15th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
Authors
Abstract
Governmental requirements to reduce ODP and GWP has led to an increased demand for modern refrigerants such as R1234ze, R290/Propane or R744/CO2. A redesign of the centrifugal compressors used in these machine poses mainly two challenges to the development. Firstly, operation in close vicinity to the two-phase region requires an accurate thermophysical description of the working fluid. Secondly, the complex flow patterns in these low flow coefficient compressors also require a robust integration of these models into the numerical algorithm. An in-house, fully-coupled and pressure based algorithm is used in the presented paper, incorporating two different real gas approaches. The first approach is using classical cubic state equations together with advanced models to account for the temperature dependency of viscosity and heat capacity. These results are compared in terms of accuracy and computational time against a look-up table approach using the NIST Refprop thermophysical library. Validation is then carried out by comparing against measurement data and analyzed with respect to known challenges of the laboratory setup. An adjoint optimization method using automatic differentiation is then integrated into the pressure-based algorithm. Single point and multipoint optimization is carried out based on predefined objective functions to improve local and overall performance of the two-stage radial compressor.
ETC2023-317
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