R&D: Numerical Investigation of Non-Ideal Gas Effects on Saturation Pressure of Water Under High Pressure and Temperature

Lubricants has published an article written by Roshan Mathew Tom, Department of Mechanical Engineering, UC Berkeley, Berkeley, CA 94720, USA, Sukumar Rajauria, Qing Dai, The CTO Office, Western Digital Technologies, San Jose, CA 95119, USA, and Qilong Cheng, Department of Mechanical Engineering, UC Berkeley, Berkeley, CA 94720, USA.

Abstract: “A typical head–disk interface of hard drives can feature pressures exceeding 50 atmospheres, where the non-ideal gas effects can play an important role. One possible consequence is a change in the rate of water evaporation from the disk. This report describes a semi-analytical procedure that employs the concept of fugacity to investigate the non-ideal gas effects on the saturation pressure of water at an elevated temperature and pressure. A vapor–liquid equilibrium equation is solved to derive the saturation pressure. The results show a deviation from the ideal gas law, which is further examined through saturation pressure isotherms. At areas of low temperature and high pressure, lighter gases such as helium show about a 10% deviation from the ideal gas law, whereas heavier gases such as nitrogen deviate by up to 100%. As temperature increases, the differences between the gases decrease.“