# Talk:Sol-air temperature

I believe that the equation for Tsol-air is incorrect as shown on this page.

Incorrect formula:

```    Tsol-air = (T0 + (Alpha * I - deltaQir)) / h0
```

I believe the correct equation is

```    Tsol-air = T0 + ((Alpha * I - deltaQir) / h0)
```

See, for example, section 8.2.2 here: http://www.aij.or.jp/jpn/symposium/2006/loads/Chapter8_com.pdf

Sorry for the crude formulas, I don't know how to create pretty equations for wikipedia.

Martin Eberhard eberhard@teslafounders.com

I think Mr. Eberhard's formular is correct:

```  Tsol-air = T0 + ((Alpha * I - deltaQir) / h0)
```

otherwise

```  Tsol-air =! T0 for the case I=0 and deltaQir=0
```

what have to be fulfilled

J. Herrmann www.wzu.uni-augsburg.de —Preceding unsigned comment added by 137.250.82.58 (talk) 08:07, 30 April 2009 (UTC)

Yes, that's correct. I have therefore now corrected the article. By the way, if one knows the actual surface convective heat transfer coefficient, then the following formulation can be used:

$T_{solair} = (h_c * T_{air} + h_r * T_{sky} + I_{sol}) / h_{cr}$

where:

$h_c$ : convection heat transfer coefficient [W/m²K]

$h_r$ : radiation heat transfer coefficient (to sky) [W/m²K]

$h_{cr}$ : combined convective & radiative heat transfer coefficient, as defined in ISO 6946, Usually =25 [W/m²K]

$T_{air}$ : dry-bulb air temperature [°C]

$T_{sky}$ : radiative sky temperature [°C], see ISO 13790