Transient boiling crisis in liquid nitrogen. Influence of heater size and heating rate

• Published in: International journal of heat and mass transfer Vol. 157; p. 119941
• Main Authors: Delov, M.I., Kuzmenkov, D.M., Lavrukhin, A.A., Kutsenko, K.V.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2020; Elsevier BV
• Subjects: Boiling crisis; Computer simulation; Critical heat flux; Critical Rayleigh number; Film boiling; Heat; Heat flux; Heat transfer; Heating rate; High temperature superconductors; Initial conditions; Liquid nitrogen; Lliquid nitrogen; Nucleate boiling; Process parameters; Transient boiling; Boiling crisis; Critical heat flux; Lliquid nitrogen; Transient boiling; Critical Rayleigh number
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2020.119941

•Presents new experimental results on the influence of the size of the heater on the minimum critical heat flux in liquid nitrogen;•Presents new experimental results on the influence of the heating rate on the critical heat flux in liquid nitrogen;•Demonstrated that the minimum critical heat flux is not dependent on the size of the heater at atmospheric pressure when the size of the heater is around 1 mm. It is known that the nucleate boiling of different refrigerants (liquid nitrogen, freons etc.) may drop to the film boiling regime at a heat flux, which is significantly lower than the value from the standard boiling curve. This happens during unsteady heating at a minimum critical heat flux, whose value depends on different parameters of the process: heater geometry, pressure, subcooling relative to saturation, fluid type, initial conditions etc. In this article, we present new experimental results on the influence of the size of the heater and the heating rate on the minimum critical heat flux. The experiments are accompanied by numerical simulations and a theoretical analysis, where we demonstrate how the minimum critical heat flux is computed for a given case. In addition, we demonstrate that the minimum critical heat flux does not depend on the size of the heater at atmospheric pressure when the size of the heater is larger than 1 mm. This parameter is also independent of the temporal history of heat supply. The derived theoretical approach finds applications in the design of the systems based on high-temperature superconductors.