Optimal control of a freeze Dryer—II: Dynamic analysis

✍ Scribed by R.J. Litchfield; A.I. Liapis

• Book ID: 103006556
• Publisher: Elsevier Science
• Year: 1982
• Tongue: English
• Weight: 729 KB
• Volume: 37
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(82)80066-3

✦ Synopsis

The unsteady state model and Lagrangian equations of the freeze-drying process presented in Part 1[4],

havebeen solved for non-fat reconstituted milk and turkey, using the control strategies presented in[4]; the results were then used to evaluate the coefficients representing the necessary conditions of optimality. The results for non-fat reconstituted milk confirm the results of the quasi-steady state analysis[4], except for a time segment very close to t =O. Simulations with turkey breast showed similar results at low pressures, but it was found that at higher pressures the assumed control policies which were based on a quasi-steady state analysis[l], were not optimal

The non-steady state results indicate that for turkey, intermediate rather than maximum, pressure control policies were optimal for cases (a) and (b) in [4]. However, in practice these optimal pressure policies might produce only minor improvements in drying time when compared with a near optimal policy. It was also found that changes in the interface constraint affected drying times only marginally, but that large heaters operating under optimal control had a pronounced effect on the drying time.