If you have not installed COMSOL 3.2 ECRE, load the COMSOL 3.2CD-ROM and follow the instal...

If you have not installed COMSOL 3.2 ECRE, load the COMSOL 3.2

CD-ROM and follow the installation instructions discussed in P8-2A(n).

(a) Before running the program, sketch the radial temperature profile down a PFR for (1) an exothermic reaction for a PFR with a cooling jacket and (2) an endothermic reaction for a PFR with a heating jacket.

(b) Run the COMSOL 3.2 ECRE program and compare with your results in (a). Double-click on the COMSOL 3.2 ECRE icon on your desktop. ln the Model Navigator, select the model denoted “3-Non-Isothermal I” and press OK. You can use this model to compare your results in (1) and (2) above. You can select “Documentation” in the “Help” menu in order to review the instructions for this model and other models in COMSOL ECRE.

Change the velocity profile from laminar parabolic to plug flow. Select “Scalar Expressions” in the “Expression” menu item in the “Options” menu. Change the expression for uz (the velocity) to “uO” (replace the expression “2*uO*(l-(r/Ra)2)”, which describes the parabolic velocity profile). Press “Apply”.

You can now continue to vary the input data and change the exothermic reaction to an endothermic one. (Hint: Select the “Constants” menu item in the “Options” menu. Do not forget “Ta0” the jacket temperature at the end of the list). Write a paragraph describing your findings.

(c) The thermal conductivity in the reactor, denoted “ke” in Figure E8-12.1, is the molecular thermal conductivity for the solution. In a plug flow reactor, the flow is turbulent. In such a reactor, the apparent thermal conductivity is substantially larger than the molecular thermal conductivity of the fluid. Vary the value of the thermal conductivity “ke” to learn its influence on the temperature and concentration profile in the reactor.

(d) In turbulent flow, the apparent diffusivity is substantially larger than the molecular diffusivity. Increase the molecular diffusivity in the PFR to reflect turbulent conditions and study the influence on the temperature and concentration profiles. Here you can go to the extremes. Find something interesting to turn in to your instructor. See other problems in the web module.

(e) See other problems in the web module.