The model recieves an input signal Q_in
which is the heat flow rate that has to be extracted from the fluid. Before the heat flow rate is extracted, the input signal passes through a limiter block with an upper and lower limit.
The upper limit ensures that the return temperature does not drops down to a value under a minimum temperature TDHNMin
defined from outside.
The lower limit is in general set to 0 in order to avoid the block to cool the fluid.