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多元醇在一定温度下发生固—固相变,大量文献都报道了它们的固—固相变焓、相变温度以及相图,并认为相变焓与氢键有关.本文以IR 光谱测试结果以及量热实验结果为基础,定量探讨了NPG(neopentylglycol),PG(pentaglycerino),PE(pentaerythritol)的固—固相变焓与氢键的关系,进一步解释了相变的机理:NPG,PG,PE分子在发生固—固相变前,—OH形成分子间氢键,分子具有层状结构.相变后,NPG,PG,PE分子沿着层面移动,移动过程中部分氢键断裂,分子发生相变时所吸收
关键词:
固—固相变
相变焓
氢键
红外光谱 相似文献
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高温相变储能换热器中传热模型的研究 总被引:1,自引:1,他引:1
1前言利用相变材料在发生相变时有很高的潜热释放或吸收的特点,将相变材料作为储热介质用于相变储能换热器中,可以大大地提高热储存的容量。本文研究的这种壳管式相变储能换热器壳内布置换热管,管壳之间填充高温储热材料,管内通以空气作为热交换流体提取储存在相变材料中的热量。定义输出功率为单位时间内热交换流体所提取到的热量,那么输出功率就成为评价这类换热器换热性能的指标。2理论模型的建立下面几点,概括了求解本文相变储能装置中传热问题的特点:a.相变储能换热器的壳侧填充的AI-Si合金属高温相变储能材料,实验始末其温… 相似文献
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多元醇在一定温度下发生固-固相变,大量文献都报道了它们的固-固相变焓、相变温度以及相图.本文以红外光谱测试结果以及量热实验结果为基础,探讨了新戊二醇/季戊四醇二元体系的固-固相变焓与氢键的关系:二元体系中部分分子间氢键变弱,变弱的氢键更易于断裂;温度上升到一定值,新戊二醇在季戊四醇中的相向塑性晶体相相变时保留下来的氢键断裂,形成二元体系的量热曲线的第二个吸收峰;高新戊二醇浓度的二元体系,可能保留下来的氢键数量少,第二个吸收峰对应的焓值小,但保留的氢键受新戊二醇影响更大,第二个吸收峰对应的温度更低. 相似文献
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与常规温差发电器相比,气液相变式温差发电器利用相变腔的结构灵活性和相变介质的高效传热特性提升发电性能。然而,目前已有的对于相变腔内复杂的沸腾–冷凝耦合传热问题的研究较少,基于此,本文试图通过开展相关实验探究有限空间内的沸腾–冷凝耦合相变传热特性。本实验搭建了沸腾和冷凝耦合相变传热实验台,主要研究了加热功率、相变介质充液率、冷凝换热面积等参数对相变传热特性的影响。结果表明:相变腔的总热阻随加热功率的增大而减小;相变腔存在最优相变介质充液率,相变介质充液率过高或过低均不利于整体的相变传热性能,在本实验条件下,最佳充液率为50%;当沸腾换热面积不变时,减小冷凝换热面积有利于强化相变腔的传热性能。 相似文献
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M. K. Rathod 《实验传热》2013,26(1):40-55
Thermal performance of a latent heat storage unit is evaluated experimentally. The latent heat thermal energy storage system analyzed in this work is a shell-and-tube type of heat exchanger using paraffin wax (melting point between 58°C and 60°C) as the phase change material. The temperature distribution in the phase change material is measured with time. The influence of mass flow rate and inlet temperature of the heat transfer fluid on heat fraction is examined for both the melting and solidification processes. The mass flow rate of heat transfer fluid (water) is varied in the range of 0.0167 kg/s to 0.0833 kg/s (1 kg/min to 5 kg/min), and the fluid inlet temperature is varied between 75°C and 85°C. The experimental results indicate that the total melting time of the phase change material increases as the mass flow rate and inlet temperature of heat transfer fluid decrease. The fluid inlet temperature influences the heat fraction considerably as compared to the mass flow rate of heat transfer fluid during the melting process of the phase change material. 相似文献
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建立自然对流作用下融化的格子Boltzmann双分布函数模型,根据非线性对流扩散方程的格子Boltzmann模型理论提出一个新的表征融化温度场的分布函数演化方程,并通过变松弛时间方法处理固液两相变热物性传热问题.应用模型对热传导融化及自然对流融化特别固液变热物的融化过程进行模拟.模拟结果与分析解、经典的关联式结果吻合较好,模型的正确性得到了验证.模拟结果表明,自然对流对融化传热过程有着重要的影响,此外固相热传导也对融化传热、融化速率及固液两相温度分布都有一定影响. 相似文献
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The goal of this article is to study numerically the mixed convection in a differentially heated lid-driven cavity with non-uniform heating of the bottom wall. The velocity field is solved by a hybrid scheme with multiple relaxation time Lattice Boltzmann(MRT-LBM) model, while the temperature field is obtained by resolution of the energy balance equation using the finite difference method(FDM). First, the model is checked and validated using data from the literature. Validation of the present results with those available in the literature shows a good agreement.A good efficiency in time simulation is confirmed. Thereafter, the model has been applied to mixed convection in a driven cavity with non-uniform heating wall at the fixed Grashof number Gr = 106. It is found that, the heat transfer is weakened as the Richardson number is augmented. For Gr = 106, we note the appearance of secondary vortices at different positions of the cavity corners. 相似文献
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采用双重分布函数的格子玻尔兹曼模型,对单脉冲激光金属打孔过程中的快速相变传热进行研究.模型考虑了金属材料熔化后熔体的流动换热,并采用浸没移动边界方案对过程中的固液界面进行追踪.采用纯导热模型和考虑对流的换热模型计算,将结果和试验进行对比,结果表明:在激光打孔过程中熔体的流动对相变传热产生较大影响,采用考虑流动换热模型的结果与实验更接近.进而对熔化速度、熔化深度以及温度场的变化进行分析,并探讨不同激光工艺参数对相变过程的影响.模拟发现一个脉冲结束后,激光的脉宽越大,孔深越小,孔径越大,且最高温度较短脉冲激光越低. 相似文献
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In this paper phase transition of van der Waals gas is simulated by the Boltzmann lattice method. Thermodynamics and chemical potentials have been taken into account. 相似文献
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