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Title:Dynamic modeling, validation, and control for vapor compression systems
Author(s):Pangborn, Herschel C.
Advisor(s):Alleyne, Andrew G.
Department / Program:Mechanical Science & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):Vapor compression system
Heat exchanger model
Humidity model
Model-based control
Switched linear control
Abstract:This thesis traces the complete process of model-based control design for vapor compression systems (VCSs), from nonlinear model development to linearization and control formulation. Addressing gaps in the previous literature, the equations behind each model and control approach are clearly stated and emphasis is placed on conducting experimental validation at every stage. Both finite volume and switched moving boundary approaches for nonlinear control-oriented heat exchanger modeling are presented, illustrating the key differences in the method of discretization between these approaches. Practical considerations for the numerical implementation of these approaches in simulation are also provided. A detailed linearization of the switched moving boundary approach leads to the creation of a family of four-component linear models for different modes of operation of a VCS. The nonlinear and linear models are then validated with experimental data to reveal the tradeoffs of each. Furthermore, an augmentation to the switched moving boundary method is derived which captures the effects of air humidity. Experimental validation demonstrates that this augmented model more accurately predicts both air-side and refrigerant-side outputs at high humidity in addition to providing accurate predictions of liquid condensate formation and air outlet humidity. Finally, the value of the linear VCS models is demonstrated by their application in model-based control. A switched LQR approach is shown in both simulation and experimental application to be capable of driving the system between operational modes in order to regulate about a desired nominal operating condition. In particular, the experiments demonstrate improved robustness at low evaporator superheat of the switched LQR approach as compared to a decentralized PI approach.
Issue Date:2015-07-20
Type:Thesis
URI:http://hdl.handle.net/2142/88074
Rights Information:Copyright 2015 Herschel Pangborn
Date Available in IDEALS:2015-09-29
Date Deposited:August 201


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