Abstract
Liquid propellants, which are typically used for regenerative cooling of rocket thrust chambers, can flow in channels at supercritical pressures and in the neighborhood of pseudocritical temperature (near-critical fluid). This could be for instance the case for the envisioned liquid-oxygen/liquid-methane engines with chamber pressures larger than about 50 bar. When the fluid is in such a near-critical condition, deterioration in heat transfer can occur if the heat transfer level is higher than a threshold value. Aiming to improve flow prediction capabilities for the design of such systems, the present study is devoted to numerical simulations of near-critical fluids flowing in uniformly heated straight tubes. After code validation against experimental data of near-critical-hydrogen flow, numerical simulations of near-critical-methane flow in heated tubes are carried out, each characterized by a different wall heat flux. Results are discussed in detail and the near-critical-methane flow condition that exhibits the heat transfer deterioration is identified and emphasized.
The study has been partially supported by ESA/ESTEC under contract no. 21881/08/NL/PA and MIUR (the Italian Ministry of University and Research).
Notes
1The pseudo-critical temperature is the temperature at which specific heat at constant pressure c p has a maximum at a specified pressure.
2In analogy with the definition introduced in the field of combustion which identifies a transcritical fluid as a fluid which is injected in the combustion chamber at supercritical pressure and subcritical temperature [Citation3].