Applicability of Ideal Gas Law in the Air-bearing of Hard Drives

TL;DR

This paper assesses how well the ideal gas law applies to the pressurized air-bearing in hard drives, especially for calculating humidity, and finds deviations at low temperatures for heavier gases.

Contribution

It introduces a semi-analytical numerical method using real gas equations to evaluate the ideal gas law's applicability in hard drive air-bearings.

Findings

Helium shows minimal deviation from ideal gas law at low temperatures.

Nitrogen deviates significantly from ideal gas law at low temperatures.

Deviations decrease as temperature increases for all gases.

Abstract

This report evaluates the applicability of the ideal gas law in the pressurized air-bearing of hard disk drives when calculating the relative humidity. We employ a semi-analytical numerical method that solves vapor-liquid equilibrium using the Redlich-Kwong and Peng-Robinson equation of state to calculate the saturation pressure of water. The deviation from the ideal gas law is quantified and examined through saturation pressure isotherms. We find that at low temperatures, lighter gases such as helium show little deviation from the ideal gas law, whereas heavier gases such as nitrogen deviate significantly. As temperature increases, the difference between the gases decreases. The results suggest that in areas of low temperature, the non-ideal nature of gases must be taken into account.