Documents disponibles écrits par cet auteur

Effect of vapor-injection technique on the performance of a cascade heat pump water heater / Chul Woo Roh in International journal of refrigeration, Vol. 38 (Février 2014) 

Public ISBD [article]  in International journal of refrigeration > Vol. 38 (Février 2014) . - pp. 168–177 Titre : Effect of vapor-injection technique on the performance of a cascade heat pump water heater Titre original : Effet de la technique d'injection de vapeur sur la performance d'un chauffe-eau à pompe à chaleur en cascade Type de document : texte imprimé Auteurs : Chul Woo Roh, Auteur ; Min Soo Kim, Auteur Année de publication : 2014 Article en page(s) : pp. 168–177 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Cascade;  Heat  pump;  Vapor  injection;  R404A;  Water  heater Résumé : In this study, we applied a vapor-injection (VI) technique in a cascade heat pump system. The VI was applied to both upper and lower stage cycles. Test results showed that heating and cooling capacities increased by using the VI technique (12% and 6%, respectively); however, the system COP decreased (6.6% at the injection ratio of 16.7%). The cascade system which has a small compression ratio and a cascade condenser, cannot fully utilize the VI's advantages to improve the system COP. However, the VI is effective for the system reliability and capacity improvement. We also found that the VI in the upper and lower stage cycles had different effect on overall cycle operating characteristic. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002545 [article] Effect of vapor-injection technique on the performance of a cascade heat pump water heater = Effet de la technique d'injection de vapeur sur la performance d'un chauffe-eau à pompe à chaleur en cascade [texte imprimé] / Chul Woo Roh, Auteur ; Min Soo Kim, Auteur . - 2014 . - pp. 168–177. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 38 (Février 2014) . - pp. 168–177 Mots-clés : Cascade;  Heat  pump;  Vapor  injection;  R404A;  Water  heater Résumé : In this study, we applied a vapor-injection (VI) technique in a cascade heat pump system. The VI was applied to both upper and lower stage cycles. Test results showed that heating and cooling capacities increased by using the VI technique (12% and 6%, respectively); however, the system COP decreased (6.6% at the injection ratio of 16.7%). The cascade system which has a small compression ratio and a cascade condenser, cannot fully utilize the VI's advantages to improve the system COP. However, the VI is effective for the system reliability and capacity improvement. We also found that the VI in the upper and lower stage cycles had different effect on overall cycle operating characteristic. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002545

Effects of intermediate pressure on the heating performance of a heat pump system using R410A vapor-injection technique / Chul Woo Roh in International journal of refrigeration, Vol. 34 N° 8 (Décembre 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 8 (Décembre 2011) . - pp. 1911–1921 Titre : Effects of intermediate pressure on the heating performance of a heat pump system using R410A vapor-injection technique Titre original : Effets de la pression intermédiaire sur la performance en mode chauffage d'un système à pompe à chaleur utilisant une technologie à injection de vapeur de R410A Type de document : texte imprimé Auteurs : Chul Woo Roh, Auteur ; Min Soo Kim, Auteur Année de publication : 2012 Article en page(s) : pp. 1911–1921 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : COP  Experimentation  Heat  pump  Injection  Performance  R410A Résumé : Recent heat pumps are actively equipped with a refrigerant vapor-injection technique to acquire better performance in severe operating conditions. In this study, the target system which has an additional expansion valve at the outlet of condenser was presented. The concept of intermediate pressure was generated in the target system. Effects of the intermediate pressure on the heating performance with various injection ratios were measured and analyzed according to the compressor frequencies ranging from 60 to 100 Hz. Unlike conventional vapor-injection cycle, the maximum injection ratio was highly affected by the intermediate pressure. The high intermediate pressure provided high initial heating capacity and COP; but it restricted the available range of vapor-injection within narrow limits. The result indicates that a proper operating strategy is needed for the vapor-injection cycle. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S014070071100185X# [article] Effects of intermediate pressure on the heating performance of a heat pump system using R410A vapor-injection technique = Effets de la pression intermédiaire sur la performance en mode chauffage d'un système à pompe à chaleur utilisant une technologie à injection de vapeur de R410A [texte imprimé] / Chul Woo Roh, Auteur ; Min Soo Kim, Auteur . - 2012 . - pp. 1911–1921. Génie mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 8 (Décembre 2011) . - pp. 1911–1921 Mots-clés : COP  Experimentation  Heat  pump  Injection  Performance  R410A Résumé : Recent heat pumps are actively equipped with a refrigerant vapor-injection technique to acquire better performance in severe operating conditions. In this study, the target system which has an additional expansion valve at the outlet of condenser was presented. The concept of intermediate pressure was generated in the target system. Effects of the intermediate pressure on the heating performance with various injection ratios were measured and analyzed according to the compressor frequencies ranging from 60 to 100 Hz. Unlike conventional vapor-injection cycle, the maximum injection ratio was highly affected by the intermediate pressure. The high intermediate pressure provided high initial heating capacity and COP; but it restricted the available range of vapor-injection within narrow limits. The result indicates that a proper operating strategy is needed for the vapor-injection cycle. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S014070071100185X#

Experimental studies on the evaporative heat transfer and pressure drop of CO2 and CO2/propane mixtures flowing upward in smooth and micro-fin tubes with outer diameter of 5 mm for an inclination angle of 45° / Jin Min Cho in International journal of refrigeration, Vol. 33 N° 5 (Août 2010) 

Public ISBD [article]  in International journal of refrigeration > Vol. 33 N° 5 (Août 2010) . - pp. 922-931 Titre : Experimental studies on the evaporative heat transfer and pressure drop of CO2 and CO2/propane mixtures flowing upward in smooth and micro-fin tubes with outer diameter of 5 mm for an inclination angle of 45° Titre original : Etudes expérimentales sur le transfert de chaleur lors de l'évaporation et la chute de pression du CO2 et des mélanges de CO2/propane en écoulement ascendant à l'intérieur de tubes à micro-ailettes avec un diamètre externe de 5 mm et un angle d'inclinaison de 45° Type de document : texte imprimé Auteurs : Jin Min Cho, Auteur ; Yong Jin Kim, Auteur ; Min Soo Kim, Auteur Année de publication : 2010 Article en page(s) : pp. 922-931 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Heat  exchanger  Smooth  tube  Micro-fin  tube  Inclined  tube  Experiment  Heat  transfer  Evaporation  Pressure  drop  Carbon  dioxide  Propane  Mixture Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Heat transfer characteristics show different tendency according to the tube orientations such as horizontal, vertical, and inclined positions. In this study, evaporative heat transfer characteristics and pressure drop of CO2 and CO2/propane mixtures flowing upward are investigated in inclined smooth and micro-fin tubes. Smooth and micro-fin tubes with outer diameter of 5 mm and length of 1.44 m with inclination angle of 45° were chosen as test tubes. Average inner diameters of test tubes are 4.0 mm (smooth tube) and 4.13 mm (micro-fin tube). The tests were conducted at mass fluxes from 212 to 656 kg/m2 s, saturation temperatures from −10 to 30 °C and heat fluxes from 15 to 60 kW/m2 for CO2. In addition, for CO2/propane mixtures, the test was carried out at inlet temperatures from −10 to 30 °C for several compositions (75/25, 50/50, 25/75 wt%) with the same mass fluxes, heat fluxes applied for CO2. Heat transfer coefficients in inclined tube are approximately 1.8–3 times higher than those in horizontal tube and the average pressure drop of inclined tube exists between that of horizontal and vertical tubes. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710000381 [article] Experimental studies on the evaporative heat transfer and pressure drop of CO2 and CO2/propane mixtures flowing upward in smooth and micro-fin tubes with outer diameter of 5 mm for an inclination angle of 45° = Etudes expérimentales sur le transfert de chaleur lors de l'évaporation et la chute de pression du CO2 et des mélanges de CO2/propane en écoulement ascendant à l'intérieur de tubes à micro-ailettes avec un diamètre externe de 5 mm et un angle d'inclinaison de 45° [texte imprimé] / Jin Min Cho, Auteur ; Yong Jin Kim, Auteur ; Min Soo Kim, Auteur . - 2010 . - pp. 922-931. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 33 N° 5 (Août 2010) . - pp. 922-931 Mots-clés : Heat  exchanger  Smooth  tube  Micro-fin  tube  Inclined  tube  Experiment  Heat  transfer  Evaporation  Pressure  drop  Carbon  dioxide  Propane  Mixture Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Heat transfer characteristics show different tendency according to the tube orientations such as horizontal, vertical, and inclined positions. In this study, evaporative heat transfer characteristics and pressure drop of CO2 and CO2/propane mixtures flowing upward are investigated in inclined smooth and micro-fin tubes. Smooth and micro-fin tubes with outer diameter of 5 mm and length of 1.44 m with inclination angle of 45° were chosen as test tubes. Average inner diameters of test tubes are 4.0 mm (smooth tube) and 4.13 mm (micro-fin tube). The tests were conducted at mass fluxes from 212 to 656 kg/m2 s, saturation temperatures from −10 to 30 °C and heat fluxes from 15 to 60 kW/m2 for CO2. In addition, for CO2/propane mixtures, the test was carried out at inlet temperatures from −10 to 30 °C for several compositions (75/25, 50/50, 25/75 wt%) with the same mass fluxes, heat fluxes applied for CO2. Heat transfer coefficients in inclined tube are approximately 1.8–3 times higher than those in horizontal tube and the average pressure drop of inclined tube exists between that of horizontal and vertical tubes. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710000381

Experimental study on the improvement of CO2 air conditioning system performance using an ejector / Jae Seung Lee in International journal of refrigeration, Vol. 34 N° 7 (Novembre 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 7 (Novembre 2011) . - pp. 1614-1625 Titre : Experimental study on the improvement of CO2 air conditioning system performance using an ejector Titre original : Etude expérimentale sur l'amélioration de la performance d'un système de conditionnement d'air au CO2 à l'aide d'un éjecteur Type de document : texte imprimé Auteurs : Jae Seung Lee, Auteur ; Mo Se Kim, Auteur ; Min Soo Kim, Auteur Année de publication : 2011 Article en page(s) : pp. 1614-1625 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Air  conditioning  Carbon  dioxide  Ejector  Performance Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Several preceding researches have evidenced that the transcritical air conditioning system using CO2 as a refrigerant has an inherent inefficiency resulting in degraded steady-state system performance of a CO2 air conditioning system compared with that of a conventional air conditioning system. As a practical improvement, two-phase ejector was considered in place of expansion device in this study. The two-phase ejector for CO2 air conditioning system was designed and developed considering the non-equilibrium state for evaluating the sonic velocity and the critical mass flux. The experiments of performance with respect to variation of ejector geometry such as the motive nozzle throat diameter, mixing section diameter and the distance between motive nozzle and diffuser were carried out. There exist optimum design parameters in each test. Experiments showed that the coefficient of performance of the system using an ejector was about 15% higher than that of the conventional system. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710001714 [article] Experimental study on the improvement of CO2 air conditioning system performance using an ejector = Etude expérimentale sur l'amélioration de la performance d'un système de conditionnement d'air au CO2 à l'aide d'un éjecteur [texte imprimé] / Jae Seung Lee, Auteur ; Mo Se Kim, Auteur ; Min Soo Kim, Auteur . - 2011 . - pp. 1614-1625. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 7 (Novembre 2011) . - pp. 1614-1625 Mots-clés : Air  conditioning  Carbon  dioxide  Ejector  Performance Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Several preceding researches have evidenced that the transcritical air conditioning system using CO2 as a refrigerant has an inherent inefficiency resulting in degraded steady-state system performance of a CO2 air conditioning system compared with that of a conventional air conditioning system. As a practical improvement, two-phase ejector was considered in place of expansion device in this study. The two-phase ejector for CO2 air conditioning system was designed and developed considering the non-equilibrium state for evaluating the sonic velocity and the critical mass flux. The experiments of performance with respect to variation of ejector geometry such as the motive nozzle throat diameter, mixing section diameter and the distance between motive nozzle and diffuser were carried out. There exist optimum design parameters in each test. Experiments showed that the coefficient of performance of the system using an ejector was about 15% higher than that of the conventional system. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710001714

Numerical study on the steady state and transient performance of a multi-type heat pump system / Jong Won Choi in International journal of refrigeration, Vol. 34 N° 2 (Mars 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 2 (Mars 2011) . - pp. 429-443 Titre : Numerical study on the steady state and transient performance of a multi-type heat pump system Titre original : Etude numérique sur le régime permanent et la performance en régime transitoire d’un système à pompe à chaleur polyvalent Type de document : texte imprimé Auteurs : Jong Won Choi, Auteur ; Gilbong Lee, Auteur ; Min Soo Kim, Auteur Année de publication : 2011 Article en page(s) : pp. 429-443 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Heat  pump  System-multi-type  Heat  exchanger  Steady-state  Transient-state  Discharge-superheat Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Numerical methods are provided to analyze dynamic characteristics as well as steady-state performance of a multi-type heat pump system. Lumped parameter method was applied to simulate the compressor and expansion device. Additionally, fully distributed method was used for analyzing the condenser and evaporators. The transient terms in the governing equations for heat exchangers were solved adopting the wave equation solutions. The simulation results predict the steady-state performance of a heat pump system with the deviation of ±10%. The transient simulation showed satisfactory responses of temperatures and pressures for various compressor speeds or expansion valve openings. From the results, it was shown that the operating conditions of secondary fluid of one indoor unit had minor influence on the performance of the other unit, while opening of expansion valve affected the transient responses of both evaporators significantly. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710002331 [article] Numerical study on the steady state and transient performance of a multi-type heat pump system = Etude numérique sur le régime permanent et la performance en régime transitoire d’un système à pompe à chaleur polyvalent [texte imprimé] / Jong Won Choi, Auteur ; Gilbong Lee, Auteur ; Min Soo Kim, Auteur . - 2011 . - pp. 429-443. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 2 (Mars 2011) . - pp. 429-443 Mots-clés : Heat  pump  System-multi-type  Heat  exchanger  Steady-state  Transient-state  Discharge-superheat Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Numerical methods are provided to analyze dynamic characteristics as well as steady-state performance of a multi-type heat pump system. Lumped parameter method was applied to simulate the compressor and expansion device. Additionally, fully distributed method was used for analyzing the condenser and evaporators. The transient terms in the governing equations for heat exchangers were solved adopting the wave equation solutions. The simulation results predict the steady-state performance of a heat pump system with the deviation of ±10%. The transient simulation showed satisfactory responses of temperatures and pressures for various compressor speeds or expansion valve openings. From the results, it was shown that the operating conditions of secondary fluid of one indoor unit had minor influence on the performance of the other unit, while opening of expansion valve affected the transient responses of both evaporators significantly. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710002331

Studies on the heating capacity control of a multi-type heat pump system applying a multi-input multi-output (MIMO) method / Il Hwan Lee in International journal of refrigeration, Vol. 34 N° 2 (Mars 2011) 

Permalink

Studies on the performance of a CO2 air conditioning system using an ejector as an expansion device / Jae Seung Lee in International journal of refrigeration, Vol. 38 (Février 2014) 

Permalink