Experimental Investigation of the Cryogenic Pool Boiling Curve

As the aerospace community prepares to establish humanity’s permanence on the Moon and Mars, Cryogenic Fluid Management (CFM) technologies have proven themselves paramount to the established architecture of interplanetary travel. It will therefore be necessary to understand the two-phase physics inherent to cryogenic fluids. This study includes experimental investigation into the saturated pool boiling curve for liquid nitrogen (LN₂), specifically nucleate boiling (NB), critical heat flux (CHF), film boiling (FB), and minimum heat flux (MHF). The obtained data aid in understanding effects of two important parameters which are underrepresented in the historical database: heated surface thermophysical properties and heated surface size. With a diameter of over 100 mm, the heated surfaces tested in this study are significantly larger than those adopted in prior studies and representative of ‘infinitely’ large surfaces for which theoretical CHF models have been constructed. This study also includes data for three surface materials: copper, aluminum, and stainless steel, and pressures ranging from 101 to 448 kPa over varied surface orientations. By comparing the present with those from the historical databases, it is possible to gauge the influence of any underrepresented effects resulting from the unique properties of the heated surfaces tested presently. As a result, the efficacy of readily available predictive tools is evaluated, and modifications are proposed where possible. Using both the current LN₂ data and those of all cryogens from historical databases, a new CHF correlation is developed which shows a MAE of 18.03% against 1181 datapoints across different cryogens, different heated surface materials and sizes, pressures, subcoolings, and surface orientations.