Figure Consider the typical control system for the double effect evaporator shown in Figure 5. Manipulating the steam in the fi effect controls the composition of the product out of the last effect (control loop not shown). Step testing carried out on double effect evaporator gives the relationship between the concentrated solution's composition and the steam flow rate 17.5e -2.755 Op = 5.0s + 1 while the relationship between the concentrated solution's composition and the feed density is given as: 12.8e-1.65 Id = 2.5s + 1 The sensor/transmitter has a dynamics expressed by: 0.12 9m = 0.008s + 1 Valve dynamics can be assumed negligible