Heat transfer characteristics of accumulator heat exchangers under various geometric and operating conditions / Hoon Kang in International journal of refrigeration, Vol. 34 N° 4 (Juin 2011)  

Public ISBD [article]  inInternational journal of refrigeration > Vol. 34 N° 4 (Juin 2011) . - pp. 1077-1084 Titre : Heat transfer characteristics of accumulator heat exchangers under various geometric and operating conditions Titre original : Caractéristiques de transfert de chaleur des échangeurs de chaleur à accumulation sous diverses conditions géométriques et de fonctionnement Type de document : texte imprimé Auteurs : Hoon Kang, Auteur ; Ilyong Cho, Auteur ; Honghee Park, Auteur Année de publication : 2011 Article en page(s) : pp. 1077-1084 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Heat exchanger transfer Sub-cooling Air-conditioner Refrigerant Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : To minimize the possibility of flash gas generation at the inlet of the expansion device in multi air-conditioners, an accumulator heat exchanger is usually adopted. In this study, the heat transfer rate and subcooling difference in an accumulator heat exchanger were measured under various operating and geometric conditions. The effect of the operating conditions on the performance of the accumulator heat exchanger was analyzed for R-22, R-134a, and R-410A. The performance of the accumulator heat exchanger was also analyzed by varying diverse geometric parameters: the inner volume and the ratio of the diameter to height of the accumulator, and the diameter, length, and bending diameter of the inner heat exchanger. In addition, the flow of the refrigerant-oil mixture inside the accumulator was visualized. Based on the measured data, a dimensionless correlation for predicting the subcooling difference across the accumulator heat exchanger was developed. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000533 [article] Heat transfer characteristics of accumulator heat exchangers under various geometric and operating conditions = Caractéristiques de transfert de chaleur des échangeurs de chaleur à accumulation sous diverses conditions géométriques et de fonctionnement [texte imprimé] / Hoon Kang, Auteur ; Ilyong Cho, Auteur ; Honghee Park, Auteur . - 2011 . - pp. 1077-1084. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 4 (Juin 2011) . - pp. 1077-1084 Mots-clés : Heat exchanger transfer Sub-cooling Air-conditioner Refrigerant Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : To minimize the possibility of flash gas generation at the inlet of the expansion device in multi air-conditioners, an accumulator heat exchanger is usually adopted. In this study, the heat transfer rate and subcooling difference in an accumulator heat exchanger were measured under various operating and geometric conditions. The effect of the operating conditions on the performance of the accumulator heat exchanger was analyzed for R-22, R-134a, and R-410A. The performance of the accumulator heat exchanger was also analyzed by varying diverse geometric parameters: the inner volume and the ratio of the diameter to height of the accumulator, and the diameter, length, and bending diameter of the inner heat exchanger. In addition, the flow of the refrigerant-oil mixture inside the accumulator was visualized. Based on the measured data, a dimensionless correlation for predicting the subcooling difference across the accumulator heat exchanger was developed. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000533

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Optimum cycle control of a two-stage injection heat pump with a double expansion sub-cooler / Jaehyeok Heo in International journal of refrigeration, Vol. 35 N° 1 (Janvier 2012)  

Public ISBD [article]  inInternational journal of refrigeration > Vol. 35 N° 1 (Janvier 2012) . - pp. 58–67 Titre : Optimum cycle control of a two-stage injection heat pump with a double expansion sub-cooler Titre original : Régulation optimale du cycle d'une pompe à chaleur biétagée à injection munie d'un système de sous-refroidissement à deux détendeurs Type de document : texte imprimé Auteurs : Jaehyeok Heo, Auteur ; Hoon Kang, Auteur ; Yongchan Kim, Auteur Année de publication : 2012 Article en page(s) : pp. 58–67 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Heat pump Two-stage Injection Control Optimization Résumé : The refrigerant injection technique has rapidly developed in recent years due to its outstanding performance at low ambient temperatures, and various control methods for a heat pump with injection have been presented. However, most studies on cycle control have been theoretical, and practical control methods for cycle optimization based on experimental results hardly have been presented. In this study, an optimum cycle control method was proposed for a refrigerant injection heat pump with a double expansion sub-cooler based on the intermediate pressure and the injection ratio. The optimum sub-cooler pressure ratio was proposed from 0.4 to 0.7 in view of the heating capacity, and from 0.7 to 0.8 in view of the COP. The optimum injection ratio increased from 0.1 to 0.3 with an increase in the compression ratio. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711002210 [article] Optimum cycle control of a two-stage injection heat pump with a double expansion sub-cooler = Régulation optimale du cycle d'une pompe à chaleur biétagée à injection munie d'un système de sous-refroidissement à deux détendeurs [texte imprimé] / Jaehyeok Heo, Auteur ; Hoon Kang, Auteur ; Yongchan Kim, Auteur . - 2012 . - pp. 58–67. Génie mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 35 N° 1 (Janvier 2012) . - pp. 58–67 Mots-clés : Heat pump Two-stage Injection Control Optimization Résumé : The refrigerant injection technique has rapidly developed in recent years due to its outstanding performance at low ambient temperatures, and various control methods for a heat pump with injection have been presented. However, most studies on cycle control have been theoretical, and practical control methods for cycle optimization based on experimental results hardly have been presented. In this study, an optimum cycle control method was proposed for a refrigerant injection heat pump with a double expansion sub-cooler based on the intermediate pressure and the injection ratio. The optimum sub-cooler pressure ratio was proposed from 0.4 to 0.7 in view of the heating capacity, and from 0.7 to 0.8 in view of the COP. The optimum injection ratio increased from 0.1 to 0.3 with an increase in the compression ratio. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711002210

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Performance characteristics of a simultaneous cooling and heating multi-heat pump at partial load conditions / Youngju Joo in International journal of refrigeration, Vol. 34 N° 4 (Juin 2011)  

Public ISBD [article]  inInternational journal of refrigeration > Vol. 34 N° 4 (Juin 2011) . - pp. 893-901 Titre : Performance characteristics of a simultaneous cooling and heating multi-heat pump at partial load conditions Titre original : Caractéristiques de la performance de plusieurs pompes à chaleur assurant le chauffage et le refroidissement simultanés, fonctionnant en charge partielle Type de document : texte imprimé Auteurs : Youngju Joo, Auteur ; Hoon Kang, Auteur ; Jae Hwan Ahn, Auteur Année de publication : 2011 Article en page(s) : pp. 893-901 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Heat pump recovery Variable speed Electronic expansion valve R410A Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A simultaneous cooling and heating multi-heat pump can improve thermal comfort and energy efficiency through heat recovery at partial load conditions. The performance of a simultaneous heating and cooling multi-heat pump with four indoor units was measured by varying the compressor speed, EEV opening, and fan speed at full and partial load conditions in five operating modes. In the cooling-only and heating-only modes, the heating and cooling capacities were properly controlled by varying the compressor speed. However, in the cooling-main and heating-main modes under partial load conditions, a large imbalance between the cooling and heating capacities was observed even though the compressor speed was optimized. This capacity imbalance under partial load conditions was optimized by adjusting the EEV openings in the mode change unit and the outdoor unit. In addition, in the entire-heat recovery mode, rating compressor speed ratios were proposed under the full and partial load conditions. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000041 [article] Performance characteristics of a simultaneous cooling and heating multi-heat pump at partial load conditions = Caractéristiques de la performance de plusieurs pompes à chaleur assurant le chauffage et le refroidissement simultanés, fonctionnant en charge partielle [texte imprimé] / Youngju Joo, Auteur ; Hoon Kang, Auteur ; Jae Hwan Ahn, Auteur . - 2011 . - pp. 893-901. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 4 (Juin 2011) . - pp. 893-901 Mots-clés : Heat pump recovery Variable speed Electronic expansion valve R410A Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : A simultaneous cooling and heating multi-heat pump can improve thermal comfort and energy efficiency through heat recovery at partial load conditions. The performance of a simultaneous heating and cooling multi-heat pump with four indoor units was measured by varying the compressor speed, EEV opening, and fan speed at full and partial load conditions in five operating modes. In the cooling-only and heating-only modes, the heating and cooling capacities were properly controlled by varying the compressor speed. However, in the cooling-main and heating-main modes under partial load conditions, a large imbalance between the cooling and heating capacities was observed even though the compressor speed was optimized. This capacity imbalance under partial load conditions was optimized by adjusting the EEV openings in the mode change unit and the outdoor unit. In addition, in the entire-heat recovery mode, rating compressor speed ratios were proposed under the full and partial load conditions. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000041

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