Documents disponibles écrits par cet auteur

Effect of the header pressure drop induced flow maldistribution on the microchannel evaporator performance / Hanfei Tuo in International journal of refrigeration, Vol. 36 N° 8 (Décembre 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 8 (Décembre 2013) . - pp. 2176–2186 Titre : Effect of the header pressure drop induced flow maldistribution on the microchannel evaporator performance Titre original : Effet de la mauvaise distribution de l'écoulement engendrée par la chute de pression dans le collecteur sur la performance d'un évaporateur à microcanaux Type de document : texte imprimé Auteurs : Hanfei Tuo, Auteur ; Pega Hrnjak, Auteur Année de publication : 2014 Article en page(s) : pp. 2176–2186 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Microchannel;  evaporator;  air-conditioning  system;  flow  distribution;  header Résumé : This paper presents an experimental and numerical investigation of the flow maldistribution caused by the pressure drop in headers and its impact on the performance of a microchannel evaporator with horizontal headers and vertically oriented tubes. Experimental results show that the flash gas bypass method almost eliminates the quality induced maldistribution. However, refrigerant flow maldistribution caused by the header pressure drop still exists. This is mainly because the pressure drop along the headers results in uneven pressure difference and therefore non-uniform liquid refrigerant mass flow rate across each microchannel tube. A microchannel evaporator model validated by experimental results is employed to quantify header pressure drop induced flow maldistribution. Parametric analysis reveals that such maldistribution impact is significantly reduced by enlarging the outlet header size, increasing heat exchanger aspect ratio, or reducing the microchannel size while other parameters are kept constant. When ratio of outlet header to the total evaporator pressure drop is less than 30%, the cooling capacity reduction is limited below 3%. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001497 [article] Effect of the header pressure drop induced flow maldistribution on the microchannel evaporator performance = Effet de la mauvaise distribution de l'écoulement engendrée par la chute de pression dans le collecteur sur la performance d'un évaporateur à microcanaux [texte imprimé] / Hanfei Tuo, Auteur ; Pega Hrnjak, Auteur . - 2014 . - pp. 2176–2186. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 8 (Décembre 2013) . - pp. 2176–2186 Mots-clés : Microchannel;  evaporator;  air-conditioning  system;  flow  distribution;  header Résumé : This paper presents an experimental and numerical investigation of the flow maldistribution caused by the pressure drop in headers and its impact on the performance of a microchannel evaporator with horizontal headers and vertically oriented tubes. Experimental results show that the flash gas bypass method almost eliminates the quality induced maldistribution. However, refrigerant flow maldistribution caused by the header pressure drop still exists. This is mainly because the pressure drop along the headers results in uneven pressure difference and therefore non-uniform liquid refrigerant mass flow rate across each microchannel tube. A microchannel evaporator model validated by experimental results is employed to quantify header pressure drop induced flow maldistribution. Parametric analysis reveals that such maldistribution impact is significantly reduced by enlarging the outlet header size, increasing heat exchanger aspect ratio, or reducing the microchannel size while other parameters are kept constant. When ratio of outlet header to the total evaporator pressure drop is less than 30%, the cooling capacity reduction is limited below 3%. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001497

Experimental investigation on air-source transcritical CO2 heat pump water heater system at a fixed water inlet temperature / Shouguo Wang 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. 701–716 Titre : Experimental investigation on air-source transcritical CO2 heat pump water heater system at a fixed water inlet temperature Titre original : Etude expérimentale sur un système de chauffage d'eau à pompe à chaleur au CO2 transcritique avec une température d'eau fixe à l'entrée Type de document : texte imprimé Auteurs : Shouguo Wang, Auteur ; Hanfei Tuo, Auteur ; Feng Cao, Auteur Année de publication : 2013 Article en page(s) : pp. 701–716 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Transcritical  cycle;  Carbon  dioxide;  Heat  pump;  Pressure;  Simulation Résumé : For clarify main affecting factors on air-source transcritical CO2 heat pump water heaters, and the influence extent of these main affecting factors, at fixed water inlet temperature of 12 °C, an experimental research was conducted on a prototype in a range of ambient temperatures (−15 °C–35 °C) and water outlet temperatures (55 °C–80 °C). Based on the experimental results, effect of water outlet temperatures and ambient temperatures on the optimal discharge pressure and system COP was illustrated, and with change of water outlet temperatures and ambient temperatures, variation of CO2 gas cooler outlet temperatures, evaporating temperatures and other cycle variables was presented and interpreted. According established simulation model, we conducted simulation for the prototype and the cycle respectively adopted another two gas coolers with difference heat transfer surface. As one conclusion, for an established plant, correlation for the optimal discharge pressure as the function of ambient temperatures and water outlet temperatures can be achieved by fitting numerous simulation or experimental results. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071200271X [article] Experimental investigation on air-source transcritical CO2 heat pump water heater system at a fixed water inlet temperature = Etude expérimentale sur un système de chauffage d'eau à pompe à chaleur au CO2 transcritique avec une température d'eau fixe à l'entrée [texte imprimé] / Shouguo Wang, Auteur ; Hanfei Tuo, Auteur ; Feng Cao, Auteur . - 2013 . - pp. 701–716. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 3 (Mai 2013) . - pp. 701–716 Mots-clés : Transcritical  cycle;  Carbon  dioxide;  Heat  pump;  Pressure;  Simulation Résumé : For clarify main affecting factors on air-source transcritical CO2 heat pump water heaters, and the influence extent of these main affecting factors, at fixed water inlet temperature of 12 °C, an experimental research was conducted on a prototype in a range of ambient temperatures (−15 °C–35 °C) and water outlet temperatures (55 °C–80 °C). Based on the experimental results, effect of water outlet temperatures and ambient temperatures on the optimal discharge pressure and system COP was illustrated, and with change of water outlet temperatures and ambient temperatures, variation of CO2 gas cooler outlet temperatures, evaporating temperatures and other cycle variables was presented and interpreted. According established simulation model, we conducted simulation for the prototype and the cycle respectively adopted another two gas coolers with difference heat transfer surface. As one conclusion, for an established plant, correlation for the optimal discharge pressure as the function of ambient temperatures and water outlet temperatures can be achieved by fitting numerous simulation or experimental results. En ligne : http://www.sciencedirect.com/science/article/pii/S014070071200271X

New approach to improve performance by venting periodic reverse vapor flow in microchannel evaporator / Hanfei Tuo in International journal of refrigeration, Vol. 36 N° 8 (Décembre 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 8 (Décembre 2013) . - pp. 2187–2195 Titre : New approach to improve performance by venting periodic reverse vapor flow in microchannel evaporator Titre original : Nouvelle approche pour améliorer la performance en évacuant l'écoulement inverse périodique de vapeur à l'intérieur d'un évaporateur à microcanaux Type de document : texte imprimé Auteurs : Hanfei Tuo, Auteur ; Pega Hrnjak, Auteur Année de publication : 2014 Article en page(s) : pp. 2187–2195 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Vapour;  periodic  reverse  flow;  boiling;  fluctuation;  venting;  evaporator;  microchannel Résumé : This paper presents a proposal for a venting reverse vapor in flash gas removal A/C system in order to improve refrigerant distribution and reduce pressure drop in microchannel evaporator and thus increase system efficiency. Introduction to the reverse vapor flow observed in parallel flow microchannel evaporator was presented in earlier IJR paper by the authors. An experimental comparison of the A/C system with new approach to an FGB system revealed that vapor venting provided a 5% increase of cooling capacity and 3% of COP when operated at identical test conditions, while the maximum COP improvement was approximately 10%–12% when capacity is matched by reduction of compressor speed. The improvement compared to direct expansion system was significantly higher. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001473 [article] New approach to improve performance by venting periodic reverse vapor flow in microchannel evaporator = Nouvelle approche pour améliorer la performance en évacuant l'écoulement inverse périodique de vapeur à l'intérieur d'un évaporateur à microcanaux [texte imprimé] / Hanfei Tuo, Auteur ; Pega Hrnjak, Auteur . - 2014 . - pp. 2187–2195. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 8 (Décembre 2013) . - pp. 2187–2195 Mots-clés : Vapour;  periodic  reverse  flow;  boiling;  fluctuation;  venting;  evaporator;  microchannel Résumé : This paper presents a proposal for a venting reverse vapor in flash gas removal A/C system in order to improve refrigerant distribution and reduce pressure drop in microchannel evaporator and thus increase system efficiency. Introduction to the reverse vapor flow observed in parallel flow microchannel evaporator was presented in earlier IJR paper by the authors. An experimental comparison of the A/C system with new approach to an FGB system revealed that vapor venting provided a 5% increase of cooling capacity and 3% of COP when operated at identical test conditions, while the maximum COP improvement was approximately 10%–12% when capacity is matched by reduction of compressor speed. The improvement compared to direct expansion system was significantly higher. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001473

Periodical reverse flow and boiling fluctuations in a microchannel evaporator of an air-conditioning system / Hanfei Tuo in International journal of refrigeration, Vol. 36 N° 4 (Juin 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 4 (Juin 2013) . - pp. 1263–1275 Titre : Periodical reverse flow and boiling fluctuations in a microchannel evaporator of an air-conditioning system Titre original : Ecoulement inverse périodique et fluctuations de l'ébullition dans l'évaporateur à microcanaux d'un système de conditionnement d'air Type de document : texte imprimé Auteurs : Hanfei Tuo, Auteur ; Pega Hrnjak, Auteur Année de publication : 2013 Article en page(s) : pp. 1263–1275 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Periodic  reverse  flow;  Flow  visualization;  Boiling  fluctuation;  Microchannel  evaporator Résumé : This paper presents the phenomenon of periodic reverse flow and associated boiling fluctuation found in experiments with a parallel microchannel evaporator used in an R134a air conditioning system. A simultaneous flow visualizations and measurements confirmed the periodic flow reversal. It caused synchronized oscillations of the evaporator inlet pressure and the pressure drop. The magnitude and frequency of oscillations increased with heat flux. Three potential impacts of flow reversal on evaporator performance are identified: 1) moderate liquid maldistribution; 2) reduced heat transfer coefficient; 3) increased refrigerant side pressure drop. Finally, to mitigate impacts of periodic reverse flow, a solution is proposed: to vent and bypass backflow vapor accumulated in the inlet header. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000236 [article] Periodical reverse flow and boiling fluctuations in a microchannel evaporator of an air-conditioning system = Ecoulement inverse périodique et fluctuations de l'ébullition dans l'évaporateur à microcanaux d'un système de conditionnement d'air [texte imprimé] / Hanfei Tuo, Auteur ; Pega Hrnjak, Auteur . - 2013 . - pp. 1263–1275. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 4 (Juin 2013) . - pp. 1263–1275 Mots-clés : Periodic  reverse  flow;  Flow  visualization;  Boiling  fluctuation;  Microchannel  evaporator Résumé : This paper presents the phenomenon of periodic reverse flow and associated boiling fluctuation found in experiments with a parallel microchannel evaporator used in an R134a air conditioning system. A simultaneous flow visualizations and measurements confirmed the periodic flow reversal. It caused synchronized oscillations of the evaporator inlet pressure and the pressure drop. The magnitude and frequency of oscillations increased with heat flux. Three potential impacts of flow reversal on evaporator performance are identified: 1) moderate liquid maldistribution; 2) reduced heat transfer coefficient; 3) increased refrigerant side pressure drop. Finally, to mitigate impacts of periodic reverse flow, a solution is proposed: to vent and bypass backflow vapor accumulated in the inlet header. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000236