In order to determine the increase in efficiency of n-octane compared to water as a propellant in ejector refrigeration systems, a pilot plant with a cooling capacity of up to 1.5 kW was set up. In both cases, water was used as the suction medium, the so-called cooling medium. From the pressure and temperature measurement data, the two mass flows, the so-called motive and suction flow, and from this the mass flow ratios could be obtained. Subsequently, a comparison of the theoretical coefficient of performance for the two propellants was carried out in the case of closed-loop operation.