A TRANSIENT-STATE TECHNIQUE FOR THE HEAT-TRANSFER COEFFICIENT MEASUREMENT IN A CORRUGATED PLATE HEAT-EXCHANGER CHANNEL BASED ON FREQUENCY-RESPONSE AND RESIDENCE TIME DISTRIBUTION

Transient techniques are widely used for the measurement of heat trans fer coefficient in heal exchangers: using such methods generally leads to simplified experimental procedures. The measured coefficient is ob tained by minimizing the distance between a model of the system and ex perimental data. In this paper, we use such a transient-state techniqu e to measure the global heat exchange coefficient between a liquid and corrugated plates. The model usually employed in the heat exchangers area is based on the hypothesis that the fluid flow is similar to a pl ug flow. Axial dispersion is then considered by defining an apparent a xial dispersion coefficient in the fluid and by considering axial or t ransversal heat conduction in the solid. We propose here to model the fluid flow by an equivalent flow pattern obtained by inert tracer expe riments. Such a representation, similar to those used to model flows t hrough chemical reactors, is then completed by the heat transfer model in the solid. In the latter, only transversal conduction is considere d. The model that we derive is in fact similar to those used to model percolation processes through porous media. We give some experimental evidences based on pressure drop measurements that such a comparison i s correct, The frequency response is then used to estimate the heat tr ansfer coefficient between the fluid and the solid. The values obtaine d by this method are very close to that already known for such corruga ted plates.