New definitions of two-phase viscosity, based on its analogy with thermal conductivity of porous media, are investigated for transcritical capillary tube flow, with CO2 as the refrigerant. Friction factor and pressure gradient quantifies are computed based on the proposed two-phase viscosity model using homogeneous modelling approach. The Proposed new models are assessed based on test results in the form of temperature profile and mass flow rate in a chosen capillary tube. It is shown that all the proposed models of two-phase viscosity models show a good agreement with the existing models such as McAdams et al., Cicchitti et al., etc. The influence of the viscosity model is found to be insignificant unlike to other conventional refrigerants in capillary tube flow.