High resolution infrared measurements of single-phase flow of R245fa and R236fa within a compact plate heat exchanger, Part 2: Heat transfer results

In the second article of the present two-part paper, upward single-phase heat transfer within a compact plate heat exchanger was investigated experimentally. The experimental setup, the data reduction technique and pressure drop results were presented in Part 1, while high resolution infrared measurements of R245fa and R236fa were implemented to obtain local (pixel-by-pixel) heat transfer coefficients in Part 2. During the experiments, the Reynolds numbers changed from 34 to 1615, Prandtl numbers from 4.9 to 6.5 and the heat fluxes from 74 to 3478 W m−2. The Nusselt number was dependent on the Reynolds and Prandtl numbers, as common in tubular flow. Local heat transfer coefficients were evaluated and the main trends against plate length, mass flux, heat flux, fluid temperature and type of refrigerants were investigated. Several of the most quoted prediction methods available in the literature were statistically evaluated against the present heat transfer database and a new model was proposed to predict the mean thermal performances of a compact plate heat exchanger. Additionally, a local heat transfer correlation that predicted 94% of the experimental data, including 510 points, within a bandwidth of ± 30%, was also proposed.