Revolutionizing 300 °C industrial steam with a novel transcritical carbon dioxide heat pump system: Thermodynamic and configuration analyses

Abstract

The industrial fields have urgent demands for up to 300°C-grade high-temperature steam, which is far beyond the capability of conventional heat pump technologies. To expand the application range of high-temperature heat pump technology for industrial steam supply, this study proposes a novel transcritical carbon dioxide heat pump capable of directly generating 300 °C steam from ambient air as the heat source. By physically separating high-pressure water heating and steam superheating through a dual gas cooler configuration, the system achieves decoupled control of steam pressure and temperature. This staged generation strategy effectively exploits the temperature glide of supercritical carbon dioxide to supply 300 °C steam, while eliminating the need for inefficient steam recompression. The thermodynamic models based on energy and exergy analyses are developed to evaluate the system performance. The results indicate that the coefficient of performance and exergy efficiency are relatively insensitive to discharge pressure, which is different from conventional systems. Sufficient internal heat recovery enhances the coefficient of performance and exergy efficiency while creating a discharge temperature margin, providing the flexibility to further increase steam temperature at a stable peak performance. A peak coefficient of performance of 1.65 and a maximum exergy efficiency of 48.5 % are achieved at a heated water outlet temperature of 255 °C. A configuration comparison reveals that the efficiency advantage of the dual-recuperator configuration over the single-recuperator configuration at lower steam pressures is primarily due to the significant reduction in exergy destruction within the heat exchangers. At higher steam pressures, while the single-recuperator configuration achieves the highest coefficient of performance under high discharge pressures, the dual-recuperator configuration is more advantageous for maintaining higher performance at reduced discharge pressures.