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Heat and Thermal Environment
Published in Masanori Shukuya, Bio-Climatology for Built Environment, 2019
Looking at Table 6.1, we find that the thermal resistivity of aluminium is remarkably small, in other words, remarkably conductive. Such a material is usually highly conductive for electric current, while on the other hand, highly reflective to electro-magnetic radiation and tends to be thermally highly conductive, that is, thermally less resistant. In Fig. 6.19, if the line for aluminium is drawn, it is almost on the horizontal axis. On the other hand, remarkably high resistivity is of vacuum insulated panel as already explained, since the convection and radiation are suppressed inside the panel and the heat has to be transferred only through fine structural members of the panel.
Smart Building Energy Systems
Published in Moncef Krarti, Energy Audit of Building Systems, 2020
Switchable insulation systems (SIS) with variable thermal properties, including dynamic insulation materials and adaptive insulation systems, have been recently proposed as effective alternatives to static insulation options for exterior building walls to reduce both heating and cooling thermal loads for both residential and commercial buildings. In particular, a systematic review of the mechanisms of heat transfer and applications in a wide range of engineering fields has revealed five main categories for switchable thermal insulation technologies that could be applied to the built environment (Cui and Overend, 2019, Dehwah and Krarti, 2020): Active vacuum thermal insulation systems that use various strategies to pressurize or evacuate filling materials or narrow gaps within the insulation layer. In particular, Berge et al. (2015) utilized a vacuum pump to module the air pressure within nanoporous fumed silica structure to vary the thermal conductivity of an aerogel blanket or a vacuum-insulated panel.Mechanical contact insulation systems that use mechanical mechanism to move panels to make a contact or separation. For instance, the switchable wall insulation system suggested by Kimber et al. (2014) is controlled by varying the distance between multilayered polymeric membranes.Suspended-particle-based switchable insulations that use external electric and/or magnetic fields to beak or form microstructures. While this technology has been considered for a wide range of applications, no insulation systems specific for building envelopes have been reported. Pipe-embedded switchable thermal insulation that deploy embedded microtubes or channels to switch or regulate the fluid flow or disturb thermal boundary layers within embedded pipes within the insulation layer. In particular, Koenders et al. (2018) considered a closed-loop dynamic insulation system that utilizes ducts and fans to induce airflows along the back and front sides of the insulation panels and enhance heat exchange between indoors and outdoors.Phase-change switchable insulation that utilizes phase-change materials and fluids to transfer heat through, for instance, an evaporation/condensation cycle. The development of micro-flat-plate heat pipes may make this technology suitable for building applications.
A comprehensive state-of-the-art review of sustainable thermal insulation system used in external walls for reduction in energy consumption in buildings
Published in International Journal of Green Energy, 2023
K. S. Dhaya Chandhran, S. Elavenil
The Vacuum Insulated panels (VIP) is an evacuated gas-impermeable heat insulation panel with a core material consisting of an inflammable pressed powder board of fumed silica. It is sealed under a vacuum with a gas-vapor-tight film. Conduction of gas is virtually eliminated by creating a vacuum. The thermal conductivities range varies between 3 to 4 mW/(m.K) in fresh condition, after 25 years of aging it has typically 8 mW/(mK) (Alotaibi and Riffat 2014; Fantucci et al. 2019; Gonçalves et al. 2020). The increase of 20 mW/mK is caused due to the damage caused in the VIP envelope due to construction practices. Hence, it cannot be cut into small panels as per the requirement in the construction site as it was enveloped and covered with steel. This is the major challenge of VIPs.