Release Time:2019-03-13  Hits:

Indexed by: Journal Article

Date of Publication: 2016-10-17

Journal: NUMERICAL HEAT TRANSFER PART A-APPLICATIONS

Included Journals: Scopus、EI、SCIE

Volume: 70

Issue: 8

Page Number: 870-886

ISSN: 1040-7782

Abstract: When a cryogenic fluid initially at a subcritical temperature is injected into a supercritical environment, it will experience a process across a pseudo-boiling point, at which the specific heat reaches its maximum value under the corresponding pressure. Large eddy simulation (LES) is conducted to explore the effects of pseudo-vaporization phenomenon around the pseudo-critical temperature on fluid jet evolution. To highlight the pseudo-vaporization effect, a cryogenic nitrogen jet with different injection temperatures, which correspond to transcritical and supercritical conditions, respectively, is injected into a chamber with same supercritical conditions. All of the thermophysical and transport properties are determined directly from fundamental theories combined with a real fluid equation of state. It is found that when the fluid transits through the pseudo-boiling point, the constant-pressure specific heat reaches a local maximum, while the thermal conductivity and viscosity become minimum. The condition-averaged constant-pressure specific heat suggests that the pseudo-boiling point has the effect of increasing the density gradients. Vorticity and Q-criterion analysis reveals that high-temperature injection facilitates the mixing of jet fluid with ambient gas. Also, the high-temperature injection of supercritical fluid can earlier transit into the full developed region.