相变微胶囊悬浮液的对流换热特性研究进展

相变微胶囊悬浮液是既具有流动性又兼具蓄热能力的功能性流体。相变微胶囊悬浮液在工作过程中涉及复杂的流体流动与传热以及储热过程,近年来成为国内外学者研究的热点。对相变微胶囊悬浮液在圆管、小(微)通道内的对流换热特性进行了综述,重点阐述了国内外学者对于相变微胶囊悬浮液是否能强化对流换热存在的分歧,并提出了自己的分析与看法。分析了圆管与小(微)通道对流换热机理的区别,最后概述了强化相变微胶囊悬浮液对流换热的方法。     

分离纯化小鼠胰岛的方法学研究

目的：探讨分离纯化小鼠胰岛的方法。方法将10～20周、体质量25～30 g 的雄性 ICR 小鼠断颈处死后,经十二指肠大乳头,进入胰管行胶原酶-P 灌注、原位消化;然后在显微镜下挑取胰岛;采用台盼蓝染色、DTZ 染色,以及葡萄糖、氯化钾刺激胰岛素分泌等方法观察胰岛的活性、纯度及功能。结果每只小鼠分离的胰岛可达200～250个,且纯度达99％、活性大于98％,20 mmol·L－1葡萄糖或40 mmol·L－1氯化钾刺激胰岛后胰岛素的分泌是基础分泌量的4～7倍。结论本方法可分离纯化到活性、纯度及生物活性高的胰岛。     

电泳粒子的研究进展及其在电子纸中的应用

电泳粒子在电泳显示型电子纸中是一种重要的显示元素。综述了颜料型、核壳复合型、胶囊型和聚合物型电泳粒子研究现状,并介绍了电泳粒子在微胶囊电泳显示和微杯电泳显示2种类型电子纸中的应用。     

Performance optimization of a photovoltaic/thermal collector using microencapsulated phase change slurry

In a photovoltaic/thermal (PV/T) collector, a portion of absorbed solar energy is transformed into electrical energy, and the remaining part is transformed into thermal energy. Increasing waste heat collection and energy conversion rates are important to improve the performance of the PV/T collector. The utilization of microencapsulated phase change slurry (MPCS) in a PV/T collector to cool photovoltaic modules is an effective way, and electrical and thermal performances of the collector are improved. To investigate influences of operating parameters on performances of PV/T collector, numerical simulation is put into effect to analyze influences of the mass fraction of MPCS on the collector performance. The influences of MPCS mass flow rate and collector channel height on collector performances are also studied. When the flow rate is 0.005 kg/s and the channel height is 0.010 m, the PV/T collector obtains the best net efficiency with a MPCS mass concentration of 20 wt%. But electrical efficiency difference between 15 and 20 wt% is not obvious. With the growth in mass fraction, PV temperature drops more and more slowly because outlet fluid has not fully melt. Take PV/T collector performances into consideration, 15 wt% MPCS is a better choice to cool photovoltaic modules.     

Microencapsulated dimethyl terephthalate phase change material for heat transfer fluid performance enhancement

Micro‐phase change materials (micro‐PCMs) are proposed to increase the thermal conductivity and the thermal energy storage capacity of a heat transfer fluid (HTF). In this work, we have selected dimethyl terephthalate (DMT) to be used as a PCM for performance enhancement of a synthetic oil in the temperature range of approximately 100 to 170 °C. Silicon dioxide (SiO₂) was used as the microencapsulant, because of its desirable properties as containment material, including thermal stability. The SiO₂‐coated DMT micro‐PCM was characterized to determine relevant properties and its suitability for HTF performance enhancement. The SiO₂‐coated DMT was found to completely disperse in the synthetic oil, Therminol SP, silicone oil, at and above 100 °C. FTIR, thermal diffusivity and differential scanning calorimetry measurements were carried out on the materials, and these tests demonstrated that the coated particles can be used for HTF enhancement in the temperature range of 100–170 °C and potentially higher temperatures if pressurized pipes/vessels are utilized. Using the measured thermal diffusivity and known data for density and specific heat capacity, the thermal conductivity of the micro‐PCM was calculated. Our calculations indicate that both the thermal conductivity and the thermal energy storage heat capacity of the HTF would be enhanced by the addition of this micro‐PCM. It is expected that the thermal conductivity increase will enhance the heat transfer of the fluid when in use at temperatures above and below the melting temperature of the PCM. At the melting point, the latent heat of the PCM will increase the thermal energy storage capacity of the fluid. Copyright © 2016 John Wiley & Sons, Ltd.     

Metal Hydride Nanoparticles with Ultrahigh Structural Stability and Hydrogen Storage Activity Derived from Microencapsulated Nanoconfinement

Metal hydrides (MHs) have recently been designed for hydrogen sensors, switchable mirrors, rechargeable batteries, and other energy‐storage and conversion‐related applications. The demands of MHs, particular fast hydrogen absorption/desorption kinetics, have brought their sizes to nanoscale. However, the nanostructured MHs generally suffer from surface passivation and low aggregation‐resisting structural stability upon absorption/desorption. This study reports a novel strategy named microencapsulated nanoconfinement to realize local synthesis of nano‐MHs, which possess ultrahigh structural stability and superior desorption kinetics. Monodispersed Mg₂NiH₄ single crystal nanoparticles (NPs) are in situ encapsulated on the surface of graphene sheets (GS) through facile gas–solid reactions. This well‐defined MgO coating layer with a thickness of ≈3 nm efficiently separates the NPs from each other to prevent aggregation during hydrogen absorption/desorption cycles, leading to excellent thermal and mechanical stability. More interestingly, the MgO layer shows superior gas‐selective permeability to prevent further oxidation of Mg₂NiH₄ meanwhile accessible for hydrogen absorption/desorption. As a result, an extremely low activation energy (31.2 kJ mol^–1) for the dehydrogenation reaction is achieved. This study provides alternative insights into designing nanosized MHs with both excellent hydrogen storage activity and thermal/mechanical stability exempting surface modification by agents.     

相变储能材料的制备及其在石膏基体中的应用研究

制备有机-无机复合壁材微胶囊相变储能材料,并与石膏掺混制备相变储能石膏复合材料。研究了不同壁材结构微胶囊和相变储能石膏复合材料的理化性质。结果表明,复合壁材微胶囊相变储能材料中,微胶囊壁材以无机硅为主,兼有少量有机硅组分,可有效防止壁材开裂且提高微胶囊包覆率;复合壁材微胶囊相变储能材料的相变温度和潜热分别为24.57℃和122.8 J/g,粒径为0.5~1.0μm;掺加微胶囊后,由于石膏结晶状态改变,石膏基体凝结时间延长且强度降低,当掺量达到10%时,相变储能石膏复合材料的潜热为16.1 J/g,具备一定的蓄热调温能力。     

Study on the microstructures and thermal properties of SiO2@NaNO3 microcapsule thermal storage materials

In this paper a novel SiO₂@NaNO₃ microcapsule thermal storage material is successfully fabricated via water-limited sol-gel method. The effects of SiO₂ nanoparticles on the microstructures, thermal conductivity, specific heat capacity, latent heat and thermal stability are investigated. SEM and TEM investigation indicates that the spherical SiO₂ nanoparticles with an average diameters of 30 nm are coated on the surface of NaNO₃ evenly to form a homogeneous and stable core-shell structure. Microencapsulated composites are characterized by XRD and FTIR to determine the chemical compositions and structures. The thermal conductivity of SiO₂@NaNO₃ microcapsules is significantly enhanced by 62.9% (0.756 W m⁻¹ K⁻¹) compared with 0.464 W m⁻¹ K⁻¹ of that of NaNO₃. In addition, the latent heat, phase change temperature, specific heat capacity and thickness of shell of the microencapsulated NaNO₃ with 18.1 wt% SiO₂ were 310.1°C, 144.7 J g⁻¹, 1.831 J/(g·K), and 80-150 nm, respectively. Furthermore, microencapsulated NaNO₃ have excellent shape and thermal stability at working temperature range. SiO₂ nanoparticles are uniformly attached to the modified NaNO₃ by electrostatic interaction to create a physical protective SiO₂ barrier, which can effectively inhibit the leakage and cauterization of melting NaNO₃.     

Recombinant Reg3α Prevents Islet β-Cell Apoptosis and Promotes β-Cell Regeneration

Progressive loss and dysfunction of islet β-cells has not yet been solved in the treatment of diabetes. Regenerating protein (Reg) has been identified as a trophic factor which is demonstrated to be associated with pancreatic tissue regeneration. We previously produced recombinant Reg3α protein (rReg3α) and proved that it protects against acute pancreatitis in mice. Whether rReg3α protects islet β-cells in diabetes has been elusive. In the present study, rReg3α stimulated MIN6 cell proliferation and resisted STZ-caused cell death. The protective effect of rReg3α was also found in mouse primary islets. In BALB/c mice, rReg3α administration largely alleviated STZ-induced diabetes by the preservation of β-cell mass. The protective mechanism could be attributed to Akt/Bcl-2/-xL activation and GRP78 upregulation. Scattered insulin-expressing cells and clusters with small size, low insulin density, and exocrine distribution were observed and considered to be neogenic. In isolated acinar cells with wheat germ agglutinin (WGA) labeling, rReg3α treatment generated insulin-producing cells through Stat3/Ngn3 signaling, but these cells were not fully functional in response to glucose stimulation. Our results demonstrated that rReg3α resists STZ-induced β-cell death and promotes β-cell regeneration. rReg3α could serve as a potential drug for β-cell maintenance in anti-diabetic treatment.