Mini-channel heat exchangers are widely used due to their compact structures and high efficiency. Integrating heat exchangers with triply periodic minimal surfaces (TPMS) has shown great potential to optimize the flow and heat transfer performance. In this study, Gyroid (G), Diamond (D), and IWP type TPMS-based heat exchangers are constructed in three dimensions. The thermal-hydraulic, entropy production, and flow-induced noise characteristics of TPMS-based heat exchangers are numerically investigated. The results indicate that the TPMS channels with larger viscosity entropy production have smaller thermal entropy production due to the greater flow disturbance. The G-channel has the highest friction factor and the lowest sound source intensity, while the D-channel obtains the strongest sound source intensity due to frequent cross-collisions of the fluid. The sound source intensity of the IWP channel is 10% lower than the D-channel. The wall dipole sound source plays a dominant role in TPMS channels. This study provides different perspectives to evaluate the performance of a TPMS heat exchanger and provides references for the design and optimization of TPMS heat exchangers.

The nuclear energy field requires the construction of heat exchangers that can withstand sufficiently high temperatures. In this paper, the etching technique was utilized to fabricate heat exchange channels on Inconel718 plates, and experiments were carried out in NaCl-ethylene glycol solution, three temperature conditions of 35 degrees C, 40 degrees C, and 45 degrees C, and two concentrations of electrolyte solutions, 0.5 mol/L and 1 mol/L, with the addition of 50 kHz ultrasound for comparison. The experimental results show that the etching rate can be as high as 2.894 mm/h, and the inter-electrode current is as high as 908 mA. The roughness characterization of the etching channel Ra and Rq measured by the aspheric surface measuring instrument can be as low as 2.416 mu m and 2.647 mu m, respectively. In the images generated by SEM scanning, it is found that uneven distribution of pits and bumps exist in the etching channel, but their diameters are all less than 0.1 mu m, which means the etched channel is acceptably smooth.

The development in manufacturing engineering has made it possible to adopt the unique porous structure known as the triply periodic minimal surface to increase energy efficiency in a variety of energy-related sectors. With the unique morphological characteristics, triply periodic minimal surface exhibits remarkable mechanical strength and thermal performance, which makes it a potential candidate for compact, high-performance heat exchanger constructions. In this study, a theoretical model based on triply periodic minimal surface porous media is developed. Based on the hypothesis that the triply periodic minimal surface is isotropic and the heat transfer intensity of fluid and solid is uniform throughout the core of the heat exchanger, the simulation of the full-size heat exchanger is simplified by using a porous media model. The flow distribution characteristics of triply periodic minimal surface heat exchangers, as well as the effect mechanism of key factors, including the channel porosity, header configuration, the type of triply periodic minimal surface, the core length and Reynolds number on the flow distribution performance, are investigated. A dual-header configuration is proposed to improve the flow uniformity of triply periodic minimal surface heat exchangers. The results indicate that the flow distribution performance of triply periodic minimal surface based heat exchangers can be enhanced by the reduction of channel porosity. When the cold-side porosity is 0.7, the flow rate deviates from the mean value by 220% at its maximum for a Primitive heat exchanger. A dual-header configuration eliminates the columnar extreme high velocity space in the core and greatly reduces the "weak zone" of flow distribution, which improves the flow nonuniformity by 45-90% over the single-inlet headers. This paper provides data and theoretical support for the optimal design and practical application of the complex, high-performance triply periodic minimal surface based heat exchangers.

Heat exchangers are one of the key components to ensure the safe and efficient operation of nuclear energy systems. Additive manufacturing offers the processing solutions of advanced heat exchangers based on triply periodic minimal surfaces (TPMS). TPMS has superior mechanical and thermal-hydraulic performance that provides excellent energy-saving potential in the energy systems. In this study, I-WP, Neovius, Fischer-Koch S, Primitive surface-based heat transfer channels with different volume shares are constructed in three dimensions. The enhanced heat transfer mechanisms of TPMS topologies are identified and parametric analysis on the thermal-hydraulic performance is performed. The results indicate that the secondary flows, periodic flow acceleration/deceleration and constant changes in flow directions play key roles in convective heat transfer of TPMS topologies. Based on a large amount of simulation data, empirical correlations for Nusselt number and friction factor in the turbulent regime are established. This study provides a database for the design and application of TPMS-based heat exchangers, which contributes to the energy-saving and sustainable future target.

An efficient intermediate heat exchanger is crucial for ensuring the safe operation, lifespan and energy efficiency of the advanced nuclear systems. Benefiting from the development of additive manufacturing technology, it is possible to design and optimize heat exchangers by introducing triply periodic minimal surface (TPMS) structures. With the excellent mechanical and thermal performance of TPMS, further improvements in the energy efficiency of advanced nuclear systems are achievable. In this study, I-WP surface, Primitive surface based heat exchangers and a printed circuit heat exchanger for accelerator driven subcritical systems are constructed in three dimensions. In order to obtain the potential enhancement of thermal performance of TPMS-based heat exchangers, the fluid flow and conjugate heat transfer characteristics in TPMS heat exchangers, especially for the specific working medium of lead-bismuth eutectic (LBE) are investigated. A parametric analysis is conducted on the key design variables including the solid volume fraction and hydraulic diameter. The results indicate that TPMS-based heat exchangers could achieve about 2–3 times the total heat transfer rate with half the volume of a printed circuit heat exchanger. The TPMS topologies contribute greater heat transfer enhancement on the Helium side than the LBE side, which helps to optimize the thermal resistance allocation in Helium-LBE heat exchangers. An increase of solid volume fraction enhances the convective heat transfer of Helium in I-WP heat exchanger, while homogenizing the local thermal performance. This study provides a database for the design and optimization of TPMS-based heat exchangers, which contributes to the sustainable future target.

Hydrogen cooler is a key equipment of the precooling unit in hydrogen refueling stations with the requirement of high heat transfer efficiency, high compactness and high pressure resistance. Printed circuit heat exchanger is a promising candidate for the hydrogen cooler due to its great performance on extremely high pressure and high temperature working environment. In this paper, a hydrogen cooler with a thermal load of 72 kW is firstly designed by using the segmented thermal design method and logarithmic mean temperature difference method. Then, the capital model of the hydrogen cooler is established to evaluate the performance using the exergoeconomic method. The results show that the operating cost, which is related to exergy destruction, accounts for 94.5% of the total cost of the hydrogen cooler. The thermal exergy destruction accounts for 92.4% of the total exergy destruction. Finally, the geometrical parameters of the channel are optimized by using the multi-objective optimization. The channel radius shows the most significant impact on the construction cost and operating cost among the three geometrical parameters. Compared with the coaxial tube evaporators, the printed circuit heat exchanger has better performance on the volume and total cost, which are reduced by 88.0% and 4.0% respectively.

本文以微博平台中的明星超级话题为观察场域,聚焦其中的粉丝及所属圈群——"饭圈"的追星实践,勾勒和阐释饭圈内部的权力关系生成及权力运作过程.研究着重考察饭圈内部的大粉、产出粉和普通粉丝三种粉丝类型,研究以线上、线下民族志相结合为主要研究方法,得出以下结论:饭圈内部秩序的建构,是以牧领权力及其治理术为核心的权力关系实践;在饭圈的数字实践中,"袒露与服从"是实现情感满足、群体认同和数字生活"自我救赎"的前提;饭圈的运行机制成为数字牧领的显现,出现了再中心化、制度化和数字劳动异化的新型权力生产特征.

Printed circuit heat exchanger (PCHE) is considered a promising candidate for accelerator driven systems (ADS) due to its high compactness and efficiency. The preeminent high-temperature, high-pressure and corrosion resistance enables it to withstand the severe conditions of ADS and ensure the safe and efficient operation. In this paper, a PCHE applied to the ADS is proposed, adopting helium as the cold source and lead-bismuth eutectic (LBE) as the heat source. On this basis, a three-dimensional model is established and the flow and heat transfer characteristics of the PCHE are numerically investigated. The thermal performance is further improved by optimizing structural and operating parameters. The results indicate that the high thermal conductivity and superior field synergy degree of LBE ensures a strong heat transfer performance of PCHE. The velocity disturbance and double-vortex secondary flow generated in modified channels, which intensify the fluid mixing and improve the field synergy level, help to further enhance the overall heat transfer coefficient. Structural and operating parameters of the helium side are more critical to the thermal-hydraulic performance, an increase of helium mass flow rate within allowable pressure drop is conducive to the comprehensive performance.

Printed circuit heat exchanger is considered as an promising candidate for floating storage and regasification unit of liquefied natural gas due to its high compactness and efficiency. The flow maldistribution is an essential issue in practical applications of the printed circuit heat exchanger, which leads to the performance degradation. In this study, the flow distribution of supercritical natural gas in a printed circuit heat exchanger plate is three-dimensionally simulated, and the thermal-hydraulic performance of the channels is investigated. To save the computational cost, a simplified two-dimensional model is proposed. The comparisons of results between the two- and three-dimensional models show that the effects of backflows, vortex, interaction between properties and flow distribution are the reasons that result in the differences between the two models. The findings suggest that the simplified two-dimensional model is capable for engineering demands with the satisfaction of computational accuracy and efficiency. It helps to overcome numerical difficulties and save computational resources in engineering applications such as the PCHE design.

The liquid lead-bismuth eutectic (LBE) is an ideal primary coolant for the fourth-generation advanced nuclear systems. Due to its special physical properties, especially the low Prandtl number and high density, the natural convection phenomenon caused by buoyancy is significant. In this study, a circular tube is three-dimensionally modeled to predict the flow and heat transfer process of LBE. On the base of the model validation, simulations of the uniformly heated tube with/without buoyancy are performed. The different thermal-hydraulic performance obtained under different tube arrangements and operating parameters are compared, and the effects of buoyancy on the convective heat transfer of LBE are discussed. The results show that for LBE flow with smaller Reynolds numbers, convective heat transfer is significantly enhanced when gravity is opposite to the flow direction, while the same gravity and flow direction slightly weakens the convective heat transfer capacity. For the higher Reynolds number LBE flow, the buoyancy impact and the tube arrangement can be ignored. When the tube is placed horizontally, the heat transfer coefficient of the lower wall is about three times that of the upper wall. For different engineering applications, an appropriate arrangement is necessary to improve the efficiency of heat exchanger. This study may contribute to the development and application of LBE-cooled reactors.

Liquefied natural gas (LNG) is a clean energy source that shows great potential for further development. In the production and transportation process of LNG, heat exchanger is an essential device that conducts the liquefaction and vaporization operations. With the booming development of floating LNG (FLNG) technology, higher requirements have been put forward for heat exchangers due to the limited space and rolling conditions. Printed circuit heat exchanger (PCHE), as a typical micro-channel heat exchanger, is considered an ideal candidate for floating storage and regasification unit (FSRU) due to preeminent compactness and efficiency. In this study, a three-dimensional model of sinusoidal channel-based printed circuit LNG vaporizer is established. The thermal–hydraulic and entropy generation characteristics of the vaporizer with various waviness factors, including the amplitude and wavelength, are numerically investigated. The results indicate that larger amplitude or smaller wavelength results in the heat transfer augmentation with greater pressure drop and minor overall entropy generation. As the secondary flows with boundary layer destructions caused by sinusoidal channel structures enhance the local heat transfer, the entropy generation concentrates at the near-wall region. For a sinusoidal channeled printed circuit LNG vaporizer, moderate amplitude and wavelength are more reasonable to obtain better comprehensive performance, and the thermal–hydraulic performance and irreversible energy loss should be considered simultaneously.

Energy conservation and efficiency improvement are critical problems for industrial process systems. Heat exchanger network retrofit has emerged as a powerful tool for energy-saving and Heat Integration, but the topology modification with new heat exchangers and re-piping is expensive and demands a long payback period. In this study, heat transfer enhancement is deployed in the heat exchanger network retrofit to avoid network topology modification. A target-evaluation method is proposed for heat exchanger network retrofit with the consideration of the thermal efficiency and the level of heat transfer enhancement. Two case studies are conducted to demonstrate the proposed method. The energy-saving of case 1 is 10.6752 MW, which is 13.3% of the original utility loads; 8.0303 MW heat loads are saved in case 2, which is 14.7% of the original utility loads. The results of return on investment indicate that enhancement of the best candidate heat exchanger can bring more energy-saving and better economic efficiency with fewer modifications to the existing heat exchangers, which is also confirmed by sensitivity analysis. The lower temperature effectiveness of the heat exchanger shows great potential for thermal efficiency improvement. The present results highlight the energy-saving effects that heat transfer enhancement has on the heat exchanger network retrofit. The proposed two-stage method supports the further development of energy conservation in different industries.