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Indoor Environment Control Effect Based on Multi-Impeller air conditioner

Journal of Thermal Science 2022年第6期31卷 2137-2154页

作者： WANG Jiahao LIU Xiaomin TIAN Chenye WU Liming XI Guang School of Energy and Power Engineering Xi’an Jiaotong UniversityXi'an 710049China

air conditioner is the key air supply device to improve the indoor air heat transfer cycle and thermal environment. In this paper, according to the similarity theory, six kinds of the multi-impeller air conditioners(MIAC) with different numbers of axial-flow impeller are first proposed based on air conditioners with cross-flow fan(CFAC). The effects of different multi-impeller air supply modes on the indoor airflow field and temperature field are investigated by using the numerical simulation method. The validity of the computational model and method is verified by comparing the experimental measurements and numerical results. Compared with other air supply modes, the air supply distance is relatively far and the indoor environment is also improved obviously when the six-impeller air conditioner(SIAC) is used. The independent multiple impellers and outlets of SIAC make the mutual interference between the outlet airflow less, which effectively reduces the friction between the airflow and the degree of loss along the way and makes the cold and heat exchange of the whole indoor space more sufficient. The indoor thermal environment is also analyzed by using the PMV-PPD method and prototype experiment. Under the working condition of no wind, the indoor thermal comfort of human body with SIAC is better than that of CFAC. Especially in the horizontal plane of 0.6 m above the human foot, the indoor thermal environment improvement effect is the most obvious. Simultaneously, the temperature difference along the indoor height direction with the SIAC is only 1.7℃, which is 70% lower than that of the CFAC. The blowing angle between the left and right side of the SIAC is 106°, which is 31% higher than that of the CFAC. Therefore, the overall thermal comfort of the six-impeller mode is better, and the control effect of indoor environment is satisfactory.

关键词： air conditioner multi-impeller indoor thermal environment thermal comfort numerical simulation experimental test

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Estimation of Vapor Quality at Compressor Suction of air conditioner

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Journal of Energy and Power Engineering 2015年第4期9卷 367-374页

作者： Kazuhiro Endoh Hitachi Research Laboratory Hitachi Ltd. Ibaraki 312-0034 Japan

To evaluate performance and reliability of an air conditioner, the states of its refrigerant in the refrigeration cycle need to be understood. Since the isentropic exponent of the next-generation refrigerant R32 is larger than that of conventional refrigerant R410A, the compressor discharge temperature of R32 is higher than that of R410A. When a wet refrigerant is entered into a compressor suction line to decrease the discharge temperature, it is generally difficult to estimate the vapor quality at the suction. This paper describes a method that estimates a vapor quality at the compressor suction by applying energy balances on the compressor with the values of suction pressure, discharge pressure, discharge temperature, etc. In the air conditioner test, the vapor qualities at the compressor suction estimated with this method agreed well with those estimated with the conventional method by measuring liquid and vapor flow-rates. Moreover, this paper derived a relational expression for estimating a compressor suction state from a discharge state and discusses the characteristics of the coefficients in the expression calculated from the test results.

关键词： air conditioner compressor wet refrigerant vapor quality R32.

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Numerical Simulation for Thermal Distribution of air-conditioner Outdoor Units

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Journal of Thermal Science 2012年第3期21卷 269-275页

作者： Li-Ge Tong Zhen Zhang Li Wang Shao-Wu Yin Jiangfeng Yu Chun Liu School of Mechanical Engineering University of Science&Technology Beijing100083China Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry 100083China Chinese people's liberation army 96819 power specialist group Beijing100015China China Dalian International Economic&Technical Cooperative Group Ltd. Dalian116011China

air-conditioners used in high-rise residential or office buildings often have outdoor units installed on the side-walls or roofs in the confined space of the *** heat released from the outdoor units causes the tem-perature rise in the confined installation space and leads to uncomfortable thermal environment and deteriorative performance of *** factors affecting the performance of air-conditioners are the heat released from the outdoor units,the solar radiation and the ventilation of the confined installation space,which are inves-tigated in this study and simulated by FLUENT using the porous model and discrete ordinates (DO) radiation *** is proved that the porous model is more reliable than the solid *** optimal installation distance from the supporting wall is *** average temperature of the exit without wind is 1.18% higher than that with *** results show that the heat released from the outdoor units and the ventilation of the confined in-stallation space are the main factors affecting the thermal environment in the confined installation *** in-fluence of the solar radiation is negligible.

关键词： high-rise building air conditioner heat rejection porous model solar radiation

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Critical assessment of R410A alternatives for mini-split air conditioners in the Egyptian market

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Energy and Built Environment 2024年第3期5卷 426-445页

作者： Omar M.Zaki Omar Abdelaziz Mechanical Power Engineering Department Faculty of EngineeringCairo UniversityGiza 12613Egypt Department of Mechanical Engineering The American University in CairoAUC AvenueNew Cairo 11835Egypt

In this study,the potential implementation of three different low-GWP refrigerants(R32,R452B,and R454B)as replacements for R410A was *** study was performed using a simulation tool developed by the authors called RACHP-Lab,which is a vapor compression system simulation tool developed based on physics-based simulation for typical mini-split air *** simulation study was carried out and validated using experimental performance data of 10 different air conditioning units available in the Egyptian *** units included fixed-speed or variable-speed compressors and operated in cooling or heating ***-in replace-ment with the new refrigerants was carried *** R32,the capacity increased between 4.9%and 13%for cooling cases,and 6.3%and 12.4%for heating ***,COP did not improve in all *** R452B and R454B with direct replacement,the capacity nearly remained the same,with an increase of COP between 1.6%and 8.0%.Soft optimization was also conducted on cooling cases where compressor suction superheat,condenser subcooling,and compressor volumetric speed were optimized to maximize COP while maintaining the original capacity of R410A.R32 showed an improvement of COP over R410A between 4.6%and 15.5%,while for R452B and R454B between 2.2%and 13.2%.

关键词： air conditioner Heat pump Alternative refrigerants Vapor compression cycle modeling

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A Comparative Study on the Performance and Environmental Characteristics of Alternatives to R22 in Residential air conditioners for Tunisian Market

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Journal of Environmental Science and Engineering 2010年第12期4卷 37-56页

作者： M.C. Zaghdoudi S. Maalej Y. Saad M. Bouchaala Laboratory Materials Measurements and Applications （MMA）-INSAT- University 7 November at Carthage Tunis Tunisia Medelim Company Ariana Tunisia

This paper presents the simulation results of a 9000 BTU/h air conditioner with some selected fluids that have been assessed for their suitability as alternatives to R22 for air conditioners. Only those refrigerants with zero Ozone Depletion Potential （ODP） are considered. The performances of 11 refrigerants were comparatively studied using the simulation software NIST Cycle_D. R134a, R290, R600, R404A, R407A, R407B, R407C, 407D, R410A, R410B, and R417A are considered in this study. The thermal performances, which are obtained with R 134a and R290, are very close to those of R22. The power consumptions of the unit operating with R404A, R407C, and R410A are higher in the range 22-31% with respect of R22. For the units operating with 407A, R407B, R407D, R407E, and R410B, the electric consumptions are higher in the range 10-23%. For R600, the power consumptions are in the range 6-8%. For all the fluids, the COP is lower by 7-24% than R22, except for R600 for which the COP is higher by 7-9%, and R134a and R290 which exhibit the same COP as R22. When considering the thermal and environmental parameters, R290 is identified as the best candidate for R22, provided the safety aspects of using R290 are addressed.

关键词： air conditioner refrigerant replacement simulation performance COP

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Demand response:a strategy to address residential air-conditioning peak load in Australia

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Journal of Modern Power Systems and Clean Energy 2013年第3期1卷 223-230页

作者： Robert SMITH Ke MENG Zhaoyang DONG Robert SIMPSON Ausgrid SydneyNSW 2000Australia enter for Intelligent Electricity Networks(CIEN) The University of NewcastleNewcastleNSWAustralia

Rapid growth in electricity network peak demand is increasing pressure for new investment which may be used for only a few hours a *** airconditioning is widely believed to be the prime cause of the rise in peak demand but,in the absence of detailed residential demand research,there is no bottom-up empirical evidence to support this supposition or to estimate its *** paper first examines the developments in network peak demand,at a national,network distribution,and local distribution feeder level to show recent trends in peak ***,this paper applies analytics to the half-hourly consumption data of a sample of Ausgrid’s interval metered customers,combined with local weather data,to develop an algorithm which can recognize air-conditioner use and can identify consumption patterns and peak *** estimate is then compared to system peaks to determine residential airconditioning’s impact on overall ***,this paper considers the future impacts of air-conditioning load on peak demand as penetration rates reaches saturation levels and new minimum energy performance standards take effect reducing new units peak impacts.

关键词： air conditioner Demand response Peak load

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Fault detection and diagnosis of electric bus air conditioning systems incorporating domain knowledge and probabilistic artificial intelligence

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Energy and AI 2024年第2期16卷 316-330页

作者： Fangzhou Guo Zhijie Chen Fu Xiao Department of Building Environment and Energy Engineering Hong Kong Polytechnic UniversityHong Kong Lawrence Berkeley National Laboratory BerkeleyCAUSA Research Institute for Smart Energy Hong Kong Polytechnic UniversityHong Kong

The air conditioning systems in electric city buses usually operate in rapidly changing ambient conditions and are more likely to suffer from mechanical faults. Although many fault detection and diagnosis (FDD) methods have been developed for building air conditioning systems, they are difficult to be applied to bus air conditioners since its operation is highly dynamic and fault-free data are usually unavailable. Therefore, this paper proposes an FDD method for electric bus air conditioners to tackle the above issues. First, the method identifies faults in an unsupervised manner by comparing selected features among a group of peer systems. Then, considering the features are influenced by the operating conditions, Gaussian process regression (GPR) models are established to find the relationships between each feature and its influential parameters. The probabilistic nature of the GPR is used to differentiate predictions with large uncertainty, which are then excluded from FDD. In this way, robustness of the method is evidently improved. Finally, fault indexes are defined to detect and diagnose mechanical faults. We applied the method to a group of air conditioners in a city bus fleet. Results showed that it can effectively identify refrigerant undercharge and indoor and outdoor fan problems with low false positive/genitive rates. Also, the method is highly robust and not sensitive to the faulty systems in the bus fleet.

关键词： Fault detection and diagnosis Predictive maintenance air conditioner Electric vehicle Data-driven model Gaussian process

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Theoretical Modeling for a Free Piston Expander in CO2 Transcritical Refrigeration System

Theoretical Modeling for a Free Piston Expander in CO2 Trans...

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第五届压缩机与制冷国际会议

＜正＞ The efficiency of trans-critical carbon dioxide refrigeration system could be greatly enhanced if high efficiency expander substitutes the expansion valve. Free piston expander is thought to be one of the most potential candidates, especially for the application such as residential air conditioner or heat pump system. Therefore, a prototype free piston expander-compressor unit is developed. In the paper, the theoretical model built for this expander is detailed introduced and discussed. Mass conservation equation, energy conservation equation and momentum conservation equation are solved simultaneously using Rounge-Kutta method. Leakage, heat transfer, friction and flowing losses are all considered in the mathematic model. Nozzle model is used to simulate the leakage from the piston ring and inlet/outlet flow. Heat transfer losses between the expander and the auxiliary compressor are calculated using a heat flux network. Friction coefficient is measured and friction losses are calculated according to the detailed structure. The model machine is tested in a carbon bench rig. The experimental results show good accordance with the simulation. The adiabatic efficiency of the expander reaches 0.52 in theoretically.

关键词： Expande Carbon dioxide Trans-critica air conditioner

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