การวิเคราะห์ความเสถียรของหอระเหยแบบฟิล์มตกโดยทฤษฎีพาสสิวิที

Stability Analysis of Falling Film Evaporators with Passivity Theorem

Name: รุ่งโรจน์ ศิริศักดิ์

Organization : มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี

Name: Rungroat Sirisak

keyword: Falling film evaporator

; Stability analysis

; passive

; passivity theorem

; Simulink model

Abstract: The passivity theorem is studied and implemented in this thesis through real-word processing; Kiwi co-op Dairies Ltd. in New Zealand. The production of milk powder can be separated into two parts. First is a falling film evaporator which most of water is evaporated from the feed milk. Second is a spray dryer to produce the milk powder. In this work, only the falling film evaporator was used in the stability analysis with passivity theorem. The mathematical model represent the falling film evaporator included the matrix transfer function of the process between five controlled variables and five manipulated variables. The controlled variables are the temperature of direct steam injection unit (Tdsi), the temperature of thermal vapor re-compression final effect (Te1), the temperature of mechanical vapor re-compression evaporator (Te3), the dry matter of mechanical vapor re-compression product (wp5) and the dry matter of thermal vapor re-compression product (wp8). The manipulated variables are steam mass flowrate of direct steam injection unit (mdsi), heat exchanger condensate flowrate (Mc), vacuum condenser water flowratre (Mvac), mechanical vapor re-compression compressor speed (Ncomp) and thermal vapor re-compression steam pressure set-point (Psp). The best control pairing in the stability point of view which is mdsi-TDSI / Mc-Te1 / Mvac-Te3 / Ncomp-wp5 / Psp-wp8 was determined by the passivity index and check with Niederlinski Index. Also the passive controllers in each control loops were determined. The transfer function of controller in control loop 1, 2 and 3 are while the transfer function of controller in control loop 4 and 5 are respectively. The simulink model was developed to verify the results and showed that even the loop failure, the process can be drived to stable state. This results also check with Nyquist plot. However the designed controllers are low performance since there do not have the integral mode and low gain.

มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี

Address: กรุงเทพมหานคร (Bangkok)

Email: info.lib@mail.kmutt.ac.th

Name: Assoc.Prof.Thongchai Srinophakun

Role: Supervisor

Created: 2545

Issued: 2005-10-03

Modified: 2006-05-10

วิทยานิพนธ์/Thesis

ISBN: 9744562005

CallNumber: CHE1361

tha

DegreeName: วิทยาศาสตรมหาบัณฑิต

Level: ปริญญาโท

Descipline: วิศวกรรมเคมี

Grantor: มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี

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