Method and system for determining the specific temperature corresponding to a viscometric fixed point for a free fluid stream

A process for measuring for determining a characteristic temperature, Tlog, corresponding to a viscometric fixed point of a free fluid stream flowing from an opening with a constant acceleration, said process comprising the following steps:

• (a) measuring one value of the dynamic viscosity and one value of the temperature of the free fluid stream within an area of interest of said free fluid stream;
• (b) providing, with a data processing device, a Vogel-Fulcher-Tammann (VFT)-like model, wherein said the adjustable parameters of the VFT-like model comprise a chemical composition-dependent adjustable parameter, T0, which depends on the chemical composition of the fluid, and wherein which the adjustable parameters of said VFT-like model are statistically adjusted over a dataset of experimental and/or simulated temperature-dynamic viscosity values for said fluid within a chemical composition range;
• (c) computing, with a data processing device, a value of said parameter, T0, from said VFT-like model, wherein the value of the dynamic viscosity and the value of the temperature of the free fluid stream within the area of interest are provided as input data to said VFT-like model;
• (d) computing, with a data processing device, a value of the characteristic temperature Tlog, corresponding to a viscometric fixed point, of a free fluid stream from said VFT-like model, wherein the value of the parameter, T0, computed at step (c) and the viscometric fixed point are provided as input data to said VFT-like model.