Short-term thermal performance evaluation of sawdust based vacuum insulation panel core material

Developing low cost and environment friendly core materials is the key in reducing the overall cost and life cycle environmental impact of Vacuum Insulation Panels (VIPs). This paper presents the short-term thermal performance evaluation of environment friendly alternative core material developed by using recycled waste sawdust powder. Small VIP samples were manufactured using new alternative core material with various mass ratios of sawdust, fumed silica and silicon carbide (SiC) at a sealing pressure of 0.5 mbar. Initial centre of panel thermal conductivity values of VIP sample containing 30% sawdust, 55% fumed silica and 15% SiC were measured to be in the range of 5.10 – 5.22 mW/mK. VIP samples were kept under accelerated ageing conditions in the laboratory to assess their change in thermal conductivity over a period of time. Trend of increase in thermal conductivity has been observed in all samples. For sample containing 30% sawdust powder, thermal conductivity value increased to 5.79 mW/mK from initial value of 5.10 mW/mK, a rise of approximately 14% in just over 100 days. A sharp increase in thermal conductivity has been measured after that period reaching to 9.42 mW/mK after 227 days of manufacturing. This rise in thermal conductivity can be due to the outgassing of VIP core and envelope material and rise in pressure within the core material over time. This study shows that the use of sawdust powder in VIP core leads to reasonable thermal conductivity values and offers a potentially low cost and low environmental impact alternative core material for use in applications requiring shorter VIP life span.