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Research Papers

A Simplified Model for Radiative Transfer in Building Enclosures With Low Emissivity Walls: Development and Application to Radiant Barrier Insulation

[+] Author and Article Information
Frédéric Miranville, Philippe Lauret

Physics and Mathematical Engineering for Energy and Environment Laboratory, University of Reunion, Reunion Island, France 97430frederic.miranville@univ-reunion.fr

Mario Medina

Department of Civil, Environmental, and Architectural Engineering, The University of Kansas, Lawrence, KS 66045–7609mmedina@ku.edu

Dimitri Bigot

Physics and Mathematical Engineering for Energy and Environment Laboratory, University of Reunion, Reunion Island, France 97430dimitri.bigot@univ-reunion.fr

Spherical approximation avoiding the geometrical description of the enclosure.

Emissivities of the faces of a RB is generally of the order of 0.05–0.1.

Noted hri on curves.

Noted hrigen on curves.

Exterior temperature (Tair-ext), relative humidity (Hrext), global (Gh) and diffuse (dh) horizontal radiation, and wind speed (Ws).

J. Sol. Energy Eng 133(2), 021009 (Apr 07, 2011) (13 pages) doi:10.1115/1.4003730 History: Received May 01, 2009; Revised December 21, 2010; Published April 07, 2011; Online April 07, 2011

This paper deals with a simplified model of radiative heat transfer in building enclosures with low emissivity walls. The approach is based on an existing simplified model, well known and used in building multizone simulation codes, for the long wave exchanges in building enclosures. This method is simply extended to the case of a cavity including a very low emissivity wall, and it is shown that the obtained formalism is similar to the one used in the case of the based model, convenient for enclosures with only black walls (blackbody assumption). The proposed model has been integrated into a building simulation code and is based on simple examples; it is shown that intermediate results between the imprecise initial simple model and the more precise detailed model, the net-radiosity method, can be obtained. Finally, an application of the model is made for an existing experimental test cell including a radiant barrier insulation product, well used in Reunion Island for thermal insulation of roofs. With an efficacy based on the very low emissivity of their surfaces and the consequent decrease in radiative heat transfer through the wall in which they are included, the proposed simplified model leads to results very close to those of the reference method, the net-radiosity method.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Standard roof including a RB in reunion

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Figure 2

Schematic overview of building simulation

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Figure 3

Synoptic of the implementation of the radiosity method

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Figure 4

Configuration of the monozone test building

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Figure 5

Climatic conditions for the simulations

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Figure 6

Evolution of the air temperature for the monozone cell

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Figure 7

Evolution of the mean radiant temperature for the monozone cell

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Figure 8

Evolution of the surface temperature of the roof for the monozone cell

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Figure 9

Error relative to the net-radiosity method for the hrigen method and the hri method

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Figure 10

Configuration of the bizone test building

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Figure 11

Evolution of air and mean radiant temperatures of the lower zone of the bizone test cell

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Figure 12

Evolution of air and mean radiant temperature for the upper zone of the bizone test cell

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Figure 13

Illustration of the used isotest cell and the experimental in situ platform

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Figure 14

Section view of the complex roof of the used isotest cell

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Figure 15

Modeling of the standard roof-zone description

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Figure 16

Comparison of predictions against measurements for dry-air temperature of zone 1 (°C)

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Figure 17

Comparison of predictions against measurements for dry-air temperature of zone 2 (°C)

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Figure 18

Comparison of predictions against measurements for dry-air temperature of zone 3 (°C)

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Figure 19

Intermodel comparison for the dry-air temperature of zone 1 (°C)

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Figure 20

Intermodel comparison for the dry-air temperature of zone 2 (°C)

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Figure 21

Intermodel comparison for the dry-air temperature of zone 3 (°C)

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