真空度對熱阻與熱傳導係數的影響

本研究主旨在探討真空度改變時對熱阻與熱傳導係數的影響。研究過程係藉由探究真空絕熱技術的原理與機制，以及仿效密集式真空保溫技術（Compact Vacuum Insulation，簡稱CVI）的製法，選擇鋁合金及不鏽鋼材料分別製成三類不同高度、厚度與外型的柱狀空心試件，利用實驗的方式探討以空氣為絕熱保溫層的構件，在絕熱保溫層的真空度改變時，對熱傳導係數與熱阻的影響。同時，將廣用於建築及大型儲槽保溫層的岩綿及玻璃棉材料，以同樣的實驗方法，研究此類保溫層之真空度的改變，對熱傳性的影響。實驗結果顯示空氣絕熱保溫層外殼使用厚0.8mm的AISI 304不鏽鋼製作，在絕熱保溫層厚度80mm以上、真空度9×10-2 Torr及輸入功率3W時的熱阻值比未抽真空時增加約75％；等效熱傳導係數值下降約43％；而在外殼換作使用厚1.2mm的AISI 304不鏽鋼製作時，在絕熱保溫層厚度90mm、真空度9×10-2 Torr及輸入功率3W時的熱阻值比未抽真空時僅增加3.7％，等效熱傳導係數值下降4.05％。以密度80 kg/m3岩棉為絕熱保溫層，在真空度9×10-2 Torr時，熱阻值比未抽真空時最多增加約68％；等效熱傳導係數值下降約40％。以密度56 kg/m3玻璃棉為絕熱保溫層，在真空度9×10-2 Torr時，熱阻值比未抽真空時增加約22％；等效熱傳導係數值下降約18％。此結果除了顯示利用改變絕熱層的真空度能有效降低熱傳導係數與提高熱阻之外，固體的熱傳導對構件絕熱保溫性能的影響也不容小覷。

關鍵字

真空度；真空絕熱；熱傳導係數；熱阻

並列摘要

This research mainly aims at probing into the impact on thermal resistance and thermal conductivity when the vacuum level changes. By investigating the principle and mechanism of the adiabatic technology of vacuum and simulating the Compact Vacuum Insulation (CVI) technology, we use aluminum alloy and stainless steel material respectively to make three kinds of hollow column form test pieces with different heights and thicknesses. The experiment is performed to study when the vacuum level of the adiabatic heat preservation changes, the impact on thermal conductivity and thermal resistance for the component taking air as adiabatic heat preservation. Also, by using the same experiment methods, we study the impact on heat-conduction with the change of the vacuum level of heat preservation for rock wool and glass wool materials that are widely used in buildings and large-scale store devices. The experimental result reveals for the material to be made with outer cover of adiabatic heat preservation using AISI 304 stainless steel of thick 0.8mm that at adiabatic heat preservation thickness more than 80mm, vacuum level 9×10-2 Torr, and input power 3W, the thermal resistance value increase by about 75% and the effective thermal conductivity value drops by about 43% comparing with the non-vacuum condition. When the outer cover is changed to use AISI 304 stainless steel of thick 1.2mm, the thermal resistance value only increases by 3.7% and the effective thermal conductivity value drops by 4.05% comparing with the non-vacuum condition in thickness 90mm of adiabatic heat preservation, vacuum level 9×10-2 Torr and input power 3W. Regarding rock wool of density 80 kg/m3 as the adiabatic heat preservation, in the vacuum level 9×10-2 Torr, the thermal resistance value increases by about 68% at most and the effective thermal conductivity value drops by about 40% comparing with the non-vacuum condition. Regarding glass wool of density 56 kg/m3 as the adiabatic heat preservation, in the vacuum level 9×10-2 Torr, thermal resistance value increases by about 22% and the effective thermal conductivity value drops by about 18% comparing with the non-vacuum condition. This result shows that by changing the vacuum level of adiabatic heat preservation layer can reduce thermal conductivity value and increase thermal resistance effectively, but the solid heat-conduction does have a large influence on the adiabatic heat preservation of component.

並列關鍵字

vacuum level ； vacuum insulation ； thermal conductivity ； thermal resistance

參考文獻

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真空度對熱阻與熱傳導係數的影響

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