The Experts below are selected from a list of 26592 Experts worldwide ranked by ideXlab platform
John E Seem - One of the best experts on this subject based on the ideXlab platform.
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efficient operation of air side Economizer using extremum seeking control
Journal of Dynamic Systems Measurement and Control-transactions of The Asme, 2010Co-Authors: Pengfei Li, Yaoyu Li, John E SeemAbstract:As the heating, ventilating, and air conditioning (HVAC) systems accounts for a major sector of energy consumption for commercial buildings, there has been a greater demand for improving the efficiency of such systems. The air-side Economizers have been developed as a class of energy-saving HVAC devices that may increase the energy efficiency by taking advantage of outdoor air during cool or cold weather. However, many Economizers do not operate in the expected manner and waste even more energy than before installation, mostly due to the unreliable sensors and actuators in practice. Better control strategy is needed for optimal and robust operation. In this paper, an extremum-seeking control (ESC) based self-optimizing strategy is proposed to minimize the energy consumption, with the feedback of chilled water supply command rather than the temperature and humidity measurements. The mechanical cooling load is minimized by seeking the optimal outdoor air damper opening in real time. Such scheme does not need temperature and humidity sensors, and depends much less on the knowledge of the Economizer model. Simulation was performed on a MODELICA based transient model of a single-duct air-handling unit developed with DYMOLA and AIRCONDITIONING LIBRARY . The simulation results demonstrated the potential of using ESC to achieve the minimal mechanical cooling load in a self-optimizing manner. In addition, an antiwindup ESC scheme is proposed to handle the ESC windup issue due to actuator (damper) saturation. The simulation results validated the effectiveness of the proposed antiwindup ESC.
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Extremum seeking control for efficient and reliable operation of air-side Economizers
2009 American Control Conference, 2009Co-Authors: Pengfei Li, Yaoyu Li, John E SeemAbstract:Economizers have been recognized as a class of energy-saving devices for heating, ventilating and air conditioning (HVAC) systems that may increase the energy efficiency by taking advantage of outdoor air during cool or cold weather. There has been a tremendous demand for reducing energy consumption of HVAC systems in commercial buildings. However, many Economizers do not operate in the expected manner and waste even more energy than before installation, mostly traceable to the unreliable sensors and actuators in practice. In this paper, an extremum seeking control (ESC) based self-optimizing strategy is proposed to minimize the energy consumption. Rather than depending on the unreliable temperature and humidity measurements, the proposed strategy is based on the feedback of chilled-water supply command. The mechanical cooling load is minimized by seeking the optimal outdoor-air damper opening in real time. Such scheme does not need temperature and humidity sensors and depends much less on the knowledge of the Economizer model. Simulation was performed on a Modelica based transient model of a single-duct air-handling unit (AHU) developed with Dymola and the AirConditioning Library. The simulation results demonstrated the potential of using ESC to achieve minimal mechanical cooling load in a self-optimizing manner. In addition, an anti-windup ESC scheme is proposed to overcome the ESC windup issue due to actuator (damper) saturation. The simulation results validated the effectiveness of the proposed anti-windup ESC.
Wenxing Shi - One of the best experts on this subject based on the ideXlab platform.
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Comparative research on air conditioner with gas-injected rotary compressor through injection port on blade
Applied Thermal Engineering, 2016Co-Authors: Baolong Wang, Xingru Liu, Wenxing ShiAbstract:Economizer technology has become a critical method to improve the performance of air conditioners with rotary compressors in low ambient temperatures. A novel vapor injection structure on the blade of the rotary compressor has been proposed in previous research to overcome the back-flow of the traditional cylinder injection structure. Based on a verified numerical model, the performance of an air conditioner adopting different economized rotary compressors has been investigated. The results indicate that: compared to the air conditioner with single-cylinder rotary compressor using traditional cylinder injection structure, the air conditioner with blade injected rotary compressor can reach enhancement of the heating capacity and COP by 12.9–15.7% and 1.5–4.1% in low ambient temperatures, respectively; and the air conditioner with blade injected rotary compressor has a competitive performance contrast to the air conditioner with twin-cylinder rotary compressor.
Ziwen Xing - One of the best experts on this subject based on the ideXlab platform.
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experimental study on p v indicator diagrams of twin screw refrigeration compressor with Economizer
Applied Thermal Engineering, 2004Co-Authors: Huagen Wu, Xueyuan Peng, Ziwen XingAbstract:This paper presents the experimental investigation on the effects of the superfeed pressure together with Economizer type on the performance of the twin-screw refrigeration compressor by means of the indicator diagram. With a pressure sensor embedded into the groove at the root of the female rotor on the discharge side, the pressure within the working chamber of a semi-hermetic twin-screw compressor with an Economizer is recorded and then transformed into the indicator diagram. The results thus obtained are utilized to investigate the thermodynamic process of the compressor. It is shown that the compressor with an Economizer has higher pressure during almost the whole compression process than without an Economizer, resulting in the increase in the indicated power. Under different superfeed pressures, the pressure within the compression experiences different changes. This results in an optimal superfeed pressure for maximized compressor efficiency, which can be identified from the calculated compressor efficiency based on the indicator diagrams. It is also found that the pressure has a rapid increase at the beginning of superfeed process, and then a slow rise even a slight drop at the end of superfeed process, which is caused by the dynamic effect during superfeed process. Furthermore, if the superfeed pressure keeps the same, the pressure during compression in the compressor with the heat exchanger Economizer is slightly higher than with the flash tank Economizer, due to the higher temperature of superfeed refrigerant gas in the former case.
Iqbal M Mujtaba - One of the best experts on this subject based on the ideXlab platform.
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a newly designed Economizer to improve waste heat recovery a case study in a pasteurized milk plant
Applied Thermal Engineering, 2013Co-Authors: Sathit Niamsuwan, Paisan Kittisupakorn, Iqbal M MujtabaAbstract:Abstract An Economizer is normally employed to perform heat recovery from hot exhaust gases to cold fluid. In this work, a newly designed Economizer is devised to achieve high heat recovery in a pasteurized milk plant. In the Economizer, the hot exhaust gas is divided into two channels flowing up on the left and right sides. After that, it is moving down passing over aligned banks of tubes, which water is flowing inside, in a triple passes fashion. Moreover, three dimensional (3D) models with heat transfer including fluid dynamic have been developed, validated by actual plant data and used to evaluate the performance of the Economizer. Simulation results indicate that the newly designed Economizer can recover the heat loss of 38% and can achieve the cost saving of 13%.
Shu Pengcheng - One of the best experts on this subject based on the ideXlab platform.
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investigation of the heat pump water heater using Economizer vapor injection system and mixture of r22 r600a
International Journal of Refrigeration-revue Internationale Du Froid, 2009Co-Authors: Cao Feng, Wang Shouguo, Xing Ziwen, Shu PengchengAbstract:This paper presents the experimental study of a heat pump water heater (HPWH) using Economizer vapor injection system and mixture of R22/R600a. Performances of HPWH using Economizer vapor injection system are compared with that at different mixed mass ratios of R22/R600a. Study demonstrates that the heating capacity and energy efficiency ratio (EER) of the unit increased, and the discharge temperature of compressor decreased when using vapor injection and mixing refrigerant of R22/R600a. It is also found that the HPWH unit with Economizer vapor injection system has a better performance for the high outlet water temperature under lower temperature conditions at 15% mass ratio of R600a for the mixing refrigerant. In addition, fundamental and practical influence of vapor injection pressure on the HPWH performance has been investigated experimentally. The simplified model is proposed for predicting the optimal vapor injection pressure of compressor using the mixing refrigerant R22/R600a.
