The multijet facility is a scaled model of a fast cooling system used in galvanizing lines. It consists of two settling chambers with a set of slot nozzles. The slot arrangement can be adjusted to investigate the effect of geometrical parameters such as the nozzle spacing, the nozzle emergence and the impinging angle.
More than 50 nozzles are available to cover the whole range of each parameter. The translation of the multijet systems allows changing the stand-off distance. A ventilator delivers a nominal flow rate of 5 m3/s at a relative pressure of 10000 Pa, which ensures a maximal slot velocity of 100 m/s. The facility has been designed to handle both cooling tests and vibrations tests.
For the cooling tests, only one settling chamber is in operation and the air jets impact on a vertical flat plate of 1.7 m long and 0.27 m wide, uniformly heated on one side by electrical means. The heated surface is exposed to the impinging flow while an infrared camera scans the other side. For the vibrations tests, the two settling chambers are used and the air jets impact on a rigid plate modeling an element of the metal strip. Its connections to a fixed frame reproduce the elasticity of the remaining part of the strip. Dedicated displacement sensors measure the oscillations of the sectional model.


The experimental test-facility RO-CO is a semi-industrial prototype of a roll coater. It consists of an arrangement of four in-line rollers tilted at 25°. A doctor blade that drains the back-up simulates the metal strip of the industrial line. All the cylinders are 400 mm wide and have a diameter of 100 mm, except the back-up which has a diameter of 275 mm.
Each roll can be positioned independently from the others by means of cranks with a precision of about 10 μm.
The rollers are driven separately by four computer-controlled DC motors that are equipped with speed-reducers to achieve the desired speed for each roll: 313 m/min for the back-up, 359 m/min for the applicator, 123 m/min for the pick-up and 49 m/min for the doctor roll. The rollers are instrumented with strain gauges to measure the force direction and amplitude with a measurable maximum of about 10000 N/m. The multi-purpose facility allows the study of forward, reverse-gravure and elasto-hydrodynamic coating modes. The simulating liquid can be water, latex or silicone oil with viscosity ranging from 0.1 to 0.3 Pas. The local thickness of the liquid film is measured by a laser triangulation probe, which is mounted on high-precision (1 μm) translation stages.
Currently, the facility RO-CO is associated with the facility LERO in the Organic Coating Process Department of the Groupe Arcelor RDCS.
