Comparison analysis of density wave oscillation type two-phase flow instability of superheated and saturated boiling tubes

•Dimensionless inequalities determining superheated system stability are established.•Dimensionless two-phase number and superheated number are first proposed.•The effects of Froude number and friction number on DWO are analyzed and compared.•The ratio of oscillation period and transit time is analyzed and compared.•Reasonable application range of the figure expressed by Nsub and Npch is discussed.