冰浆固相含量测量及蓄融冰动态特性研究

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	冰浆固相含量测量及蓄融冰动态特性研究
其他题名	Study on Ice Mass Fraction Measurement and Dynamic Storage and Melting Characteristics of Ice Slurry
	青春耀
导师	冯自平
	2009-09-24
学位授予单位	中国科学院广州能源研究所
学位授予地点	广州能源研究所
学位名称	博士
学位专业	热能工程
关键词	冰浆固相含量测量蓄冰融冰动态特性 Metal Foam Pool Boiling Flow Boiling Heat Transfer Flow Characteristics
摘要	The fluidly dynamic ice storage technology which uses Ice Slurry (IS) as a secondary cooling medium can effectively realize cold energy storage and electric power peak leveling; it has been showing promising application during recent years. The central air conditioning and district cooling system have excellent energy saving effect for the high-density latent heat transportation characteristics of IS. Measuring the IS mass fraction precisely on line can calculate the latent heat transportation capacity, studying on the dynamic storing and melting process in the ice storage tank can provide theoretical guides on improving the ice packing factor and accelerating the ice melting, ensuring the optimal operation of the fluidly dynamic ice storage system. A theoretical model was developed for the IS mass fraction measurement on the base of summarizing domestic and foreign research results. The corresponding ice mass fraction measurement device was set up which consists of three pairs of circular arc electrodes and a creative micro electrode sensor. A series of experiments were done which verified the reliability and precision of the device. Experimental results showed that the device is reliable when using the square wave excitation signal whose frequency range is 150Hz~1.5 KHz. The general measurement deviation of the device are ±7.5% and ±4% when measuring the flowing IS and the static IS, respectively. The experimental stand of dynamic ice storage was set up and the particle size distribution of ice granule in the ice slurry was measured by image processing method. By changing the flow rate and ice mass fraction of inlet ice slurry, the initial liquid level in tank, the inlet pipe parameters, several works are as follows. (1) The real-time ice slurry piling process was observed. (2) The effects of ice-making solution and ice particle size on the non-saturated Ice Rich Layer (IRL) were analyzed. (3) The contour variation rules of IRL during ice slurry piling process were gained. (4) The rules of sedimentation velocity and uniformity of saturated IRL affected by the parameters above were obtained. Experimental results indicated that the uniformity of IRL could be improved by increasing the flow rate or ice mass fraction of inlet ice slurry, it contributed to the IRL piling of tank centre at the initial phase by reducing the initial liquid level, however, the final uniformity of the IRL was hardly affected by this parameter. The ideal piling model of ice slurry was derived to analyze the mechanism of ice slurry piling, and the ideal piling law of ice slurry was obtained by solving the model. The calculation results showed that the bigger diameter of the ice granular is, the larger floating speed the ice granule has, and the smaller porosity the IRL has. By analyzing the force of ice granule, the Discrete Phase Model (DPM) of ice slurry flow in the ice storage tank was ultimately established based on the turbulent flow RNG k-εmodel and the random walk model which can be used to simulate ice particles trajectory. The flow field of the solution and the ice particles trajectory were acquired by using the DPM, and the real-time piling process of the ice slurry was simulated by varying the inlet flow, the ice mass fractions, etc. The effects of different parameters on the dynamic piling process of ice-slurry were analyzed, too. The DPM could basically reflect the ice-slurry piling process of the single-tube injection ice slurry, and it also could theoretically predict the tendency of ice-slurry piling process. A dynamic ice slurry melting experimental system was built up based on the dynamic ice storage experimental stand, the dynamic melting characteristics of the ice slurry in the tank was studied experimentally under the conditions of varied inlet melting solution flow rates and temperature, etc. The variations and its reason of the temperature distribution in the tank and the Volumetric Heat Transfer Coefficient (VHTC) were analyzed with above parameters changed. The results showed that changing the parameters such as inlet solution flow rate or temperature will form “channel” in the IRL; The VHTC descends rapidly when the dimensionless ice melting time is at the range of 0~0.2, and then drops down slightly until the end of the ice melting process. Inlet melting solution temperature has slight effect on the VHTC. However, the VHTC increases when elevating the inlet solution flow rate. By analyzing the experimental results using modified Stanton (St) number, it illustrated that the “channel” produced during the ice melting process played an essential role on temperature distribution and VHTC.
其他摘要	以冰浆为蓄冷介质的流态化动态冰蓄冷技术可以实现蓄冷和电力的削峰填谷，日益展示出其良好的应用前景，而且使用冰浆在中央空调、区域供冷等领域进行高密度潜热输送具有良好的节能效果。冰浆固相含量的准确在线测量可以确定潜热输送量，而对蓄冰槽中冰浆蓄融冰动态特性的研究则能为流态化冰蓄冷系统实现高蓄冰率、快速融冰提供理论指导，实现流态化冰蓄冷系统的优化运行。在整理和归纳国内外已有研究成果的基础上建立了冰浆固相含量测量模型，设计和开发了三组对圆弧电极和一个微电极组成的固相含量测量传感器，通过实验测试了在不同频率和不同波型的激励信号下，测量系统对静态和动态冰浆固相含量测量的可靠性和精度。实验结果表明：测量系统结果可靠，当采用150Hz~1.5KHz的方波激励信号时测量精度较高，系统的静态测量误差为±4%，动态测量整体误差保持在±7.5%的范围。搭建了冰浆动态蓄冰实验台，利用图像处理方法测定了冰浆中冰粒子的粒径分布，通过改变入口冰浆流量、固相含量、蓄冰槽内溶液初始液面高度及进口管布置参数，观测冰浆实时堆积的过程，分析研究制冰溶液及冰粒子粒径对非饱和富冰层形成的影响，得到了冰浆堆积过程形成的富冰层轮廓变化规律及各参数条件对饱和富冰层沉降速度及富冰层均匀度的影响规律。实验结果表明：增大入口冰浆的流量或者固相含量，将增加冰浆堆积形成富冰层的均匀度，减小初始液面高度有助于富冰层初始阶段在蓄冰槽中心的堆积，但最终堆积的富冰层均匀度几乎不受此参数影响。为了分析冰浆堆积过程机理，推导了冰浆理想堆积模型，通过模型计算得到了冰浆在蓄冰槽内理想堆积的规律，计算结果表明冰浆中冰粒子的直径越大，上浮越快，形成的富冰层空隙率越小；通过对冰浆在蓄冰槽内流动时冰粒子的受力分析，基于湍流流动的RNG k-ε模型、模拟冰粒子颗粒群轨迹的随机游走模型，最终建立了蓄冰槽内冰浆流动的离散项（DPM）模型；并利用此模型得到了冰浆流动的流场及冰粒子在蓄冰槽内的运行轨迹，模拟了冰浆在改变进口流量、固相含量等参数的实时堆积过程，分析了各参数对冰浆动态堆积过程的影响，模型基本可以反映出单口入射冰浆的堆积过程，从理论上预测冰浆堆积过程的发展方向。在冰浆动态蓄冰实验台的基础上搭建了动态融冰实验台，实验研究了进槽溶液流量、温度等参数对蓄冰槽内堆积冰浆的动态融冰特性的影响。分析了各影响因素下蓄冰槽内温度分布、融冰容积换热系数的变化，并指出变化出现的原因。实验结果表明：改变进槽溶液流量、温度等参数均将使冰浆堆积的富冰层出现融冰“通道”；融冰无量纲时间τ=0~0.2时容积换热系数快速下降，随后τ>0.2时容积换热系数缓慢下降直到融冰结束；同时发现，进槽溶液温度对容积换热系数的影响不大，增大其值并不能使容积换热系数增大，相同τ值时容积换热系数随进槽溶液流量增大而增大，但是增大的幅度并不明显。应用修正Stanton（St）数对实验结果分析发现，融冰时产生的“通道”效应是影响蓄冰槽内温度分布及容积换热系数的本质原因。
页数	134
语种	中文
文献类型	学位论文
条目标识符	http://ir.giec.ac.cn/handle/344007/5774
专题	中国科学院广州能源研究所
推荐引用方式 GB/T 7714	青春耀. 冰浆固相含量测量及蓄融冰动态特性研究[D]. 广州能源研究所. 中国科学院广州能源研究所,2009.

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