Documents disponibles écrits par cet auteur

Compensation of flow maldistribution in fin-and-tube evaporators for residential air-conditioning / Martin Ryhl Kærn in International journal of refrigeration, Vol. 34 N° 5 (Août 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 5 (Août 2011) . - pp. 1230-1237 Titre : Compensation of flow maldistribution in fin-and-tube evaporators for residential air-conditioning Titre original : Compensation de la mauvaise distribution de l'écoulement dans les évaporateurs à tubes ailetés utilisés dans le conditionnement d'air résidentiel Type de document : texte imprimé Auteurs : Martin Ryhl Kærn, Auteur ; Wiebke Brix, Auteur ; Brian Elmegaard, Auteur Année de publication : 2011 Article en page(s) : pp. 1230-1237 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Flow  distribution  Compensation  Air-conditioning  Finned  tube  Modelling  Simulation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Compensation of flow maldistribution in multi-channel fin-and-tube evaporators for residential air-conditioning is investigated by numerical modeling. The considered sources of maldistribution are distribution of the liquid and vapor phases in the distributor and non-uniform airflow distribution. Fin-and-tube heat exchangers usually have a predefined circuitry, however, the evaporator model is simplified to have straight tubes, in order to perform a generic investigation. The compensation of flow maldistribution is performed by control of the superheat in the individual channels. Furthermore, the effect of combinations of individual maldistribution sources is investigated for different evaporator sizes and outdoor temperatures. It is shown that a decrease in cooling capacity and coefficient of performance by flow maldistribution can be compensated by the control of individual channel superheat. Alternatively, a larger evaporator may be used. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000740 [article] Compensation of flow maldistribution in fin-and-tube evaporators for residential air-conditioning = Compensation de la mauvaise distribution de l'écoulement dans les évaporateurs à tubes ailetés utilisés dans le conditionnement d'air résidentiel [texte imprimé] / Martin Ryhl Kærn, Auteur ; Wiebke Brix, Auteur ; Brian Elmegaard, Auteur . - 2011 . - pp. 1230-1237. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 5 (Août 2011) . - pp. 1230-1237 Mots-clés : Flow  distribution  Compensation  Air-conditioning  Finned  tube  Modelling  Simulation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Compensation of flow maldistribution in multi-channel fin-and-tube evaporators for residential air-conditioning is investigated by numerical modeling. The considered sources of maldistribution are distribution of the liquid and vapor phases in the distributor and non-uniform airflow distribution. Fin-and-tube heat exchangers usually have a predefined circuitry, however, the evaporator model is simplified to have straight tubes, in order to perform a generic investigation. The compensation of flow maldistribution is performed by control of the superheat in the individual channels. Furthermore, the effect of combinations of individual maldistribution sources is investigated for different evaporator sizes and outdoor temperatures. It is shown that a decrease in cooling capacity and coefficient of performance by flow maldistribution can be compensated by the control of individual channel superheat. Alternatively, a larger evaporator may be used. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000740

Modelling distribution of evaporating CO2 in parallel minichannels / Wiebke Brix in International journal of refrigeration, Vol. 33 N° 6 (Septembre 2010) 

Public ISBD [article]  in International journal of refrigeration > Vol. 33 N° 6 (Septembre 2010) . - pp. 1086-1094 Titre : Modelling distribution of evaporating CO2 in parallel minichannels Titre original : Modélisation de la distribution de CO2 en évaporation dans les microcanaux parallèles Type de document : texte imprimé Auteurs : Wiebke Brix, Auteur ; Martin Ryhl Kærn, Auteur ; Brian Elmegaard, Auteur Année de publication : 2010 Article en page(s) : pp. 1086-1094 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Heat  exchanger  Microchannel  Modelling  Simulation  Carbon  dioxide  Boiling  Two-phase  flow  Distribution Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The effects of airflow non-uniformity and uneven inlet qualities on the performance of a minichannel evaporator with parallel channels, using CO2 as refrigerant, are investigated numerically. For this purpose a one-dimensional discretised steady-state model was developed, applying well-known empirical correlations for calculating frictional pressure drop and heat transfer coefficients. An investigation of different correlations for boiling two-phase flow shows that the choice of correlation is insignificant regarding the overall results. It is shown that non-uniform airflow leads to maldistribution of the refrigerant and considerable capacity reduction of the evaporator. Uneven inlet qualities to the different channels show only minor effects on the refrigerant distribution and evaporator capacity as long as the channels are vertically oriented with CO2 flowing upwards. For horizontal channels capacity reductions are found for both non-uniform airflow and uneven inlet qualities. For horizontal minichannels the results are very similar to those obtained using R134a as refrigerant. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710000824 [article] Modelling distribution of evaporating CO2 in parallel minichannels = Modélisation de la distribution de CO2 en évaporation dans les microcanaux parallèles [texte imprimé] / Wiebke Brix, Auteur ; Martin Ryhl Kærn, Auteur ; Brian Elmegaard, Auteur . - 2010 . - pp. 1086-1094. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 33 N° 6 (Septembre 2010) . - pp. 1086-1094 Mots-clés : Heat  exchanger  Microchannel  Modelling  Simulation  Carbon  dioxide  Boiling  Two-phase  flow  Distribution Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : The effects of airflow non-uniformity and uneven inlet qualities on the performance of a minichannel evaporator with parallel channels, using CO2 as refrigerant, are investigated numerically. For this purpose a one-dimensional discretised steady-state model was developed, applying well-known empirical correlations for calculating frictional pressure drop and heat transfer coefficients. An investigation of different correlations for boiling two-phase flow shows that the choice of correlation is insignificant regarding the overall results. It is shown that non-uniform airflow leads to maldistribution of the refrigerant and considerable capacity reduction of the evaporator. Uneven inlet qualities to the different channels show only minor effects on the refrigerant distribution and evaporator capacity as long as the channels are vertically oriented with CO2 flowing upwards. For horizontal channels capacity reductions are found for both non-uniform airflow and uneven inlet qualities. For horizontal minichannels the results are very similar to those obtained using R134a as refrigerant. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710000824

Performance of residential air-conditioning systems with flow maldistribution in fin-and-tube evaporators / Martin Ryhl Kærn in International journal of refrigeration, Vol. 34 N° 3 (Mai 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 3 (Mai 2011) . - pp. 696-706 Titre : Performance of residential air-conditioning systems with flow maldistribution in fin-and-tube evaporators Titre original : Performance des systèmes de conditionnement d'air résidentiels avec une mauvaise distribution de l'écoulement dans les évaporateurs à tubes ailetés Type de document : texte imprimé Auteurs : Martin Ryhl Kærn, Auteur ; Wiebke Brix, Auteur ; Brian Elmegaard, Auteur Année de publication : 2011 Article en page(s) : pp. 696-706 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Cooling  Air  conditioning  Finned  tube  Modeling  Simulation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Refrigerant and airflow maldistribution in fin-and-tube evaporators for residential air-conditioning was investigated with numerical modeling. Fin-and-tube heat exchangers usually have a pre-defined circuitry. However, the objective in this study was to perform a generic investigation of each individual maldistribution source in an independent manner. Therefore, the evaporator and the condenser were simplified to be straight tubes for the purposes of this study. The numerical model of the R410A system, its verification and an investigation of individual maldistribution sources are presented in this paper. The maldistribution sources of interest were: inlet liquid/vapor phase distribution, feeder tube bending and airflow distribution. The results show that maldistribution reduced the cooling capacity and the coefficient of performance of the system. In particular, different phase distribution and non-uniform airflow distribution reduced the performance significantly. Different feeder tube bendings only caused a minor decrease in performance. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710002859 [article] Performance of residential air-conditioning systems with flow maldistribution in fin-and-tube evaporators = Performance des systèmes de conditionnement d'air résidentiels avec une mauvaise distribution de l'écoulement dans les évaporateurs à tubes ailetés [texte imprimé] / Martin Ryhl Kærn, Auteur ; Wiebke Brix, Auteur ; Brian Elmegaard, Auteur . - 2011 . - pp. 696-706. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 3 (Mai 2011) . - pp. 696-706 Mots-clés : Cooling  Air  conditioning  Finned  tube  Modeling  Simulation Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Refrigerant and airflow maldistribution in fin-and-tube evaporators for residential air-conditioning was investigated with numerical modeling. Fin-and-tube heat exchangers usually have a pre-defined circuitry. However, the objective in this study was to perform a generic investigation of each individual maldistribution source in an independent manner. Therefore, the evaporator and the condenser were simplified to be straight tubes for the purposes of this study. The numerical model of the R410A system, its verification and an investigation of individual maldistribution sources are presented in this paper. The maldistribution sources of interest were: inlet liquid/vapor phase distribution, feeder tube bending and airflow distribution. The results show that maldistribution reduced the cooling capacity and the coefficient of performance of the system. In particular, different phase distribution and non-uniform airflow distribution reduced the performance significantly. Different feeder tube bendings only caused a minor decrease in performance. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710002859