This model simulates a simple continuous-time control system for the HRB. The water outlet temperature is controlled to the set point by a PI controller acting on the gas flow rate, rejecting the disturbances due to the changing water flow rate.
The system starts at steady state; at t = 50 s, the water flow rate is reduced by 10%; at t = 200 s, the water temperature set point is increased by 10 K.