Experimental Investigation into the Effects of Deep-Sea Environment on Thermophysical Properties of Hydraulic System Working Fluids

Abstract

The thermophysical properties of working fluids serve as a fundamental basis for the design and analysis of subsea hydraulic systems. Precise characterization of hydraulic oil properties—including bulk modulus, thermal conductivity, and viscosity—is critical for optimizing system efficiency and energy conservation in deep-sea applications. However, no existing model accurately describes the variation patterns of these parameters across full-ocean-depth pressure ranges (0.1–110 MPa) and wide temperature intervals (2–70 °C). In this study, No. 10 aviation hydraulic oil was selected as the test medium. An experimental apparatus was developed to measure its properties, with subsequent data analysis revealing distinct temperature- and pressure-dependent trends. Empirical equations for bulk modulus, thermal conductivity, and viscosity–temperature–pressure relationships were derived, achieving coefficients of determination (R2) of 97.96%, 98.27%, and 94.608%, respectively.

Bibliographic Information