回热回质型吸收式热力系统及送风-溶液膜除湿关键技术研究

The efficiency of heat and mass transfer in the traditional absorption thermodynamic cycle is not high, and the liquid entrainment and air pollution are often happened between the wet air and the desiccant solution because of the direct contact mode in traditional absorption system. A novel vapor transmission mode based on the hydrophobic microporous fiber membrane is proposed in this project, the sensible heat and latent heat transferred between the hot feed of the regenerator outlet and the cold feed of the absorber outlet can improve the heat and mass transfer performance remarkably. The path of liquid entrainment is cut off because of the closed cycle of liquid desiccant in membrane regenerator and membrane absorber with the performance of micro construction and the hydrophobicity in membrane material. The main works are as the following, theoretically, the simulation model of heat and mass transfer across the membrane material in micro scale is built, and then the principle mechanism, the key factors and the control parameters of heat and mass transfer across membrane material is revealed. Experimentally, the empirical correlation of micro membrane structure, fluid properties and flow parameters which affect the vapor transfer effect across membrane is concluded by the orthogonal experiment, and then the numerical model and the optimization direction of thermodynamic cycle is proposed. Finally, A dynamic thermodynamic model and an experimental system about the liquid desiccant system with heat and mass recovery are set up, the testing and the optimized design about the liquid desiccant system is cross validated in order to clarify the basic principle of the liquid desiccant system with heat and mass recovery in building energy saving and thermal and humid environment.it is important to lay the theoretical foundation for practical application.

针对传统吸收式热力系统热质传递效率不高，溶液除湿系统中吸收器和再生器的气液直接接触式热质传递所带来的雾沫夹带和室内送风污染问题，本项目提出了以疏水性高分子微孔膜材料为界面的水蒸气跨膜传递新思路，在传统回热型的溶液间形成了显热和潜热的全热传递，显著提高系统热质传递性能；以此为基础，通过构建溶液除湿系统的膜再生器和膜吸收器，实现除湿溶液的封闭式循环，切断送风过程中除湿剂的污染路径。主要研究工作包括：理论方面，建立微尺度下膜界面的蒸气传递和能量传输模型，揭示微孔膜的热质传递规律和关键影响因素，获得影响热质传递效能和送风阻力的控制参量；实验方面，归纳影响水蒸气传递的膜微观结构、流体物性及流动参数的经验关联式，提出数值模型和热力循环的优化方向。最后，构建回热回质型溶液除湿系统动态热力学模型和实验装置，进行优化设计与测试，阐明系统在节能和热湿环境控制方面的基本原理，为系统今后的实用化奠定理论基础。

吸收式热力系统是建筑热湿环境调控的重要技术，本项目以溶液除湿系统为研究对象，解决吸收器和再生器的气液直接接触式热质传递中所带来的雾沫夹带和室内送风污染问题，提高溶液除湿系统效能这两大关键技术问题展开研究，提出了基于高分子疏水膜材料为热质传递界面的新方法，并以提高吸收剂溶液与湿空气之间的传质驱动力为目标，对12种吸收剂及其混合溶液的表面蒸气压、焓值、定压比热容、密度、动力粘度、表面张力等基础物性参数进行详细计算，并对单工质溶液108种工况、混合溶液2040种工况进行实际水蒸气表面压力的测量；在此基础上，对中空纤维膜溶液除湿和再生过程进行数值模拟和实验研究；建立了复合内热源型溶液除湿系统的数学模型和实验测量，以实验数据为基础，获得了溶液除湿系统的气相总传质系数关联式。研究结果表明：1）常压状态情况下，吸收剂及其混合溶液的实际水蒸气表面压力大于其饱和水蒸气压力，而且随着温度和浓度增加，这种差距逐渐加大；2）以疏水膜为界面的除湿和再生过程中，混合吸收剂溶液LiBr:CaCl2=2:1，LiBr:LiCl=1:0.25的体积比在除湿过程较好，而LiBr:LiCl=1:0.25，LiCl: CaCl2=1:0.25的体积比在再生过程较好；3）在复合内热源型溶液除湿系统中，从除湿和再生过程的综合性能来看，混合吸收剂溶液在LiBr:LiCl=1:0.5的体积比最适合。通过本项目的研究，获取了吸收剂混合溶液基础物性参数和大量的关键实测数据，同时，获取了19种混合除湿剂溶液在不同工况下的膜除湿和膜再生性能关键数据，为构建回热回质型吸收式热力系统及溶液膜除湿系统提供了详实的理论和实验支撑。本项目在执行期间，参加学术会议5次，发表学术论文12篇，论文获奖2项，申请国家发明专利6项（授权4项），授权2项实用新型专利。