For supercritical fluids, viscosity determination is difficult by contact sensors because contact sensors may be affected by the high pressure, high temperature and distinctive properties of supercritical fluids. In this paper, a non-contact method is presented for determining viscosity of supercritical fluids based on the linear pressure dependence of fluid Raman spectra and the principles of laminar flow in rectangular micro channels. The pressure drop along a micro channel can be determined by mapping the Raman spectra along the channel and the flow rate can be simultaneously determined by mapping the pressures at adjacent locations with different cross areas based on the Bernoulli equation for gases. Thus, the fluid viscosity can be determined combined with the pressure drop and the flow rate. Cases of methane, carbon dioxide and hydrogen at various pressures and temperatures are simulated to analyze the sensitivity and uncertainty of this method. The total viscosity uncertainty for methane at 300 K and 10 MPa is 2.9%. The viscosity uncertainties for carbon dioxide at 313.15 K, 9 MPa and 313.15 K, 12 MPa are respectively estimated as 2.1% and 9.7%. For hydrogen, this method is most suitable at low temperatures. The viscosity uncertainty for hydrogen at 85 K and 5 MPa is 1.84% and increases to 24.1% at 315 K and 15 MPa. This Raman spectra method still remains to be experimentally validated.
|Title of host publication||Proceedings of the 15th International Heat Transfer Conference|
|Place of Publication||Kyoto, Japan|
|Number of pages||14|
|Publication status||Published - Aug 10 2014|