Boiling heat transfer and two-phase pressure drops within compact plate heat exchangers: Experiments and flow visualizations

Infrared (IR) thermography was used to measure the local heat transfer coefficients within two plate heat exchanger geometries. The chevron patterns were machined into polycarbonate and IR transparent calcium fluoride plates, both of which were electrically heated using flexible film heaters at heat fluxes up to 0.8 W cm−2. The test fluid was a refrigerant (HFE7100) at mass fluxes between 25 and 100 kg m−2 s−1, and qualities from 0 to 0.9. The apparatus and data reduction technique were validated by comparing the single-phase heat transfer and pressure drop data against the prediction methods from the literature. Adiabatic flow visualizations were conducted to link the flow patterns with the observed heat transfer. The frictional pressure gradient and heat transfer coefficient were compared with available correlations. It was shown that the heat transfer coefficient and the frictional pressure gradient increased with mass flux and quality. The comparison indicated the need for new prediction methods for predicting the local thermal-hydraulic performance over a wide range of operating conditions.