Description Compressible fluids change their density due to pressure change in the flow. Flows with velocities less than Ma 0,3 are regarded as incompressible and the change in density is negligible. At higher velocities, the density has to be included in calculations. These conditions must be taken into consideration when designing e.g. turbo compressors, jets and fast planes. A radial fan with infinitely variable speed control draws in air from the environment. At the intake the air flow is accelerated in a measuring nozzle. Further down the measuring section the air flows through interchangeable measuring objects. Drawing in the air and the arrangement of the measuring objects on the intake side of the fan minimise turbulence when flowing into the measuring objects. All measuring objects are made of transparent material and provide excellent insight into the inner structure. Pressure losses are studied in a pipe elbow, various pipe sections and a nozzle with sudden enlargement. The nozzle with gradual enlargement (de Laval nozzle) provides an introduction to the topic of sonic flow. The volumetric flow rate is measured in an orifice using a differential pressure manometer. The orifice is fitted with four interchangeable orifice disks for different measurement ranges. The fan’s characteristic curve can also be recorded by using a throttle valve. Specification investigate flow of compressible fluids subsonic and sonic air flow variable speed on the radial fan for adjusting the mass flow rate minimised turbulence by drawing in air and optimum arrangement of the measuring objects transparent measuring objects with connectors for pressure measurement provide insight into the internal structure measuring nozzle for determining the mass flow rate pressure losses in subsonic flow in pipe elbows and various pipe sections pressure curve at subsonic and sonic nozzle flow orifice for determining volumetric flow rate by differential pressure measurement record fan characteristic curve using a throttle valve digital displays for pressures, velocity and speed