Documents disponibles écrits par cet auteur

Cost optimization of heat exchanger inventory for mechanical subcooling refrigeration cycles / Bilal Ahmed Qureshi 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. 1243–1253 Titre : Cost optimization of heat exchanger inventory for mechanical subcooling refrigeration cycles Titre original : Optimisation du coût des échangeurs de chaleur utilisés pour les cycles de sous-refroidissement mécaniques Type de document : texte imprimé Auteurs : Bilal Ahmed Qureshi, Auteur ; Syed M. Zubair, Auteur Année de publication : 2013 Article en page(s) : pp. 1243–1253 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Thermoeconomic;  Subcooling;  Optimization;  Heat  exchanger;  Inventory Résumé : In this paper, thermoeconomic considerations are given to heat exchanger inventory allocation in vapor compression cycles with mechanical subcooling. Investigation is made with respect to constant work rate, heat rejection and cooling rates as well as heat transfer in the subcooler. It was found that no minima exist for any of the cost functions with respect to the absolute temperature ratio (ξ) and the average subcooling absolute temperature ratio (θ3). The derivatives for the integrated subcooling cycle can be generated from the derivatives of the dedicated subcooling cycle. It was concluded that the cost optimization of the integrated mechanical subcooling system is qualitatively the same as the dedicated subcooling system. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000340 [article] Cost optimization of heat exchanger inventory for mechanical subcooling refrigeration cycles = Optimisation du coût des échangeurs de chaleur utilisés pour les cycles de sous-refroidissement mécaniques [texte imprimé] / Bilal Ahmed Qureshi, Auteur ; Syed M. Zubair, Auteur . - 2013 . - pp. 1243–1253. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 4 (Juin 2013) . - pp. 1243–1253 Mots-clés : Thermoeconomic;  Subcooling;  Optimization;  Heat  exchanger;  Inventory Résumé : In this paper, thermoeconomic considerations are given to heat exchanger inventory allocation in vapor compression cycles with mechanical subcooling. Investigation is made with respect to constant work rate, heat rejection and cooling rates as well as heat transfer in the subcooler. It was found that no minima exist for any of the cost functions with respect to the absolute temperature ratio (ξ) and the average subcooling absolute temperature ratio (θ3). The derivatives for the integrated subcooling cycle can be generated from the derivatives of the dedicated subcooling cycle. It was concluded that the cost optimization of the integrated mechanical subcooling system is qualitatively the same as the dedicated subcooling system. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713000340

Mechanical sub-cooling vapor compression systems: Current status and future directions / Bilal Ahmed Qureshi 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. 2097–2110 Titre : Mechanical sub-cooling vapor compression systems: Current status and future directions Titre original : Sous-refroidissement mécanique des systémes de compression de vapeur: situation actuelle et orientations futures Type de document : texte imprimé Auteurs : Bilal Ahmed Qureshi, Auteur ; Syed M. Zubair, Auteur Année de publication : 2014 Article en page(s) : pp. 2097–2110 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Subcooling;  vapor  compression;  refrigeration  system;  performance  improvement Résumé : Using mechanical sub-cooling systems to increase COP of vapor compression cycles is a known method in literature to save energy and increase efficiency. Recently, much progress has been made with respect to investigation into its different aspects that can help to put it into practice. Numerical and experimental works are considered for the purpose of highlighting this progress. These can be categorized as: a) simulation of performance characteristics resulting from different refrigerant combinations in dedicated mechanical sub-cooling systems, b) variation in performance characteristics for a vapor compression cycle using integrated mechanical sub-cooling because of fouling, c) experimental study about consequences of employing a dedicated mechanical subcooling cycle with a simple vapor compression system, and d) experimental investigation about consequences of employing a subcooler in a two-stage refrigeration cycle. Some important results are discussed. Finally, some suggestions are made to provide direction into future research in this area to help put it into practice. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002041 [article] Mechanical sub-cooling vapor compression systems: Current status and future directions = Sous-refroidissement mécanique des systémes de compression de vapeur: situation actuelle et orientations futures [texte imprimé] / Bilal Ahmed Qureshi, Auteur ; Syed M. Zubair, Auteur . - 2014 . - pp. 2097–2110. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 8 (Décembre 2013) . - pp. 2097–2110 Mots-clés : Subcooling;  vapor  compression;  refrigeration  system;  performance  improvement Résumé : Using mechanical sub-cooling systems to increase COP of vapor compression cycles is a known method in literature to save energy and increase efficiency. Recently, much progress has been made with respect to investigation into its different aspects that can help to put it into practice. Numerical and experimental works are considered for the purpose of highlighting this progress. These can be categorized as: a) simulation of performance characteristics resulting from different refrigerant combinations in dedicated mechanical sub-cooling systems, b) variation in performance characteristics for a vapor compression cycle using integrated mechanical sub-cooling because of fouling, c) experimental study about consequences of employing a dedicated mechanical subcooling cycle with a simple vapor compression system, and d) experimental investigation about consequences of employing a subcooler in a two-stage refrigeration cycle. Some important results are discussed. Finally, some suggestions are made to provide direction into future research in this area to help put it into practice. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713002041

Performance degradation of a vapor compression refrigeration system under fouled conditions / Bilal Ahmed Qureshi in International journal of refrigeration, Vol. 34 N° 4 (Juin 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 4 (Juin 2011) . - pp. 1016-1027 Titre : Performance degradation of a vapor compression refrigeration system under fouled conditions Titre original : Détérioration de la performance d'un système frigorifique à compression de vapeur sous des conditions d'encrassement Type de document : texte imprimé Auteurs : Bilal Ahmed Qureshi, Auteur ; Syed M. Zubair, Auteur Année de publication : 2011 Article en page(s) : pp. 1016-1027 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Vapour  compression  Refrigeration  Performance  Degradation  Fouling  R134a  R407C  R410A  R404A  R717  R290 Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Performance degradation due to fouling in a vapor compression cycle is investigated for various applications. Considering the first set of refrigerants i.e. R134a, R410A and R407C, from a first law standpoint, the COP indicates that R134a always performs better unless only the evaporator is being fouled. In contrast to this, from a second-law standpoint, the second-law efficiency indicates that R134a performs the best in all cases. Considering the second set of refrigerants i.e. R717, R404A and R290, from a first law standpoint, the COP indicates that R717 always performs better unless only the evaporator is being fouled. In contrast to this, from a second-law standpoint, the second-law efficiency indicates that R717 performs the best in all cases. Volumetric efficiency of R410A and R717 remained the highest under the respective conditions studied. Furthermore, performance degradation of the evaporator often has a larger effect on compressor power requirement while that of the condenser has an overall larger effect on the COP. A new performance degradation law is presented in light of the data generated, which can reduce the amount of experimentation and help predict relevant quantities of the refrigeration system. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000582 [article] Performance degradation of a vapor compression refrigeration system under fouled conditions = Détérioration de la performance d'un système frigorifique à compression de vapeur sous des conditions d'encrassement [texte imprimé] / Bilal Ahmed Qureshi, Auteur ; Syed M. Zubair, Auteur . - 2011 . - pp. 1016-1027. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 4 (Juin 2011) . - pp. 1016-1027 Mots-clés : Vapour  compression  Refrigeration  Performance  Degradation  Fouling  R134a  R407C  R410A  R404A  R717  R290 Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Performance degradation due to fouling in a vapor compression cycle is investigated for various applications. Considering the first set of refrigerants i.e. R134a, R410A and R407C, from a first law standpoint, the COP indicates that R134a always performs better unless only the evaporator is being fouled. In contrast to this, from a second-law standpoint, the second-law efficiency indicates that R134a performs the best in all cases. Considering the second set of refrigerants i.e. R717, R404A and R290, from a first law standpoint, the COP indicates that R717 always performs better unless only the evaporator is being fouled. In contrast to this, from a second-law standpoint, the second-law efficiency indicates that R717 performs the best in all cases. Volumetric efficiency of R410A and R717 remained the highest under the respective conditions studied. Furthermore, performance degradation of the evaporator often has a larger effect on compressor power requirement while that of the condenser has an overall larger effect on the COP. A new performance degradation law is presented in light of the data generated, which can reduce the amount of experimentation and help predict relevant quantities of the refrigeration system. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711000582

The effect of refrigerant combinations on performance of a vapor compression refrigeration system with dedicated mechanical sub-cooling / Bilal Ahmed Qureshi in International journal of refrigeration, Vol. 35 N° 1 (Janvier 2012) 

Public ISBD [article]  in International journal of refrigeration > Vol. 35 N° 1 (Janvier 2012) . - pp. 47–57 Titre : The effect of refrigerant combinations on performance of a vapor compression refrigeration system with dedicated mechanical sub-cooling Titre original : Les effets de différentes combinaisons de frigorigènes sur la performance d' à compression de vapeur muni d'un dispositif de sous-refroidissement mécanique Type de document : texte imprimé Auteurs : Bilal Ahmed Qureshi, Auteur ; Syed M. Zubair, Auteur Année de publication : 2012 Article en page(s) : pp. 47–57 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Refrigeration  system  Refrigerant  Subcooling  Compressor  Multistage  system Résumé : Performance characteristics due to use of different refrigerant combinations in vapor compression cycles with dedicated mechanical sub-cooling are investigated. For scratch designs, R134a used in both cycles produced the best results in terms of COP, COP gain and relative compressor sizing. In retrofit cases, considering the high sensitivity of COP to the relative size of heat exchangers in the sub-cooler cycle and the low gain in COP obtained due to installation of a dedicated sub-cooling cycle when R717 is the main cycle refrigerant, it seems that dedicated mechanical sub-cooling may be more suited to cycles using R134a as the main cycle refrigerant rather than R717. With R134a as the main cycle refrigerant, no major difference was noted, by changing the sub-cooler cycle refrigerant, in the degradation of the performance parameters such as COP and cooling capacity, due to equal fouling of the heat exchangers. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711002258 [article] The effect of refrigerant combinations on performance of a vapor compression refrigeration system with dedicated mechanical sub-cooling = Les effets de différentes combinaisons de frigorigènes sur la performance d' à compression de vapeur muni d'un dispositif de sous-refroidissement mécanique [texte imprimé] / Bilal Ahmed Qureshi, Auteur ; Syed M. Zubair, Auteur . - 2012 . - pp. 47–57. Génie mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 35 N° 1 (Janvier 2012) . - pp. 47–57 Mots-clés : Refrigeration  system  Refrigerant  Subcooling  Compressor  Multistage  system Résumé : Performance characteristics due to use of different refrigerant combinations in vapor compression cycles with dedicated mechanical sub-cooling are investigated. For scratch designs, R134a used in both cycles produced the best results in terms of COP, COP gain and relative compressor sizing. In retrofit cases, considering the high sensitivity of COP to the relative size of heat exchangers in the sub-cooler cycle and the low gain in COP obtained due to installation of a dedicated sub-cooling cycle when R717 is the main cycle refrigerant, it seems that dedicated mechanical sub-cooling may be more suited to cycles using R134a as the main cycle refrigerant rather than R717. With R134a as the main cycle refrigerant, no major difference was noted, by changing the sub-cooler cycle refrigerant, in the degradation of the performance parameters such as COP and cooling capacity, due to equal fouling of the heat exchangers. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711002258

A unified approach to predict evaporation losses in evaporative heat exchangers / Bilal Ahmed Qureshi 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. 1866–1876 Titre : A unified approach to predict evaporation losses in evaporative heat exchangers Titre original : Approche unifiée de la prévision des pertes par évaporation dans les échangeurs de chaleur évaporatifs Type de document : texte imprimé Auteurs : Bilal Ahmed Qureshi, Auteur ; Syed M. Zubair, Auteur Année de publication : 2012 Article en page(s) : pp. 1866–1876 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Evaporative  heat  exchanger  Evaporation  Correlation  Prediction Résumé : In this paper, the rules of thumb used to predict evaporation losses in different evaporative heat exchangers are unified. The accurate prediction of all aspects of evaporative heat exchanger behavior is very important. Accurately predicting evaporation losses is significant since water, in this class of heat exchangers, is cooled primarily by evaporation of a portion of the circulating water that causes the concentration of impurities to increase. Furthermore, the design of hybrid cooling towers requires that the amount of evaporation be known. A single correlation is, therefore, developed for this class of heat exchangers that is simple and accurate with a wide range of applicability. The predicted values are in good agreement with experimental values as well as predictions made by reliable mathematical models. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711001538# [article] A unified approach to predict evaporation losses in evaporative heat exchangers = Approche unifiée de la prévision des pertes par évaporation dans les échangeurs de chaleur évaporatifs [texte imprimé] / Bilal Ahmed Qureshi, Auteur ; Syed M. Zubair, Auteur . - 2012 . - pp. 1866–1876. Génie mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 8 (Décembre 2011) . - pp. 1866–1876 Mots-clés : Evaporative  heat  exchanger  Evaporation  Correlation  Prediction Résumé : In this paper, the rules of thumb used to predict evaporation losses in different evaporative heat exchangers are unified. The accurate prediction of all aspects of evaporative heat exchanger behavior is very important. Accurately predicting evaporation losses is significant since water, in this class of heat exchangers, is cooled primarily by evaporation of a portion of the circulating water that causes the concentration of impurities to increase. Furthermore, the design of hybrid cooling towers requires that the amount of evaporation be known. A single correlation is, therefore, developed for this class of heat exchangers that is simple and accurate with a wide range of applicability. The predicted values are in good agreement with experimental values as well as predictions made by reliable mathematical models. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711001538#