Exercise 5.13 A heat exchanger is used to exchange heat between two streams a coolant with owrate q

 kgs is used to cool a hot stream with inlet temperature T

  C to the outlet temperature T which should be   C  The measurement delay for T is s The main disturbance is on T The following model in terms of deviation variables is derived from heat balances T s





s  

s  

q s



 s 

s  

s  

T s



where T and T are in C q is in kgs and the unit for time is seconds Derive the scaled model Is the plant controllable with feedback control

Solution The delay poses no problem
performance but the eect of the disturbance is a bit too large at high frequencies
input saturation so the plant is not controllable