EAGER: Fundamentals of soft heat exchangers

高度可伸缩的热交换器可以极大地改进目前用于紧急和医疗应用的温度调节服装，如消防、危险材料清理和医疗要求的温度调节。这些类型的热交换器也将是未来软性和可穿戴电子技术热管理的基础。在许多这样的应用中，需要主动液体冷却来驱散来自电子设备和用户身体的综合热量。由于超弹性液态金属和弹性体复合材料等新型材料的发展，直到最近才有可能制造出可伸展的、可分散热负荷的液体冷却垫。可拉伸热交换器的另一个好处是，拉伸材料可以去除在许多工业环境中恶化此类设备性能的污垢沉积物，这将为目前使用的化学和擦洗清洁方法提供一种经济高效、环境友好的替代方法。本研究项目旨在论证软式换热器在运行过程中发生形状变化的新概念，并开发预测其热性能的理论框架。作为这项研究项目的一部分，为期一学期的“软式换热器设计挑战”课程项目正在开发和布置中，这将增加参与这项研究的学生数量，并加速软式、液体冷却、可穿戴技术的设计和产生。拉伸将违反传统换热器设计中使用的大多数假设(例如，恒定的面积和横截面、换热系数和流量)。因此，软式换热器的设计需要发展新的理论方法来预测其热性能。这一建议的基本假设是，如果器件的形状变化发生在比最慢的热传递过程更长的时间尺度上(即，器件运行在逐渐的形状调制机制中)，则准静态形状模型可以预测器件内发生的热传输过程。单流管式换热器和同心管式换热器轴向拉伸和压缩的时间标度和准静态形状模型正在建立和实验验证。如果假设得到验证，则准静态模型可用作设计工作在渐变形状调制区域的器件的预测工具。在设备运行在“快速形状调节机制”的情况下，其中形状变化的时间尺度比至少一个热传递过程短或相当，需要求解具有移动边界条件的瞬变控制方程。这项研究项目是发展在这种体制下工作的设备的理论的动力，并为它们的验证提供了初步的实验数据。

Highly stretchable heat exchangers could dramatically improve current thermoregulatory garments used in emergency and medical applications, such as firefighting, hazardous material cleanup, and medically required thermoregulation. These types of heat exchangers also would be the future basis for the thermal management of soft and wearable electronic technologies. In many such applications, active liquid cooling would be needed to dissipate combined heat from the electronics and the user's body. The fabrication of a stretchable, liquid cooled pad that could dissipate thermal loads only recently became possible due to the development of new classes of materials, such as hyperelastic liquid metal and elastomer composites. An added benefit of stretchable heat exchangers is that stretching the material could remove fouling deposits that deteriorate the performance of such devices in many industrial settings, which would provide a cost-effective, environmentally friendly alternative to currently utilized chemical and scrubbing cleaning methods. This research project aims to demonstrate a novel concept of soft heat exchangers that undergo shape change during operation and to develop a theoretical framework for prediction of their thermal performance. As part of this research project, semester-long "soft heat exchanger design challenge" class projects are being developed and assigned, which will increase the number of students involved in this research and accelerate the design and generation of soft, liquid cooled, wearable technologies.Stretching will violate most assumptions used in design of conventional heat exchangers (e.g. constant areas and cross sections, heat transfer coefficients, and flow rates). Consequently, the design of soft heat exchangers requires development of new theoretical approaches for predicting their thermal performance. The primary hypothesis of this proposal is that quasi-static shape model can predict the thermal transport processes occurring within the device if its shape change occurs on a much longer time scale than the slowest heat transfer process (i.e., the device operates in the "gradual shape modulation regime"). Time scaling and the quasi-static shape models for single stream and concentric tube heat exchangers undergoing axial stretching and compression are being developed and tested experimentally. If the hypothesis is validated, then the quasi-static models can be used as a predictive tool to design devices operating in the gradual shape modulation regime. In case where the device operates in the "rapid shape modulation regime," in which time scales for the shape change are shorter or comparable to at least one heat transfer process, transient governing equations with moving boundary conditions are being solved. This research project serves as motivation for the development of theories for devices operating in this regime and provides preliminary experimental data for their validation.