About the project

Despite the vast literature about the thermo-hydraulic performance of tube-finned evaporators, there is a shortage of specific experimental data for the evaporators in the frostutilizados in domestic refrigerators, especially when it comes to frost formation. Comparing them with the conventional tube-finned exchangers, there are some striking features that distinguish the evaporators in the frost and make them unique. First, the geometry of these is such that the face area is smaller than conventional exchangers. Thus, the number of tubes can be considerably larger in the direction of airflow. Furthermore, to prevent blockage by accumulation of frost, the spacing between flaps can be non-uniform along the coil, and considerably higher compared to conventional heat exchangers. Electrical resistors are also used to remove frost from time to time.

In order to study the formation of frost, POLO developed experimental techniques and mathematical models to characterize and predict the process. To this end, the coolers are tested with an insulating glass window in the rear wall, to allow viewing, and water reservoirs immersed electric resistors or door opening devices, are used to induce moisture increase and accelerate the formation frost. A test stand was also specially constructed to be coupled to the refrigerator and allow control of the evaporation temperature of the evaporator and the degree of superheat. Thus, the coolant can be tested in real operating conditions, maintaining the distribution of original internal air.

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