Zhao Zhao, Nan Jin, Li Min
Institute of Solid Mechanics, Beihang University (BUAA), Beijing 100191, China.
School of Mechanics and Civil Engineering, China University of Mining and Technology, Beijing 100083, China.
Micromachines (Basel). 2022 Apr 15;13(4):622. doi: 10.3390/mi13040622.
Flexible heaters can perfectly fit with undevelopable surfaces for heating in many practical applications such as thermotherapy, defogging/deicing systems and warming garments. Considering the requirement for stretchability in a flexible heater, certain spacing needs to be retained between serpentine heat sources for deformation which will inevitably bring critical challenges to the thermal uniformity. In order to reconcile these two conflicting aspects, a novel method is proposed by embedding the serpentine heat source in orthotropic layers to achieve comprehensive performance in stretchability and uniform heating. Such a scheme takes advantage of the ability of orthotropic material to control the heat flow distribution via orthotropic thermal conductivity. In this paper, an analytical heat conduction model with orthotropic substrate and encapsulation is calculated using Fourier cosine transform, which is validated by finite element analysis (FEA). Meanwhile, the effects of the orthotropic substrate or encapsulation with different ratios of thermal conductivity and the geometric spacing on the thermal properties are investigated, which can help guide the design and fabrication of flexible heaters to achieve the goal of uniform heating.
柔性加热器能够完美贴合不可展开的表面，用于许多实际应用中的加热，如热疗、除雾/除冰系统和保暖衣物。考虑到柔性加热器对拉伸性的要求，蜿蜒的热源之间需要保留一定的间距以实现变形，这将不可避免地给热均匀性带来严峻挑战。为了协调这两个相互矛盾的方面，提出了一种将蜿蜒热源嵌入正交各向异性层的新方法，以实现拉伸性和均匀加热的综合性能。这种方案利用了正交各向异性材料通过正交各向异性热导率控制热流分布的能力。本文使用傅里叶余弦变换计算了具有正交各向异性基底和封装的解析热传导模型，并通过有限元分析（FEA）进行了验证。同时，研究了不同热导率比的正交各向异性基底或封装以及几何间距对热性能的影响，这有助于指导柔性加热器的设计和制造，以实现均匀加热的目标。
