EAGER: Fundamentals of soft heat exchangers

高度可拉伸的热交换器可以极大地改善目前用于紧急和医疗应用的温度调节服装，例如消防，有害物质清理和医疗所需的温度调节。这些类型的热交换器也将成为软性和可穿戴电子技术的热管理的未来基础。在许多这样的应用中，需要主动液体冷却来消散电子设备和使用者身体的热量。由于新型材料（如超弹性液态金属和弹性体复合材料）的发展，最近才有可能制造出一种可拉伸的、可以消散热负荷的液冷垫。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降低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、环保的替代方案。本研究项目旨在展示在运行过程中经历形状变化的软热交换器的新概念，并为其热性能预测开发一个理论框架。作为该研究项目的一部分，正在开发和分配长达一学期的“软热交换器设计挑战”课程项目，这将增加参与该研究的学生数量，并加速软、液冷、可穿戴技术的设计和生成。拉伸将违反传统换热器设计中使用的大多数假设（例如，恒定面积和横截面，传热系数和流量）。因此，软热交换器的设计需要发展新的理论方法来预测其热性能。该提议的主要假设是，如果其形状变化发生在比最慢的传热过程更长的时间尺度上（即，设备在“渐变形状调制制度”中运行），准静态形状模型可以预测设备内发生的热传递过程。建立了单流和同心管换热器轴向拉伸和压缩的时间标度模型和准静态形状模型，并进行了实验验证。如果假设被验证，那么准静态模型可以作为预测工具来设计在渐变形状调制体制下工作的器件。如果该装置在“快速形状调制制度”中运行，其中形状变化的时间尺度较短或与至少一个传热过程相当，则求解具有移动边界条件的瞬态控制方程。该研究项目为在该制度下运行的设备的理论发展提供了动力，并为其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.