MIL-101Cr@GO/水双床回热回质循环的吸附式制冷非平衡吸附动态特性

Metal organic frameworks (MOFs) are new micro-porous materials with exceptionally high porosity, uniform structure and large surface area, great water adsorption capacity(1.0g water/g adsorbent),good ability of heat and mass transfer.Adsorption refrigeration system using MOFs/water as working pair has attracted a considerable scientific interest recently. Hydrophilic amino functionality and GO added are introduced into MIL-101Cr in order to achieve water loading at lower p/p0 values for possible use in thermally driven adsorption chillers. MIL-101Cr@GO/water showed the best water loadings (about 1.4g water/g MIL) as well as water stability over 40 adsorptiondesorption cycles. After 40 cycles,the X-ray powder diffractogram and BrunauerEmmettTeller (BET) surface determination of amino-functionalized materials indicated structural integrity with ΔBET = 6.3% after 40 cycles. Linear driving force(LDF) mass transfer model，and a two-dimensional non-equilibrium adsorption coupled with heat and mass transfer model, condensor,evaporator thermal dynamic model as well as entropy and exergy equations will be proposed for MIL-101Cr@GO/water two beds adsorption refrigeration system with heat and mass recovery，and the equations will be solved with control volume method．Theory and performance of non-equilibrium adsorption, dynamic performance of refrigeration cycle, heat and mass transfer performance of two beds, variation of characteristics of all parts and running states on COP and SCP will be investigated. Experimental rig will be made, and running characteristics and stability will be analyzed. All the models of the research project will be tested by experimental results. This research project will highlight the potential of using MOF/water pair in adsorption cooling applications.

金属有机骨架材料MOFs的吸附能力强、传热传质性能好，与水配对在吸附式制冷中的研究日益得到重视。本项目提出将MIL-101Cr@GO/水工质对应用于双床回热回质循环吸附式制冷系统，该系统的吸附剂材料较普通MOFs材料相比，稳定性好，而且整体性能显著提高。基于非平衡吸附和动态分析的思想，建立MIL-101Cr@GO/水吸附速率方程和双床回热回质循环吸附式制冷系统传热传质耦合非平衡吸附的吸附床热力学模型、冷凝器和蒸发器的动态热力学模型、吸附剂衰减机理模型等，并通过数值计算和性能实验相结合的方法，验证和厘清MIL-101Cr@GO/水工质对的非平衡吸附机理及吸附性能衰减机理；通过热力学理论分析、系统建模计算和实验，探索此新型吸附剂材料/水工质对的吸附式制冷循环的动态特性，分析系统各部件参数及运行参数的动态变化规律对系统运行特性的影响机制。

金属有机骨架材料MOFs的吸附能力强、传热传质性能好，与水配对在吸附式制冷中的研究日益得到重视。本项目将MOFs及MOFs复合材料/水工质对应用于双床回热回质循环吸附式制冷系统。基于非平衡吸附和动态分析的思想，建立了MOFs及MOFs复合材料/水吸附速率方程和双床回热回质循环吸附式制冷系统传热传质耦合非平衡吸附的吸附床热力学模型、冷凝器和蒸发器的动态热力学模型等，并通过数值计算和性能实验相结合的方法，验证和厘清了MOFs及MOFs复合材料/水工质对的非平衡吸附机理；通过热力学理论分析、系统建模计算和实验，探索了此新型吸附剂材料/水工质对的吸附式制冷循环的动态特性，分析了系统各部件参数及运行参数的动态变化规律对系统运行特性的影响机制。研究了 MIL-101@GO 复合材料的制备及其水蒸汽吸附性能。结果表明，298 K下，MIL-101@GO 复合材料的水蒸汽饱和吸附容量可以达到 1.58 g/g, 相比 MIL-101 提高近 30%。MIL-101@GO 具有较快的水蒸汽吸附速率，水蒸汽在复合材料上的扩散系数为 0.133-4.485×10(-10)cm2/s（298-313 K）。经过多次次吸附-脱附循环后，复合材料脱附效率仍高达 94%，展现出了优良的再生性能和稳定性；通过浸泡法将原始MIL-101(Cr)与不同质量分数的CaCl2复合，从而得到MIL-101(Cr)/CaCl2复合材料。MIL-101(Cr)/CaCl2-20%作为实验系统最终的实验材料。MIL-101(Cr)/CaCl2-20%复合材料的水蒸气吸附热在42-58kJ/mol之间，接近水的蒸发焓值（ (44 kJ/mol，25℃ ）。此外，吸附动力学表明MIL-101(Cr)/CaCl2-20%的吸附速度较为均匀；本项目将MIL-101(Cr)与水配对成工质对应用于吸附式制冷技术的研究，通过亲水基团氨基对MIL-101(Cr)进行改性提高其在中低等湿度下的水蒸汽吸附性能。研究成果对于固体吸附制冷和吸附除湿的应用奠定了重要的基础。