Consequences of excessive heat exchanger margin
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According to available information, the margin for heat exchangers is between 10% and 20%. What are the consequences if this margin is too large, exceeding 20%?
1. High cost! 2. The heat exchange efficiency does not improve much!
The consequence is increased costs, but it has indeed been seen that the margin can reach 50% or even higher
A margin of 10%–20% is reasonable, as future corrosion and scaling need to be taken into account; essentially, it operates at full load. Beyond this range, first, it increases equipment investment ； Second, it provides more space for installation and maintenance ； Third, there is a matching issue with the entire process system.
The actual operating load is half of the designed value, which results in the heat exchanger requiring a much smaller heat exchange area than what was designed; the margin in this regard is 55%. Yet, the temperature at the outlet of the heat exchanger is 20°C lower than the designed value. If the heat exchange area is sufficient in theory, then why isn’t the temperature at the outlet reaching the designed level?
Will the heat exchange efficiency deteriorate if the margin is too high?
As the pipe flow velocity decreases, the heat transfer coefficient drops!
This issue is likely caused by an excessive deviation in the heat transfer coefficient K value during the calculation; it is necessary to redo the calculation.