In the using process of the finned tube, the temperature on the top of the windward face of the fin in the first and second row of finned tube is the highest temperature of finned tube. It restricts and determines the high temperature conditions and application fields of finned tube heat exchanger. This paper establishes the research model of the first row and second row finned tube, to carry out the numerical simulation calculation of the fluid flow and heat transfer of high temperature air flowing through the finned tube and exchanging heat with cooled liquid water, and to research the influence of different tube transverse spacing, fin spacing and other factors on the fluid flow and heat transfer characteristics of finned tube and the highest fin temperature. The air outlet temperature, heat exchange capacity, Nu number, pressure drop and maximum fin temperature are obtained in the conditions of different tube transverse spacing and fin spacing, and the variation characteristic, mechanism and law of temperature field and velocity vector for the finned tube are also gained.

Excessive heat losses and water consumption in cooling units are significant constraints restricting the application circumstances and performances for the SCO2 Brayton cycle, and the heat exchange capacity in the precooler (PRC) is typically 1.5 times that of power generation. Therefore, this research offers a high-integrated combined power/cooling system in which two waste heat exchangers (WHEs) and a rectifier (RET) are used instead of the PRC to achieve 100% exhaust heat recovery. Each component’s energy and exergy models are developed, and the operational characteristics, coupling relationships, and exergy destruction distribution are examined. Results indicate that, when compared to the Brayton cycle, the thermal and exergy efficiency is considerably increased, and the concentration difference and WHE1 pitch point difference have significant influences on system performance. Further exergoeconomic and optimization analysis reveals that the superior exergy case is mostly recommended for relevant thermal and exergy efficiency increasing rates of 13.7% and 9.17%, respectively, and the unit cost is 81.33% that of the base case. Turbine 1 (TUR1) and main compressor (MCP) are the first and second highest cost rates, respectively, and RET and generator (GEN) account for roughly 34% exergy destruction rate and 20% exergy destruction cost rate, respectively. In addition, reducing heat transfer differences in relevant equipment can further promote system performance.