Modelling thermostatic expansion valves / Ian W. Eames in International journal of refrigeration, Vol. 38 (Février 2014)  

Public ISBD [article]  inInternational journal of refrigeration > Vol. 38 (Février 2014) . - pp. 189–197 Titre : Modelling thermostatic expansion valves Titre original : Modélisation thermostatique des détendeurs Type de document : texte imprimé Auteurs : Ian W. Eames, Auteur ; Adriano Milazzo, Auteur ; Graeme G. Maidment, Auteur Année de publication : 2014 Article en page(s) : pp. 189–197 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Vapour compression refrigerator  Simulation  Modelling  Thermostatic expansion valve  Software Résumé : This paper describes and evaluates the development of generalised steady state and transient mathematical models for thermostatic expansion valves (TEVs) of the types used in commercial refrigeration systems. The model is of a generalised nature, because it is not necessary to input performance or geometrical data for a particular valve to operate the model. However, if required, the models can provide an accurate correlation of valve manufacturer's data. Derivations are provided and validating data is presented. The mathematical models described in the paper form part of computer software that simulates the thermal operation of whole refrigeration systems. The software is titled Vapour Compression Refrigeration System (VCRS) simulator, and by way of example the paper presents results from the VCRS simulator which are used to aid a discussion of operating faults, such as hunting and under damping and their possible causes, where these can be attributed to the expansion valve. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001576 [article] Modelling thermostatic expansion valves = Modélisation thermostatique des détendeurs [texte imprimé] / Ian W. Eames, Auteur ; Adriano Milazzo, Auteur ; Graeme G. Maidment, Auteur . - 2014 . - pp. 189–197. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 38 (Février 2014) . - pp. 189–197 Mots-clés : Vapour compression refrigerator  Simulation  Modelling  Thermostatic expansion valve  Software Résumé : This paper describes and evaluates the development of generalised steady state and transient mathematical models for thermostatic expansion valves (TEVs) of the types used in commercial refrigeration systems. The model is of a generalised nature, because it is not necessary to input performance or geometrical data for a particular valve to operate the model. However, if required, the models can provide an accurate correlation of valve manufacturer's data. Derivations are provided and validating data is presented. The mathematical models described in the paper form part of computer software that simulates the thermal operation of whole refrigeration systems. The software is titled Vapour Compression Refrigeration System (VCRS) simulator, and by way of example the paper presents results from the VCRS simulator which are used to aid a discussion of operating faults, such as hunting and under damping and their possible causes, where these can be attributed to the expansion valve. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001576

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Prediction of condensation in steam ejector for a refrigeration system / Giuseppe Grazzini in International journal of refrigeration, Vol. 34 N° 7 (Novembre 2011)  

Public ISBD [article]  inInternational journal of refrigeration > Vol. 34 N° 7 (Novembre 2011) . - pp. 1641-1648 Titre : Prediction of condensation in steam ejector for a refrigeration system Titre original : Prévision de la condensation dans l'éjecteur à vapeur d'un système frigorifique Type de document : texte imprimé Auteurs : Giuseppe Grazzini, Auteur ; Adriano Milazzo, Auteur ; Samuele Piazzini, Auteur Année de publication : 2011 Article en page(s) : pp. 1641-1648 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Ejector Condensation Subcooling Water Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : An experimental refrigeration system based on a two-stage steam ejector was set-up in the Thermodynamics and Heat Transfer Laboratory of our Department. The system optimization and realization have been described elsewhere ( [Grazzini and Mariani, 1998] and [Grazzini and Rocchetti, 2008] ). In both stages, primary flows are highly supersonic and reach low pressure and temperature levels. As usual in the literature, an ideal gas model was used during the design process. This paper is intended to check the validity of this assumption. In order to understand the actual working condition of our system, several models have been compared. The presence of high flow speed suggests the existence of metastable conditions. To set the border for the metastable region, the spinodal curve has been drawn. Isentropic expansion of vapour through the nozzle, modelled as ideal gas, seems well within the metastable zone. However, the Classic Nucleation Theory shows that the Wilson line is crossed at the nozzle throat. Condensation produces a marked difference in the conditions at the nozzle exit. Results coming from the present analysis will be used in further optimization of the experimental ejector design. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710002264 [article] Prediction of condensation in steam ejector for a refrigeration system = Prévision de la condensation dans l'éjecteur à vapeur d'un système frigorifique [texte imprimé] / Giuseppe Grazzini, Auteur ; Adriano Milazzo, Auteur ; Samuele Piazzini, Auteur . - 2011 . - pp. 1641-1648. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 7 (Novembre 2011) . - pp. 1641-1648 Mots-clés : Ejector Condensation Subcooling Water Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : An experimental refrigeration system based on a two-stage steam ejector was set-up in the Thermodynamics and Heat Transfer Laboratory of our Department. The system optimization and realization have been described elsewhere ( [Grazzini and Mariani, 1998] and [Grazzini and Rocchetti, 2008] ). In both stages, primary flows are highly supersonic and reach low pressure and temperature levels. As usual in the literature, an ideal gas model was used during the design process. This paper is intended to check the validity of this assumption. In order to understand the actual working condition of our system, several models have been compared. The presence of high flow speed suggests the existence of metastable conditions. To set the border for the metastable region, the spinodal curve has been drawn. Isentropic expansion of vapour through the nozzle, modelled as ideal gas, seems well within the metastable zone. However, the Classic Nucleation Theory shows that the Wilson line is crossed at the nozzle throat. Condensation produces a marked difference in the conditions at the nozzle exit. Results coming from the present analysis will be used in further optimization of the experimental ejector design. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710002264

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