Nuclear thermal propulsion (NTP) systems is regarded as a promising technology for human space exploration in the near future due to its large thrust and high specific impulse. Hydrogen serves as both the system coolant and engine propellant here. Convective heat transfer to hydrogen flow is a complicated process accompanying large properties variation of hydrogen due to high heat flux. In this paper, the strongly heated internal hydrogen flow is investigated numerically. According to the previous work, it has been found that the standard k-ε model with the assistance of enhanced wall treatment shows the excellent agreement with the experimental data. Based on this validated approach, the effects of heat flux profile on flow and heat transfer characteristics are evaluated. Results show high dependency of the thermal hydraulics characteristics such as wall temperature distribution and heat transfer coefficient on the heat flux profile imposed at the tube wall. Besides, the results suggest that the flow acceleration to a flat velocity profile contributes to the heat transfer deterioration, while the distorted velocity to “M-shape” is considered to be more often related to the recovery of turbulence production and subsequent heat transfer.

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