Infrared imaging of a multi-zone condenser for heat transfer coefficients assessment

Although crucial for simulations, a proper identification of the convective heat transfer coefficients in multi-zone heat exchangers is a challenging task. While well instrumented thermal systems permit to accurately record the energy balance in such components, the sole knowledge of the global heat transfer rate is not enough to reliably assess these coefficients. In this work, it is proposed to use the zones spatial distribution (i.e. the spatial fraction occupied by the liquid phase, the vapour phase and/or the two-phase regions) as a second identification criteria. An air-cooled condenser into which flows R245fa is considered as case study and a dedicated infrared imaging method is presented to assess the spatial distribution of its different phases. These new data, combined with standard heat transfer rate measurements, are exploited to identify the best heat transfer correlations pre-selected from the scientific literature. In order to further improve the model predictions, the original heat transfer correlations are ultimately adjusted so as to best fit both the global heat transfer rate and the zones distribution data.