This paper analyses heat transfer by natural convection in domestic unventilated refrigerators. A literature review of natural convection in an empty cavity, between vertical plates and air, and between a cylinder and air, was conducted in order to gain an insight into the mechanism of heat transfer. A model is proposed in order to quantify heat exchange by convection, conduction and radiation in a typical refrigerator; the predicted mean air temperature and refrigerating capacity are close to the experimental values. Another numerically solved model was carried out in order to estimate the time required to cool warm food which is placed inside the refrigerator. Good agreement was obtained when calculated and experimental temperatures were compared.