Three-Dimensional CFD Modelling and Analysis of the Thermal Entrainment in Open Refrigerated Display Cabinets

Abstract

This study presents a three-dimensional Computational Fluid Dynamics (CFD) simulation of the air flow pattern and the temperature distribution in a refrigerated display cabinet. The thermal entrainment is evaluated by the variations of the mass flow rate and thermal power along and across the air curtain considering the numerical predictions of abovementioned properties. The evaluation on the ambient air velocity for the three-dimensional (3D) effects in the pattern of this type of turbulent air flow is obtained. Additionally, it is verified that the longitudinal air flow oscillations and the length extremity effects have a considerable influence in the overall thermal performance of the equipment. The non uniform distribution of the air temperature and velocity throughout the re-circulated air curtain determine the temperature differences in the linear display space and inside the food products, affecting the refrigeration power of display cabinets. The numerical predictions have been validated by comparison with experimental tests performed in accordance with the climatic class n.° 3 of EN 441 Standard (Tamb = 25 °C, φamb = 60%; νamb = 0,2 m s−1). These tests were conducted using the point measuring technique for the air temperature, air relative humidity and air velocity throughout the air curtain, the display area of conservation of food products and nearby the inlets/outlets of the air mass flow.

Influence of Ambient Air Velocity Orientation in Thermal Behaviour of Open Refrigerated Display Cabinets

“…The results of this work can be compared with those of Gaspar et al [13], as most of the boundary conditions (BCs) have been assumed to be the same. The BC imposed on the computational domain are those of common practice in numerical simulations, defined for the climatic class n.º 3 of EN-ISO Standard 23953 [14] (T amb = 25 ºC,  amb = 60 %).…”

“…The ORDC model used in this study is a simplified 3D model based on the original one developed by Gaspar et al [13]. The geometry was developed in SolidWorks CAD software, and transferred to Gambit software to build the computational mesh.…”

“…The CFD code Fluent 6.3.26 was used to simulate the air flow and heat transfer in the ORDC. Since Gaspar et al [13] made experimental measurements of air velocity, temperature and relative humidity based on this ORDC, the results of the simulation are compared to their experimental results.…”

“…However, none of these studies have modeled the air flow and heat transfer in ORDC for different orientation of ambient air velocity. The work described in this paper intends to combine the characteristics of the aforementioned works, thus performing 3D CFD simulations of an ORDC being the model developed by Gaspar et al [13] modified to consider the ambient air flow parallel, oblique and perpendicular to the ORDC frontal opening in order to evaluate its influence on the thermal behaviour.…”

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

“…Billiard and Gautherin (1993) reported the different sources of heat gain in displays cabinets: infiltration, radiant heat transfer, conductive heat transfer through cabinet walls, lighting, fan, defrost and anti-sweat. Gaspar et al (2008) reported that 72% of the cooling load is constituted by infiltration of ambient air across the curtain. The indoor environment in which display cabinets operate greatly influences the performance of air curtains (Chen and Yuan, 2005).…”