Dépouillements

Flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures in Revue internationale du froid, vol 32, Issue 2 (2009)

Public ISBD [article]  inRevue internationale du froid > vol 32, Issue 2 (2009) . - pp. 185-202 Titre : Flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures Titre original : Caractéristiques de l'ébullition en écoulement et visualisation de la configuration de l'écoulement des mélanges frigorigène/huile de lubrification Type de document : texte imprimé Année de publication : 2011 Article en page(s) : pp. 185-202 Langues : Anglais (eng) Français (fre) Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Frigorigène  Transfert de Chaleur  Chute de pression Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : A comprehensive review of flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures is presented in this paper. First, various parameters influenced by the lubricant oil in convective boiling of refrigerants, such as mass velocity, vapor quality, oil concentration and geometric characteristics of the heat transfer tube are discussed. The effects of the unavoidable introduction of the lubricant oil on the thermodynamics properties of a refrigerant are described. Then, a review of the main experimental studies of flow boiling of refrigerant/lubricant oil mixtures is presented and also describes research with halocarbons, carbon dioxide, hydrocarbons and ammonia. There is no agreement among these studies regarding the effect of the oil in the evaporator, with studies showing an increase or decrease in the heat transfer coefficient. However, in relation to pressure drop, all the results presented the same trend, increasing the pressure drop with increasing oil concentration. Next, the flow patterns of refrigerant/oil mixtures are illustrated together with a selection of video images. It is possible to notice the difference in frothing formation with respect to the particular refrigerant and tube geometry. Some predictions of oil effects on the heat transfer coefficient and pressure drops based on the mixture physical properties are then presented and the trends compared to data. Finally, some suggestions for future work are given. [article] Flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures = Caractéristiques de l'ébullition en écoulement et visualisation de la configuration de l'écoulement des mélanges frigorigène/huile de lubrification [texte imprimé] . - 2011 . - pp. 185-202. Langues : Anglais (eng) Français (fre) in Revue internationale du froid > vol 32, Issue 2 (2009) . - pp. 185-202 Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Frigorigène  Transfert de Chaleur  Chute de pression Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : A comprehensive review of flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures is presented in this paper. First, various parameters influenced by the lubricant oil in convective boiling of refrigerants, such as mass velocity, vapor quality, oil concentration and geometric characteristics of the heat transfer tube are discussed. The effects of the unavoidable introduction of the lubricant oil on the thermodynamics properties of a refrigerant are described. Then, a review of the main experimental studies of flow boiling of refrigerant/lubricant oil mixtures is presented and also describes research with halocarbons, carbon dioxide, hydrocarbons and ammonia. There is no agreement among these studies regarding the effect of the oil in the evaporator, with studies showing an increase or decrease in the heat transfer coefficient. However, in relation to pressure drop, all the results presented the same trend, increasing the pressure drop with increasing oil concentration. Next, the flow patterns of refrigerant/oil mixtures are illustrated together with a selection of video images. It is possible to notice the difference in frothing formation with respect to the particular refrigerant and tube geometry. Some predictions of oil effects on the heat transfer coefficient and pressure drops based on the mixture physical properties are then presented and the trends compared to data. Finally, some suggestions for future work are given.

Numerical and experimental investigations on the use of mist flow process in refrigerated display cabinets in Revue internationale du froid, vol 32, Issue 2 (2009)

Public ISBD [article]  inRevue internationale du froid > vol 32, Issue 2 (2009) . - pp. 203-219 Titre : Numerical and experimental investigations on the use of mist flow process in refrigerated display cabinets Titre original : Etudes numériques et expérimentales sur l'écoulement diphasique (air + gouttelettes) dans les meubles frigorifiques de vente Type de document : texte imprimé Année de publication : 2011 Article en page(s) : pp. 203-219 Langues : Anglais (eng) Français (fre) Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Modélisation  Écoulement diphasique  Brumisation  Performance  Système évaporatif Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : This study concerns the use of mist flow whereby fine water droplets are injected into the air curtain to improve the performance of Refrigerated Display Cabinets (RDCs). The deposition and evaporation of droplets on the surface of products partially compensate the radiative heat gained by the products by removing from it the amount of latent heat of the evaporated droplets. The experiments were carried out on an actual display cabinet. Numerical modelling was performed using Fluent Computational Fluid Dynamics (CFD) software. In two-phase flow, an Euler–Lagrange approach was adopted to predict the transport of droplets by the air curtain and their spatial distribution on the product surface of the RDC. An original numerical procedure was built in the CFD model in order to compute the deposited droplets while taking into account the evaporative flux of droplets on the product surface. The two-phase flow model was used to analyse the performance of the mist cooling process in terms of surface temperature decrease and the homogeneity of droplet deposition on the product surface of the RDC as a function of inlet droplet injection configurations. [article] Numerical and experimental investigations on the use of mist flow process in refrigerated display cabinets = Etudes numériques et expérimentales sur l'écoulement diphasique (air + gouttelettes) dans les meubles frigorifiques de vente [texte imprimé] . - 2011 . - pp. 203-219. Langues : Anglais (eng) Français (fre) in Revue internationale du froid > vol 32, Issue 2 (2009) . - pp. 203-219 Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Modélisation  Écoulement diphasique  Brumisation  Performance  Système évaporatif Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : This study concerns the use of mist flow whereby fine water droplets are injected into the air curtain to improve the performance of Refrigerated Display Cabinets (RDCs). The deposition and evaporation of droplets on the surface of products partially compensate the radiative heat gained by the products by removing from it the amount of latent heat of the evaporated droplets. The experiments were carried out on an actual display cabinet. Numerical modelling was performed using Fluent Computational Fluid Dynamics (CFD) software. In two-phase flow, an Euler–Lagrange approach was adopted to predict the transport of droplets by the air curtain and their spatial distribution on the product surface of the RDC. An original numerical procedure was built in the CFD model in order to compute the deposited droplets while taking into account the evaporative flux of droplets on the product surface. The two-phase flow model was used to analyse the performance of the mist cooling process in terms of surface temperature decrease and the homogeneity of droplet deposition on the product surface of the RDC as a function of inlet droplet injection configurations.

Air velocity characteristics within vented pallets loaded in a refrigerated vehicle with and without air ducts in Revue internationale du froid, vol 32, Issue 2 (2009)

Public ISBD [article]  inRevue internationale du froid > vol 32, Issue 2 (2009) . - pp. 220-234 Titre : Air velocity characteristics within vented pallets loaded in a refrigerated vehicle with and without air ducts Titre original : Caractéristiques de la vitesse de l'écoulement d'air à l'intérieur de palettes munies de ventilation chargées à bord d'un véhicule frigorifique avec ou sans gaines d'air Type de document : texte imprimé Année de publication : 2011 Article en page(s) : pp. 220-234 Langues : Anglais (eng) Français (fre) Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Transport frigorifique  Palette  Modélisation  Dynamique numérique des fluides Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : During transport using refrigerated vehicles, this being a vital link in the cold chain, the maintaining of even temperature throughout the cargo is essential in order to preserve the quality, safety and shelf life of perishable food. Within the refrigerated container, the temperature level and its homogeneity are directly governed by airflow patterns. The design of the air-distribution system should allow these airflows to compensate heat fluxes exchanged through the insulated walls or generated by the products. In this paper, a reduced-scale model and CFD predictions were used to investigate experimentally and numerically the airflow patterns within a typical refrigerated truck configuration loaded with vented pallets filled with spherical objects. The experiments were carried out using a laser Doppler velocimetry and thermal sphere-shaped probes located inside the pallets. The aim was to investigate air velocity characteristics above and within pallets. The performance of ventilation was characterized with and without supply air duct systems. Both configurations are extensively used in refrigerated transport. Full-scale measurements were also performed within a load of fruit during transport in a refrigerated truck in order to evaluate the temperature distribution under given operating conditions. The numerical modelling of airflow was performed using the computational fluid dynamics (CFD) fluent code and the Reynolds Stress Model (RSM) turbulence model. Numerical and experimental data make it possible to evaluate the air ventilation levels and their heterogeneity between the pallets. The numerical predictions show reasonable agreement with experimental data. The studied supply air duct system improves significantly the homogeneity of ventilation in the vehicle. [article] Air velocity characteristics within vented pallets loaded in a refrigerated vehicle with and without air ducts = Caractéristiques de la vitesse de l'écoulement d'air à l'intérieur de palettes munies de ventilation chargées à bord d'un véhicule frigorifique avec ou sans gaines d'air [texte imprimé] . - 2011 . - pp. 220-234. Langues : Anglais (eng) Français (fre) in Revue internationale du froid > vol 32, Issue 2 (2009) . - pp. 220-234 Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Transport frigorifique  Palette  Modélisation  Dynamique numérique des fluides Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : During transport using refrigerated vehicles, this being a vital link in the cold chain, the maintaining of even temperature throughout the cargo is essential in order to preserve the quality, safety and shelf life of perishable food. Within the refrigerated container, the temperature level and its homogeneity are directly governed by airflow patterns. The design of the air-distribution system should allow these airflows to compensate heat fluxes exchanged through the insulated walls or generated by the products. In this paper, a reduced-scale model and CFD predictions were used to investigate experimentally and numerically the airflow patterns within a typical refrigerated truck configuration loaded with vented pallets filled with spherical objects. The experiments were carried out using a laser Doppler velocimetry and thermal sphere-shaped probes located inside the pallets. The aim was to investigate air velocity characteristics above and within pallets. The performance of ventilation was characterized with and without supply air duct systems. Both configurations are extensively used in refrigerated transport. Full-scale measurements were also performed within a load of fruit during transport in a refrigerated truck in order to evaluate the temperature distribution under given operating conditions. The numerical modelling of airflow was performed using the computational fluid dynamics (CFD) fluent code and the Reynolds Stress Model (RSM) turbulence model. Numerical and experimental data make it possible to evaluate the air ventilation levels and their heterogeneity between the pallets. The numerical predictions show reasonable agreement with experimental data. The studied supply air duct system improves significantly the homogeneity of ventilation in the vehicle.

The freezing and supercooling of garlic (Allium sativum L.) in Revue internationale du froid, vol 32, Issue 2 (2009)

Public ISBD [article]  inRevue internationale du froid > vol 32, Issue 2 (2009) . - pp. 53-260 Titre : The freezing and supercooling of garlic (Allium sativum L.) Titre original : Congélation et surfusion d'ail (Allium sativum L.) Type de document : texte imprimé Année de publication : 2011 Article en page(s) : pp. 53-260 Langues : Anglais (eng) Français (fre) Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Expérimentation  Congélation  Surfusion  entreposage frigorifique Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : This work shows that peeled garlic cloves demonstrate significant supercooling during freezing under standard conditions and can be stored at temperatures well below their freezing point (?2.7 °C) without freezing. The nucleation point or ‘metastable limit temperature’ (the point at which ice crystal nucleation is initiated) of peeled garlic cloves was found to be between ?7.7 and ?14.6 °C. Peeled garlic cloves were stored under static air conditions at temperatures between ?6 and ?9 °C for up to 69 h without freezing, and unpeeled whole garlic bulbs and cloves were stored for 1 week at ?6 °C without freezing. [article] The freezing and supercooling of garlic (Allium sativum L.) = Congélation et surfusion d'ail (Allium sativum L.) [texte imprimé] . - 2011 . - pp. 53-260. Langues : Anglais (eng) Français (fre) in Revue internationale du froid > vol 32, Issue 2 (2009) . - pp. 53-260 Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Expérimentation  Congélation  Surfusion  entreposage frigorifique Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : This work shows that peeled garlic cloves demonstrate significant supercooling during freezing under standard conditions and can be stored at temperatures well below their freezing point (?2.7 °C) without freezing. The nucleation point or ‘metastable limit temperature’ (the point at which ice crystal nucleation is initiated) of peeled garlic cloves was found to be between ?7.7 and ?14.6 °C. Peeled garlic cloves were stored under static air conditions at temperatures between ?6 and ?9 °C for up to 69 h without freezing, and unpeeled whole garlic bulbs and cloves were stored for 1 week at ?6 °C without freezing.

Experimental investigation on diabatic flow of R-134a through spiral capillary tube in Revue internationale du froid, vol 32, Issue 2 (2009)

Public ISBD [article]  inRevue internationale du froid > vol 32, Issue 2 (2009) . - pp. 261-271 Titre : Experimental investigation on diabatic flow of R-134a through spiral capillary tube Titre original : Etude expérimentale sur l’écoulement diabatique du R-134a dans un capillaire en spirale Type de document : texte imprimé Année de publication : 2011 Article en page(s) : pp. 261-271 Langues : Anglais (eng) Français (fre) Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Système frigorifique  Système à compression  Expérimentation  Tube hélicoïdal  Géométrie Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : The present experimental investigation has been carried out to investigate the effects of various geometric parameters on the mass flow rate of R-134a through diabatic spiral capillary tube. In diabatic flow, the capillary tube is bonded with the compressor suction-line to form a counter-flow exchanger. The lateral type of diabatic capillary tube has been investigated in the present experimental study. The major geometric parameters investigated are capillary tube diameter, capillary tube length and coil pitch. In addition, effect of inlet subcooling on the mass flow rate through diabatic spiral capillary tube is also done. A comparison of the performance of diabatic spiral capillary tube has been made with adiabatic spiral capillary tube. Generalized empirical correlation for diabatic spiral capillary tube has also been proposed. It has been found that the predictions of the proposed correlation lie in the error band of ±7%. [article] Experimental investigation on diabatic flow of R-134a through spiral capillary tube = Etude expérimentale sur l’écoulement diabatique du R-134a dans un capillaire en spirale [texte imprimé] . - 2011 . - pp. 261-271. Langues : Anglais (eng) Français (fre) in Revue internationale du froid > vol 32, Issue 2 (2009) . - pp. 261-271 Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Système frigorifique  Système à compression  Expérimentation  Tube hélicoïdal  Géométrie Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : The present experimental investigation has been carried out to investigate the effects of various geometric parameters on the mass flow rate of R-134a through diabatic spiral capillary tube. In diabatic flow, the capillary tube is bonded with the compressor suction-line to form a counter-flow exchanger. The lateral type of diabatic capillary tube has been investigated in the present experimental study. The major geometric parameters investigated are capillary tube diameter, capillary tube length and coil pitch. In addition, effect of inlet subcooling on the mass flow rate through diabatic spiral capillary tube is also done. A comparison of the performance of diabatic spiral capillary tube has been made with adiabatic spiral capillary tube. Generalized empirical correlation for diabatic spiral capillary tube has also been proposed. It has been found that the predictions of the proposed correlation lie in the error band of ±7%.

Computational modeling of airflow patterns and heat transfer prediction through stacked layers' products in a vented box during cooling in Revue internationale du froid, vol 32, Issue 2 (2009)

Public ISBD [article]  inRevue internationale du froid > vol 32, Issue 2 (2009) . - pp. 295-306 Titre : Computational modeling of airflow patterns and heat transfer prediction through stacked layers' products in a vented box during cooling Titre original : Produits empilés dans un conteneur muni d'orifices d'aération : modélisation de la configuration de l'écoulement d'air et prévision du transfert de chaleur Type de document : texte imprimé Année de publication : 2011 Article en page(s) : pp. 295-306 Langues : Anglais (eng) Français (fre) Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Transport frigorifique  Modélisation  Température Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : Efficiency of forced-air cooling processes is measured by process time and product temperature uniformity. Ventilated packaging is required to achieve a rapid and uniform cooling process. Product type, produce positioning and orientation and container venting have significant effects on airflow patterns. To optimize the design, airflow patterns and temperature distributions inside a ventilated package should be known. The objective of this study was to determine airflow patterns and temperature distribution in ventilated containers including stacked layers of spheres using computational fluid dynamics and turbulence model. Effects of flow dimensionality, turbulence intensity, mesh sensitivity, opening size and ratios for venting and air inflow rate were investigated. This study is expected to provide a better method for analyzing cooling performance of ventilated packages. [article] Computational modeling of airflow patterns and heat transfer prediction through stacked layers' products in a vented box during cooling = Produits empilés dans un conteneur muni d'orifices d'aération : modélisation de la configuration de l'écoulement d'air et prévision du transfert de chaleur [texte imprimé] . - 2011 . - pp. 295-306. Langues : Anglais (eng) Français (fre) in Revue internationale du froid > vol 32, Issue 2 (2009) . - pp. 295-306 Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Transport frigorifique  Modélisation  Température Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : Efficiency of forced-air cooling processes is measured by process time and product temperature uniformity. Ventilated packaging is required to achieve a rapid and uniform cooling process. Product type, produce positioning and orientation and container venting have significant effects on airflow patterns. To optimize the design, airflow patterns and temperature distributions inside a ventilated package should be known. The objective of this study was to determine airflow patterns and temperature distribution in ventilated containers including stacked layers of spheres using computational fluid dynamics and turbulence model. Effects of flow dimensionality, turbulence intensity, mesh sensitivity, opening size and ratios for venting and air inflow rate were investigated. This study is expected to provide a better method for analyzing cooling performance of ventilated packages.

Experimental evaluation of the inter-stage conditions of a two-stage refrigeration cycle using a compound compressor in Revue internationale du froid, vol 32, Issue 2 (2009)

Public ISBD [article]  inRevue internationale du froid > vol 32, Issue 2 (2009) . - pp. 307-315 Titre : Experimental evaluation of the inter-stage conditions of a two-stage refrigeration cycle using a compound compressor Titre original : Evaluation expérimentale des conditions entre les étages dans un cycle frigorifique biétagé muni d’un compresseur compound Type de document : texte imprimé Année de publication : 2011 Article en page(s) : pp. 307-315 Langues : Anglais (eng) Français (fre) Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Système frigorifique  Système à compression  Expérimentation Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : The aim of the present paper is to detail an analysis, based on experimental data, of the inter-stage working conditions of a two-stage vapour compression facility equipped with a compound compressor, which operates with the most usual inter-stage configurations (two-stage with direct liquid injection and two-stage with subcooler) in medium- and low-capacity commercial refrigeration applications. The experimental analysis is performed in an evaporating temperature range between ?36 and ?20 °C, and in a condensing temperature range between 30 and 47 °C, using one of the fluids most widely-used in Europe for low-temperature applications, the R-404a. The inter-stage working temperature/pressure obtained in the tests has been contrasted with the two usual criterion of the optimum working conditions definition: the arithmetical mean of the refrigerant condensing and evaporating temperatures and the criterion of equal pressure ratios in both stages. This paper presents the differences and affinities with the criterion and analyses the influence of the intermediate systems (direct liquid injection and subcooler) on the inter-stage operating conditions. [article] Experimental evaluation of the inter-stage conditions of a two-stage refrigeration cycle using a compound compressor = Evaluation expérimentale des conditions entre les étages dans un cycle frigorifique biétagé muni d’un compresseur compound [texte imprimé] . - 2011 . - pp. 307-315. Langues : Anglais (eng) Français (fre) in Revue internationale du froid > vol 32, Issue 2 (2009) . - pp. 307-315 Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Système frigorifique  Système à compression  Expérimentation Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : The aim of the present paper is to detail an analysis, based on experimental data, of the inter-stage working conditions of a two-stage vapour compression facility equipped with a compound compressor, which operates with the most usual inter-stage configurations (two-stage with direct liquid injection and two-stage with subcooler) in medium- and low-capacity commercial refrigeration applications. The experimental analysis is performed in an evaporating temperature range between ?36 and ?20 °C, and in a condensing temperature range between 30 and 47 °C, using one of the fluids most widely-used in Europe for low-temperature applications, the R-404a. The inter-stage working temperature/pressure obtained in the tests has been contrasted with the two usual criterion of the optimum working conditions definition: the arithmetical mean of the refrigerant condensing and evaporating temperatures and the criterion of equal pressure ratios in both stages. This paper presents the differences and affinities with the criterion and analyses the influence of the intermediate systems (direct liquid injection and subcooler) on the inter-stage operating conditions.

Decoupling features for diagnosis of reversing and check valve faults in heat pumps in Revue internationale du froid, vol 32, Issue 2 (2009)

Public ISBD [article]  inRevue internationale du froid > vol 32, Issue 2 (2009) . - pp. 316-326 Titre : Decoupling features for diagnosis of reversing and check valve faults in heat pumps Titre original : Pompes à chaleur : diagnostic des anomalies de robinets d’inversion et des clapets anti-retour Type de document : texte imprimé Année de publication : 2011 Article en page(s) : pp. 316-326 Langues : Anglais (eng) Français (fre) Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Pompe à chaleur  Détection  Robinet inverseur  Frigorigène Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : Recently, a decoupling-based (DB) fault detection and diagnosis (FDD) method was developed for diagnosing multiple-simultaneous faults in air conditioners (AC) and was shown to have very good performance. The method relies on identifying diagnostic features that are decoupled (i.e., insensitive) to other faults and operating conditions. The current paper extends the DB FDD methodology to heat pumps. Heat pumps have all the same faults as occur for air conditioners with additional faults associated with components that accommodate heating mode, including reversing valve leakage and check valve leakage. Decoupling features were developed for these additional faults and laboratory evaluations were performed to evaluate diagnostic performance. It was found that check valve leakage could be detected and diagnosed before the heating capacity degradation reached 5% for a system with a fixed orifice expansion (FXO) device and 3% for the same system retrofit with a thermal expansion valve (TXV). Furthermore, the feature for check valve leakage is very insensitive to other faults and operating conditions. The decoupling feature for reversing valve leakage could successfully detect and diagnose faults for a TXV system before the heating capacity degraded 6% and was also insensitive to other faults and operating conditions. However, this feature did not work well for a system with an FXO in heating mode because the refrigerant exiting the evaporator and entering the reversing valve was typically a two-phase mixture. Fortunately, it was possible to diagnose this particular fault at many operating conditions in cooling mode for the system with an FXO. [article] Decoupling features for diagnosis of reversing and check valve faults in heat pumps = Pompes à chaleur : diagnostic des anomalies de robinets d’inversion et des clapets anti-retour [texte imprimé] . - 2011 . - pp. 316-326. Langues : Anglais (eng) Français (fre) in Revue internationale du froid > vol 32, Issue 2 (2009) . - pp. 316-326 Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Pompe à chaleur  Détection  Robinet inverseur  Frigorigène Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : Recently, a decoupling-based (DB) fault detection and diagnosis (FDD) method was developed for diagnosing multiple-simultaneous faults in air conditioners (AC) and was shown to have very good performance. The method relies on identifying diagnostic features that are decoupled (i.e., insensitive) to other faults and operating conditions. The current paper extends the DB FDD methodology to heat pumps. Heat pumps have all the same faults as occur for air conditioners with additional faults associated with components that accommodate heating mode, including reversing valve leakage and check valve leakage. Decoupling features were developed for these additional faults and laboratory evaluations were performed to evaluate diagnostic performance. It was found that check valve leakage could be detected and diagnosed before the heating capacity degradation reached 5% for a system with a fixed orifice expansion (FXO) device and 3% for the same system retrofit with a thermal expansion valve (TXV). Furthermore, the feature for check valve leakage is very insensitive to other faults and operating conditions. The decoupling feature for reversing valve leakage could successfully detect and diagnose faults for a TXV system before the heating capacity degraded 6% and was also insensitive to other faults and operating conditions. However, this feature did not work well for a system with an FXO in heating mode because the refrigerant exiting the evaporator and entering the reversing valve was typically a two-phase mixture. Fortunately, it was possible to diagnose this particular fault at many operating conditions in cooling mode for the system with an FXO.

Practical methods for measuring refrigerant mass distribution inside refrigeration system in Revue internationale du froid, vol 32, Issue 2 (2009)

Public ISBD [article]  inRevue internationale du froid > vol 32, Issue 2 (2009) . - pp. 327-334 Titre : Practical methods for measuring refrigerant mass distribution inside refrigeration system Titre original : Méthodes pratiques pour mesurer la masse du frigorigène à l'intérieur d'un système frigorifique Type de document : texte imprimé Année de publication : 2011 Article en page(s) : pp. 327-334 Langues : Anglais (eng) Français (fre) Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Système frigorifique  système à compression  Charge en frigorigène Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : The purpose of this paper is to present methods for measuring refrigerant mass distribution inside a refrigeration system conveniently and accurately. The quasi on-line measurement method (QOMM) was presented for measuring refrigerant mass inside heat exchangers. Compared with the existing liquid nitrogen method (LNM), QOMM can avoid the refrigerant waste and accelerate the measurement process. For measuring refrigerant mass inside the compressor, QOMM was used together with the oil level observation method. The liquid level method (LLM) was used to measure the refrigerant mass inside the accumulator and the receiver. In order to verify the accuracy of the measurement methods, not only the deviation of the measurement method for refrigerant in single component was analyzed, but also the prediction of the total refrigerant charge in an air conditioner was verified. The results showed that the maximal prediction deviation of the refrigerant charge in the whole refrigeration system is 1.7%. [article] Practical methods for measuring refrigerant mass distribution inside refrigeration system = Méthodes pratiques pour mesurer la masse du frigorigène à l'intérieur d'un système frigorifique [texte imprimé] . - 2011 . - pp. 327-334. Langues : Anglais (eng) Français (fre) in Revue internationale du froid > vol 32, Issue 2 (2009) . - pp. 327-334 Catégories : 621.5 : Technique pneumatique, du vide, des basses températures Mots-clés : Système frigorifique  système à compression  Charge en frigorigène Index. décimale : 621.56 Technique des basses températures : réfrigération, pompe à chaleur Résumé : The purpose of this paper is to present methods for measuring refrigerant mass distribution inside a refrigeration system conveniently and accurately. The quasi on-line measurement method (QOMM) was presented for measuring refrigerant mass inside heat exchangers. Compared with the existing liquid nitrogen method (LNM), QOMM can avoid the refrigerant waste and accelerate the measurement process. For measuring refrigerant mass inside the compressor, QOMM was used together with the oil level observation method. The liquid level method (LLM) was used to measure the refrigerant mass inside the accumulator and the receiver. In order to verify the accuracy of the measurement methods, not only the deviation of the measurement method for refrigerant in single component was analyzed, but also the prediction of the total refrigerant charge in an air conditioner was verified. The results showed that the maximal prediction deviation of the refrigerant charge in the whole refrigeration system is 1.7%.