With the rapid development of supercritical water gasification (SCWG) technology, investigation on thermal radiation property of water up to critical state (22.1 MPa, 647 K) is becoming important for precisely analyzing thermo-chemical process in this engineering. This paper explores radiative absorption coefficients ${\kappa }_{\eta }$ of water under thermodynamic states of (20−25) MPa and (773–1273) K based on line-by-line (LBL) calculations. The results are validated against experimental data and molecular dynamic (MD) simulation values. It is shown that near- and super-critical water (NSCW) has five major radiation bands within spectral range of (1−50) $\mathrm{\mu }\mathrm{m}$. Compared to atmospheric water vapor (0.1 MPa), NSCW holds unique spectral characteristics, including dramatically smoothed spectrum, enormous absorption coefficient, and redshift or blueshift on spectral peak positions. Based on calculation results, a gray-band model for NSCW is proposed to solve problems of radiative heat transfer in SCWG engineering.

随着超临界水气化（SCWG）技术的快速发展，研究水达到临界状态（22.1 MPa，647 K）的热辐射特性对于精确分析该工程中的热化学过程变得越来越重要。本文探讨了辐射吸收系数${\kappa }_{\eta }$基于逐行 (LBL) 计算的 (20−25) MPa 和 (773–1273) K 热力学状态下的水。结果根据实验数据和分子动力学 (MD) 模拟值进行了验证。结果表明，近临界和超临界水 (NSCW) 在 (1−50) 的光谱范围内有五个主要辐射带$\mathrm{\mu }\mathrm{米}$. 与大气水汽（0.1 MPa）相比，NSCW 具有独特的光谱特性，包括显着平滑的光谱、巨大的吸收系数以及光谱峰位置的红移或蓝移。基于计算结果，提出了NSCW的灰带模型，以解决SCWG工程中的辐射传热问题。