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

Abstract

Transient techniques are widely used for the measurement of heat transfer coefficient in heat exchangers: using such methods generally leads to simplified experimental procedures. The measured coefficient is obtained by minimizing the distance between a model of the system and experimental data. In this paper, we use such a transient-state technique 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 plug flow. Axial dispersion is then considered by defining an apparent axial dispersion coefficient in the fluid and by considering axial or transversal heat conduction in the solid. We propose here to model the fluid flow by an equivalent flow pattern obtained by inert tracer experiments. Such a representation, similar to those used to model flows through chemical reactors, is then completed by the heat transfer model in the solid. In the latter, only transversal conduction is considered. 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 is correct. The frequency response is then used to estimate the heat transfer coefficient between the fluid and the solid. The values obtained by this method are very close to that already known for such corrugated plates.