Numerical Analysis of Performance, Rotor Temperature Distributions, and Rotor Thermal Deformation of an R134a Screw Compressor

A numerical analysis is performed to systematically calculate the performance, rotor temperature distributions, and rotor thermal deformation of an R134a screw compressor. The analysis procedure includes three major steps. The first step calculates the efficiencies and the temperature- and pressure-time histories of the refrigerant during a compression cycle of the screw compressor. The calculation is performed based on a theoretical model, which considers the mass and energy conservation laws, the leakages through various paths, and the discharges of gas and oil. The heat transfer between gas and oil is also considered. The second step calculates the temperature distributions in the rotors by numerically solving the set of Helmholtz equations derived from the partial differential equations for transient heat conduction of the rotors. Each of the two rotors is subject to a periodic convective boundary condition and five steady boundary conditions. The third step calculates thermal deformations of rotors by a finite element method based on the calculated temperature distributions from the second step. The proposed theoretical models and numerical procedures are shown to be able to efficiently calculate the performance, rotor temperature distributions, and rotor thermal deformations. The calculated information is important and useful in the design of a refrigerant screw compressor