Development and Validation of a Segregated Conjugate Heat Transfer Procedure On a sCO2 Dry Gas Seal Test Bench

Abstract

Abstract Carbon Dioxide at supercritical state shows favorable thermodynamic properties for closed loop Brayton and Rankine cycles. High density, close to a liquid, and low viscosity, close to a gas, drive to achieve higher energy conversion efficiency with smaller size turbines and components. DGSs are gas-lubricated, noncontacting, endface seals, consisting of a mating (rotating) ring and a primary (stationary) ring. Due to high rotational speeds, small size sealing gaps, high fluid pressure and density, the heat generated by friction through the seal has a large impact on the temperature distribution, therefore a thermal design is needed to stay below the seal allowable temperature. Nowadays, numerical Conjugate Heat Transfer (CHT) analysis is a good industrial practice to quantify the thermal distribution in turbomachinery components. On the other hand, due to different order of magnitude of secondary flows cavity sizes and DGS seal gaps, simulating the whole fluid domain with 3D Computational Fluid Dynamic (CFD) calculation could drive to prohibitive computational costs. This paper presents a fast numerical iterative procedure based on a commercial 1D flow network modeler (Altair Flow Simulator) coupled with a commercial finite element solver (Ansys Mechanical). The proposed procedure is applied and validated in a DGS test bench operated by Flowserve. Validation data set has been generated operating the DGS in the test bench at different conditions in terms of angular velocity and housing temperature with sCO2 as working fluid. Results have shown a good agreement with experimental data at each operating condition with extremely low computational times.