Modélisation en dynamique des transferts thermiques dans un meuble frigorifique de vente fermé

International audienceThis study proposes a simplified heat transfer model of a closed refrigerated display cabinet using a zonal approach. The dynamic model was developed and solved with a spectral method to predict the temperature fluctuations occurring with "on/off" compressor regulation. The equivalent load thickness in which the temperature fluctuations were of the same order as those at the load surface was estimated as a function of on/off compressor operating frequency. The air temperature fluctuations are dampened whenever the air exchanges heat with solid surfaces (e.g. walls, loads) and with the ambient air (e.g. through the doors). Despite exposure to large air temperature fluctuations (up to 5 °C), the load surface temperature showed only small fluctuations (∆Tl ≤ 0.5 °C). Good agreement was found between the predicted and the measured temperature fluctuations. The model can also be applied in order to predict air and load temperature increases during defrost operation

Investigation expérimentale et numérique de la performance des meubles frigorifiques de vente

International audienceRefrigerated display cabinets are widely used to keep chilled/frozen food products in retail food stores. Storage temperatures must be efficiently controlled to ensure that the product temperature is maintained under the recommended value. As a part of the food cold chain, numerous surveys show that refrigerated display cabinets seem to be a weak link apart from household practices. A great deal of effort has been performed in order to investigate and improve the performance of the cabinets in terms of both temperature homogeneity and energy efficiency. In this review article, the investigation on refrigerated display cabinet performance, from basic experimental field and laboratory studies to advanced numerical simulation, are presented. The field investigation allows the knowledge of real use conditions and the identification of problems during food storage, however, it is usually high cost and time-consuming. The Computational Fluid Dynamics (CFD) approach becomes promising alternative to study the influence of different design parameters and operating conditions on the cabinet performance. This review provides the background, problematic, state of the art and future trends related to this type of refrigeration equipment

Comment prédire l'évolution de température d'un produit transporté dans une boite isotherme équipée d'un pain de glace

International audienceAn experiment was carried out to monitor food temperature changes with time in two insulated boxes equipped with an ice pack. The first experiment was carried out in a test room under well controlled ambient temperature and with a box of reinforce lateral insulation. The second experiment was in real use condition and with 2 different boxes. Two models were developed to predict product temperature changes until the ice is completely melted: an analytical 1-D and a 3-D model. The 1D model predictions are in good agreement for the first experiment. But in real use condition, the 1D model underestimates the temperature evolution, while the 3-D model gives better prediction. A comparison of the advantages and disadvantages of these two models was performed. The 1-D approach enables prediction of the main parameters (warmest temperature, ice melting time). A correction factor was proposed to improve the prediction precision using the 1-D model

Caractérisation expérimentale et numérique des écoulements d'air dans un meuble frigorifique de vente fermé par les techniques PIV et CFD

International audienceAir velocity measurements were carried out using the Particle Image Velocimetry (PIV) technique in a display cabinet under two configurations: closed and open doors. Two conditions (refrigeration system turned "on" and turned "off") were studied in the closed configuration. The airflow pattern was almost the same for both conditions. The air curtain was quite stable. In the upper part of the cabinet, air recirculation occurred, and this phenomenon induces external air infiltration through the door gaps. The air curtain in the open configuration (refrigeration system turned "off") was less stable than the closed configuration. Large unsteady eddies developed in the mixing layers, thereby promoting greater external air infiltration. A two-dimensional computational fluid dynamic (2D-CFD) model was developed and showed the ability to reproduce the main flow phenomena observed in the experiment. The trend of predicted product temperature profile was also in agreement with the experimental values, despite slight underestimation

Analyse expérimentale de l'écoulement et du transfert thermique dans un meuble frigorifique de vente fermé

International audienceThis study presents the experimental investigations on heat transfer and airflow in a closed refrigerated display cabinet. Air and product temperatures and air velocity were measured with thermocouples and a hot-wire anemometer, respectively. Temperature variation in the cabinet depends on the positions. The front areas contributed to higher temperature, whereas the rear areas were at a lower temperature. Benefits of doors were also examined by comparing the results of air and product temperatures with the case without doors

Influence des conditions opératoires sur la performance thermique d'un meuble frigorifique de vente fermé

International audienceAn experimental study was performed in order to investigate the effects of operating conditions, including door opening frequency, ambient air temperature and product-occupied volume, on the air and product temperature distributions inside a closed refrigerated display cabinet. The product position in the cabinet is a determining factor of its temperature: a high temperature was observed at the front, particularly at the top of the cabinet, and a low temperature was observed at the back. Air infiltration due to door openings caused a product temperature increase at the front and a temperature decrease at the back. At a higher door opening frequency (more than 60 openings per hour per door), the product temperature at the level of the front middle shelf was the most affected. Both the ambient temperature and occupied volume also affected product temperature variations in the closed display cabinet. In comparison to an open display cabinet, a closed display cabinet achieves lower product temperature and better temperature homogeneity, even with a high door-opening frequency. These findings indicate that the use of closed refrigerated display cabinets should be advocated in order to achieve better food preservation

Meuble frigorifique de vente: Cela vaut la peine pour la qualité de produit?

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEE [ADD1_IRSTEA]Sûreté alimentaireInternational audienceThe use of closed refrigerated display cabinets in supermarkets is in progression because of the potential energy saving compared to the open ones with an air infiltration at the front. However, the influence of the presence of doors on product temperatures (determining factor of product quality) is much less studied. For better understanding the interest of the use of closed display cabinets, this chapter presents the state of the art of field studies, the airflow and temperature profile in the closed display cabinet, the influence of the presence of doors/the frequency of door openings and the room temperature. Finally, a literature review of studies on food quality in the closed display cabinet is presented

Meuble frigorifique de vente: Cela vaut la peine pour la qualité de produit?

International audienceThe use of closed refrigerated display cabinets in supermarkets is in progression because of the potential energy saving compared to the open ones with an air infiltration at the front. However, the influence of the presence of doors on product temperatures (determining factor of product quality) is much less studied. For better understanding the interest of the use of closed display cabinets, this chapter presents the state of the art of field studies, the airflow and temperature profile in the closed display cabinet, the influence of the presence of doors/the frequency of door openings and the room temperature. Finally, a literature review of studies on food quality in the closed display cabinet is presented