直接蒸发蓄冷过程动态模拟及实验研究

【作者】 刘建；

【导师】 连之伟； 龚毅；

【作者基本信息】 西安建筑科技大学 ， 供热、通风及空气调节， 2001， 硕士

【摘要】 为了平衡电网负荷高峰与低谷、调节我国工业及民用制冷系统昼夜用电量的巨大差额，国家电力部门逐步放松管制进一步以电价为杠杆，实行分时电价，缓解国内用电峰谷差距。同时，由于我国正逐步转变能源结构，改变以煤为主的结构体系，采取以天然气为主的方式。这也将推动电力部门在材料、设备等方面进一步更新，将来我国电价还会继续增长。因此，能源市场和用电价格的变化为制冷行业的发展提供了一个契机。 总的来说，蓄冰过程的发生主要有两种方式：静态冰蓄冷和动态冰蓄冷。由于运行上的简单、方便，静态方式已广泛应用在工程实际中，然而由于静态蓄冷方式自身结冰特性的限制，随着管外冰层厚度的增加，管外热阻同时增加，导致管内制冷剂蒸发温度的降低，使制冷效率降低，系统耗能增加。为了克服静态蓄冷的弊端，动态蓄冷技术开始发展起来。本文研究重点：（1）通过建立动态螺旋盘管结冰的数学模型，模拟动态结冰过程的结冰特性。（2）通过对静态和动态两种方式在直接蒸发式螺旋盘管管外蓄冰机理和实验的研究，分析了两种方式下螺旋盘管蓄冰的结冰特性及蓄冰槽槽体空间温度分布。 本研究主要根据螺旋盘管内、外流体的流动和热质交换特性，建立了动态变参数的数学模型。对于管内两相流动部分，运用分布参数的数学方法，（考虑由于温度的变化而导致物性参数的变化）建立管内制冷齐剂相工质的质量、动量和能量方程，运用全隐迎风格式进行差分求解；对于管外采用准静态方法进行动态结冰过程的数学模拟，保持系统的能量平衡。本论文的另一部分为通过实验研究，对静态蓄冷和动态蓄冷两种方式进行对比，总结两种蓄冷方式的结冰特性，并对系统蓄冷方式的选择提出建议。实验装置为自行设计和组装的一套制冷热动力学实验系统，由直接蒸发式螺旋盘管蓄冷槽及小型半封闭式压缩机组成；数据采集主要采用北京研华集团的ADMA4000型多路数据采集系统。通过测量冰 蓄冷系统中温度、压缩机功耗等参数随时间变化的一系列特性曲线，验证数学模型求解的合理性和可靠性，并完善模型。 论文的研究对动、静态两种蓄冷方式的结冰特点作了具体的分析，为冰蓄冷系统的选 择，提供了实验依据。同时系统动态参敷模型的模拟结果为计算产品质量验证、优化产品 结构和准确计算打下基础。更多还原

【Abstract】 To balance peak and valley load of electrical net and adjust the consumption of runningcosts of refrigeration system. Recently much attention has focused on the development of icethermal storage conditioning system. Generally speaking, there are two major kinds of ice-makingproduct(two kinds of performance of ice storage system): the static and the dynamic icestorage system. Nevertheless, because of simplicity, convenient, the former has been frequentlyapplied in practical applications. But, with the increasing of ice thickness, the thermal resistancebetween water and cooling media become greater, so the temperature of evaporator is alsodecreasing. It leads to the decrease of ice-making rate, and more energy been exhausted. Thoughit has been well developed for many years, the performance efficiency is still need to be furtherimproved. To overcome the shortcomings of the static ice-making, the dynamic ice-makingtechnology has been studied. Through the experimental research of dynamic ice-on-helical coilcooling system, we can realize the characteristics of the system(change of the temperature, icingthickness, ice-making rate, compressor power and COP), verify that dynamic ice-making is a efficient method to improve the efficiency of refrigeration system. According to the flow and heat transfer characteristics of helical-coil, a dynamic unsteadymathematical model of evaporator is build, with the method of distributed. Considering therefrigerant property parameters’ change, refrigerant dynamic equations in coil were set up, andan steady energy equation which can connected the equation of liquid-phase with vapor-phase isproposed. The dynamic system model can be used to predicted the system performance at variousstate. The other part of this master dissertation, the experimental research on the mechanism ofice-storage processes on external surface of helical coil is studied. The comparisons between thestatic cooling storage and the dynamic cooling storage can supply experimental data to select themp orbo ~ ~ peThe work for a good for to the - Of pe for bo pe TondIhe the W wh to ds the pe of for bo, whl - the We pesds edIbe the’ ch pe ofpe be -更多还原