Characteristics of boiling transitions during liquid oxygen chill-down in a horizontal pipe with an injector on the exit

Chill-down by the constant rate of liquid oxygen was investigated experimentally in a pipe with an inner diameter (D-i) of 20 mm upstream of an injector. For fitting the condition in cryogenic engine, the pressure range was extended to around 0.6 similar to 3.5 MPa. The present set of data was combined with the previous set from a D-i = 15 mm pipe to examine the reliabilities and generalities of the correlations on the temperature and heat flux of the inner wall when boiling transition happening (Zhang et al., 2020). The conclusions show that, pressure dominates the inner wall temperatures on both the Leidenfrost point (LFP) and critical heat flux (CHF), which causes by involving the effect of pressure, inner wall temperatures on LFP and CHF could be well correlated. New correlations were recommended by fitting the combined data and by which reliable predictions could be given. On the other hand, both pressure and pipe length play significant roles on the heat fluxes on LFP and CHF. In this way heat flux on CHF was correlated well to pressure and pipe length. However, the present correlation on heat flux on LFP has not involve the effect of pipe length for more experimental studies have to be given.

Automated summary

Experimental investigation on chill-down by the constant rate of liquid oxygen was conducted in a pipe with an inner diameter of 20 mm, upstream of an injector. The study showed that pressure significantly affects the inner wall temperatures on both the Leidenfrost point (LFP) and critical heat flux (CHF), and new correlations were recommended based on the combined data for reliable predictions. Additionally, both pressure and pipe length play important roles in the heat fluxes on LFP and CHF.