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- Analysis of the air infiltration through the doorway of a refrigerated room using different approachesPublication . Gonçalves, J. C.; Costa, J.J.; Lopes, A.M.G.This paper presents the study of the air movement through the doorway of a refrigerated room, using both numerical and experimental approaches. Firstly, a comparison is made between the experimentally observed infiltration rates and the predictions by seven empirical models. For different test conditions of the specific laboratory configuration under analysis (a refrigerated room at laboratory scale), the infiltration rate was measured using the tracer gas technique. A three-dimensional numerical model was developed to simulate the heat and mass transfer phenomena, using a commercial CFD code (ANSYS-CFX®). For the simulations, turbulence effects were taken into account using the k- SST turbulence model. CFD results showed a good agreement with experimental data, confirming that the numerical model is appropriate to evaluate this physical phenomenon. The experimental and numerical results showed that the neutral flow level is located above the doorway mid-height and that the maximum airflow velocity occurs near the doorposts. Results also evidenced that, although most of the empirical models tend to overestimate the infiltration rate, some of them present a quite good prediction ability. Measurements in a real scale refrigerated room confirmed the trend obtained in the laboratory installation.
- A Study on the Sealing Efficiency of Air Curtains: 2D and 3D ApproachesPublication . Goncalves, J. C.; Costa, J.; Figueiredo, R.; Lopes, A.In industrial refrigerated spaces, such as retail stores, where sometimes doors must be open for long periods, the infiltration loads can represent more than half of the total refrigeration load. The use of air curtains can significantly reduce the air infiltration through doorways and, at the same time, it allows the free access by persons and equipment [1]. Besides the experimental research, computational fluid dynamics (CFD) has been commonly used, either adopting a two dimensional (2D) approach [1] or, more recently, through a three-dimensional (3D) perspective [2,3]. This work presents a numerical and experimental study on the performance of air curtain devices in the aerodynamic sealing of access doors of refrigerated spaces. For this propose, a 3D numerical model was developed aiming at the simulation of the turbulent non-isothermal airflow generated by the air curtain since the moment the door is opened. The calculation domain represents a laboratory scale model consisting of two similar adjacent rooms connected by a doorway over which the air curtain device is installed. One of these rooms represents a refrigerated chamber and the other, the outdoor environment. The numerical study was carried out using a commercial CFD code (ANSYS-CFX) and the turbulence effects were approached by k-_SST turbulent model. In the experimental study, the tracer gas technique was used to estimate the air exchange rate through the doorway in the initial period of the transient process and consequently assess the sealing effect obtained with the air curtain device operating at different jet velocities. The numerical results show that the air curtain simulated is appropriate to protect the doorway in its whole width, and a good agreement is verified with the experimental measurements. Results of a simplified 2D approach are also shown and compared with the 3D simulation