Documents disponibles écrits par cet auteur

Component-based, gray-box modeling of ductless multi-split heat pump systems / Howard Cheung in International journal of refrigeration, Vol. 38 (Février 2014) 

Public ISBD [article]  in International journal of refrigeration > Vol. 38 (Février 2014) . - pp. 30–45 Titre : Component-based, gray-box modeling of ductless multi-split heat pump systems Titre original : Modélisation à « boite grise » définie par l'utilisateur et basée sur les composants, de systèmes de pompe á chaleur multi-split sans conduit Type de document : texte imprimé Auteurs : Howard Cheung, Auteur ; James E. Braun, Auteur Année de publication : 2014 Article en page(s) : pp. 30–45 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Multi-split  heat  pump;  Ductless  heat  pump;  Variable-speed  heat  pump;  Modeling;  Performance  analysis Résumé : Multi-split ductless heat pumps are touted as an energy efficient option for air conditioning and heating in residential and small commercial applications. However, their use of multiple indoor units with variable speed compressor and fans and complicated controls leads to difficulties in understanding their characteristics by experiments only. A method to model the system using gray-box component models and an empirical control algorithm is described in this paper. The model was constructed from experimental results of an 8 kW R410A dual-unit ductless heat pump system having an accumulator. Strategies for modeling systems with accumulators and saturated control inputs are presented. Parametric studies with varying indoor air temperature, individual indoor unit load ratio, indoor fan speed and total indoor load were conducted. The results show that the model predicts system performance accurately and can help to understand the effect of saturated control inputs and changes of accumulator status on system performance. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002855 [article] Component-based, gray-box modeling of ductless multi-split heat pump systems = Modélisation à « boite grise » définie par l'utilisateur et basée sur les composants, de systèmes de pompe á chaleur multi-split sans conduit [texte imprimé] / Howard Cheung, Auteur ; James E. Braun, Auteur . - 2014 . - pp. 30–45. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 38 (Février 2014) . - pp. 30–45 Mots-clés : Multi-split  heat  pump;  Ductless  heat  pump;  Variable-speed  heat  pump;  Modeling;  Performance  analysis Résumé : Multi-split ductless heat pumps are touted as an energy efficient option for air conditioning and heating in residential and small commercial applications. However, their use of multiple indoor units with variable speed compressor and fans and complicated controls leads to difficulties in understanding their characteristics by experiments only. A method to model the system using gray-box component models and an empirical control algorithm is described in this paper. The model was constructed from experimental results of an 8 kW R410A dual-unit ductless heat pump system having an accumulator. Strategies for modeling systems with accumulators and saturated control inputs are presented. Parametric studies with varying indoor air temperature, individual indoor unit load ratio, indoor fan speed and total indoor load were conducted. The results show that the model predicts system performance accurately and can help to understand the effect of saturated control inputs and changes of accumulator status on system performance. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002855

A computationally efficient hybrid leakage model for positive displacement compressors and expanders / Ian H. Bell in International journal of refrigeration, Vol. 36 N° 7 (Novembre 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 7 (Novembre 2013) . - pp. 1965–1973 Titre : A computationally efficient hybrid leakage model for positive displacement compressors and expanders Titre original : Modèle hybride des fuites fiable sur le plan des calculs, pour les compresseurs volumétriques et les détendeurs Type de document : texte imprimé Auteurs : Ian H. Bell, Auteur ; Eckhard A. Groll, Auteur ; James E. Braun, Auteur Année de publication : 2014 Article en page(s) : pp. 1965–1973 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Compressor;  Expanders;  Simulation;  Leakage Résumé : An empirical frictional correction factor to the isentropic nozzle model has been developed for application to refrigerant leakage modeling in scroll, rotary and other similar compressors and expanders. This correction factor is derived by calculating the leakage mass flow rate with a compressible, variable area, real gas properties model and referencing the results to an isentropic nozzle model. The ratio of flows is correlated to the Reynolds number, a characteristic length and the leakage gap width. A representative selection of fluids and geometries are employed. For all the correlations, at least 93% of the points are predicted within an absolute error band of 20%. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000200 [article] A computationally efficient hybrid leakage model for positive displacement compressors and expanders = Modèle hybride des fuites fiable sur le plan des calculs, pour les compresseurs volumétriques et les détendeurs [texte imprimé] / Ian H. Bell, Auteur ; Eckhard A. Groll, Auteur ; James E. Braun, Auteur . - 2014 . - pp. 1965–1973. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 7 (Novembre 2013) . - pp. 1965–1973 Mots-clés : Compressor;  Expanders;  Simulation;  Leakage Résumé : An empirical frictional correction factor to the isentropic nozzle model has been developed for application to refrigerant leakage modeling in scroll, rotary and other similar compressors and expanders. This correction factor is derived by calculating the leakage mass flow rate with a compressible, variable area, real gas properties model and referencing the results to an isentropic nozzle model. The ratio of flows is correlated to the Reynolds number, a characteristic length and the leakage gap width. A representative selection of fluids and geometries are employed. For all the correlations, at least 93% of the points are predicted within an absolute error band of 20%. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000200

Experimental testing of an oil-flooded hermetic scroll compressor / Ian H. Bell in International journal of refrigeration, Vol. 36 N° 7 (Novembre 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 7 (Novembre 2013) . - pp. 1866–1873 Titre : Experimental testing of an oil-flooded hermetic scroll compressor Titre original : Essais expérimentaux effectués sur un compresseur à spirale hermétique noyé par l'huile Type de document : texte imprimé Auteurs : Ian H. Bell, Auteur ; Eckhard A. Groll, Auteur ; James E. Braun, Auteur Année de publication : 2014 Article en page(s) : pp. 1866–1873 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Air  conditioning;  Refrigeration;  Flooded  compression Résumé : In this work, a residential air conditioning compressor designed for vapor injection has been modified in order to inject large quantities of oil into the working chamber in order to approach an isothermal compression process. The compressor was tested with oil injection mass flow fractions of up to 45%. At an evaporating temperature of −10 °C and condensing temperature of 30 °C, the overall isentropic efficiency was up to 70% at the highest oil injection rate. Overall, over the testing envelope investigated, there are no significantly negative effects experienced for the compressor and the compressor isentropic efficiency and refrigerant mass flow rate improve monotonically as the oil injection rate is increased. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000212 [article] Experimental testing of an oil-flooded hermetic scroll compressor = Essais expérimentaux effectués sur un compresseur à spirale hermétique noyé par l'huile [texte imprimé] / Ian H. Bell, Auteur ; Eckhard A. Groll, Auteur ; James E. Braun, Auteur . - 2014 . - pp. 1866–1873. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 7 (Novembre 2013) . - pp. 1866–1873 Mots-clés : Air  conditioning;  Refrigeration;  Flooded  compression Résumé : In this work, a residential air conditioning compressor designed for vapor injection has been modified in order to inject large quantities of oil into the working chamber in order to approach an isothermal compression process. The compressor was tested with oil injection mass flow fractions of up to 45%. At an evaporating temperature of −10 °C and condensing temperature of 30 °C, the overall isentropic efficiency was up to 70% at the highest oil injection rate. Overall, over the testing envelope investigated, there are no significantly negative effects experienced for the compressor and the compressor isentropic efficiency and refrigerant mass flow rate improve monotonically as the oil injection rate is increased. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000212

Modeling of a novel spool compressor with multiple vapor refrigerant injection ports / Margaret M. Mathison in International journal of refrigeration, Vol. 36 N° 7 (Novembre 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 7 (Novembre 2013) . - pp. 1982–1997 Titre : Modeling of a novel spool compressor with multiple vapor refrigerant injection ports Titre original : Modélisation d'un compresseur à rotor innovant muni de plusieurs orifices d'injection du frigorigène sous forme de vapeur Type de document : texte imprimé Auteurs : Margaret M. Mathison, Auteur ; James E. Braun, Auteur ; Eckhard A. Groll, Auteur Année de publication : 2014 Article en page(s) : pp. 1982–1997 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Spool  compressor;  Novel  compressor;  Compressor  modeling;  Injection;  Economizing;  Air  conditioning  units Résumé : A model of a novel rotary spool compressor has been developed to explore the effect of multiple injection ports on compressor and cycle performance. The thermodynamic model includes the effects of heat transfer and leakage and is numerically solved to predict the compressor power consumption and mass flow rate. Saturated vapor injection is modeled assuming that the injection pressures and the timing of the injection process can be controlled. The model predicts that adding a single injection port will provide a 12% increase in the cycle coefficient of performance (COP) when the compressor runs at 1907 rpm with R-22 evaporating at −7 °C, condensing at 49 °C, and 15 °C of superheat. Adding a second, non-optimized injection port increases the COP by 16% compared to the cycle without injection. The model is used to investigate the effect of injection pressure, port location, and port diameter on cycle performance. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000765 [article] Modeling of a novel spool compressor with multiple vapor refrigerant injection ports = Modélisation d'un compresseur à rotor innovant muni de plusieurs orifices d'injection du frigorigène sous forme de vapeur [texte imprimé] / Margaret M. Mathison, Auteur ; James E. Braun, Auteur ; Eckhard A. Groll, Auteur . - 2014 . - pp. 1982–1997. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 7 (Novembre 2013) . - pp. 1982–1997 Mots-clés : Spool  compressor;  Novel  compressor;  Compressor  modeling;  Injection;  Economizing;  Air  conditioning  units Résumé : A model of a novel rotary spool compressor has been developed to explore the effect of multiple injection ports on compressor and cycle performance. The thermodynamic model includes the effects of heat transfer and leakage and is numerically solved to predict the compressor power consumption and mass flow rate. Saturated vapor injection is modeled assuming that the injection pressures and the timing of the injection process can be controlled. The model predicts that adding a single injection port will provide a 12% increase in the cycle coefficient of performance (COP) when the compressor runs at 1907 rpm with R-22 evaporating at −7 °C, condensing at 49 °C, and 15 °C of superheat. Adding a second, non-optimized injection port increases the COP by 16% compared to the cycle without injection. The model is used to investigate the effect of injection pressure, port location, and port diameter on cycle performance. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000765

Performance evaluation of a virtual refrigerant charge sensor / Kim, Woohyun in International journal of refrigeration, Vol. 36 N° 3 (Mai 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 3 (Mai 2013) . - pp. 1130–1141 Titre : Performance evaluation of a virtual refrigerant charge sensor Titre original : Evaluation de la performance d'un capteur de la charge en frigorigène virtuelle Type de document : texte imprimé Auteurs : Kim, Woohyun, Auteur ; James E. Braun, Auteur Année de publication : 2013 Article en page(s) : pp. 1130–1141 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Air  conditioner;  Refrigerant  charge;  Sensor;  Refrigerant  leakage;  Fault  detection Résumé : The primary goal was to evaluate and enhance a virtual refrigerant charge (VRC) sensor developed by Li and Braun (2006, 2009). Based on the evaluation, the VRC sensor was found to work well in estimating refrigerant charge for systems that do not utilize accumulators when using the default parameters. For systems with accumulators, however, the parameters needed to be improved for better accuracy. To overcome those limitations, a simulation method for estimating parameters was developed that depends on test data at rated conditions and system information. The simulation parameters decreased the errors between the actual and predicted charge. Even better performance was achieved for the VRC sensor when the parameters were tuned by minimizing charge prediction errors using test data and linear regression. The overall RMS error for the VRC sensors using tuned parameters was 3.8% over a wide range of operating conditions for different types of systems. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700712003039 [article] Performance evaluation of a virtual refrigerant charge sensor = Evaluation de la performance d'un capteur de la charge en frigorigène virtuelle [texte imprimé] / Kim, Woohyun, Auteur ; James E. Braun, Auteur . - 2013 . - pp. 1130–1141. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 3 (Mai 2013) . - pp. 1130–1141 Mots-clés : Air  conditioner;  Refrigerant  charge;  Sensor;  Refrigerant  leakage;  Fault  detection Résumé : The primary goal was to evaluate and enhance a virtual refrigerant charge (VRC) sensor developed by Li and Braun (2006, 2009). Based on the evaluation, the VRC sensor was found to work well in estimating refrigerant charge for systems that do not utilize accumulators when using the default parameters. For systems with accumulators, however, the parameters needed to be improved for better accuracy. To overcome those limitations, a simulation method for estimating parameters was developed that depends on test data at rated conditions and system information. The simulation parameters decreased the errors between the actual and predicted charge. Even better performance was achieved for the VRC sensor when the parameters were tuned by minimizing charge prediction errors using test data and linear regression. The overall RMS error for the VRC sensors using tuned parameters was 3.8% over a wide range of operating conditions for different types of systems. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700712003039

Performance limit for economized cycles with continuous refrigerant injection / Margaret M. Mathison in International journal of refrigeration, Vol. 34 N° 1 (Janvier 2011) 

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Performance of vapor compression systems with compressor oil flooding and regeneration / Ian H. Bell in International journal of refrigeration, Vol. 34 N° 1 (Janvier 2011) 

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