مهندسی مکانیک شریف (May 2019)
THERMAL BEHAVIOR ANALYSIS OF NEAR-CRITICAL CRYOGENIC FLUIDS IN COOLING CHANNELS
Abstract
Recently exploiting the methane in comparison with the hydrogen as a coolant fluid in launch vehicles captured the interest of space propulsion research community. A few of the main advantages are: it is denser and lower-cost, and it has a lower storage cost. Recognition and analyzing the thermal behavior of coolant flow in regenerative cooling paths are of great importance in the optimum design and performance enhancement of air vehicle engines. In the present study, near-critical fluids heat transfer under supercritical pressure and close to pseudo-critical temperature conditions are investigated. Thermal behavior of cryogenic coolant fluids in the regenerative cooling channels is also analyzed. Solving equations and simulations of fluid flow are conducted with a commercial CFD package, which contains applications and utilities for finite volume solvers. This software gives the possibility to use the self-developed object-oriented C++ programming for applying the boundary conditions, the state equation, and transport properties. Furthermore, coolant flows of methane and hydrogen in the transcritical and supercritical regimes inside the three-dimensional cooling channels are studied. Solver validation is performed through simulation of hydrogen in the uniformly heated circular channel. Further, real gas equations of state and transport property relations in transcritical and supercritical regimes have been explored. Also due to the significance of the near-wall phenomena inside coolant channels, the accuracy of Spalart-Allmaras and k-\u{03c9} family turbulence models are compared with each other and numerical results are validated with experimental data. In the cooling channels with high heat fluxes, heat transfer from the hot wall to the coolant fluid suffers in some areas and thus the wall-temperature increases. One observes that the transcritical regime and heat transfer deterioration regions through the behavior of specific heat at constant pressure, transport property and thermodynamic parameters of coolant fluid could be identified.
Keywords
