Summary

Energy e fficien cy o f household refrigerators depends both on  the thermodynamics of the refrigeration, i.e., compressor, condenser, evaporator and capillary tube performance and on the heat transfer characteristics of the refrigerator cabinet and door gaskets. Most of the brazilian units are assembled with roll-bond evaporators. This type of evaporator is formed by two plates of aluminum, with channels for the refrigerant flow. The actual practice is to select the area of such component simply as a function of the internal volume of the refrigerator,  without taking into account, for instances, the diameter and distribution of the channels, in despite of their influence on the evaporator pressure drop and thus on the compressor suction pressure. An experimental investigation was then carried out to study the heat transfer in such type of heat exchanger as a function of geometry and positioning inside the cabinet. Besides the conventional techniques to indirectly evaluate the heat transfer, it was also directly measured by heat flux transducers. The heat flux meters were also used to evaluate the UA value (product of the overall heat transfer coefficient and the cabinet external area) for the refrigerator walls. Experiments were performed with the roll-bond evaporator placed in three different positions inside the cabinet: original position, tilted forward, tilted backward. The effect of positioning,  refrigerant  mass flow rate and suction pressure on the heat transfer coefficient was then assessed.

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