Thermohydrodynamic Modeling and Analysis of Thrust Gas Bearings for High-Density Refrigerants

Thrust gas bearings find applications in refrigerant compressors designed to operate with high-density refrigerants at high speeds and under strenuous conditions. Localized heating due to high-speed operation, viscous shearing, and compressibility characteristics of the refrigerant gas warrants a detailed understanding of the flow field within the gas film at such operating conditions. Further, due to the convective inertia effects of high-density refrigerants and highspeed operation, a thorough understanding of prediction discrepancy is greatly insightful to a designer, depending upon the designer’s modeling approach. This paper presents a detailed thermohydrodynamic (THD) analysis of the gas film in a rigid surface gas thrust bearing for a high-density refrigerant gas compressor operation. The study presents a comparison of the modeling approach from two models for thin fluid gas film. Model 1 solves a THD model based on the solution of the Reynolds equation along with the gas film energy equation for the thrust gas bearing. Model 2, presents a 3D Computational fluid dynamics (CFD)THD model of the gas film by solution of the compressible Navier-Stokes equations along with the gas film energy equation. The predictions of gas film characteristics from the two models are compared in detail and important features including discrepancies in pressure profiles, load carrying capacity, and flow streamlines of the developed flow field are highlighted. Further, in the presence of cooling flow in the leakage direction, the impact of the choice of modeling approach and inclusion of detailed flow in the inlet dead volume (IDV) region on predictions of performance are highlighted.