each correlation through the length of the heat exchanger as can be seen in Fig. 3. The Moisseytsev correlation in cold side behaves differently, increasing the heat convection coefficient at an approximate constant rate, from 2122 W/m2K at the inlet to 2459 W/m2Kat the outlet (Fig. 3). The lower number of channels calculated with this correlation produces a higher Reynolds number difference between the correlations. This influences the Nusselt number and therefore the heat transfer coefficient (at the hot side the Nusselt number obtained with each correlation is similar). There is also a visible change at position 0.25 m with the Dittus–Boelter correlation, because at this point the Reynolds number decreases from10,000 and then the Gnielinsky correlation is used. In the BBR the heat transfer coefficient is also nearly constant. The values obtained are shown in Table 2. Finally, in the PC the heat transfer coefficient in CO2side suffers a peak when CO2reaches the critical point. This occurs due to the considerable changes in the fluid properties. As can be seen the values obtained are very high which favor the heat transfer between both streams (Fig. 4).