On the Onset of Heat Transfer Deterioration in Supercritical Coolant Flow Channels

Abstract

The deterioration of forced convection heat transfer can affect channel flows of supercritical fluids, and therefore has to be taken in consideration when dealing with regenerative cooling of liquid rocket engines. A threshold value of the ratio between the heat flux and the specific mass flow rate is identified as the main parameter controlling the heat transfer deterioration onset. The threshold parameter depends on the specific thermodynamic conditions of the coolant and in particular on its pressure level. In the present study, a parametric numerical analysis has been carried out on the flow of supercritical methane in heated channels, for an assigned inlet temperature level and varying the inlet pressure. A correlation for the threshold parameter as a function of pressure is then proposed on the basis of the obtained results. Nomenclature A Helmholtz free energy [J/kg] Bo * Jackson Buoyancy parameter: Bo * = Gr * /(Re 3.425 D P r 0.8 ) G specific mass flow rate [kg/s/m 2 ] Gr * Grashof Number based on the heat flux: Gr * = gβq w D 4 /(kν 2 ) N u Nusselt Number: Dh c /k b P r Prandtl Number: µ b c p,b /k b R gas constant [J/kg/K] Re Reynolds Number: ρu b D/µ b a reduced Helmholtz free energy a = A/(RT ) c p specific heat at constant pressure [J/kg/K] D channel cross section diameter [m] F parabolized vector of fluxes in the streamwise direction g sea level gravitational acceleration constant, g = 9.81 m/s 2 G, H vectors of fluxes in the transverse directions h enthalpy [J/kg] h c heat transfer coefficient [conductivity [W/m/K] m mass flow rate [kg/s] P pressure term vector for PNS p pressure [Pa] Q source terms vector q +reduced heat flux, q + = (q w /G)/(c p /β) * PhD Student,

Modeling and Simulation of Supercritical-Pressure Turbulent Heat Transfer of Aviation Kerosene with Detailed Pyrolytic Chemical Reactions

“…As a result, the regenerative cooling technology, which uses engine fuel as a coolant prior to combustion, attracts significant research interests. , The regenerative cooling process operates under high pressures, generally higher than the thermodynamic critical pressure of the engine fuel (coolant), thus leading to fluid flows and heat transfer at supercritical pressures. Supercritical-pressure fluid flows and heat transfer of various propellants, including hydrogen and hydrocarbon fuels, have been experimentally and numerically investigated in recent years, − intended for a fundamental understanding and practical application of the regenerative cooling technology in the propulsion and power-generation systems. A number of peculiar features, including strong thermophysical property variations and heat-transfer deterioration in the near-critical region, have been revealed and analyzed. − , …”

“…Supercritical-pressure fluid flows and heat transfer of various propellants, including hydrogen and hydrocarbon fuels, have been experimentally and numerically investigated in recent years, − intended for a fundamental understanding and practical application of the regenerative cooling technology in the propulsion and power-generation systems. A number of peculiar features, including strong thermophysical property variations and heat-transfer deterioration in the near-critical region, have been revealed and analyzed. − , …”

Parametric Analysis of Cooling Properties of Candidate Expander-Cycle Fuels

“…On the contrary, the behavior of wall temperature and heat transfer coefficient for propane is not different from the case of lower heat flux, therefore still showing a normal heat transfer. The fact that heat transfer deterioration occurs for methane and ethane but not for propane is due to their different thermophysical properties, which directly influence the threshold heat flux that a flow can bear without heat transfer deterioration [40]. As a consequence, propane has a higher heat transfer coefficient followed by ethane and methane, as can be observed in Fig.…”

“…The analysis of wall temperature requires one to observe that, dealing with forced convection heat transfer to supercritical pressure fluids in channels, the heat transfer can be either normal, enhanced, or deteriorated, depending on the heat flux level and on the fluid thermophysical characteristics [18,22,[35][36][37][38][39][40]. ‡ For the lower heat flux, a normal heat transfer occurs for the three propellants.…”

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