Measurement of liquid film distribution in near-horizontal pipes with an array of wire probes

• Conductance probes are developed to measure liquid film distribution in a pipe.
• Array of probes permit a better spatial resolution of film height measurements.
• Theoretical predictions of probe conductance in a complex geometry are presented.
• Film height measurements are compared with theoretical/numerical predictions.
• Wire induced perturbations to liquid flow are estimated with numerical simulations.

A test section consisting of a circumferential array of conductance probes has been developed to measure the thickness distribution around the pipe wall of a liquid layer flowing in near horizontal pipes. When the film thickness is known, the array can be employed to measure the local film flow rate by injecting a high conductivity tracer into the liquid flowing at pipe wall.The test section consists of a short pipe made of a non-conducting material installed in a flow rig designed to operate at an appreciable pressure (40 bar). The flow loop is made of metallic pipes connected to the electrical earth. The conductance probes are made of three parallel, rigid wires spaced along the flow direction and are used to measure the height or the electrical conductivity of the liquid layer. The three-electrode geometry is aimed at minimizing current losses toward earth. The simultaneous operation of all the probes of the array, without multiplexing, allows a substantial reduction of current dispersion and a good circumferential resolution of film thickness or conductivity measurements. The probe geometry may generate an appreciable disturbance to the gas–liquid interface. This aspect of the proposed method has been studied with an experimental and numerical investigation relative to free falling liquid layers.