INTERNATIONAL. STANDARD. ISO. First edition. Thermal performance of windows, doors and shading devices — Detailed calculations. 5 Jan ET ISO Thermal performance of windows, doors and shading devices [ archiveorg width= height= The standard is identical with ISO Thermal performance of windows, doors and shading devices — Detailed calculations published by International.

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NOTE See [4] for more information. For diffuse radiation, the following properties iso 15099 required: The effect of three-dimensional heat transfer in frames and glazing units is not considered.

## ET ISO 15099: Thermal performance of windows, doors and shading devices — Detailed calculations

If the view between two radiating surfaces is obstructed by iso 15099 third surface, the effect of this obstruction iso 15099 be included. ESA has the copyright of all its publications. Complete windows and doors ENGlass in building — Determination of the emissivity 3 Symbols 3. Air may cross the shading device and thus move from one gap to the other or from the environment into iso 15099 gap behind the shading device and vice versa.

Any other method that can be shown to provide an exact solution is acceptable.

Use the following criteria to determine if it is necessary to apply the above procedure. The shading device is usually also permeable for air, either due to its porous structure or due to openings at iso 15099 perimeter. These include the temperature difference between the surface and the air, the iso 15099 and direction of any air movement wind over the building, and the shape and roughness of the building surface.

If these flanges are intended to be covered up by the exterior cladding e. Using the bulk model, the optical indices of the material can then be calculated iso 15099 used to derive the hemispherical properties.

It also absorbs, reflects and transmits solar radiation. The governing heat transfer equation is solved for thermal 1599 for a given meshing arrangement. Clause 8 describes the procedure iso 15099 determining and applying boundary conditions.

For those situations where natural convection occurs, see 8. Accurate determination of this convective heat transfer on both internal and external 1599 surfaces is extremely difficult and can only be done by careful measurements and computer simulation.

It is necessary to determine the portion of incident solar radiation, at a given wavelength, that is absorbed at each of the glazing layers. In this regard, the layer type of shading device may be defined in the model as a layer between two gaps. For these cavities, the following procedure shall be used to determine which surfaces belong to vertical and horizontal surfaces of equivalent rectangular iso 15099 see also Figure For iso 15099 velocity, the equations for the ventilated gap iso 15099 to the equations for iso 15099 non-vented case.

### ISO – Thermal performance of windows, doors and shading devices — Detailed calculations

Diffuse radiation transmitted or reflected by the solar shading device is assumed to remain diffuse. Since SF 6 violates this condition it has not been presented in these tables. For cases where the slit is less than or equal iso 15099 2 mm, iso 15099 the cavity as completely enclosed in accordance with 6.

An appropriate value is to be determined on the basis of experiments or calculations [computational fluid dynamic CFD modelling]. An appropriate value shall be determined on the basis of experiments or calculations [computational fluid dynamic CFD modelling]. Once a beam transmitting through or reflecting iso 15099 a solar shading device is split into a direct and a diffuse part, the diffuse part continues its route through the system.

Nu t is a function of the Rayleigh number, Ra tthe iso 15099 aspect ratio, A gv tand the cavity slope, j. These are the temperatures of the external and internal facing surfaces, T fti and T bj iso 15099 the radiant heat leaving the front and back facing surfaces i. The extra term is: First, use Equation A. Iso 15099 is assumed that all material thermal conductivity values are constant with respect to temperature.

The procedure is to consider two adjacent slats and to subdivide the slats into five equal parts see Figure 1 8. A t 13 where iso 15099 q and r f are the individual iso 15099 solar energy transmittance values of the vision area and frame area, respectively.

The convective heat transfer coefficient, h cvin is determined from heat transfer correlations iso 15099 in 8. The mesh iso 15099 made finer either uniformly or in regions of high two- dimensional heat flow and a new iso 15099 transmittance determined.

More detailed two-dimensional or three-dimensional calculations, including the effects of off-normal solar radiation, shading, reflected solar radiation and solar radiation isk iso 15099 the internal frame surfaces, can be performed in a manner analogous to Equation 14and subject to boundary conditions given in 8.

It is found by calculating the difference between the net heat flow 150099 into the internal environment with and without incident solar radiation.