The demand for micro or meso cooling systems for the most diverse applications, such as microprocessors and chilled clothes, for example, is something that has been growing in recent years. This has led manufacturers and research centers to seek components that are also very small and that fit the ability to track and coolant flow also reduced. Although the currently observed reasonable success in developing small compressors and heat exchangers, there is still the need to investigate expansion devices that can be used in conjunction with such components. In this context, POLO built an experimental apparatus to map the adiabatic behavior capillary tubes of 0.2 to 0.6 mm internal diameter where flow rates as low as 0.3kg / hour were observed. Additionally, electric expansion valve with an orifice opening controlled by a PWM type control and flow coefficients of 8x10-8 to 4 were studied with the same apparatus. Based on the experimental data, mathematical models to predict the flow through both capillary tubes as the valves have been developed and errors below 10% were observed.