Heat Exchanger

Heat exchangers are devices built for efficient heat transfer from one medium to another and are widely used in engineering processes. Some examples are intercoolers, pre-heaters, boilers and condensers in power plants.
Application
The hot tube side and cool shell side liquids do not mix. Rather, the cooling liquid surrounds the hot tubes and pulls off heat energy as it passes through the exchanger. As the flow rate of cooling liquid around the tubes increases (as the valve opens), more heat is removed and the temperature of the exiting hot liquid decreases.
A side stream of warm liquid combines with the hot liquid entering the exchanger and acts as a disturbance to our process in this case study. As the warm stream flow rate increases, the mixed stream temperature decreases (and vice versa).
The measured process variable (PV) is the hot liquid temperature exiting the exchanger. The controller output (CO) signal moves a valve to manipulate the flow rate of cooling liquid on the shell side to maintain the PV at set point (SP). The warm liquid flow acts as a disturbance (D) to the process.