Recent Developments in the Open Cell Foam-Filled Vacuum Insulated Panels for Appliances Applications

Abstract

Polyurethane foam is the preferred insulator material in a wide range of appliances such as refrigerators and freezers. The recent phase out of CFC-11 has however decreased its insulation performance due to the need to adopt environmentally more benign blowing agents, such as HCFCs and hydrocarbons, all having higher gas thermal conductivity. This represents a serious drawback since specific regulations to reduce the energy consumption in refrigerators have been issued in recent years, and even more demanding reductions are under debate and expected to be applied worldwide by the turn of the century. In response to these requirements, Vacuum Insulated Panels (VIPs) technology has been studied and developed. Suitable components, filler, bag and a getter to maintain the necessary vacuum, have to be selected to ensure the high super-insulation properties which can be exhibited by VIPs. Among various core materials for VIPs, open cell foams present specific advantages in terms of performance, weight, processability and cost. In the present paper, the recent developments in the VIP technology are reviewed and discussed focusing the attention on the open cell polyurethane. The various gas sources deteriorating the vacuum during the panel life have been experimentally determined and evaluated by means of outgassing, permeation and gas analysis measurements on VIP components and finished devices. A suitable getter system able to cope with the gas load and to ensure vacuum performance and reliability is also described.

A Review of Maintenance of Vacuum inside Vacuum Insulation Panels

“…In a log-log plot of speciˆc outgassing rate versus time, the decay exponent ranges from 0.62 to 0.8 with temperature changes from 20°C to 70°C. Related research works are also shown in other papers 28,29) , in which the outgassing rates for speciˆed gas type are given by means of quadrupole mass spectrometer.…”

“…Pressure increase due to outgassing of the core into the panel will in‰uence the long-term performance of the VIPs, especially for VIPs with core of open-celled foams [26][27][28][29][30][31] , which were commonly used in refrigerators (open-celled foam is in contrast with the traditional close-celled foam used as heat insulation material. Up to 95z cells in the open-celled foam are not closed but connected with atmosphere).…”

“…Getters are necessary to ensure the required vacuum level during the service life of a VIP, which will eŠectively adsorb gases like H 2 O, N 2 , O 2 , CO, CO 2 , H 2 as well as blowing agent gas used in producing the foams. Without getters, even not accounting for water, the total pressure in a 0.5 m×0.5 m×0.02 m VIP with open-celled foam as core will exceed 300Pa after 20 years 29) . Getters can be either evaporable or nonevaporable.…”

Optimization about multilayer laminated film and getter device materials of vacuum insulation panel for using at high temperature

“…VIPs are also starting to be used in vending machines and cold storage applications in order to comply with energy-saving regulations, So far, the research and development of VIPs has led to the development of a first generation of VIP materials consisting of a core material filled with an inorganic powder (Yoneno et al, 1984). Later, VIPs using interconnected urethane foams, polystyrene foams or aerogels were introduced in response to CFC legislation (Tao et al, 1996;Sasaki and Gotou, 1999;Manini, 1997;Tabor, 1994). VIP materials have also been developed in which the core material is glass wool made from mineral fibers with improved insulation performance, and these materials have been employed in appliances such as refrigerators as a high-performance insulation material for greater internal capacity and reduced power consumption.…”

“…So far, research has mainly concentrated on the study of core materials and the like used in VIPs (Yoneno et al, 1984;Tao et al, 1996;Sasaki and Gotou, 1999;Manini, 1997;Tabor, 1994;MichaelFay, 1991;Katsube et al, 2006). Recent studies have also investigated the long-term reliability of VIPs based on their use as building materials, and the use of VIPs in composite structures as structural panel materials (Platzer et al, 2005a,b;Winker and Mainka, 2005).…”