The hybrid personal cooling system (PCS) could effectively reduce the heat strain while exercising in a hot and moderate humid environment

This study aimed to examine the effectiveness of a hybrid personal cooling system (PCS) in mitigating body heat stain while exercising in a hot environment. Eight subjects underwent two trials: PCS and CON (i.e. no cooling). All trials were conducted at an air temperature of 36 ± 0.5 °C and RH = 59 ± 5%. The key findings demonstrated that the PCS could significantly reduce the core temperature, mean skin temperature, heart rate and physiological strain index during both exercise and recovery periods (p < 0.05). Subjective perceptions were also significantly alleviated in PCS at the end of the exercise and during the recovery (p < 0.05). Besides, the PCS could also bring remarkable benefits in lowering local skin temperatures and in improving perceptual sensations in both upper and lower body during both exercise and recovery periods (p < 0.05). It was thus concluded that the hybrid PCS is effective in mitigating body heat strain while exercising in a hot environment.

Practitioner Summary: In hot and humid environments, body heat dissipation through sweating is greatly restricted. Our newly developed hybrid PCS could effectively alleviate heat strain while exercising in hot environments. The findings contribute to the body of knowledge in improving the health and well-being of sportsmen while exercising in hot environments.     

石墨填充复合相变储能材料导热性能和稳定性能研究

以三水醋酸钠作为储能单元、环氧树脂为载体制得复合相变储能材料,它在熔点温度时表现出很强的稳定性和储能效果.通过向复合相变储能材料中添加导热率高的且具有多孔吸附性的膨胀石墨,可进一步提高导热性能和密封性能.结果表明,当三水醋酸钠质量分数为60％,膨胀石墨为5％时,相变储能材料相变焓为148.5 J/g,导热率为0.891 W/(m℃),且稳定性良好.     

基于PC总线的多参数测试系统的研制

基于ＰＣ总线建立一套同时利用热电偶、集成温度传感器、电感式传感器的精确的温度、热位移等多参数测量试系统为研究相变复合恒温构件的特征表征,本构关系提供了实验前提。介绍了其系统原理,结构,软硬件设计等。     

聚氨酯相变材料的非等温结晶动力学研究

以聚乙二醇-6000(PEG-6000)、4,4'-二苯基甲烷二异氰酸酯(MDI)、1,4-丁二醇(BDO)为原料制备了软段含量为86%的聚氨酯相变材料(PUPCMs)。采用DSC测试手段,并且以Ozawa方程和莫志深方程为主要模型,分析研究了聚氨酯相变材料非等温结晶动力学。结果表明:Ozawa方程与莫志深方程的结果差别较大,而Ozawa方程更加符合实际的结晶过程。     

太阳能蓄热技术研究进展

太阳能蓄热根据储热机制的不同可分为显热蓄热、潜热蓄热与化学蓄热。介绍了三种蓄热方式的研究现状与各种蓄热材料的优缺点,并且对比分析了三种蓄热方式的特性。其中潜热蓄热,特别是相变材料的蓄热技术应用最为广泛;显热蓄热如混凝土蓄热技术目前正在研究之中;化学蓄热则在实验阶段。     

Second law analysis of latent thermal storage for solar system

A theoretical model has been developed for analysis and optimization of the solar system using phase change material (PCM). The later consists of a solar air heating collector coupled with a cylindrical storage tank which contains spherical capsules filled with a PCM. Energy and exergy analyses are carried out to understand the behavior of the system using single PCM or multiple PCMs. Numerical results show that the performance of the latent thermal storage system can be ameliored by the judicious choice of the melting temperature of the PCM.     

Modification of urea–sodium acetate trihydrate mixture for solar energy storage

The system urea–sodium acetate trihydrate has been mentioned in the literature as an energy storage system. Due to its low melting point (30 °C), the system is not suitable for use in a hot climate. Modifying the system composition is shown in the present work through adding lead acetate trihydrate to the binary mixture in the ratio of 16.6% with the object of raising its melting point to a practical value. A melting point of 44.5 °C could be reached for the new system.The mixtures of urea–sodium acetate trihydrate and urea–sodium acetate trihydrate–lead acetate trihydrate are tested in the present work as phase change storage mixtures and comparison between both mixtures was carried out.The results showed that the system composed of urea–sodium acetate–lead acetate stored 286 kJ/kg of the storage mixture.     

Electrospun ultrafine composite fibers of binary fatty acid eutectics and polyethylene terephthalate as innovative form‐stable phase change materials for storage and retrieval of thermal energy

In this study, four fatty acids of lauric acid (LA), myristic acid (MA), palmitic acid (PA), and stearic acid (SA) were selected to prepare six binary fatty acid eutectics of LA‐MA, LA‐PA, LA‐SA, MA‐PA, MA‐SA, and PA‐SA; thereafter, electrospun ultrafine composite fibers with the binary fatty acid eutectics encapsulated in the supporting matrices of polyethylene terephthalate (PET) were prepared as innovative form‐stable phase change materials for storage and retrieval of thermal energy. The morphological structures and thermal energy storage properties of the ultrafine composite fibers were characterized by scanning electron microscope (SEM) and differential scanning calorimeter (DSC), respectively. The SEM results indicated that the fibers had the cylindrical morphology with diameters of 1–2 µm; some had smooth surfaces, while others had wrinkled surfaces with grooves. The DSC results indicated that the phase transition temperatures of binary fatty acid eutectics were lower than those of individual fatty acids; the enthalpy values associated with melting and crystallization for the eutectics encapsulated in the composite fibers were considerably reduced, whereas there were no appreciable changes on the phase transition temperatures. Copyright © 2012 John Wiley & Sons, Ltd.     

Designing behenic acid microcapsules as novel phase change material for thermal energy storage applications at medium temperature

Fatty acids are bio-based materials that can be used as phase change materials (PCMs). Microencapsulation of low carbon number fatty acids for mainly building applications have been realized in previous studies. In this study, behenic acid (BA), a fatty acid with medium melting range (65°C-85°C), has been microencapsulated for the first time. PMMA and its three copolymers were used as shell material of these novel encapsulated PCMs prepared by emulsion polymerization technique. The influences of using different comonomers in shell materials on the thermal, morphological, and chemical properties were investigated. Melting phase change temperature ranges were found as 65°C to 85°C for all capsule candidates. Capsules had uniform spherical geometry with size ranges under 500 nm. The capsules are suggested as novel PCM candidates in this temperature range that has potential applications in industrial waste heat, electronics, solar residential heating, lithium-ion batteries, and automotive application.     

砌块用纤维混凝土材料的保温性能研究

为了解决小型混凝土空心砌块墙体保温隔热性能差的缺点,研制了一种新型砌块用纤维混凝土材料。通过改变纤维的种类、内部结构、长度、掺入量等因素来研究纤维参数对混凝土材料保温性能的影响规律。同时在此基础上采用相变材料对纤维进行处理,研究相变材料对混凝土材料保温性能的影响规律。