This study presents a coupled one-dimensional and two-dimensional conjugate heat transfer (CHT) framework for the design and analysis of regenerative cooling systems in a 10 kN-class nuclear thermal propulsion engine using supercritical hydrogen. Unlike chemical propulsion systems, nuclear thermal propulsion engines employ pure hydrogen as both propellant and coolant, making empirical correlations such as the Bartz equation unreliable. This study employs a two-dimensional Reynolds-averaged Navier–Stokes solver for the hot-gas-side with a quasi-one-dimensional solver for the coolant-side, accounting for fin efficiency, variable thermal conductivity, and pressure losses. Application to a conceptual NTP nozzle shows that the finned cooling configuration reduces the maximum hot-gas-side wall temperature by 260 K (from 824 K to 565 K), placing the throat temperature at ∼560 K, well below the softening limit of copper alloys (∼800 K), thereby enhancing structural integrity. The framework proposed in this study estimates the convective heat transfer coefficient, which is approximately a factor of two higher than the Quasi-1D CHT analysis, through a relatively detailed nozzle internal flow analysis, and presents a new perspective on the thermal analysis of rocket engines targeting pure hydrogen.
Kang et al. (Sun,) studied this question.