差示扫描量热法(DSC)测定全密度聚乙烯结晶度

本文自建了用差示扫描量热仪测定全密度聚乙烯的熔融温度、结晶温度、结晶度等指标参数的分析方法,讨论了测定过程中热历史、样品制备、升温速率等因素对测试结果的影响;并对某乙烯厂的多批次全密度聚乙烯进行了测试,通过重复性试验,表明该方法具有准确、简便、快速的技术特点。     

差示扫描量热法(DSC)及其在沥青研究中的应用

介绍了差示扫描量热法(DSC)的原理、设备、用途及注意事项，从DSC的曲线图和性能评定两方面，对其在沥青性能研究中的应用作了进一步的阐述，指出差示扫描量热法在沥青性能研究中有着广阔的应用前景。     

A new kind of phase change material (PCM) for energy-storing wallboard

A new kind of phase change material (PCM) for energy-storing wallboard is introduced in this paper. By establishing the one-dimensional non-linear mathematical model for heat conduction of the PCM energy-storing wallboard and according to the “effective heat capacity method”, simulation and calculation were made using the software MATLAB to analyze and solve the heat transfer problem of the PCM room. Meanwhile, the property can be found that the heat storing/releasing ability of the new PCM is significantly higher than that of ordinary materials by the experiment-based method. The result indicates that applying proper PCM to the inner surface of the north wall in the ordinary room can not only enhance the indoor thermal-comfort dramatically, but also increase the utilization rate of the solar radiation. So the heating energy consuming is decreased and the goal of saving energy has been achieved. If the parameters of the PCM is given as follows: the phase change temperature is set at 23 °C, the thickness is set at 30 mm, the phase change enthalpy is set at 60 kJ/kg, and the heating temperature is set at 20 °C, the energy-saving rate of heating season η can get to 17% or higher. So the energy is effectively used and saved obviously.     

低温定形相变材料在相变墙体中应用的可行性研究

低温定形相变材料是应用于建筑物墙体中的理想储能材料,它可增加墙体的蓄热能力,节约建筑能耗。研究了2种以高密度聚乙烯为支撑材料的低温定形相变石蜡在不同石蜡含量下材料的相变潜热、相变温度、均匀性和稳定性,并讨论了石蜡在材料中的最佳含量范围。研究结果证明了石蜡用于相变墙体中的优越性和可行性,为日后实际应用提供依据。     

Study on phase change material and its appropriate thickness for controlling solar cell module temperature

ABSTRACT

Appropriate thickness of phase change material (PCM) to control the solar cell module temperature for increasing power generation was carried out. A PCM, RUBITHERM RT42, with the melting point at 42°C and a thickness of 50?mm was used to absorb heat at the back of a 250?W_p polycrystalline solar cell. A numerical enthalpy method to predict the melting phenomenon of the PCM, RT35, 42, 47, and 55, and the solar cell module temperature was developed. The results agreed well with those of the experimental data. It was found that the maximum generated power was around 167?W in comparison with 147?W of the normal unit at a solar radiation of 867?W/m². The daily power outputs were 0.707 and 0.642?kWh, respectively. From the simulation under Chiang Mai climate, for RT42 PCM, it was found that the appropriate thickness was around 40?mm.     

相变材料应用于外墙表面隔热的研究

根据表面隔热机理,通过对普通外墙的理论计算分析,设计了新型的相变墙体。相变材料应用于外墙体外表面,夏季能有效的改善建筑物的外表面热环境,降低传入室内的热量,缓解室内空调冷负荷。同时,提出隔热相变材料的相变温度、掺量在不同气候环境下的选择方法。     

相变材料蓄冷堆积床的优化设计

根据相变材料蓄冷堆积床的传热特性,提出了一种堆积床的优化设计方法。以一种新型相变材料为蓄冷媒介,以堆积床的总费用为优化目标,以蓄冷量、蓄冷时间及载冷流体温度作为约束条件建立优化模型,得出了给定蓄冷量条件下系统初投资和年运行费用总和最低时的蓄冷单元数量、定性尺寸和换热流体温差等优化参数。定量分析了谷峰电价比对系统运行电费的影响。     

Thermal performance of caprylic acid/1-dodecanol eutectic mixture as phase change material (PCM)

Differential scanning calorimetry (DSC) is used to investigate the thermal properties of caprylic acid, 1-dodecanol and their binary system. The experimental results show that the caprylic acid/1-dodecanol binary system presents eutectic point. The eutectic melting temperature (T_em) is 6.52 °C, and the latent heat of melting of eutectic mixture (ΔH_em) is 171.06 J g⁻¹. The corresponding mass fraction of 1-dodecanol in eutectic mixture is 30%. The eutectic melting temperature and the latent heat of phase change of eutectic mixture have not obvious variations after 60 and 120 thermal cycles, which proves that the eutectic mixture has good thermal stability.     

石蜡-膨胀珍珠岩复合相变材料研究

以石蜡熔合膨胀珍珠岩制备复合相变材料,对复合相变材料的容留量、渗透性以及耐久性进行了研究.研究结果表明,石蜡-膨胀珍珠岩复合相变材料耐久稳定性良好.容留量结果表明浸渍时间为2 h,浸渍温度为50 ℃时,石蜡与膨胀珍珠岩融合较好.     

三水醋酸钠复合相变材料的制备与性能

本文以2wt%十二水磷酸氢二钠(DSP)为成核剂、2 wt%羟乙基纤维素(HEC)为增稠剂、1wt%纳米二氧化硅为稳定剂,采用熔融共混法制备了含10 wt%额外水的三水醋酸钠复合相变材料。利用水热法并对材料的蓄热性能进行了测试。通过熔融—固化循环与步冷曲线,系统性地研究了三水醋酸钠相变复合材料在循环过程中的相变结晶稳定性。实验表明,复合材料的相变潜热高达232.91 k J/kg,材料在200次循环过程中过冷度始终保持在1.68~6.75℃,相变平台温度保持在56.07~57.94℃。同时,X射线衍射分析证实,循环实验结束后样品中未出现三水醋酸钠的相分离产物(无水醋酸钠),该材料的循环稳定性良好。