Optimal Subcooling in Vapor Compression Systems via Extremum Seeking Control

2013 ◽  
Author(s):  
Justin P. Koeln ◽  
Andrew G. Alleyne
Keyword(s):  
System Architecture ◽  
Operating Conditions ◽  
Extremum Seeking ◽  
Vapor Compression ◽  
System Efficiency ◽  
Limited Information ◽  
Extremum Seeking Control ◽  
Additional Degree ◽  
Alternative System ◽  
Vapor Compression Systems

Building systems constitute a significant portion of the overall energy consumed each year in the U.S., and a large portion of this energy is used by air-conditioning systems. Therefore, the efficiency of these systems is important. This paper presents a method to increase system efficiency using an alternative system architecture for vapor compression systems. This architecture creates an additional degree of freedom which allows for independent control of condenser subcooling. It is found that there exists a non-zero subcooling that maximizes system efficiency; however, this optimal subcooling can change with different operating conditions. Thus, extremum seeking control is applied to find and track the optimal subcooling using only limited information of the system. In a simulation case study, a 10% reduction in energy consumption is reported when using the alternative system architecture and extremum seeking control when compared to a conventional system configuration.

scholarly journals Model-Free Extremum Seeking Control of Bioprocesses: A Review with a Worked Example

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1209
Author(s):  
Laurent Dewasme ◽  
Alain Vande Wouwer
Keyword(s):  
Dynamic Models ◽  
Operating Conditions ◽  
Extremum Seeking ◽  
Usual Practice ◽  
Extremum Seeking Control ◽  
Model Free ◽  
Worked Example ◽  
Current Trends ◽  
Simple Simulation ◽  
Recent Developments

Uncertainty is a common feature of biological systems, and model-free extremum-seeking control has proved a relevant approach to avoid the typical problems related to model-based optimization, e.g., time- and resource-consuming derivation and identification of dynamic models, and lack of robustness of optimal control. In this article, a review of the past and current trends in model-free extremum seeking is proposed with an emphasis on finding optimal operating conditions of bioprocesses. This review is illustrated with a simple simulation case study which allows a comparative evaluation of a few selected methods. Finally, some experimental case studies are discussed. As usual, practice lags behind theory, but recent developments confirm the applicability of the approach at the laboratory scale and are encouraging a transfer to industrial scale.

A Graph-Based Approach for Dynamic Compressor Modeling in Vapor Compression Systems

2017 ◽  
Author(s):  
Christopher T. Aksland ◽  
Justin P. Koeln ◽  
Andrew G. Alleyne
Keyword(s):  
Transient Behavior ◽  
Operating Conditions ◽  
Working Fluid ◽  
Vapor Compression ◽  
Thermal Dynamics ◽  
Thermal Capacitance ◽  
Initial Work ◽  
Fast Dynamic ◽  
Significant Effort ◽  
Vapor Compression Systems

Vapor compression systems are widely used as thermal management systems. To satisfy thermal demands, models are used to control and optimize the system’s performance, reliability, and efficiency. Significant effort has been made to model the condenser and evaporator, while there has been minimal focus on control-oriented modeling of the compressor. Initial work illustrates that during transient behavior, the working fluid exhibits a fast dynamic. However, during a startup and shutdown sequence, the working fluid follows a slower dynamic believed to be associated with heat transfer to the shell. To address both thermal dynamics, a graph-based modeling approach is used to incorporate the compressor shell’s thermal capacitance into the model. Experimental and simulation data are compared for a range of operating conditions including shutdown and startup dynamics.

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