Heat transfer modeling for supercritical methane flowing in rocket engine cooling channels Marco Pizzarelli a, * , Francesco Nasuti a , Marcello Onofri a , Pietro Roncioni b , Raffaele Votta b , Francesco Battista b a University of Rome “La Sapienza”, Dipartimento di Ingegneria Meccanica e Aerospaziale, Via Eudossiana 18, 00184 Rome, Italy b CIRA (Italian Aerospace Research Center), Via Maiorise, 81043 Capua, CE, Italy highlights  Numerical simulation of methane in supercritical pressure and subcritical to supercritical temperature.  Fluid and structure thermal coupling.  Asymmetrically heated channels of rectangular cross section.  Supercritical-pressure methane may exhibit heat transfer deterioration.  Heat transfer deterioration is mitigated increasing coolant pressure and/or surface roughness. article info Article history: Received 12 March 2014 Accepted 3 October 2014 Available online 16 October 2014 Keywords: Liquid rocket engine Regenerative cooling Supercritical methane Heat transfer deterioration Computational Fluid Dynamics (CFD) Conjugate Heat Transfer (CHT) Channel roughness abstract To investigate the methane behavior inside rocket engine cooling channels, a test article has been specifically designed by the Italian Aerospace Research Center. In this study, the expected wall and coolant behavior of this test article is analyzed by a three-dimensional conjugate heat transfer model. Different coolant pressure and surface roughness levels are considered in order to understand their influence on the heat transfer capability of the cooling system. Results show that heat transfer deteri- oration may occur in principle when methane is operated in near-critical condition. However, the resultant wall temperature peak reduces for increasing coolant pressure and for increasing surface roughness. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction The hot gas environment within a modern liquid rocket com- bustion chamber can be characterized by gas temperatures as large as 3600 K and heat fluxes as large as 160 MW/m 2 , depending on propellants, mixture ratio and chamber pressure [1]. In order to keep the temperatures of the thrust chamber walls within their allowed limits, an intense cooling effort is necessary, which, in case of regenerative cooling, is achieved by flowing one of the two propellants into suitable channels surrounding the thrust chamber. In this case, high supply pressure is required because of the inevi- table losses which occur in the cooling circuit [2]. Regenerative cooling performance is especially important in case of reusable or long-duration-expendable engines, where an effective and efficient cooling system is crucial to extend the engine life, or in expander cycle engines, where coolant heating provides the available power for turbo-machinery. In the latter case, thermal analysis of regen- eratively cooled engines is essential to predict not only wall tem- perature but also coolant temperature and pressure at the channel exit. The study of heat transfer to near-critical fluids, that is to su- percritical pressure fluids whose temperature is close to the pseudo-critical value (i.e., the temperature at which specific heat at constant pressure has a maximum at a specified pressure), has recently captured the interest of liquid rocket engine designers because of the possible use of methane as a denser and cheaper replacement of hydrogen in launch vehicles and as a cheaper replacement of toxic storable propellants for space propulsion [3,4]. In case of liquid-oxygen/liquid-methane engines with chamber * Corresponding author. E-mail address: marco.pizzarelli@uniroma1.it (M. Pizzarelli). Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng http://dx.doi.org/10.1016/j.applthermaleng.2014.10.008 1359-4311/© 2014 Elsevier Ltd. All rights reserved. Applied Thermal Engineering 75 (2015) 600e607