What are the problems with an excessively large heat exchanger area?
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The plant has an evaporation process: the material is heated to saturation temperature in the tube side of a shell-and-tube heat exchanger, and then enters the evaporation chamber where it evaporates； Saturated steam is used as the heating medium and is condensed in the shell side of the shell-and-tube heat exchanger ； The calculated heat exchange area of around 100 m2 should be sufficient ； Now, it is necessary to make use of the old shell-and-tube heat exchanger equipment. The heat exchange area of these old exchangers is 200 m2, which is much larger than the value calculated; can these old devices be utilized? What problems will arise?
It can be used, but the operation is rather difficult as steam flow rate needs to be controlled.
As long as impurity deposition and blockage do not occur due to too low flow rates of the medium, there is no problem. However, it is not feasible either if the heat exchange area is too small, as scaling and blockage tend to occur easily in such cases, and it becomes difficult to meet the requirement of performing maintenance every 3 to 4 years. We also have ones that use a heat exchange area more than three times the calculated value.
It can be used to control the amount of steam used; in addition, the issue of a reduced heat transfer coefficient of the heat exchange tubes due to equipment aging must also be taken into account. Operation may be difficult at first, but the evaporation requirements can still be met
It should work, but you need to clean your old device. Old equipment suffers from significant scaling, yet standard process calculations do not take into account scaling in old equipment; they only account for the scaling that occurs in new equipment. And the amount of scaling has a significant impact on the heat exchange performance of the equipment.