Regarding error in Transient simulation
 

Hello all,
I am performing transient simulation of a rectangular Natural Circulation loop operating between two temperatures of 299K-339K. I have given the operating temperature as average of the above mentioned temperature and o/p press is 90 bar. Fluid is CO2.
After the simulation is run for a few iterations, it shows an error(see the attachment)-->
"Primitive Error at Node 0: REFPROP_error (203) from function: tprho (density)

Primitive Error at Node 1: REFPROP_error (203) from function: tprho (density)

[TPRHO error 203] vapor iteration has not converged for T = 299.42 K, P = 7.1370 MPa, rho (last guess) = 6.6129 mol/L, x (mol frac) = 1.00000

[TPRHO error 203] vapor iteration has not converged for T = 299.29 K, P = 7.1370 MPa, rho (last guess) = 6.5994 mol/L, x (mol frac) = 1.00000

WHAT might be causing this?
Any help is appreciated. Thanks

Anybody here
Hello
Does anybody know the solution?

I am surprised this question is still not answered.
If anybody have solution to this problem, it will be helpful.
I am simulating a supersonic flow of supercritical CO2 through convergent divergent nozzle.
Inlet condition
Inlet : Pressure Inlet ;P0 = 95.7 bar
T0 = 315K
Real gas model : NIST