DOI: 10.2514/1.46769 In this paper, comprehensive numerical studies of the turbulent convective heat transfer of the cryogenicpropellant methane flowing inside a horizontal minitube under supercritical pressures have been conducted, based on a complete set of conservation equations and accurate evaluations of the thermophysical properties. The present numerical investigations focus on fundamental understanding of the effects of many key parameters, including the inlet pressure, wall heat flux, inlet velocity, and inlet temperature, on the supercritical heat transfer phenomena and the variations of the Nusselt number. Results indicate that drastic property variations at the pseudocritical temperature under a supercritical pressure would cause local heat transfer deterioration. Increasing the inlet methane pressure would result in improved heat transfer at supercritical pressures, particularly under a high wall heat flux,i.e.,7 MW=m 2 .Theconventionalempiricalexpressions,i.e.,theGnielinskiequation,cannotbeusedforthe supercritical heat transfer predictions of the cryogenic-propellant methane at supercritical pressures. A modified heattransferexpression,whichisapplicabletothesupercriticalcryogenicmethane,hasbeensuccessfullyestablished in this paper.

Numerical Studies of Supercritical Turbulent Convective Heat Transfer of Cryogenic-Propellant Methane

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 exhi...

Numerical analysis of deterioration in heat transfer to near-critical rocket propellants

The status of the research on the heat transfer deterioration in supercritical fluids: A review

The knowledge of the flow behavior inside asymmetrically heated channels is of great importance to improve design and performance of regeneratively cooled rocket engines. The modeling of the coolant flow is a challenging task because of its particular features, such as the high wall temperature gradient, the high Reynolds number, the three-dimensional geometry of the passages, and the possible supercritical conditions of the fluid. In the present work, a numerical approach to study the turbulent flow of supercritical fluids is presented and validated by comparison with experimental data. Solutions of the supercritical nitrogen flowfield in an asymmetrically heated three-dimensional channel with a high-aspect ratio (channel height-to-width ratio) are presented and discussed. Emphasis is given to the analysis of the peculiar behavior and cooling performance of the supercritical fluid as compared with perfect gas. In particular, a long channel is considered, such that entrance effects are negligible, to analyze in detail wall heat-flux evolution throughout the channel.

Numerical Analysis of Three-Dimensional Flow of Supercritical Fluid in Asymmetrically Heated Channels

Numerical Analysis of Three-Dimensional Flow of Supercritical Fluid in Cooling Channels

The knowledge of the flow behavior inside cooling channels is of great importance to improve design and performance of regeneratively cooled rocket engines. The modeling of the coolant flow is a challenging task because of its particular features, such as the high wall temperature gradient, the high Reynolds number and the three-dimensional geometry of the passages. In case of methane as coolant, a further complication is the transcritical operating condition of the fluid. In this thermodynamic regime large changes of the fluid properties can greatly influence the coolant flow-field and the heat transfer. Numerical simulations of transcritical methane flow-field in asymmetrically heated rectangular channel with high aspect ratio and strong wall temperature differences are carried out by a suitable CFD solver. Results are discussed in detail and compared with supercritical methane flow-fields. Finally the aspect ratio effect on methane flow is analyzed by comparison of four different rectangular cooling channel geometries with fixed hydraulic diameter and coolant flows with the same mass flow-rate per unit area. Emphasis is given to the comparison of fluid cooling performance and pressure loss.

Marco Pizzarelli

Papers

Numerical analysis of deterioration in heat transfer to near-critical rocket propellants

The status of the research on the heat transfer deterioration in supercritical fluids: A review

Numerical Analysis of Three-Dimensional Flow of Supercritical Fluid in Asymmetrically Heated Channels

Numerical Analysis of Three-Dimensional Flow of Supercritical Fluid in Cooling Channels

CFD analysis of transcritical methane in rocket engine cooling channels