Experimental study of heat transfer and air flow in a refrigerated display cabinet

► Infiltration of ambient air contributes to rapid velocity fluctuations in air curtain. ► Air velocities measured by hot wire anemometer and PIV were compared. ► These two measurements show the same results for the internal side of the air curtain. ► Results quite different for the external side du...

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Bibliographic Details
Published in:Journal of food engineering 2012-11, Vol.113 (2), p.310-321
Main Authors: Laguerre, O., Hoang, M.H., Osswald, V., Flick, D.
Format: Article
Language:English
Subjects:
Air curtains
Air flow
Biological and medical sciences
Display cabinets
Ducts
Food engineering
Food industries
Fundamental and applied biological sciences. Psychology
General aspects
Heat transfer
Instability
Life Sciences
Refrigerated display cabinet
Temperature
Thermocouples
Unsteady state
Velocity
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Summary:► Infiltration of ambient air contributes to rapid velocity fluctuations in air curtain. ► Air velocities measured by hot wire anemometer and PIV were compared. ► These two measurements show the same results for the internal side of the air curtain. ► Results quite different for the external side due to complex air flow in this region. ► Higher Radiative exchange at the top of the display cabinet than at the bottom. The heat transfer and air flow in a vertical open refrigerated display cabinet loaded with packages of test product was studied in order to analyse unsteady state phenomena. The product and air temperatures in the curtain were measured using tiny thermocouples, air velocity using a hot wire anemometer and PIV (Particle Image Velocimetry). A comparison between the air velocities measured by these two methods shows a good agreement at the internal side of the air curtain. However, these two methods give quite different result at the external side of the air curtain which can be explained by the complex air flow in this region. The temporal variation of the air temperature inside the air curtain is due partly to the “on/off” compressor cycle and partly to the introduction of ambient air via vortices. The latter phenomena contribute to the rapid velocity fluctuations which are greatest in the mixing layer of the air curtain. The product position in the cabinet is a determining factor of its temperature. The convective and radiative heat flux between the products located at the front of the display cabinet and the air was also measured. Near the air supply and return ducts, the convective heat transfer coefficient was higher than between these two positions because of the high instability of air flow near the inlet and return ducts. The radiative exchange is more significant at the top of the display cabinet than at the bottom.
ISSN:0260-8774
1873-5770
DOI:10.1016/j.jfoodeng.2012.05.027