Every refrigeration system has at least four main components: compressor, condenser, expansion device and evaporator. Among these, the expansion device is responsible for lowering the pressure in the cycle and for the proper control of the refrigerant flow that feeds the evaporator. Such devices can be classified as fixed and variable action devices. The most common example of a fixed-action device is the capillary tube. POLO has been practicing for almost three decades in characterizing not only experimentally, but also numerically the flow of the most diverse refrigerants through capillary tubes. To do so, it has a database with more than 1000 experimental points involving refrigerant fluids such as R-12, R-22, R134a, R600a, CO2 and capillary tubes with internal diameters of 0.3 to 1.05mm. In addition, POLO has simulation models capable of reliably predicting the mass flow rate or pipe geometry depending on the operating conditions for both adiabatic and non-adiabatic capillary tubes. With regard to variable-action expansion devices, the laboratory has given special attention to electric valves for domestic and commercial light applications. The search for an adequate control of the cooling capacity and of an expansion device that adapts to variations of thermal load, has motivated the POLO to study valves with adequate orifice and drive, and to construct experimental benches for the characterization of the flow through Such valves.