diameter holes near the door the air exit is through the bottom of the floor with a fan 5 functioning as extractor and in the end near the evaporator 3 in this option the following could be observed the faster the speed of the fan in the duct the higher the heat transfer is the addition of wings or fins 8 to the aluminum sheet 6 for the duct die increased heat transfer in the duct no ice was created since the air temperature inside the duct never reaches a level below 0 u00b0 c because the air passes very quickly and only cools a little this was observed even after 36 hours of compressor working time it consists of a duct made on a sheet that separates the evaporator from the freezer in this case the air entrance to the duct is through two 2 inch diameter holes located at the sides and bottom of the upper part of the refrigerator the air exit is located in the central part and the air is extracted by means of a fan this option offered the following information the nearness of the duct with regard to the evaporator which is the lowest temperature zone allows to transfer easily a sufficient amount of cold to the refrigerator the air that exits the duct reaches temperatures slightly above zero this is improved diminishing the duct size the vertical form of the duct allows a natural cold air flow towards the refrigerator even without operating the fan because of the chimney effect it generates even though no ice is formed in the duct because temperatures are above 0 u00b0 c in.