AbstractA new measurement method for determining the local liquid‐phase velocities in multiphase flows is presented. It is based on a tracer technique, using heat introduced into the flow, seemingly at random, instead of a material tracer. The input of heat pulses and measurement of temperature at an adjacent point is performed by small probes. As an intermediate result, the flow time distribution of the heat‐labelled fluid elements is calculated on‐line as a cross‐correlation function between the pseudo‐random input and the measured output signals. This calculation and the automatic control of measurements is carried out by a simple microprocessor unit. The device produced excellent results in gas‐liquid flows at high gas throughputs and high liquid‐pha