The performance of radiant barriers is often evaluated through simulations and the type of modeling employed influences the results. The use of low-emissivity materials in roofing offers a low-cost solution to reduce the demand for cooling in countries with hot climates. For multi-layer insulation designed for the insulation of packed frozen food in the shape of a rectangle, it was recommended to apply film transmittance as small as possible for the internal parts of the structure.
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The model was verified experimentally showing its compatibility and obtaining a significant influence of thermal resistance according to the type of film used to make air structures, the number and thickness of its layers as well as the gaps between internal folds. Thermal properties depending on different transparency, reflectivity and emissivity of the film were analyzed. Mathematical model based on heat exchange equations, including conduction, convection and radiation throughout a number of parallel internal sheets of film of multilayer structures was proposed.
RADIANT BARRIER INSULATION HOW TO
The paper presents how to improve an effective material designed for food freezing and transport aiming to enhance its thermal resistance through the application of different transparency, reflectivity and emissivity of the film. The insulation can be prepared by means of plastic film featuring various properties.
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One of them, proposed by the authors is a multilayer structure of insulation made of rectangular air cells. There are different kinds of thermal insulation used for food packaging. A protective function of packaging strongly depends on the material used and its composition. One of the basic factors that affects the quality of chilled and frozen food products during storage and transport is packaging. The popular and effective food preservation technology based on refrigeration is not sufficient for high-quality products while undergoing logistic operations (transport and retail). Hence, it is imperative to ensure a low-emittance surface for a sustainable performance of both insulation systems in the long run. It was discovered that emittance of upward facing reflective foil used in both radiant barrier and reflective insulation system are also susceptible to degradation due to dust accumulation, moisture condensation and corrosion. However, this method may tend to over predict the value given the limitations from which its basis was formed. Calculation using theoretical approach provides a more simplified method to predict the resistance value. Heat flow meter was used to test smaller specimen. The most commonly used method to measure the resistance value is guarded hot box which can simulate large-scale assemblies that are closer to real conditions. Although many research works have been conducted on reflective insulation, there are still many uncertainties exist in predicting the correct resistance value. Fundamentally, reflective insulation system works under enclosed reflective airspace(s) and thus its key thermal performance is usually measured by level of thermal resistance produced by the enclosed air cavity. Researchers found that on average radiant barrier installed on attic space could reduce heat flux by 26% to 50% and cooling load by 6% to 16% during cooling seasons. Based on studies, radiant barrier is effective in reducing heat flux, thermal load and attic air temperature during summer and to a lesser extent during winter.
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The main parameters in evaluating the performance of radiant barrier system are reduction of heat flux, thermal load and attic air temperature. This article strives to make an overall review of reflective thermal insulation system which focuses on radiant barrier and reflective insulation. The concerns over depletion of fossil fuel resources and negative environmental impact arising from energy generation have prompted increasing attention on the use of thermal insulation in building energy conservation.