regarding common errors in HTRI
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Hello, everyone in the marine community. I encountered some error messages during the HTRI simulation, and I hope experts can help me resolve them. Thank you. The issues are as follows: 1. What is the definition of R-V-SQ, and what is its physical meaning? 2. For fluids with a very high fouling coefficient, the software suggests entering the thickness of the fouling layer. What is the basis for entering this thickness, and where should it be entered? Will the software stop using the dirt coefficient for calculations after the thickness is entered? 3. When I was calculating a horizontal single-pass reboiler, I encountered the error message “Stratified flow: 2 baffle spaces are predicted to be under phase separation. Phase separation can lead to poorer than predicted performance because correlations assume a well-mixed flow. Phase separation can also lead to partial tube dryout, which can cause tube damage. (MN 2056)”. I’m not quite sure how to resolve this error. 4. When calculating the condenser, since the gas phase flows in the shell side, I had to increase the spacing between the baffle plates in order to enlarge stream B. However, if the spacing between the baffle plates is too large, an alarm is triggered indicating an excessively large unsupported span. How can this issue be resolved? 5. When calculating the kettle-type reboiler, the following error occurs: The crossflow velocity exceeds 80% of the critical velocity, indicating that fluidelastic instability and flow-induced vibration damage are possible. Fluidelastic instability can lead to large-amplitude vibrations and tube damage. (MN 0013) What is the cause of this issue? How should it be handled? I earnestly ask the experts here to kindly provide guidance regarding the above errors! Including, if anyone has any questions, they can post them as well; we can exchange ideas and learn together*
1. In HTRI, R-V-SQ usually refers to the square of the effective radial velocity of heat conduction. The physical meaning is to consider the radial flow rate of the fluid within the pipe. 2. The input for the fouling layer thickness is usually based on actual operational experience or design guidelines, and can be entered in the fouling model settings of HTRI. After entering the thickness, the software will take into account both the dirt coefficient and the thickness in its calculations. 3. This error indicates that during calculation, phase separation between the two baffles is predicted, which may result in performance below expectations. Solutions may include adjusting design parameters such as flow rate and baffle spacing to reduce phase separation. 4. The problem of excessive unsupported span caused by too large a spacing between baffle plates can be addressed by adding support structures, or by using other methods to reduce the span, such as increasing the number of baffle plates. 5. A cross-flow velocity exceeding 80% of the critical velocity may cause fluid-elastic instability and flow-induced vibration damage. To solve this problem, one can try reducing the flow rate or enhancing the fixation and support of the pipes. .
Expert, thank you for sharing; I’ve learned something
Thank you for sharing, I really appreciate it
Regarding the vibration issue: I recently was calculating a condenser and noticed that the Vortex shedding ratio and Turbulent buffeting ratio have asterisks next to them at the inlet of the shell side, as shown in the figure below. A error message was also displayed. What could be the cause of these abnormal values? I’ve heard others give lectures saying that as long as the Chen number isn’t high, it’s fine. But can these two numbers really be ignored? I have now changed the heat exchanger type to BXS, with four inlets and four outlets, but the problem still persists. Since this is part of the external process package, I’m not able to change the size of the equipment at will. Therefore, I would be extremely grateful if anyone could offer some advice
Acoustic vibration problems are usually caused by vortex shedding and turbulence (buffeting) that occur as fluid flows through the tube bundle. The vortex shedding ratio and the turbulent buffeting ratio are two parameters used to assess acoustic vibration risks. The asterisks next to these two parameters indicate that they are outside the range recommended by HTRI. The error message indicates a possible vibration issue, which can affect the safe operation of the device. The Chen number is indeed an important parameter, but it is not the only factor to consider. Even if the Chen number is not high, the above parameters cannot be ignored if they are too high. Since the size of the equipment cannot be changed, the following measures can be tried: – Reduce the liquid flow rate to minimize the disturbances caused by the fluid. - Adjust the tube bundle layout to change the fluid flow path and reduce vortex formation. - Increase the distance between the tube bundle and the shell to give the fluid more space to flow. - Increase the baffles or change their angle to reduce the fluid impact on the tube bundle. If the problem cannot be resolved even after adjusting the parameters, professional acoustic vibration analysis may be required to find a more specific solution. .
Thank you all for your replies. I encountered the following issue while calculating the reboiler: what is the meaning of the ratio of this threshold to the actual liquid inflow rate? Where can I find the raw data for the ratio of threshold to inflow rate?
The ratio mentioned in the calculations related to reboilers, which is the ratio of the threshold value to the actual liquid inflow rate, generally refers to the comparison between the operating parameters of the reboiler and its design or safe operating thresholds. This ratio helps to determine whether the current operating conditions exceed the limits set by the device’s design, and it can also indicate potential performance issues or safety hazards. Generally, such threshold data comes from design standards, experimental data, or performance parameters provided by the manufacturer. In the HTRI software, it may be necessary to refer to the guidelines or user manuals provided by the software in order to find specific threshold information. Sometimes these values also need to be determined based on specific process conditions and experience. If you cannot find the original data in the software, it is recommended to consult the device design documents, contact the device manufacturer, or refer to industry standards. In actual process operations, these thresholds can also be determined through experiments or on-site data. .