Advancement in Solid-Liquid Heat Transfer and Latent Heat Energy Storage Applications

固液相变过程广泛应用于能源、环境、材料加工和微电子等领域。它们的应用包括：潜热储能系统 (LHESS)、温度控制和管理。 **LHESS 用于通过相变材料 (PCM) 的熔化来储存热能；当相变材料凝固时，这种能量可以恢复。这使得热能输入和输出的时间解耦可用于可再生能源（太阳能、风能）或废热应用等。此外，与水等物质的显热加热相比，通过这种相变过程，PCM 中可以储存更多的热能。然而，PCM 的热导率非常低，这使得存储或检索热能成为一个漫长的过程，除非采用适当的设计和控制策略来增强表观热导率或优化热交换过程。 **这些系统的研究涉及传热和流体力学的研究；申请人和其他人已经证明，传导和自然对流在 LHESS 内部的整体相变行为中都起着重要作用。然而，大多数关于该主题的现有文献提出的研究仅考虑一种传热模式，通常是传导，这使得对耦合过程的完整理解仍然遥不可及。 LHESS 的优化和热增强需要完全了解系统内自然对流和熔化/凝固传热过程的影响。 **为了解决这些研究缺陷，本研究计划的目标是： *1) 研究固-液相变传热的基本原理，以进一步了解液态熔体中的自然对流对各种系统几何形状和使用各种相变材料的整体相变过程的影响； *2) 设计和优化用于可再生能源和废热应用的热存储的 LHESS，以抵消 PCM 的低导热率，并在实时太阳能热操作下进行测试。 **这项研究的结果将是对熔化过程中自然对流的详细而准确的理解，以及在 LHESS 的每种操作模式（充电、放电、同时）期间增强传热的策略。 实验结果将用于验证在商业软件上准备的相变传热数值模型，以促进实践工程师早期采用模型。最后，将开发一种设计 LHESS 内部热交换器的方法，以优化其运行以及作为存储应用函数的能量输入和输出率。**这是一个重要的实验和理论研究领域，因为正确理解这些过程及其在能源和热系统中的应用将有助于能源需求、使用和生产的管理。 例如，LHESS可用于在非高峰用电需求期间储存热能，从而减少高峰时段的发电量以满足需求。类似的存储系统可用于存储太阳能，以便在当天晚些时候太阳落山时使用。 作为另一个示例，可以将少量的 PCM 合并到电子设备中，以管理和延迟间歇操作期间的温度升高。 我国与世界其他国家一样，将在未来几十年面临能源危机。在这种背景下，热/能源工程领域的研究有可能推动加拿大新的重要能源技术的发展。

Solid-liquid phase change processes are encountered in a wide variety of fields including: energy, environmental, material processing and microelectronics. They are found in such applications as: latent heat energy storage systems (LHESS), temperature control and management. **LHESS are used to store thermal energy through the melting of phase change materials (PCMs); this energy can be recuperated when the PCMs solidifies. This enables the temporal decoupling of thermal energy input and output useful for renewable (solar, wind) or waste heat applications for example. Also, through this phase change process significantly more thermal energy can be stored in PCMs compared to sensible heating of a substance like water. However, PCMs have very low thermal conductivities which can make storing or retrieving thermal energy from them a lengthy process unless proper design and control strategies are applied to enhance the apparent thermal conductivity or optimize the heat exchange process.**Study of these systems involves research in heat transfer and fluid mechanics; and it has been shown by the applicant and others that both conduction and natural convection play a significant role in the overall phase change behaviour inside LHESS. However, most existing literature on the subject presents studies where only one heat transfer mode is considered, typically conduction, which places a complete understanding of the coupled processes still out of reach. Optimization and thermal enhancement of LHESS requires a complete understanding of the impact of natural convection and the melting/solidification heat transfer processes within the systems. **To address these research deficiencies, the objectives of this research program are to: *1) study the fundamentals of solid-liquid phase change heat transfer to further the understanding of the impact of natural convection in the liquid melt on the overall phase change process in various system geometries and using various PCMs; *2) design and optimize LHESS for thermal storage for renewable energy and waste heat applications to counteract the low thermal conductivity of PCM and test under real-time solar thermal operations. **Outcomes from this research will be a detailed and accurate understanding of natural convection during melting and strategies to enhance heat transfer during every mode of operation of LHESS (charging, discharging, simultaneous). Experimental results will serve to validate numerical models of phase change heat transfer prepared on commercial software used to facilitate the early adoption of the models by practicing engineers. Finally, a methodology to design the heat exchangers found inside LHESS to optimize their operation, and energy input and output rates as a function of the storage application will be developed.**This is an important experimental and theoretical research area because proper understanding of these processes, and their application to energy and thermal systems, will facilitate the management of energy demand, use and production. For example, LHESS can be used to store thermal energy during off-peak electricity demand periods, reducing the amount of electricity produced to meet the demand during peak periods. Similar storage systems can be used to store solar energy in order to use it later in the day when the sun is down. As another example, small amounts of PCM can be incorporated into electronic devices to manage and delay temperature increase during intermittent operations. Our country, along with the rest of the world, will face an energy crisis in the decades to come. In that context, research in the area of thermal/energy engineering has the potential to lead to the development of new and vital energy technologies for Canada.