Vertical tube heat exchanger leakage
Thread Content
Recently I encountered a problem, that is, desalted water flows through the shell side of the vertical tube-type heat exchanger, and flue gas flows through the tube side. The flue gas temperature is 250-180°C, the water temperature is 35-95°C, and the water side pressure is 1.1Mpa. The flue gas is used on site from top to bottom, and the water is from bottom to top, forming an inverse relationship with the flue gas. The flow is carried out for heat exchange, but leaks have occurred at the welds between the heat exchange tube and the upper tube plate many times. I wonder if the local high temperature at the flue gas inlet is caused by the reverse flow. Now because the on-site flue gas pipeline is difficult to adjust, I hope to start from the water side. The water enters the upper part of the shell side and the water flows out of the lower part. Since this has not been arranged before? I have never seen such an arrangement in the books. Is there something wrong with it? I hope the experts from all walks of life can give me some advice.
Now considering changing from counter-current to co-current, I wonder if weld cracking can be avoided.
This may be related to frequent starts and stops, and it is more likely to be caused by repeated stress changes. It doesn't matter if it's parallel flow. The key is to see whether the manufacturing process, material and structure of the heat exchanger are reasonable. The corrosion of the flue gas also needs to be considered, for reference.
Parallel flow, the problem is more serious, as shown in the figure：
As far as heat exchange is concerned, a problem here is the length of the heat exchanger. If the temperature is changed on one side, there will be no flow direction. For reference.
Moving it downstream probably won't help. According to the poster's feedback, the leak occurs in the high-temperature area of the intake air. Let's do a laboratory analysis. It is estimated that corrosion is the main factor. Pulling off due to thermal stress should probably be the next best thing.
Demineralized water, there is no problem after testing
My equipment supplier was undergoing maintenance. The equipment was newly installed last year. It had not been used for 3 months. The post was shut down for maintenance and the equipment was out of service. Suddenly, it was discovered that there was a water leak. There was a "hole" in the tube, which was probably the size of a soybean grain.