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Author: Richard J. Otten Publisher: ISBN: Category : Languages : en Pages :
Book Description
Ever since the invention of air conditioning and refrigeration in the late nineteenth century, there has been tremendous interest in increasing system efficiency to reduce the impact these systems have on global energy consumption. Efficiency improvements have been accomplished through component design, refrigerant design, and most recently control system design. The emergence of the electronic expansion valve and variable speed drives has made immense impacts on the ability to regulate system parameters, resulting in important strides towards efficiency improvement. This research presents tools and methodologies for model development and controller design for air conditioning and refrigeration systems. In this thesis, control-oriented nonlinear dynamic models are developed and validated with test data collected from a fully instrumented experimental system. These models enable the design of advanced control configurations which supplement the performance of the commonly used proportional-integral-derivative (PID) controller. Evaporator superheat is a key parameter considered in this research since precise control optimizes evaporator efficiency while protecting the system from component damage. The controllers developed in this thesis ultimately provide better transient and steady state performance which increases system efficiency through low superheat set point design. The developed controllers also address the classical performance versus robustness tradeoff through design which preserves transients while prolonging the lifetime of the electronic expansion valve. Another notable contribution of this thesis is the development of hardware-in-the-loop load emulation which provides a method to test component and software control loop performance. This method alleviates the costs associated with the current method of testing using environmental test chambers.
Author: Richard J. Otten Publisher: ISBN: Category : Languages : en Pages :
Book Description
Ever since the invention of air conditioning and refrigeration in the late nineteenth century, there has been tremendous interest in increasing system efficiency to reduce the impact these systems have on global energy consumption. Efficiency improvements have been accomplished through component design, refrigerant design, and most recently control system design. The emergence of the electronic expansion valve and variable speed drives has made immense impacts on the ability to regulate system parameters, resulting in important strides towards efficiency improvement. This research presents tools and methodologies for model development and controller design for air conditioning and refrigeration systems. In this thesis, control-oriented nonlinear dynamic models are developed and validated with test data collected from a fully instrumented experimental system. These models enable the design of advanced control configurations which supplement the performance of the commonly used proportional-integral-derivative (PID) controller. Evaporator superheat is a key parameter considered in this research since precise control optimizes evaporator efficiency while protecting the system from component damage. The controllers developed in this thesis ultimately provide better transient and steady state performance which increases system efficiency through low superheat set point design. The developed controllers also address the classical performance versus robustness tradeoff through design which preserves transients while prolonging the lifetime of the electronic expansion valve. Another notable contribution of this thesis is the development of hardware-in-the-loop load emulation which provides a method to test component and software control loop performance. This method alleviates the costs associated with the current method of testing using environmental test chambers.
Author: Ankush Gupta Publisher: ISBN: Category : Languages : en Pages :
Book Description
The survey from US Department of Energy showed that about one-third of energy consumption in US is due to air conditioning and refrigeration systems. This significant usage of electricity in the HVAC industry has prompted researchers to develop dynamic models for the HVAC components, which leads to implementation of better control and optimization techniques. In this research, efforts are made to model a multi-evaporator system. A novel dynamic modeling technique is proposed based on moving boundary method, which can be generalized for any number of evaporators in a vapor compression cycle. The models were validated experimentally on a commercial supermarket refrigeration unit. Simulation results showed that the models capture the major dynamics of the system in both the steady state and transient external disturbances. Furthermore the use of MEMS (microelectromechanical) based Silicon Expansion Valves (SEVs) have reportedly shown power savings as compared to the Thermal Expansion Valves (TEVs). Experimental tests were conducted on a supermarket refrigeration unit fitted with the MEMS valves to explain the cause of these potential energy savings. In this study an advanced cascaded control algorithm was also designed to control the MEMS valves. The performance of the cascaded control architecture was compared with the standard Thermal Expansion Valves (TEVs) and a commercially available Microstaq (MS) Superheat Controller (SHC). The results reveal that the significant efficiency gains derived on the SEVs are due to better superheat regulation, tighter superheat control and superior cooling effects in shorter time period which reduces the total run-time of the compressor. It was also observed that the duty cycle was least for the cascaded control algorithm. The reduction in duty cycle indicates early shut-off for the compressor resulting in maximum power savings for the cascaded control, followed by the Microstaq controller and then the Thermal Expansion Valves. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148111
Author: Yitong Gao Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 159
Book Description
The impact of individual upstream superheat control on a two-pass water-cooled refrigeration system has been studied. Previous research has verified that the loss of cooling capacity and coefficient of performance (COP) of the system due to non-uniform superheat can be recovered by applying upstream individual superheat control. This thesis presents the analysis of upstream individual superheat control. The experiment apparatus consisted of a two-pass water-cooled refrigeration system composed of a 2040 watts scroll type compressor, a water-cooled coaxial type condenser and two water-cooled coaxial type evaporators. R410A was selected as refrigerant. The design phase was based on refrigeration cycle of thermodynamics. AUTOCAD and Pro/Engineering 4.0 were used in order to do the simulation. Agilent 34980A was used as data acquisition hardware and Agilent BenchLink Data Logger Pro was used as data acquisition software. Engineering Equation Solver (EES) was used to do all the calculations, including the superheat, subcooling, enthalpy, cooling capacity and coefficient of performance (COP). Three different conditions were considered in this thesis. Condition I: without control. Condition II: with control. Condition III : minimum stable superheat (MSS) phenomenon. In condition I, no control was applied and non-uniform superheat was observed. In condition II, upstream individual superheat control was applied, and the superheats in two evaporating circuits were observered almost evenly distributied. In condition III, close the control valve on the corresponding circuit of 98%, and observed the sudden change of superheat. Results showed that there exist significant benefits of system cooling capacity and coefficient of performance (COP) by using upstream individual superheat control method. In Condition I, the cooling capacity was found to be 7.671kw and the COP was 3.715. In Condition II, the cooling capacity was found to be 8.138kw and the COP was 3.955. By applied the upstream individual superheat control method, the cooling capacity increased about 5.739% and the COP increased about 6.068%. Furthermore, the minimum stable superheat (MSS) phenomenon was examined. Close one of the control valves on the corresponding circuit of 98%. Instead of getting superheat increased, it was found that the superheat of this circuit suddenly decreased. This phenomenon is referred as minimum stable superheat (MSS). The exact reasons that cause MSS haven`t been found yet. But some reasonable factors that may affect MSS were presented. First, the suddenly change of heat transfer coefficient inside the evaporator. Second, different types of refrigerant may affect MSS.
Author: Ye Yao Publisher: Springer ISBN: 3662533138 Category : Technology & Engineering Languages : en Pages : 496
Book Description
This book investigates the latest modeling and control technologies in the context of air-conditioning systems. Firstly, it introduces the state-space method for developing dynamic models of all components in a central air-conditioning system. The models are primarily nonlinear and based on the fundamental principle of energy and mass conservation, and are transformed into state-space form through linearization. The book goes on to describe and discuss the state-space models with the help of graph theory and the structure-matrix theory. Subsequently, virtual sensor calibration and virtual sensing methods (which are very useful for real system control) are illustrated together with a case study. Model-based predictive control and state-space feedback control are applied to air-conditioning systems to yield better local control, while the air-side synergic control scheme and a global optimization strategy based on the decomposition-coordination method are developed so as to achieve energy conservation in the central air-conditioning system. Lastly, control strategies for VAV systems including total air volume control and trim & response static pressure control are investigated in practice.
Author: Wenyi Wang Publisher: ISBN: Category : Air source heat pump systems Languages : en Pages :
Book Description
Air source heat pump (ASHP) has been a well-received technology to provide space and/or water heating for building and industrial applications, while its efficiency and heating capacity can be severely limited when operated in cold climate. Various modifications have been proposed for cold-climate operation of ASHP over the single-stage refrigeration cycle, such as vapor injection techniques and cascade configuration. However, there has been a lack of effective control strategies for such systems to maintain the optimal energy efficiency for operations across different combinations of ambient and load conditions. Previous work has paid great efforts in model based strategies, anchored on deriving system models with simulation and experimental testing. Such approaches can be prohibitively expensive due to the inherent nonlinear nature of refrigeration systems and unmeasurable equipment degradation. This dissertation investigates on model-free control strategies for real-time efficiency optimization for several configurations of cold-climate ASHP, by use of Extremum Seeking Control (ESC). By utilizing periodic dither inputs for online gradient estimation, ESC bears significant robustness against process variation and external disturbance, which has proved to be more advantageous in handling the challenging applications like heating, ventilation and air conditioning (HVAC) systems. Three types of ASHP configurations are studied in this dissertation: the internal heat exchanger vapor injection, flash-tank vapor injection, and cascade configuration. For both vapor injection ASHP configurations, the intermediate pressure setpoint is optimized by standard ESC and Newton-based ESC based on the feedback of the total power consumption, with the constant heating load considered. For the cascade ASHP, multivariable ESC is designed to handle two operational scenarios: minimizing the total power for fixed heating capacity and maximizing the coefficient of performance (COP) for variable heating capacity. For the power based ESC, the manipulated inputs include the intermediate temperature, high temperature cycle superheat and low temperature cycle superheat; while for the COP based ESC, the high- and low-temperature cycle compressor speeds and evaporator fan mass flow rate are adopted as inputs. The proposed ESC strategies are evaluated with Modelica based dynamic simulation models of the three system configurations. Simulations have been conducted under both fixed and realistic ambient temperature profiles. The simulation results show good steady-state and transient performance of real-time efficiency optimization with the proposed strategies, in terms of tracking unknown and dynamic optimum settings.
Author: William S. Levine Publisher: CRC Press ISBN: 1420073672 Category : Technology & Engineering Languages : en Pages : 3526
Book Description
At publication, The Control Handbook immediately became the definitive resource that engineers working with modern control systems required. Among its many accolades, that first edition was cited by the AAP as the Best Engineering Handbook of 1996. Now, 15 years later, William Levine has once again compiled the most comprehensive and authoritative resource on control engineering. He has fully reorganized the text to reflect the technical advances achieved since the last edition and has expanded its contents to include the multidisciplinary perspective that is making control engineering a critical component in so many fields. Now expanded from one to three volumes, The Control Handbook, Second Edition brilliantly organizes cutting-edge contributions from more than 200 leading experts representing every corner of the globe. They cover everything from basic closed-loop systems to multi-agent adaptive systems and from the control of electric motors to the control of complex networks. Progressively organized, the three volume set includes: Control System Fundamentals Control System Applications Control System Advanced Methods Any practicing engineer, student, or researcher working in fields as diverse as electronics, aeronautics, or biomedicine will find this handbook to be a time-saving resource filled with invaluable formulas, models, methods, and innovative thinking. In fact, any physicist, biologist, mathematician, or researcher in any number of fields developing or improving products and systems will find the answers and ideas they need. As with the first edition, the new edition not only stands as a record of accomplishment in control engineering but provides researchers with the means to make further advances.
Author: William S. Levine Publisher: CRC Press ISBN: 1420073613 Category : Technology & Engineering Languages : en Pages : 944
Book Description
At publication, The Control Handbook immediately became the definitive resource that engineers working with modern control systems required. Among its many accolades, that first edition was cited by the AAP as the Best Engineering Handbook of 1996. Now, 15 years later, William Levine has once again compiled the most comprehensive and authoritative resource on control engineering. He has fully reorganized the text to reflect the technical advances achieved since the last edition and has expanded its contents to include the multidisciplinary perspective that is making control engineering a critical component in so many fields. Now expanded from one to three volumes, The Control Handbook, Second Edition organizes cutting-edge contributions from more than 200 leading experts. The second volume, Control System Applications, includes 35 entirely new applications organized by subject area. Covering the design and use of control systems, this volume includes applications for: Automobiles, including PEM fuel cells Aerospace Industrial control of machines and processes Biomedical uses, including robotic surgery and drug discovery and development Electronics and communication networks Other applications are included in a section that reflects the multidisciplinary nature of control system work. These include applications for the construction of financial portfolios, earthquake response control for civil structures, quantum estimation and control, and the modeling and control of air conditioning and refrigeration systems. As with the first edition, the new edition not only stands as a record of accomplishment in control engineering but provides researchers with the means to make further advances. Progressively organized, the other two volumes in the set include: Control System Fundamentals Control System Advanced Methods
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
As energy efficient devices become more necessary, it is desired to increase the efficiency of air conditioning systems. Current systems use on/off control, where the unit primarily operates in the long lasting start up transients. A proposed solution is an air conditioning unit that runs continuously with active computer control implemented to maximize efficiency. The objective of this thesis is to develop a mathematical model for a specific air conditioning unit and to compare this model to measurements made on the specific unit. This model can then be used to develop a multi-input multi-output control law in the future. In this thesis, a linearized moving interface lumped parameter model is presented, and the derivation verified with great detail. The model predicts transient perturbations from a steady state operating point. The air conditioner tested in this work required several modifications including the addition of sensors and controllers. A description of the system is provided. Methods used to determine all of the parameters for the model are given with explanation. The model is simulated with computer software and compared with experimental data. Simulations predict the final value of superheat and pressures in the evaporator and condenser well for step changes in the compressor speed and expansion valve opening.
Author: Angui Li Publisher: Springer Science & Business Media ISBN: 3642395813 Category : Technology & Engineering Languages : en Pages : 825
Book Description
Proceedings of the 8th International Symposium on Heating, Ventilation and Air Conditioning is based on the 8th International Symposium of the same name (ISHVAC2013), which took place in Xi’an on October 19-21, 2013. The conference series was initiated at Tsinghua University in 1991 and has since become the premier international HVAC conference initiated in China, playing a significant part in the development of HVAC and indoor environmental research and industry around the world. This international conference provided an exclusive opportunity for policy-makers, designers, researchers, engineers and managers to share their experience. Considering the recent attention on building energy consumption and indoor environments, ISHVAC2013 provided a global platform for discussing recent research on and developments in different aspects of HVAC systems and components, with a focus on building energy consumption, energy efficiency and indoor environments. These categories span a broad range of topics, and the proceedings provide readers with a good general overview of recent advances in different aspects of HVAC systems and related research. As such, they offer a unique resource for further research and a valuable source of information for those interested in the subject. The proceedings are intended for researchers, engineers and graduate students in the fields of Heating, Ventilation and Air Conditioning (HVAC), indoor environments, energy systems, and building information and management. Angui Li works at Xi’an University of Architecture and Technology, Yingxin Zhu works at Tsinghua University and Yuguo Li works at The University of Hong Kong.
Author: Richard J. Otten
Author: Richard J. Otten
Author: Ankush Gupta
Author: Yitong Gao
Author: Ye Yao
Author: Bryan Philip Rasmussen
Author: Wenyi Wang
Author: William S. Levine
Author: William S. Levine
Author: 
Author: Angui Li