Enter the outdoor air temperature (°C), the solar radiation absorptivity α (dimensionless), the net longwave (infrared) radiation term ΔR (W/m²), the overall exterior surface heat transfer coefficient h (W/m²-K), and the global solar irradiance I (W/m²) into the Sol-Air Temperature Calculator. The calculator will evaluate the Sol-Air Temperature.
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Sol-Air Temperature Formula
The following formula is used to calculate the Sol-Air Temperature.
T_{sa} = T_o + (\alpha I - \Delta R) / hVariables:
- Tsa is the Sol-Air Temperature (°C)
- To is the outdoor air temperature (°C)
- α is the solar radiation absorptivity (dimensionless, typically between 0 and 1)
- I is the global solar irradiance (W/m²)
- ΔR is the net longwave (infrared) radiation term (W/m²). With the sign convention used here, ΔR is positive when the surface loses heat to the sky.
- h is the overall exterior surface heat transfer coefficient (W/m²-K), typically including both convection and longwave radiation
How to Calculate Sol-Air Temperature?
The following steps outline how to calculate the Sol-Air Temperature.
- First, determine the outdoor air temperature (°C).
- Next, determine the solar radiation absorptivity α (dimensionless).
- Next, determine the global solar irradiance I (W/m²).
- Next, determine the net longwave term ΔR (W/m²) and the overall exterior surface heat transfer coefficient h (W/m²-K).
- Next, gather the formula from above: Tsa = To + (α·I - ΔR) / h.
- Finally, calculate the Sol-Air Temperature and compare your answer with the calculator above.
Example Problem:
Use the following variables as an example problem to test your knowledge.
outdoor air temperature (°C) = 4
solar radiation absorptivity α = 0.59
global solar irradiance I (W/m²) = 122
net longwave term ΔR (W/m²) = 20
overall exterior surface heat transfer coefficient h (W/m²-K) = 20
Tsa = To + (α·I - ΔR) / h = 6.599 °C (≈ 6.60 °C)
