All over the world, the nuclear reactor technology has been in the critical stage of transformation and upgrading. Also, there have been the higher requirements for the key technical indicators, such as the power level, the miniaturization and the security. According to analyzing the engineering requirements of typical nuclear reactor devices, the authors demonstrated the scientific problems and the physical mechanisms behind the limitation of thermal-hydraulic parameters, such as the fuel assembly, the steam generator, and the special safe system. Thus, the technical route of heat transfer enhancement was put forward in this paper. The technology of heat transfer enhancement referred to the application of various engineering means to improve the heat transfer performance of component and reduce the power consumption of coolant, the component temperature, as well as the device size. In this paper, the heat transfer enhancement technology was divided into the passive technology and the active technology. Meanwhile, the passive technology could be subdivided into the structure innovation technology and the surface modification technology. The active technology could be subdivided into the magnetic field technology and the electric filed technology. Based on the analyses of this paper, it was considered that the effects of different heat transfer enhancement technologies on the single-phase and two-phase conditions were quite different. Moreover, the corresponding technical development maturity and the manufacturing process were also much different. First of all, the structure innovation technology mainly included two categories: the micro-channel technology and the longitudinal vortex technology. By increasing the specific surface area of thermal component, enhancing the turbulent mixing degree of flow field, and disturbing the near-wall thermal boundary layer, the heat transfer performance of single-phase and two-phase conditions could be significantly improved. The above technology had been widely applied to many heat transfer fields, and the manufacturing technology was mature as well as diversified, which had the strong application prospect in the field of reactor core and heat exchanger without nuclear conditions. It should be noted that the technical difficulty of structure innovation technology lied in the optimization of structure design to obtain the best enhanced heat transfer performance. As for the surface modification technology, it mainly included the surface micro-nano structure technology and the surface coating technology. Moreover, it was suggested that the structural dimensions of above two technologies were far smaller than that of the near-wall thermal boundary layer, and the corresponding effects on the sing-phase heat transfer condition was not obvious. However, the above two technologies could significantly affect the bubble dynamics and the two-phase interface evolution under boiling condition, which could obviously improve the heat transfer performance under two-phase condition. In addition, the magnetic field technology and the electric field technology belonged to the active heat transfer enhancement technology, which relied on the coolant physical properties and the intervention technology of flow field. It should be noted that the above two technologies could effectively improve the heat transfer performance under the single-phase and two-phase conditions. However, this kind of technology was still in the stage of scientific research, and there was no practical engineering application. Based on the current technology development, the application of these two technologies was weak in the reactor core, and the application in non-nuclear environment was also limited. (C) 2021 Elsevier Ltd. All rights reserved.
