EFFECTS OF THE AIRFLOW MALDISTRIBUTION ON THE PERFORMANCE OF AN OPEN REFRIGERATED DISPLAY CABINET

Airflow maldistribution in heat exchangers and air channels is a common problem in air conditioning and refrigeration systemsas it negatively affects heat transfer between the evaporator and the surrounding airflow. Furthermore, in the refrigeration field, temperature and velocity maldistribution downstream the evaporator can reach the discharge air grille (DAG), negatively influencing the heat removal from the exposed goods. The development of air maldistribution models, not only on the evaporator scale, but extended to the whole air circuit, might help in understanding and improving cooling issues. In the present paper the effects of the flow maldistribution in the air channel of an open refrigerated display cabinet is studied by means of computational fluid dynamics simulations. A fluid dynamic isothermal model based on experimental boundary conditions and validated by comparison with PIV measurements is presented. Due to the different geometrical scales, the evaporator is modeled using the equivalent resistance approach. The heat exchange process is then studied in a single fin model in order to assess the relationship between heat exchange coefficients, temperature and air velocity. Such a relationship is finally used in the governing equations, as an energy source term, and applied to the full channel model. This thermal fluid dynamic model allows to evaluate the effects of the maldistribution in terms of temperature, heat transfer coefficients, and cooling power. Discussion of the results is reported.