Control of Net Radiative Heat Transfer With a Variable-Emissivity Accordion Tessellation
Control of Net Radiative Heat Transfer With a Variable-Emissivity Accordion Tessellation
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DOI：
10.1115/1.4042442
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发表时间：
2019-03-01
影响因子：
--
通讯作者：
Iverson, Brian D.
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文献类型：
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作者：
Mulford, Rydge B.;Dwivedi, Vivek H.;Iverson, Brian D.
折纸镶嵌已经被提出作为一种通过使用腔效应来控制辐射热传递的机制。本文探讨了由V形槽组成的手风琴式褶皱的投影面积和表观辐射特性的变化对净辐射传热的影响。手风琴镶嵌的净辐射传热是通过在腔开口处的热能平衡获得的，其中腔的辐射特性作为各种腔参数的函数给出。分析模型的结果进行了实验验证。由不锈钢垫片材料构成的手风琴镶嵌被定位以实现指定的折叠角度，并放置在真空环境中，同时通过焦耳加热进行加热。热成像仪记录不同折叠角度下的腔开口的表观温度。结果进行了比较与分析模型预测的表观温度。分析和实验获得的温度在5%内一致，所有测量值均在实验不确定度范围内。对于漫辐射的表面，投影表面积的减少占主导地位，导致净辐射热传递的崩溃手风琴折叠的连续减少。暴露于漫射照射的高反射镜面表面在小角度范围内经历大的调节比（热传递减少7.5倍）。暴露于准直照射的镜面反射表面在120度和150度的V形槽角度之间实现3.35的调节比。这里概述的方法可以扩展到模拟其他折纸镶嵌的净辐射热传递。
Origami tessellations have been proposed as a mechanism for control of radiative heat transfer through the use of the cavity effect. This work explores the impact of a changing projected surface area and varying apparent radiative properties on the net radiative heat transfer of an accordion fold comprised of V-grooves. The net radiative heat transfer of an accordion tessellation is obtained by a thermal energy balance at the cavity openings with radiative properties of the cavities given as a function of various cavity parameters. Results of the analytical model are experimentally confirmed. An accordion tessellation, constructed of stainless-steel shim stock, is positioned to achieve a specified fold angle and placed in a vacuum environment while heated by Joule heating. A thermal camera records the apparent temperature of the cavity openings for various fold angles. Results are compared to apparent temperatures predicted with the analytical model. Analytically and experimentally obtained temperatures agree within 5% and all measurements fall within experimental uncertainty. For diffusely irradiated surfaces, the decrease in projected surface area dominates, causing a continuous decrease in net radiative heat transfer for a collapsing accordion fold. Highly reflective specular surfaces exposed to diffuse irradiation experience large turn-down ratios (7.5 x reduction in heat transfer) in the small angle ranges. Specular surfaces exposed to collimated irradiation achieve a turn down ratio of 3.35 between V-groove angles of 120 deg and 150 deg. The approach outlined here may be extended to modeling the net radiative heat transfer for other origami tessellations.