Dynamic Performance of Control Loops and Their Interactions in a VAV HVAC System PDF Download

Author: Ziyu Fan
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Hanfei Cao
Publisher:
ISBN:
Category :
Languages : en
Pages : 101

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This research focuses on gain scheduling control of a dual duct system and its local loop interactions. To reach these objectives, experiments were conducted in a dual duct system. The test facility consists three control loops. (cold air temperature control, hot air temperature control, and mixed air temperature control). The steady state and dynamic characteristics of the dual duct system were studied. Two control strategies were employed to improve the system performance: (i) conventional PI control, and (ii) gain scheduling control. The experimental results subject to load disturbances (set-point changes and initial condition changes) showed that the performance of the gain scheduling controller is better than the conventional PI controller. However, it was found that the gain scheduling control method caused significant oscillations and took nearly 25 minutes to reach a stable final value under low load conditions. Therefore, an adaptive gain scheduling (AGS) controller was developed to improve the disturbance rejection properties of the controller. Experimental and simulation results show that the adaptive gain scheduling controller has dramatically increased controller performance under low load conditions. The prioritization of control loops due to loop interactions was evaluated and the gain scheduling-adaptive controller was applied to the entire system to minimize loop interactions. The experimental results showed that, compared to conventional PI controller, the dynamic responses of adaptive gain scheduling controller are better.

Author: Guy W. Gupton
Publisher: The Fairmont Press, Inc.
ISBN: 0881733946
Category : Technology & Engineering
Languages : en
Pages : 354

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In the eight years since the publication of the first edition of this book, there have been quantum changes in the automated temperature control (ATC) industry due to the widespread & growing use of direct digital control (DDC) systems. The fully updated second edition fully addresses these technology changes, from equipment characteristics & operation, to troubleshooting & maintenance, to training of operating & maintenance personnel. The full range of topics pertinent to the effective operation of all types of HVAC control systems currently in use today are explored, including equipment-to-control interactions, control system set-up & functions, local loop to building automation system interfaces, performance prediction & assessment, operational parameters, & maintenance & testing.

Author: Guo Rong Zheng
Publisher: National Library of Canada = Bibliothèque nationale du Canada
ISBN: 9780612259270
Category : Air conditioning
Languages : en
Pages : 206

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Energy conservation and indoor environment concerns have motivated extensive research on various aspects of control of Heating, Ventilating and Air-Conditioning (HVAC) and building systems. The study on optimal operation as well as modeling of HVAC and building systems is one of the fastest growing fields that contribute to saving energy and improving indoor environment. This thesis is devoted to the development of a comprehensive modeling and optimization methodology for global multiple-stage optimal operation of HVAC and building systems. Two different dynamic models of a multizone variable air volume (VAV) system have been developed using (i) bottom-up and (ii) top-down approaches. The models take account of the dynamic interactions between building shell, VAV system components and control systems. The models describe the dynamics of fan, air distribution system, zone(s), cooling coil and primary plant (chiller) as one multivariable nonlinear system in a way that is useful for control analysis. Using the bottom-up approach a large-scale VAV system model has been developed. This model considers the interactions between flow field and thermal field via distributed capacity and variable air density considerations. An alternate model which is computationally more efficient was developed using the top-down approach. Model reduction techniques were applied to develop a reduced-order state space model of the VAV system. Results show that predictions from the reduced order model are within 5% of those from the large scale model. Optimal control schemes are developed for the efficient operation of VAV systems. In the control scheme proposed it is necessary to compute optimal setpoint profiles for local controllers. The optimal control profiles so computed can be used as tracking signals for local controllers for moving the system states from one setpoint to another. In order to determine optimal setpoint profiles an optimization methodology for formulating and solving the multiple stage optimal operation problems has been developed. The methodology is based on the maximum principle of Pontryagin and perturbation method in order to deal with the multiple time-scale of the HVAC processes and building operating schedules. A solution methodology and the corresponding computer models have been developed for solving the multiple stage optimal operation problems. The applications of the VAV model and the multistage optimization methodology have been demonstrated by considering several practical examples. The examples include (i) a comparison of optimal strategies for constant and variable air volume systems with and without time-of-day price structure for electrical energy, (ii) a two-zone VAV heating system and (iii) a five-zone VAV cooling system. Results showing the 24-hour optimal setpoint profiles, energy cost savings and the output responses such as zone temperatures and humidity ratios are given for different building operation schedules. These applications show that the developed models and optimization methodology can be used to determine energy efficient operating strategies for VAV systems without violating the thermal comfort in buildings.

Author: Kaustubh P Phalak
Publisher:
ISBN:
Category :
Languages : en
Pages :

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The change of weather conditions and occupancy schedules makes heating ventilating and air-conditioning (HVAC) systems heavily dynamic. The mass and thermal inertia, nonlinear characteristics and interactions in HVAC systems make the control more complicated. As a result, some conventional control methods often cannot provide desired control performance under variable operating conditions. The purpose of this study is to develop control methods to improve the control performance of HVAC systems. This study focuses on optimizing the airflow-pressure control method of air side economizers, identifying robust building pressurization controls, developing a control method to control outdoor air and building pressure in absence of flow and pressure sensors, stabilizing the cooling coil valve operation and, return fan speed control. The improvements can be achieved by identifying and selecting a method with relatively linear performance characteristics out of the available options, applying fans rather than dampers to control building pressure, and improving the controller's stability range using cascade control method. A steady state nonlinear network model, for an air handling unit (AHU), air distribution system and conditioned space, is applied to analyze the system control performance of air-side economizers and building pressurization. The study shows that traditional controls with completely interlinked outdoor air, recirculated air, relief air dampers have the best control performance. The decoupled relief damper control may result in negative building static pressure at lower outdoor airflow ratio and excessively positive building static pressure at higher outdoor airflow ratio. On the other hand, return fan speed control has a better controllability on building pressurization. In absence of flow and pressure sensors fixed interlinked damper and linear return fan speed tracking control can maintain constant outside air ratio and positive building pressure. The cascade control method is applied to improve the stability of cooling coil valve operation in single zone air handling unit systems, and return fan speed for building pressure control. The system dynamic response is studied using root locus analysis. It was found that the cascade control improved the stability range in two applications under consideration and made the HVAC feedback control loops more robust and adaptive.

Author: Chris Underwood
Publisher: John Wiley & Sons
ISBN: 1405153008
Category : Technology & Engineering
Languages : en
Pages : 312

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Climate change mitigation and sustainable practices are now at the top of political and technical agendas. Environmental system modelling provides a way of appraising options and this book will make a significant contribution to the uptake of such systems. It provides knowledge of the principles involved in modelling systems, builds confidence amongst designers and offers a broad perspective of the potential of these new technologies. The aim of the book is to provide an understanding of the concepts and principles behind predictive modelling methods; review progress in the development of the modelling software available; and explore modelling in building design through international case studies based on real design problems.

Author: Roger W. Haines
Publisher: Springer Science & Business Media
ISBN: 0387306331
Category : Technology & Engineering
Languages : en
Pages : 376

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Book Description
Control Systems for Heating, Ventilating and Air Conditioning, Sixth Edition is complete and covers both hardware control systems and modern control technology. The material is presented without bias and without prejudice toward particular hardware or software. Readers with an engineering degree will be reminded of the psychrometric processes associated with heating and air conditioning as they learn of the various controls schemes used in the variety of heating and air conditioning system types they will encountered in the field. Maintenance technicians will also find the book useful because it describes various control hardware and control strategies that were used in the past and are prevalent in most existing heating and air conditioning systems. Designers of new systems will find the fundamentals described in this book to be a useful starting point, and they will also benefit from descriptions of new digital technologies and energy management systems. This technology is found in modern building HVAC system designs.

Author: Michael F. Hordeski
Publisher: The Fairmont Press, Inc.
ISBN: 0881733997
Category : Technology & Engineering
Languages : en
Pages : 398

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1-Heat, Ventilation and Damper Control Trends2-Energy and Power Management, Distributed Control Trends3-Control Technology, Microelectronics and Nanotechnology4-Advance HVAC Control, Information Technology and Open Systems5-PC-based Control, Software and Bus Trends6-Artificial Intelligence, Fuzzy Logic and Control7-Computer Networks and Security8-Systems and Device Networks9-Building automation, Wireless Technology and the InternetIndex

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 88

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The Bulletin of the Atomic Scientists is the premier public resource on scientific and technological developments that impact global security. Founded by Manhattan Project Scientists, the Bulletin's iconic "Doomsday Clock" stimulates solutions for a safer world.

Author: Roger W. Haines
Publisher: Blue Ridge Summit, PA : Tab Professional and Reference Books
ISBN:
Category : Computers
Languages : en
Pages : 232

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