3D Conjugate heat transfer model for simulation of Heat Transfer by High Roughness Cooling Channels
Creators: name:  V. FERRETTI 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: PROPULSION PHYSICS
LIQUID ROCKET ENGINE
CHAMBER COOLING

description: A 3D conjugate heat transfer model has been developed for the simulation of the heat transfer problem in rectangular cooling channels characterized by high roughness surfaces. The main objective of the model is a complete and detailed description of coupled solid/coolant behaviour characterizing the liquid rocket engine cooling systems. Different objectives have been considered for the model development: to describe the behaviour of coolant within the channel (three-dimensional effects and possible supercritical behaviour of the coolant) and to describe the solid thermal behaviour. The development of this model combines the industrial necessity to obtain proper results in reasonable times with a detailed description of the involved phenomena and specific characteristics of the configuration. One of the most important aspects involved in this process is the introduction of a proper high roughness model able to describe the effects of high roughness wall on the internal flow and on the cooling channel performance in terms of thermal behaviour. The defined model also represents a proper tool to obtain a good description of possible propellant stratification close to the hot wall surface. Indeed, only the coupled description of fluid stratification and roughness effects allow the correct evaluation of thermal behaviour of the cooling systems because they directly affect the wall temperature, the corresponding heat flux coefficient, and the fluid bulk temperature. The analyses have been performed by Ansys Fluent 2021 R2. The model is a 3D conjugate heat transfer model coupling a RANS Spalart-Allmaras turbulence model for the coolant flow with Fourier equations for the thermal conduction in the solid volume. The model is completed by a high roughness wall modelling that has been properly set to be fully representative for the case of interest. The model validation has been realized by means of two different test cases requiring the modelling of two different cooling fluid, water and methane, characterized by different stratification behaviour. For both test case the validation has been obtained with respect to experimental data. A first step of the analyses is the model validation with respect to both experimental data and numerical results obtained considering the rebuilding of experimental data obtained during a test campaign performed by NASA on full scale equipment of a liquid rocket engine with water cooling. The results show full agreement with respect to the available experimental data (pressure and temperature distribution along the cooling channel). After the model calibration and validation with NASA experimental test, the model has been applied to obtain prediction of M10 liquid cryogenic rocket engine cooling system. The model has been so extended to methane cooling, that requires further attention to the verification of fluid stratification close to the hot surfaces. A dedicated User Defined Function (UDF) has been written and implemented to assign to methane a proper and accurate material properties database. The model so improved has been validated with respect to numerical and experimental data obtained from MIRA motor experimental test campaign. For methane cooling a full agreement has been also obtained with respect to the experimental data both n terms of pressure and temperature distribution.