Abstract
The aim of the paper is a steady-state inverse heat transfer problem for
plate-fin and tube heat exchangers. The objective of the process control
is to adjust the number of fan revolutions per minute so that the water
temperature at the heat exchanger outlet is equal to a preset value. Two
control techniques were developed. The first is based on the presented
mathematical model of the heat exchanger while the second is a digital
proportional-integral-derivative (PID) control. The first procedure is
very stable. The digital PID controller becomes unstable if the water
volumetric flow rate changes significantly. The developed techniques were
implemented in digital control system of the water exit temperature in a
plate fin and tube heat exchanger. The measured exit temperature of the
water was very close to the set value of the temperature if the first
method was used. The experiments showed that the PID controller works also
well but becomes frequently unstable.
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