در پژوهش حاضر، رفتار حرارتی متان و هیدروژن در رژیم گذربحرانی در کانالهای خنککاری بهصورت عددی تحلیل شدهاست. این سیالات با فشار فوقبحرانی و دمای زیربحرانی وارد مجرای خنککاری شده و با گرفتن گرما از دیواره داغ با دمای فوقبحرانی از کانال خارج میشوند. حلگری با استفاده از توسعه برنامهنویسی شیگراء C++ در نرمافزار اپنفوم تدوینشده که برپایه روش حجم محدود است. روابط خواص ترمودینامیکی و انتقال متناسب با شرایط سیال خنککننده در رژیم گذربحرانی ارایه شدهاست. همچنین، بهدلیل اهمیت پدیدههای نزدیک دیواره در کانالهای خنککننده، دقت الگوهای آشفتگی مختلف مورد بررسی قرار گرفتهاست. اعتبارسنجی مدلهای استفادهشده با استفاده از دادههای تجربی هیدروژن در لولهای دایروی انجام شدهاست. نتایج نشان میدهند که شروع و محدوده افت انتقال حرارت مطابق با محدوده تغییرات شدید خواص انتقال و دمای دیواره است. همچنین، اثر دبی جرمی و دمای دیواره بر رفتار حرارتی سیال (مانند افت انتقال حرارت و تغییر حالت سیال) نشانداده شدهاست.
Thermal Behavior Analysis of Near-critical Cryogenic Fluids in Cooling Channels
نویسندگان [English]
Maryam Shokri2؛
چکیده [English]
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 lower storage cost. Recognition and analyzing the thermal behavior of coolant flow in regenerative cooling paths is of great importance in optimum design and performance enhancement of air vehicle engines. Due to certain phenomena that occur in cooling channels, such as near-wall high-temperature gradient, high Reynolds number, and three-dimensional flow, coolant fluid will face conditions including regime change and heat transfer deterioration. 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 analyzed. Solving equations and simulations of fluid flow are conducted using OpenFOAM CFD package, which contains applications and utilities for finite volume solvers. Moreover, OpenFOAM 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-ω 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.
کلیدواژهها [English]
Transcritical, Supercritical, Heat Transfer Deterioration, Real Gas Equation of State, Cryogenic Fluid