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Author: search.filters.author.Chaomuang, NattawutSubject: search.filters.subject.Closed refrigerated display cabinet

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    Dynamic heat transfer modeling of a closed refrigerated display cabinet
    (2019-10-01)
    Chaomuang, Nattawut
    ;
    Laguerre, Onrawee
    ;
    Flick, Denis
    This 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 (ΔT<inf>l</inf> ≤ 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.
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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.
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    A simplified heat transfer model of a closed refrigerated display cabinet
    (2019-01-01)
    Chaomuang, Nattawut
    ;
    Laguerre, Onrawee
    ;
    Flick, Denis
    A simplified heat transfer model for a closed refrigerated display cabinet was developed based on a zonal approach. The developed model allows the prediction of time-averaged air and load temperatures at various positions in the display cabinet. These predicted values were compared with measured air and load temperatures. Good agreement was found between them with the maximum difference of 0.5°C for every studied position and the overall mean absolute error of 0.2°C. Air and load temperatures vary with positions. High temperature was observed at the front (highest value at the front top) and low at the back (lowest value at the back bottom). Based on the simulation, the cabinet thermal performance can be enhanced by minimizing the size of door gaps.