In most refrigerators, the frost to accumulate only on the evaporator. However, depending on environmental conditions, operation and construction, frost is sometimes found on the inner walls of the enclosure, which increases the number of service calls and consequently maintenance costs and quality. To avoid this, manufacturers have been pressured to consider new concepts coolers, so that both the cost and the power consumption is reduced. Despite the extensive literature available, none of the work actually bother to provide for frost formation on the inner walls of refrigerators, focusing on the most important parameters that lead to the nucleation of crystals, such as air temperature, humidity, velocity and conditions the surface (temperature, roughness and contact angle). In order to study the phenomenon, POLO has developed a mathematical model of heterogeneous nucleation for flat surfaces, based on the classical theory of nucleation, and thus set a criterion to evaluate when and under what conditions will be frost formation on the walls of the refrigerator . This model can be used in real applications, where a coolant can be tested in a climatic chamber with an automatic door opening. Samples of different wall materials can be analyzed and the contact angle can be measured with the aid of a microscope camera. Thus, for each surface type, the maximum degree of supercooling can be plotted as a function of contact angle and then compared with the limits of nucleation.