The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Per Lundqvist - One of the best experts on this subject based on the ideXlab platform.
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Capacity Control in ground source heat pump systems part i modeling and simulation
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Hatef Madani, Joachim Claesson, Per LundqvistAbstract:Abstract The present paper, as the first part of two, suggests a method to approach the challenge of Capacity Control in Ground Source Heat Pumps (GSHP). The paper describes the development of a model of the system which includes several sub-models such as the heat pump unit, building, ground source, thermal storage tank, auxiliary heater, and climate. The developed computer model can be used for comparative analysis of different Control methods and strategies aiming at the improvement of the system seasonal performance. With this model, on/off Controlled and variable Capacity GSHPs, with a single speed or variable speed pumps in the systems, can be evaluated in a wide range of operating conditions and more energy efficient methods of the system Control can be found. The computer model is developed in the two environments EES and TRNSYS utilizing so-called co-solving technique.
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Experimental Analysis of a Variable Capacity Heat Pump System Focusing on the Compressor and Inverter Loss Behavior
International refrigeration and air conditioning onference, 2010Co-Authors: Hatef Madani, Joachim Claesson, Navid Ahmadi, Per LundqvistAbstract:Capacity Control with variable speed compressors in heat pump systems is one of the techniques having a potential for efficiency improvement in heat pump systems. It is anticipated that the compressor and inverter efficiency are influenced by changes of the compressor speed. The present experimental study evaluates these losses in a variable speed heat pump system. The experimental results show that increasing the compressor speed reduces the heat pump COP up to 30%. The inverter loss increases as the compressor speed is increased, although the inverter loss as the percentage of the total compressor power decreases. Increasing the compressor speed increases the pressure ratio from 2.7 to 5.8, increasing the loss due to the pressure ratio mismatch drastically. Finally, the highest total isentropic efficiency of the compressor is obtained when the compressor frequency is close to 50Hz.
Hatef Madani - One of the best experts on this subject based on the ideXlab platform.
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Capacity Control in air-water heat pumps: Total cost of ownership analysis
Energy and Buildings, 2014Co-Authors: Gunda Mader, Hatef MadaniAbstract:Adjusting Capacity to changing demand by variable speed Control is known to offer efficiency improvement over classical on/off Control. With a total cost of ownership analysis the economic viability of both Control schemes is assessed for residential air-water heat pumps operating in different climate zones. Component sizes are optimized for both Control methods individually. Results show optimal compressor displacement volumes to be smaller for variable speed than for on/off Control. The optimal ratio of evaporator to condenser size is smaller for the variable speed system. Variable speed Control is shown to be uneconomic for space heating in warmer climate while for average climate cost-effectiveness depends on the economic framework. For colder climate variable speed Control is the more profitable choice in all considered cases; savings of up to 5000 EUR compared to on/off Control can be achieved within 15 years of operation. © 2014 Elsevier B.V.
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Capacity Control in ground source heat pump systems part i modeling and simulation
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Hatef Madani, Joachim Claesson, Per LundqvistAbstract:Abstract The present paper, as the first part of two, suggests a method to approach the challenge of Capacity Control in Ground Source Heat Pumps (GSHP). The paper describes the development of a model of the system which includes several sub-models such as the heat pump unit, building, ground source, thermal storage tank, auxiliary heater, and climate. The developed computer model can be used for comparative analysis of different Control methods and strategies aiming at the improvement of the system seasonal performance. With this model, on/off Controlled and variable Capacity GSHPs, with a single speed or variable speed pumps in the systems, can be evaluated in a wide range of operating conditions and more energy efficient methods of the system Control can be found. The computer model is developed in the two environments EES and TRNSYS utilizing so-called co-solving technique.
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Experimental Analysis of a Variable Capacity Heat Pump System Focusing on the Compressor and Inverter Loss Behavior
International refrigeration and air conditioning onference, 2010Co-Authors: Hatef Madani, Joachim Claesson, Navid Ahmadi, Per LundqvistAbstract:Capacity Control with variable speed compressors in heat pump systems is one of the techniques having a potential for efficiency improvement in heat pump systems. It is anticipated that the compressor and inverter efficiency are influenced by changes of the compressor speed. The present experimental study evaluates these losses in a variable speed heat pump system. The experimental results show that increasing the compressor speed reduces the heat pump COP up to 30%. The inverter loss increases as the compressor speed is increased, although the inverter loss as the percentage of the total compressor power decreases. Increasing the compressor speed increases the pressure ratio from 2.7 to 5.8, increasing the loss due to the pressure ratio mismatch drastically. Finally, the highest total isentropic efficiency of the compressor is obtained when the compressor frequency is close to 50Hz.
A. Hiramatsu - One of the best experts on this subject based on the ideXlab platform.
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Integration of ATM call admission Control and link Capacity Control by distributed neural networks
IEEE Journal on Selected Areas in Communications, 1991Co-Authors: A. HiramatsuAbstract:An adaptive call admission Control using neural networks was recently proposed for asynchronous transfer mode (ATM) communications networks. The author proposes adaptive link Capacity Control using neural networks. Neural networks are trained to estimate the call loss rate from link Capacity and observed traffic, and link Capacity assignment is optimized by a random optimization method according to the estimated call loss rate. The integration of adaptive call admission Control and adaptive link Capacity Control yields an efficient ATM traffic Control system suitable for multimedia communication services with unknown traffic characteristics. Computer simulation results using a simple network model are also given to evaluate the accuracy and efficiency of the proposed method.
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Integration of ATM call admission Control and link Capacity Control by distributed neural networks
[Proceedings] GLOBECOM '90: IEEE Global Telecommunications Conference and Exhibition, 1990Co-Authors: A. HiramatsuAbstract:An adaptive link Capacity Control method which uses the adaptive nature of a neural network to estimate call loss rate from observed traffic and link Capacity is discussed. Link Capacity assignment is optimized by a random optimization method according to the estimated call loss rate. The integration of adaptive call admission Control and adaptive link Capacity Control is shown to yield all efficient asynchronous transfer mode (ATM) traffic Control system suitable for multimedia communication services with unknown traffic characteristics. Preliminary computer simulation results of the method are presented.
Joachim Claesson - One of the best experts on this subject based on the ideXlab platform.
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Capacity Control in ground source heat pump systems part i modeling and simulation
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Hatef Madani, Joachim Claesson, Per LundqvistAbstract:Abstract The present paper, as the first part of two, suggests a method to approach the challenge of Capacity Control in Ground Source Heat Pumps (GSHP). The paper describes the development of a model of the system which includes several sub-models such as the heat pump unit, building, ground source, thermal storage tank, auxiliary heater, and climate. The developed computer model can be used for comparative analysis of different Control methods and strategies aiming at the improvement of the system seasonal performance. With this model, on/off Controlled and variable Capacity GSHPs, with a single speed or variable speed pumps in the systems, can be evaluated in a wide range of operating conditions and more energy efficient methods of the system Control can be found. The computer model is developed in the two environments EES and TRNSYS utilizing so-called co-solving technique.
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Experimental Analysis of a Variable Capacity Heat Pump System Focusing on the Compressor and Inverter Loss Behavior
International refrigeration and air conditioning onference, 2010Co-Authors: Hatef Madani, Joachim Claesson, Navid Ahmadi, Per LundqvistAbstract:Capacity Control with variable speed compressors in heat pump systems is one of the techniques having a potential for efficiency improvement in heat pump systems. It is anticipated that the compressor and inverter efficiency are influenced by changes of the compressor speed. The present experimental study evaluates these losses in a variable speed heat pump system. The experimental results show that increasing the compressor speed reduces the heat pump COP up to 30%. The inverter loss increases as the compressor speed is increased, although the inverter loss as the percentage of the total compressor power decreases. Increasing the compressor speed increases the pressure ratio from 2.7 to 5.8, increasing the loss due to the pressure ratio mismatch drastically. Finally, the highest total isentropic efficiency of the compressor is obtained when the compressor frequency is close to 50Hz.
Pengfei Li - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Modeling and Stability Analysis of Water-Cooled Centrifugal Chillers
ASME 2010 Dynamic Systems and Control Conference Volume 2, 2010Co-Authors: Pengfei Li, Yaoyu Li, John E SeemAbstract:This paper presents a study on the dynamics of a water-cooled centrifugal chiller from two aspects: dynamic simulation modeling and stability analysis. First, the transient model is developed in Modelica with Dymola and the TLK/IfT Library (TIL). The centrifugal compressor is modeled in detail based on the turbomachinery theory. The chiller Capacity Control is achieved by the combination of variable inlet guide vane (VIGV) and variable speed drive (VSD). The shell-and-tube heat exchangers are discretized based on the finite volume method with convenient and numerically efficient two-phase property evaluations. A thermal expansion valve (TXV) is used to regulate the mass flow rate. These models are interconnected to form a centrifugal chiller system. Second, the stability of the chiller is studied based on Lyapunov analysis. The centrifugal chiller is effectively a "closed-loop" concatenation of the centrifugal compressor, condenser, expansion device and evaporator because the refrigerant flow stays within the closed path of the chiller system. The inherent unstable aspect of the compressor dynamics (e.g. surge) becomes more intrigued because the input and output flow are correlated, as compared to the typical "open-loop" centrifugal compressor applications such as compressed air systems or turbochargers. The Lyapunov stability analysis presented herein constructs partial foundation for future nonlinear Control design for the centrifugal chiller systems. Copyright © 2010 by ASME.
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Modelica Based Dynamic Modeling of Water- Cooled Centrifugal Chillers
International Refrigeration and Air Conditioning Conference, 2010Co-Authors: Pengfei LiAbstract:In this paper, the transient model of a water-cooled centrifugal chiller is developed in Modelica with Dymola and the TLK/IfT Library (TIL). The centrifugal compressor is modeled in detail based on the turbomachinery theory. The chiller Capacity Control is achieved by the combination of variable inlet guide vane (VIGV) and variable speed drive (VSD). The shell-and-tube heat exchangers are discretized based on the finite volume method with convenient and numerically efficient two-phase property evaluations. A thermal expansion valve (TXV) is used to regulate the pressure levels at the condenser and evaporator sides. These models are interconnected to form a centrifugal chiller system. The developed chiller model could be easily integrated to various Control applications and it is proposed to validate the Controller performance at the simulation phase prior to experimentation.
