Concerning the overall heat transfer coefficientU (W m-2K-1), it has been computed with Eq. (9), wheresplis the plate thickness (m). The convective heat transfer coefficient α(W m-2 K-1) for both fluids can be evaluated with Eq. (10). The Nusselt number for the supercritical CO2 is calculated using the Jackson correlation [22], which includes a correction factor that neutralizes the effect of the variation of the thermophysical properties around the pseudo-critical point. The Jackson's correlation is reported in Eq. (11), which operational ranges are available in [16].