Investigation on the choked mass-flow characteristics of the helium fluid during the Joule-Thomson process in micro-orifice under different high pressures
Investigation on the choked mass-flow characteristics of the helium fluid during the Joule-Thomson process in micro-orifice under different high pressures
The micro-orifices during the Joule-Thomson process are used in a variety of energy applications such as microfluidic systems and large-scale cryogenic helium systems. The structure of the micro-orifice impacts the cooling capacity by adapting the mass flow rate and pressure drop in the refrigeration system. The pressure drops and flow characteristics in micro-orifices with diameters of 20-40 mu m and thicknesses of 50 mu m were numerically and experimentally investigated. Helium was used as the working fluid, and the simulations using CFD (Computational Fluid Dynamics) method were conducted with upstream pressure (pu) of 0.5-2.0 MPa (MegaPascal) and downstream pressure (pd) of 0.1-1.5 MPa at 293 K (Kelvin). The simulations found that the completely choked pressure ratio of each micro-orifice is smaller than the theoretical critical pressure ratio lambda*=0.487 and revealed the flow field characteristics in micro-orifices flow under different working conditions. Experiments were carried out with four micro-orifices with the thickness of 50 mu m and the effective diameter of 23.88 mu m, 26.53 mu m, 33.30 mu m, 40.69 mu m under different pressure conditions (pu 0.5-2.0 MPa, pd 0.1-1.5 MPa), respectively. The errors between the numerical and experimental mass flow rates in different micro-orifices corresponding to the pressures are within 10 %. The W. B. Brower model was used to predict the mass flow rates that are consistent with the experiments and simulations. The semi-empirical model is developed using the data set for the modifications to W. B. Brower model and with an error range of +/- 0.08 mg/s in the calculated flow rate compared to the experimental value.
NSTL
Elsevier