To estimate [[epsilon].sup.m] and [[tau].sup.m.sub.lw] of a diathermanous sample, the procedure outlined by Christie and Hunter (1984) is used.
S1 = system 1 (diathermanous layer with backing surface 1)
Total infrared radiation property measurements of diathermanous films with a reflectometer.
The known heat transfer coefficients are then used to construct a resistance network making it possible to calculate U-factor and SHGC for a system that includes one or more diathermanous layers.
The code is based on the theory developed in (Wright 2008) and provides all of the generality of that theory except for two restrictions: (1) SHGC cannot be calculated for situations with zero solar radiation and (2) even though the system can include any combination of glazing and shading layers, indices of merit cannot be calculated for systems with more than one consecutive diathermanous layer.
Progress in this category includes a multilayer solar analysis to track the beam and diffuse radiation, a method to measure off-normal, beam and diffuse components of solar reflection and transmission for shade materials, methods to calculate off-normal solar optical properties of shading materials, net radiation models for venetian blinds and pleated drapes, a simple method to estimate longwave properties of shading layer materials and the development of a new heat balance approach allowing (a) evaluation of U-factor and SHGC for any combination of opaque and diathermanous layers, exposed to any environment, and (b) a one-equation model offering the potential of on-the-fly heat balance calculations in the context of a time-step analysis.
This new method is sufficiently general to handle any combination of diathermanous and opaque layers comprising a glazing/ shading system.
The procedure presented here is similar to Gebhart's analysis of diffuse, grey enclosures (Gebhart 1957, 1959, 1961), a "unified method for radiation exchange", with an extension to specifically account for diathermanous layers.
At the same time we wish to develop a method that is general in the sense that any layer may be diathermanous. See, for example, Figure 7.
Unfortunately, a shading layer such as a venetian blind is diathermanous by virtue of its openness.
The first window is a generic triple glazing, while the second has a diathermanous center layer.
For fenestration without diathermanous layers, the calculation of standard window performance indices is relatively simple.