The effects of vacuum level on the thermal conductivity and resistance

• Main Authors: Chao-Hsin Lo, 羅肇欣
• Other Authors: 蘇程裕
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/h6kq9v

碩士 === 國立臺北科技大學 === 製造科技研究所 === 97 === 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.