Selection issues for plate heat exchangers
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When studying*, I came across a heat exchanger, and the questions are as follows: 1. The purpose of this heat exchanger is to condense water vapor into a liquid, reducing the temperature from over 100 degrees Celsius to 95 degrees Celsius. In the original text of the introduction, it says “both condense and sub-cool the stream”; I’m not quite clear about what is meant by sub-cooling. It is also for this reason that plate heat exchangers were recommended. 2. The heat-side inlet pipe of the heat exchanger has a diameter of 14", while the outlet pipe has a diameter of 4". At the inlet, there is a 1" pipe that leads to the vent line, and a manual valve is installed on this pipe. Regarding the function of the pipeline, the manual states that it is to prevent the agglomeration of gas without condensation. The inlet pipeline is 14\", and this 1\" pipeline is located on the inlet pipeline rather than on the heat exchanger; moreover, the pipeline size of 1\" seems a bit small. I’m not quite sure what the function of this pipeline is. Since the exchanger is required to both condense and sub-cool the stream, a Compabloc exchanger is preferred. For alternative types of exchangers, it may be necessary to use two separate exchangers, one for condensation and another for sub-cooling. A vent line to the AV is required to prevent the accumulation of non-condensable vapors. Please help! gratitude
For your reference, here is my understanding: 1. The condenser is a device that condenses steam, while the sub-cooler is used to cool the condensed liquid to a specified temperature. Due to its complex channels, the plate exchanger can achieve excellent heat transfer efficiency even when the flow rate of the condensate is very low. So a set of plate exchangers can serve two functions at the same time. 2. After condensation, the steam contains a small amount of non-condensable gases (such as oxygen), which can affect the heat exchange efficiency of the resulting condensed liquid. So it needs to be discharged in a timely manner. As for why it is being imported, more information is needed to determine that.
Thank you! Based on your answer, may I understand that as the hot fluid passes through the front section of the heat exchanger, it changes from gas to liquid, which is a process of condensation; however, the temperature at this point has not yet reached the required level of 95°C. In the subsequent section, the fluid is then sub-cooled to reach the desired temperature? The doubt regarding the second question is whether a 1-inch vent pipe, given that the pipeline at the inlet side is 14 inches in diameter, will be sufficient to serve its purpose. Also, since the 14-inch pipeline is filled with gas, can venting at this point remove the gas that has accumulated inside the heat exchanger?
Have you considered thinking in a different way? Perhaps this pipeline isn’t used during operation. It is merely a process auxiliary pipeline, such as exhaust gas during startup and shutdown.