Thermal energy storage and thermodynamic properties of (E)-3-m-tolylbut-2-enoic acid as a medium temperature phase change material

Phase change materials (PCMs) that can store and release heat energy over the temperature range from 363 to 393 K are crucial for solar absorption cooling, and it is worthy to seek new solid-liquid PCMs candidates that melt and crystallize in this temperature range. In this paper, (E)-3-m-tolylbut-2-enoic acid (mTBEA) was applied as a PCM candidate. Its thermal energy storage properties and thermal stability were systematically investigated. The results showed that mTBEA melted at 382.9 ± 0.5 K and crystallized at about 364 K, with a melting enthalpy (Δ_fusH) of 138.4 ± 6.9 J g^?1 and showed good long-term cyclic stability and thermal stability. The supercooling of mTBEA was stabilized at about 20 K, indicating that the conservation condition of melted mTBEA could be simple. In addition, the melted mTBEA could release all the absorbed thermal energy upon crystallizing. Besides, mTBEA exhibited good thermal stability for it to be applied as PCM. Hence, mTBEA is a promising PCM candidate for solar absorption cooling. Furthermore, the heat capacity of mTBEA was measured by modulated temperature differential scanning calorimetry (MTDSC) over the temperature range from 198.15 to 431.15 K, and the molar thermodynamic functions, [H_T-H_298.15]_m and [S_T-S_298.15]_m, were calculated based on the fitted molar heat capacity data.     

广东省火电污染物排放特征及其对大气环境的影响

采用物料衡算及排放因子法建立了2012年广东省火电大气污染物排放(下称火电排放)清单,并运用WRF/SMOKE/CAMx模型分析火电排放对大气环境质量的影响. 结果表明:SO₂、NO_x、CO、PM₁₀、PM_2.5、VOCs和NH₃排放量分别为269 408、539 565、301 257、135 920、65 050、18 790、1 949 t. 300 MW以上的机组对火电排放的贡献较大,但125 MW以下的机组单位煤耗污染物排放较高. 春季、夏季、秋季、冬季火电排放所占比例分别为27.1%、25.4%、24.0%和23.5%,24 h排放呈“三峰三谷”特征;排放量较大的城市为广州、佛山、东莞、江门、汕头、潮州和梅州,不同区域火电排放贡献率顺序为珠三角 (46.2%~52.3%)>广东省东部(26.9%~34.3%)>广东省西部(11.9%~14.4%)>广东省北部(5.5%~10.0%). 8月火电排放对珠三角城市ρ(SO₂)、ρ(NO₂)月均值的贡献率较高,分别为17.0%、11.1%,其次为10月、4月、1月,其影响集中于火电厂所在城市及下风向区域,对不同城市的贡献差异性较大,具有局地特征;火电排放10月对ρ(PM₁₀)、ρ(PM_2.5)月均值贡献率(9.1%、10.6%)较高,其次为8月、4月和1月,影响区域更广,对不同城市的贡献差异较小,呈现区域性特征.      

金属离子对双氧水热稳定性的影响研究

为了研究金属离子对双氧水在绝热条件下分解特性的影响,利用泄放尺寸设计装置VSP2模拟双氧水及分别掺杂0.01%质量分数Fe~(2+)、Fe~(3+)、Gu~(2+)的双氧水在绝热条件下的反应失控过程,得到绝热分解过程的热力学和动力学参数,依此推算出该4种试样25 kg包装下的自加速分解温度SADT,以及绝热条件下到达最大反应速率的时间TMRad。结果表明,Fe~(2+)、Fe~(3+)、Gu~(2+)使双氧水的起始分解温度T0、SADT、TMRad均降低,提高了双氧水的热危险性。在Fe~(3+)的作用下,双氧水在常温下就发生缓慢分解,发生失控的可能性最大;掺杂了Gu~(2+)的双氧水分解反应最剧烈,热失控严重度最高。     

Gd2O3-NiO 共掺对钇稳定氧化锆材料热物理性能的影响

目的研究Gd_2O_3-NiO共掺对钇稳定氧化锆材料热物理性能的影响。方法采用高温固相反应法制得Gd_2O_3-NiO共掺YSZ陶瓷材料。分别利用XRD、扫描电镜观察、激光导热仪、傅立叶红外光谱仪对陶瓷材料的晶体结构、微观结构、热扩散系数及红外透过率进行表征,并对其热导率进行分析。结果 Gd_2O_3-NiO共掺YSZ后,陶瓷材料单斜相含量减少,室温至1300℃的热导率相比YSZ降低,在2.5~5μm波长范围内红外透过率降低。结论 Gd_2O_3-NiO共掺对YSZ陶瓷材料热导率的影响机理为掺杂Gd_2O_3和NiO导致YSZ中单斜相(M)、四方相(T)和立方相(C)含量发生变化,同时YSZ晶格发生畸变。对YSZ辐射传热的影响机理为通过在YSZ中掺杂过渡金属元素Ni使陶瓷材料吸收特定波长的光,进而有效地降低在2.5~5μm短波长的红外透过率,降低其高温下的红外辐射传热。     

基于状态空间法的大型气候环境实验室热负荷仿真模型

目的建立可用于大型气候环境实验室初期设计热负荷计算的方法和模型,对实验室的热负荷进行计算,为制冷系统选型提供依据。方法通过分析实验室的组成结构和热负荷来源,基于状态空间法建立各部分的热负荷计算方法,在Simulink中搭建以制冷量为输入参数的实验室热负荷计算仿真模型,对实验室空载降温过程进行仿真。结果该仿真模型可以快速对实验室热负荷进行计算,并且可以方便地增减热负荷模块,实验室在降温过程中热负荷达3500 k W以上,地板结构的热负荷占到了总热负荷50%以上。结论热负荷计算结果可应用于空调系统和制冷系统的设计和选型,以及控制策略的优化。     

蓄热式热氧化炉处理涂布有机废气可行性分析研究

智能节能膜生产的涂布干燥过程中产生大量有机废气,主要污染因子是乙酸乙酯、丁酮等,通过对蓄热式热氧化炉运行原理及对涂布干燥产生的有机废气处理效率的介绍,举例计算去除有机废气过程中天然气消耗量和燃烧天然气产生的二次污染物氮氧化物的量,同时介绍多种常用有机废气处理方法的原理,并对多种有机废气的处理效率、主要优点、缺点等对比,从经济、技术角度对蓄热式热氧化炉处理智能节能膜涂布干燥有机废气的可行性进行分析.     

火电厂NOx污染排放控制方法探讨

NOx的排放控制是火电厂未来环境保护的重要任务。从控制燃烧过程中NOx的生成以及在燃烧后脱除烟气中NOx两个方面探讨了减少NOx排放的有效技术。     

混酸中甲苯半间歇硝化过程的危险性研究

为了解甲苯在混酸中硝化的危险性,用差示扫描量热法(DSC)测试甲苯、混酸及一硝基甲苯的热分解情况,用反应量热仪(RC1e)研究搅拌速度、温度及硝酸过用率3因素对目的反应的影响。结果表明,混酸分解温度最低,而当目的反应的3因素出现异常,以及反应过程中发生冷却失效时,均可导致硝化反应体系不稳定,此时若不停止加料,并采取措施,易引起混酸的分解,进一步可引起一硝基甲苯的分解,导致严重后果。     

Performance analysis of different orc power plant configurations using solar and geothermal heat sources

ABSTRACT

Energy optimization is performed on hybrid solar-geothermal power plant working according to Organic Rankine Cycle and installed in southern Tunisia. The performances of four different configurations of the power plant are studied. Mass and energy balances are established for the different compounds. The effects of the main operating parameters such as the geothermal water temperature, ambient temperature and direct normal irradiation on the power plant performances are analyzed. A code is established using Engineering Equation Solver software (EES) to perform the required calculations. Obtained results show that the hybrid solar-geothermal power plant with a heat recovery system is the most suitable configuration design giving a better overall energy efficiency of 15.77 and13.11% and a maximum net power of 1089 and 1882 kW in winter and summer, respectively. However, in the summer season, using a heat recovery system can valuable only when the water temperature is higher than 66°C. For air-cooled condenser, the suitable condensing pressure is 1 bar in winter and 1.9 bars in summer.     

RESPONSE OF PHYSICAL AND CHEMICAL PARAMETERS TO ELIMINATING THERMAL STRATIFICATION IN A RESERVOIR1

ABSTRACT The effects of maintaining a 19 ha Colorado montane reservoir in a thermally destratified condition for one year were evaluated. Water temperatures were kept nearly vertically agd horizontally isothermal throughout the year. The weighted mean temperature of the lake was 1-4°C colder in winter and 1-2°C warmer in summer than normal. Deep water in summer was up to 6°C warmer than typical hypolimnion temperatures, but summer surface temperature was unaltered. Without destratification dissolved oxygen depletion develops in summer and winter, but by eliminating stratification, oxygen was kept near saturation throughout the year. Alkalinity, pH, conductivity, and total residue were not significantly affected. Seston decreased which was probably due to declines in planktonic diatom populations. Increases in iron and manganese did not occur in deep water during destratification. Calcium concentrations increased slightly. Magnesium and most anions (chloride, nitrate-N, and silica) were not greatly altered, but sulfate concentration was reduced. Artificial destratification, as a reservoir management tool, will be very useful in altering chemical problems; particularly increasing oxygen and decreasing iron and manganese concentrations.