Vacuum insulation panels for refrigerators

Abstract

Globally, the electrical energy consumption of domestic refrigerators is approximately 6% of the total consumed. Typically, refrigerators are insulated with materials, such as foams (thermal conductivity >20 mWm−1K−1). Alternatively, using Vacuum Insulation Panels (VIPs) (thermal conductivity < 7 mWm−1K−1) would significantly reduce their overall energy consumption and improve their energy efficiency index whilst maximising the usable inner volume. This paper reviews previous published research into VIPs covering core, envelope, heat transfer phenomena and ageing. The choice of core material significantly affects both the heat transfer coefficient and the overall cost of a VIP. To improve cost effectiveness and ageing properties, research has focused on the development of alternative core materials. This development requires a fundamental understanding of the effect of several interfering factors on the performance of VIPs. In this paper, these factors have been extensively reviewed and the results presented in a systematic manner. The factors are grouped into three sections viz. material properties (pore/particle size, particle's mechanical strength and conductivity), design properties (sealing pressure, compaction density) and operating conditions (mean operating temperature, relative humidity). The effect of each factor, on heat transfer modes, radiation and conduction, has been thoroughly discussed, along with the physics involved, by objectively reviewing studies reporting these.