Pressure drop in zig-zag channels
 

Hi,
I'm just registered to the forum, i'm kind of lost doing this.
I'm validating some experimental data with the software, I'm using SST for viscosity, and energy obviusly.
I'm supposed to get a low pressure drop, but im getting like 300000Pa more in two of the three channels, and 3000000Pa more in the other one. Heat transfer is ok, Im just getting problems with the pressure.
My inlets are:
Mass flow rate and temperature in 3 inlets.
My outlets are:
Pressure-outlet different from atmospheric is between 2.52e6 Pa and 8.28e6 Pa in 3 outlets.
Those outlet pressures are supposed to give me my inlet pressure, but as i wrote before is giving me bigger numbers than the one from experimental data.
I dont really know whats the problem, if anyone can help me it would be awesome.

JM

New issue
 

Actually I checked everything and the big mistake I was making is to set density as constant in a supercritical CO2 analysis.
However, Im facing a big problem right now, I dont even know how to make AnsysFluent to change the density of CO2 during the flow.
Two of the channels are not in supercritical, pressure is like 2.52 MPa and temperature is over 250°C, but the last channel is above supercritical region, pressure is like 8.28 MPa and temperature is over 100°C.
I was trying to import or to use NIST-real gas model, but when is setting it shows that limit pressure is 20000Pa, nevertheless I try to calculate that, and it is showing me and error that the fluid got out of region.
I really need your help.
JM