高效太阳能空调相变蓄冷调控机理及输冷过程动态特性研究

The chilled water temperature is always heightened to improve the operation performance of solar cooling systems. The working temperature of cold delivery process is potential to match that of phase change cold storage. Consequently, the phase change cold storage is supposed to be used to adjust and control the energy of cold delivery process of solar cooling systems, which helps to solve the drawbacks of existed solar cooling systems. As a result, the match of load and capability of adjustment and control of solar cooling systems can be improved. Because the operation of solar cooling systems has the characteristics of unsteady state and variable behaviour, the heat transfer of phase change cold storage under the fluctuant cold source of solar cooling systems is a complex process with the characteristics of unsteady state and non-equilibrium. Therefore, both theoretical and experimental methods will be used in this project to deeply study the dynamic characteristics of phase change cold storage as well as the characteristics of adjustment and control of cold energy in high-performance solar cooling systems. The research contents mainly include: a) phase change cold storage material and its thermophysical characteristics; b) physical characterization of the high-performance working condition of solar cooling systems as well as the mechanism of nonequilibrium phase change heat transfer in the cold storage process; c) thermal dynamic characteristics of phase change cold storage process as well as its effects on the cold delivery process of solar cooling systems; d) the optimization of phase change cold storage heat exchanger based upon the match between dynamic building load and unsteady cold supply of solar cooling systems as well as the matched design of system and control characters. As a result, the theoretical foundation will be supplied for the purpose of the application of adjustment and control by phase change cold storage in high-performance solar cooling systems. Besides, such a novel idea will be exploited by way of the profound development and efficient utilization of solar cooling technology.

太阳能空调通常采用较高的制冷温度实现高效运行，其输冷过程工作温度与相变蓄冷具有潜在的适配性。因此，本项目设想利用相变蓄冷对高效太阳能空调的输冷过程进行能量调控，以克服现有太阳能空调负荷匹配性差以及调控能力弱的缺陷。由于太阳能空调运行的非稳态以及变工况特点，太阳能空调波动冷源作用下的相变蓄冷换热过程必然是一个非稳态、非平衡的复杂过程。为此，本项目将从理论和实验两方面对高效太阳能空调的相变蓄冷动态特性以及系统能量调控特性进行深入研究，内容主要包括：相变蓄冷材料及其热物理特性；太阳能空调高效运行工况物理表征及蓄冷过程非平衡相变换热机理；相变蓄冷过程热动力特性及其对太阳能空调冷量输运过程的影响机理；基于建筑动态负荷与太阳能空调非稳态供冷相匹配的相变蓄冷换热器优化及系统匹配设计与控制特性。为相变蓄冷调控方式在高效太阳能空调中的应用提供理论依据，也为太阳能空调技术的深入发展和高效利用开辟新的思路。

由于受到太阳能资源间歇性及周期性的影响，太阳能空调通常具有非稳态、变工况的运行特性。因此，太阳能空调系统存在着冷量供需不匹配及室内热舒适性差等问题。为了解决上述问题，本课题提出了太阳能空调相变蓄冷系统，并对该系统的可行性、性能优化及相关应用展开了研究。研究的内容主要包括：适宜的相变材料的制备与筛选，适用于太阳能空调系统的相变蓄冷器的设计与研究，以及太阳能空调相变蓄冷系统的运行特性研究。通过一系列的探索，确定出了适用于高效太阳能空调系统的相变蓄冷材料的相变温度应该在15℃左右。制备出了癸酸-月桂酸/油酸复合相变蓄冷材料，其相变焓值为114.1kJ/kg，热导率为0.417W/(m•K)。并向其中添加高导热性的纳米粒子及膨胀石墨以提升其导热性能。通过实验与模拟研究了球形封装相变蓄冷填充床及高效管肋式相变蓄冷换热管的稳态运行特性。在此基础上，搭建了高效太阳能空调相变蓄冷实验系统，并且结合模拟仿真，研究了该系统的非稳态运行特性并且探讨了其调控机理。结果表明，太阳能空调相变蓄冷系统的运行稳定性得到了提升，从而有利于室内热舒适性的改善；同时，蓄冷系统可以起到冷量缓冲的作用，可以有效解决冷量供需不匹配的问题。该研究对于高效太阳能空调系统的应用和普及具有推进作用。