GASFLOW is a finite-volume computer code that solves the time-dependent, two-phase homogeneous equilibrium model, compressible Navier-Stokes equations for multiple gas species with turbulence. The fluid-dynamics algorithm is coupled with conjugate heat and mass transfer models to represent walls, floors, ceilings, and other internal structures to describe complex geometries, such as those found in nuclear containments and facilities. Recent applications involve simulations of cryogenic hydrogen tanks at elevated pressures. These applications, which often have thermodynamic conditions near the critical point, require more accurate real-gas equations of state (EOS) and transport properties than the standard ideal gas EOS and classical kinetic-theory transport properties. The standard for real-gas modeling is provided by the National Institute for Standards and Technology (NIST) in Boulder, Colorado. We have implemented Leachman?s NIST hydrogen EOS as well as two simpler models: (1) a modified van der Waals EOS and (2) a modified Nobel-Abel EOS. Testing and verifying the real-gas EOS implementations is difficult, but most important to provide confidence in the new EOS model developments. A ?numerically exact benchmark? problem has been especially developed to address these concerns. This report describes the rigorous implementation of the generalized real-gas EOS into the GASFLOW CFD code, as well as the specific implementation of respective real-gas models; it also includes a logical testing procedure based upon a numerically exact benchmark problem. An example of GASFLOW simulations is presented for an ideal cryocompressed hydrogen tank.