Design and Operation of a Centrifugal Compressor in a High Temperature Heat Pump

orc2019 Tracking Number 83

This article presents the design, simulation and operation of a single stage 800 kWe centrifugal compressor operating with HFO R1234ZE(E). The compressor is integrated inside a high temperature heat pump that converts heat from saturated steam at 50°C into 3 MWth of heat at 75°C for a district heating network. The compressor specifications require a high pressure ratio (above 3), a high isentropic efficiency and a wide operation range. The compressor design process is discussed in detail, starting from the preliminary optimization based on the mean-line model and then focusing on the aerodynamic design of each component of the compressor. In particular, the design of the inlet guide vanes (IGV), of the impeller, of the vaneless and vaned diffusers, and finally of the exhaust volute are presented in detail. Nominal and off design performances are then assessed by means of computational fluid dynamics (CFD), performed by applying the commercial solver ANSYS CFX. The simulations are based on the two-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations supplemented by a k- turbulence model; the thermodynamic properties of the working fluid are modelled by an equation of state based on a Helmoltz free energy approach, implemented as look-up tables in both the design and simulation steps. Preliminary experimental results of a test campaign aimed at partially mapping the compressor performance in terms of pressure ratio, electrical power and rotation speed are presented, and a thorough comparison between experimental data and simulation results concludes the paper.