全金属胶囊储热系统用于高温余热回收利用的模拟研究

发布时间：2018-11-14 07:56

【摘要】：相变储热技术因其储热密度大、可固定温度放热、循环使用等优点而获得大量关注。但适用于高温领域,特别是1273.15 K以上的高温相变储热系统的研究报道较少,且现有技术主要是关于熔盐相变储热系统的。用于高温的全金属相变胶囊式储热系统的研究报道还很少,且对全金属相变胶囊式储热系统的储热和滤热机理研究不够。本文以Cu@Cr@Ni高温金属相变胶囊、concrete、Ni和MgCl2@304L不锈钢作为储热单元,以高温转炉烟气为传热流体,采用固定堆积床式储热系统,从储热材料堆积方式、容器长径比、流体进口速度、流体进口温度的波动周期和波动幅度等几方面研究储热系统的储热性能和滤热性能。对于固定堆积床式储热系统,球形储热材料的堆积方式有两种,分别为Specially Packed Bed(SPB)和Randomly Packed Bed(RPB)。分别对填充Cu@Cr@Ni、concrete、Ni和MgCl2@304L不锈钢的SPB和RPB储热系统的储热性能和滤热性能进行数值模拟。结果表明,由于RPB储热系统中储热材料的错排会增强系统中流体的湍流扰动,从而增强流体与储热材料间的热交换能力,RPB储热系统的储热效率增加,滤热性能增强;另外,同一系统中,填充Cu@Cr@Ni胶囊的储热系统储热效率和滤热性能更好。数值模拟了储热系统结构对填充Cu@Cr@Ni的RPB储热系统性能的影响。结果表明,容器长径比值小的储热系统,流体在储热系统中的运动速度减小,从而使Cu@Cr@Ni与烟气间的热交换能力减弱,胶囊的升温速率减缓,完成相变所需时间延长,储热系统的储热效率降低,滤热性能降低;容器长径比为1566/340和340/1566的RPB储热系统调控温度波动的衰减率分别为92.2%和87.8%。数值模拟了传热流体参数对填充Cu@Cr@Ni胶囊的RPB储热系统性能的影响。结果表明,在RPB储热系统中,当流体温度一定时,相变材料与传热流体间的能量传递效率随进口速度的增加而减小;当流体进口温度处于波动状态,出口温度达到稳态波动后,进口温度波动周期对出口温度的波动幅度几乎无影响,均为15.7 K;随进口温度振幅的增加出口温度幅度增加;但是进口温度波动周期和波动振幅与相变储热系统的衰减率无关,储热系统的衰减率几乎都为92.2%。
[Abstract]:Phase change heat storage technology has attracted much attention because of its advantages such as high heat storage density, heat release at fixed temperature, recycling and so on. However, there are few reports on high temperature phase change heat storage systems, especially those above 1273.15 K, and the existing technologies are mainly about molten salt phase change heat storage systems. There are few reports on the all-metal phase-change capsule heat storage system for high temperature, and the research on the heat storage and filtration mechanism of the all-metal phase change capsule type heat storage system is not enough. In this paper, Cu@Cr@Ni high temperature metal phase change capsule, concrete,Ni and MgCl2@304L stainless steel are used as heat storage units, and high temperature converter flue gas is used as heat transfer fluid. The heat storage performance and heat filtration performance of the heat storage system are studied in terms of the fluid inlet velocity, the fluctuation period and the fluctuation amplitude of the fluid inlet temperature. For the fixed packed bed type heat storage system, there are two kinds of stacking methods of spherical heat storage materials, Specially Packed Bed (SPB) and Randomly Packed Bed (RPB)., respectively. The thermal storage performance and heat filtration performance of SPB and RPB thermal storage systems filled with Cu@Cr@Ni,concrete,Ni and MgCl2@304L stainless steel were simulated respectively. The results show that the misalignment of the heat storage materials in the RPB heat storage system will enhance the turbulence disturbance of the fluid in the system, thus enhancing the heat exchange ability between the fluid and the heat storage material. The heat storage efficiency of the RPB heat storage system will increase and the heat filtration performance will be enhanced. In addition, in the same system, the heat storage efficiency and heat filtration performance of the heat storage system filled with Cu@Cr@Ni capsule are better. The effect of heat storage system structure on the performance of RPB heat storage system filled with Cu@Cr@Ni was numerically simulated. The results show that in the heat storage system with small ratio of length to diameter, the velocity of fluid moving in the heat storage system decreases, the heat exchange between Cu@Cr@Ni and flue gas decreases, the heating rate of capsule slows down, and the time required to complete phase transition is prolonged. The heat storage efficiency and the heat filtration performance of the heat storage system are decreased. The attenuation rates of temperature fluctuation in RPB heat storage system with aspect ratio of 1566 / 340 and 340 / 1566 are 92.2% and 87.8%, respectively. The effect of heat transfer fluid parameters on the performance of RPB thermal storage system filled with Cu@Cr@Ni capsule was numerically simulated. The results show that the energy transfer efficiency between the phase change material and the heat transfer fluid decreases with the increase of inlet velocity when the temperature of the fluid is constant in the RPB heat storage system. When the inlet temperature of the fluid is in a fluctuating state and the outlet temperature reaches a steady state, the fluctuation period of the inlet temperature has almost no effect on the fluctuation of the outlet temperature, which is 15.7 K, and increases with the increase of the amplitude of the inlet temperature. However, the fluctuation period and amplitude of the inlet temperature are independent of the attenuation rate of the phase change heat storage system, and the attenuation rate of the thermal storage system is almost 92.22.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34

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