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Author: search.filters.author.Denis, AlainSubject: search.filters.subject.Experimental study

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    Experimental and numerical characterization of airflow in a closed refrigerated display cabinet using PIV and CFD techniques
    (2020-03-01)
    Chaomuang, Nattawut
    ;
    Flick, Denis
    ;
    Denis, Alain
    ;
    Laguerre, Onrawee
    Air 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.
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    Influence of operating conditions on the temperature performance of a closed refrigerated display cabinet
    (2019-07-01)
    Chaomuang, Nattawut
    ;
    Flick, Denis
    ;
    Denis, Alain
    ;
    Laguerre, Onrawee
    An 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.
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    Experimental analysis of heat transfer and airflow in a closed refrigerated display cabinet
    (2019-03-01)
    Chaomuang, Nattawut
    ;
    Flick, Denis
    ;
    Denis, Alain
    ;
    Laguerre, Onrawee
    This 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. The cabinet with doors provided less temperature heterogeneity (ΔT<inf>max</inf>= 2.1 °C) compared to the case without door (ΔT<inf>max</inf>= 4.9 °C). The maximum air velocity in the air curtain of 0.6 m s<sup>−1</sup> was observed at the discharge grille. The horizontal air velocity from the perforated plate was low (<0.2 m s<sup>−1</sup>) for all shelves. The loading percentage in the cabinet did not significantly affect the airflow rate through the perforated plate.