为获得高温钠热管传热性能，开展真空条件下钠热管启动性能和等温性能试验，获得了钠热管真空条件下启动速度与等温性能数据；开展强制冷却工况条件下传热性能试验，获得了钠热管声速限特性与试验工况下的最大传热功率。经试验验证，所研制高温钠热管在真空条件下，580 ℃时完全启动，启动用时20 min，轴向壁面温差低于11 ℃，等温性能良好；钠热管传热功率在工作温度为500～650 ℃时受声速极限限制，在650 ℃以上受携带极限限制；在750 ℃和850 ℃时，测得热管最大散热功率分别为4.78 kW与8.02 kW，对应的最大轴向热流密度分别为1.51 kW/cm²与2.53 kW/cm²。试验结果表明，所研制钠热管具有较强传热能力，可满足热管式核反应堆等工程应用需求。

In order to obtain the heat transfer performance of high temperature sodium heat pipe, the start-up performance and isothermal performance tests of sodium heat pipe under vacuum conditions were carried out, and the start-up speed and isothermal performance data of sodium heat pipe under vacuum conditions were obtained. Heat transfer performance tests under the forced cooling conditions were carried out, and the sonic limit characteristics of sodium heat pipe and the maximum heat transfer power under test conditions were obtained. The experimental results show that the developed high temperature sodium heat pipe is fully started at 580 ℃ under vacuum condition, and the start-up time is 20 minutes, the axial wall temperature difference is lower than 11 ℃, and the isothermal performance is good. The heat transfer power of sodium heat pipe is limited by the sonic limit in the temperature range of 500-650 ℃, and is limited by carrying limit in the operating temperature above 650 ℃. When the working temperature is 750 ℃ and 850 ℃, the measured maximum heat transfer power of the heat pipe is 4.78 kW and 8.02 kW, respectively, and the maximum axial heat flux density was 1.51 kW/cm² and 2.53 kW/cm², respectively. The test results show that the developed sodium heat pipe has strong heat transfer capability which can meet the needs of heat pipe nuclear reactors and other engineering applications.

安全可靠的能源供给是无人水下潜航器（UUV）发展的关键基础，本研究面向我国重型海洋UUV研发的能源需求，提出了海洋静默式热管反应堆（NUSTER-100）小型核电源概念设计。建立了包括堆芯功率模型、堆芯通道传热模型、热管传热模型、热电转换模型及冷端换热模型等热管反应堆系统数学物理模型，基于高效稳健的数值算法和模块化编程思想，开发了具有自主知识产权的热管反应堆稳态和瞬态热工水力特性分析程序HEART，采用热管实验、温差发电实验等数据对HEART程序关键模块进行了验证与确认。采用HEART程序对NUSTER-100的稳态、冷启动瞬态及反应性引入瞬态工况进行了计算分析，获得了NUSTER-100满功率稳态工况下的热工水力特性，基于冷启动瞬态热工水力分析，提出了具有较高安全性的三段式热管反应堆启动方案，评估了反应性引入瞬态工况下热管反应堆的自稳特性和安全性。本研究可为我国UUV及热管反应堆技术的发展提供理论和技术支持。

Safe and reliable energy supply is the key foundation for the development of unmanned underwater vehicle (UUV). Unlike land and space missions, underwater missions are more demanding on energy, which requires higher power level, longer operating time, faster response time, and better concealment. Heat pipe cooled reactor has the advantages of large power capacity, simple structure, easy control of reactivity, and rapid thermal response. The solid-state reactor core does not require coolant and relies entirely on heat pipes to dissipate heat, thereby providing good inherent safety, controllability and concealment. Therefore, heat pipe cooled reactor is considered as one of the most promising options for UUV energy supply. In this study, a conceptual design of Nuclear Silent Thermal-Electrical Reactor (NUSTER-100) was proposed to meet the energy requirement of China’s heavy ocean UUV research and development. 109 sodium heat pipes were arranged in the reactor core for passive cooling, and the thermoelectric generators (TEGs) were employed in the reactor to convert fission heat to electric power. A set of heat pipe cooled reactor system-wild mathematical and physical models were established, including core neutron physics model, core channel heat transfer model, heat pipe model, thermoelectric conversion model and cold junction heat transfer mode. Based on the efficient and robust numerical algorithm and modular modeling ideas, heat pipe advanced reactor transient analysis code HEART was developed with independent intellectual property rights, and the key modules of HEART were validated and verified by heat pipe experiment and thermoelectric power experiment. The steady-state, cold-start transient and reactivity insertion transient conditions of NUSTER-100 were calculated and analyzed by HEART, and the full power operation characteristics of NUSTER-100 were obtained. Steady-state performance of the NUSTER-100 indicates that the solid-state core has good temperature flattening ability. The surface temperature of the heat pipe is less than 1 300 K, and the average temperature drop of the TEG module in central channel is 724 K, which can produce an electrical power of 1 207.8 W. Based on the cold-start transient thermal-hydraulic analysis, a three-stage heat pipe cooled reactor start-up scheme with high safety was proposed, and the stability and safety of heat pipe reactor under reactivity insertion transient were evaluated. The results show that the three-stage heat pipe cooled reactor start-up scheme can improve the reactor start-up efficiency. This study can provide support for the development of UUV and heat pipe cooled reactor technology in China.

Evaporation from nanopores plays an important role in various natural and industrial processes that require efficient heat and mass transfer. The ultimate performance of nanopore-evaporation-based processes is dictated by evaporation kinetics at the liquid-vapor interface, which has yet to be experimentally studied down to the single nanopore level. Here we report unambiguous measurements of kinetically limited intense evaporation from individual hydrophilic nanopores with both hydrophilic and hydrophobic top outer surfaces at 22 °C using nanochannel-connected nanopore devices. Our results show that the evaporation fluxes of nanopores with hydrophilic outer surfaces show a strong diameter dependence with an exponent of nearly -1.5, reaching up to 11-fold of the maximum theoretical predication provided by the classical Hertz-Knudsen relation at a pore diameter of 27 nm. Differently, the evaporation fluxes of nanopores with hydrophobic outer surfaces show a different diameter dependence with an exponent of -0.66, achieving 66% of the maximum theoretical predication at a pore diameter of 28 nm. We discover that the ultrafast diameter-dependent evaporation from nanopores with hydrophilic outer surfaces mainly stems from evaporating water thin films outside of the nanopores. In contrast, the diameter-dependent evaporation from nanopores with hydrophobic outer surfaces is governed by evaporation kinetics inside the nanopores, which indicates that the evaporation coefficient varies in different nanoscale confinements, possibly due to surface-charge-induced concentration changes of hydronium ions. This study enhances our understanding of evaporation at the nanoscale and demonstrates great potential of evaporation from nanopores.

A semianalytical, continuum analysis of evaporation of water confined in a cylindrical nanopore is presented, wherein the combined effect of electrostatic interaction and van der Waals forces is taken into account. The equations governing fluid flow and heat transfer between liquid and vapor phases are partially integrated analytically, to yield a set of ordinary differential equations, which are solved numerically to determine the flow characteristics and effect on the resulting shape and rate of evaporation from the liquid-vapor interface. The analysis identifies three important parameters that significantly affect the overall performance of the system, namely, the capillary radius, pore-wall temperature, and the degree of saturation of vapor phase. The extension of meniscus is found to be prominent for smaller nanoscale capillaries, in turn yielding a greater net rate of evaporation per unit pore area. The effects of temperature and ambient vapor pressure on net rate of evaporation are shown to be analogous. An increase in pore-wall temperature, which enhances saturation pressure, or a decrease in the ambient vapor pressure result in enhancing the net potential for evaporation and increasing the curvature of the interface.© 2011 American Chemical Society

Disjoining pressure effect is the key to describe contact line dynamics, micro/nanoscale liquid-vapor phase change heat transfer, and liquid transport in nanopores. In this paper, by combining a mesoscopic approach for nanoscale liquid-vapor interfacial transport and a mean-field approximation of the long-range solid-fluid molecular interaction, a mesoscopic model for the disjoining pressure effect in nanoscale thin liquid films is proposed. The capability of this model to delineate the disjoining pressure effect is validated. We demonstrate that the Hamaker constant determined from our model agrees very well with molecular dynamics (MD) simulation and that the transient evaporation/condensation mass flux predicted by this mesoscopic model is also consistent with the kinetic theory. Using this model, we investigate the characteristics of the evaporating extended meniscus in a nanochannel. The nonevaporating film region, the evaporating thin-film region, and the intrinsic meniscus region are successfully captured by our model. Our results suggest that the apparent contact angle and thickness of the nonevaporating liquid film are self-tuned according to the evaporation rate, and a higher evaporation rate results a in larger apparent contact angle and thinner nonevaporating liquid film. We also show that disjoining pressure plays a dominant role in the nonevaporating film region and suppresses the evaporation in this region, while capillary pressure dominates the intrinsic meniscus region. Strong evaporation takes place in the thin-film region, and both the disjoining pressure and capillary pressure contribute to the total pressure difference that delivers the liquid from the intrinsic meniscus region to the evaporating thin-film region, compensating for the liquid mass loss due to strong evaporation. Our work provides a new avenue for investigating thin liquid film spreading, liquid transport in nanopores, and microscopic liquid-vapor phase change heat/mass transfer mechanisms near the three-phase contact line region.