Airflow and heat transfer in a slot-ventilated enclosure apllication to refrigerated trucks

Slot-ventilated enclosures are extensively used in many engineering applications such as buildings, animal houses and equipments for food transport and storage. The level and the uniformity of ambiance parameters such as temperature and humidity are highly governed by airflow patterns and in most of the applications different obstacles also interact with airflow. The study concerns a slot ventilated long enclosure (L/H=5.3, W/H=1) loaded with porous boxes. This configuration corresponds to a refrigerated truck loaded with crates containing fruit or vegetable. The rectangular inlet section (hi/H=0.056, wi/W=0.4) is near the ceiling and the outlet is located near the floor on the same face. The inlet wall jet is turbulent (Re=1.9 105). Isothermal case and anisothermal case (including heat generation in the boxes and heat losses trough the walls) were simulated and compared. The Reynolds Averaged Navier-Stokes equations were solved using an RSM turbulence closure model. Darcy-Forchheimer terms were added in porous medium zone. Boussinesq approximation was used to take account of mixed convection. The governing equations were solved using the finite volume method. In the isothermal case, velocity is very low at rear part of the enclosure. In the anisothermal case, a secondary recirculation appears in the rear part of the enclosure due to free convection and therefore the velocity magnitude is higher. But in the front part, airflow pattern which reflects the wall jet expansion is very similar because flow is governed by forced convection. A different inlet configuration, in which the airflow is blown at three positions along the enclosure, was also investigated. In this case, ventilation and temperature levels within boxes were found to be more homogeneous.