Extended Thermal Model of a Hydraulic Piston Accumulator

Hydraulic piston accumulators are widely used for energy storage and shock absorption in a broad range of industrial applications. While simplified models are often sufficient for general dimensioning, detailed design, energy optimization, and condition monitoring require more accurate representations of thermal and gas dynamics. This paper presents an extended thermal model of a steel-type hydraulic piston accumulator, in which the accumulator is segmented longitudinally to better capture spatial temperature variations. The model is validated experimentally using surface-mounted thermocouples and compared with the widely used benchmark model based on a single thermal time constant. Five operating scenarios are evaluated, including both natural and forced convection conditions. The extended model consistently demonstrates improved accuracy in estimating piston position, with steady-state errors reduced by up to 93% compared to the benchmark. Sensitivity analyses further investigate the influence of thermal parameters, indicating the robustness of the extended model across varied conditions. The proposed model offers a more reliable framework for simulation, monitoring, and control of hydraulic accumulators in practical applications.