Radiant Heat Windows

Overview

Engineering reference data for Radiant Heat Windows in HVAC systems.

Key Formulas

Sensible Heat

$Q = \dot{m} c_p \Delta T$

Heat causing temperature change.

Latent Heat

$Q = \dot{m} h_{fg} \Delta\omega$

Heat causing moisture change.

COP (Cooling)

$COP = Q_c / W$

Coefficient of performance.

Variables

Symbol	Description	Unit
$Q$	Heat transfer	W
$\dot{m}$	Mass flow rate	kg/s
$c_p$	Specific heat of air	J/(kg·K)
$\Delta T$	Temperature difference	K

Shading Performance Properties

The Fraction of Gain represents the ratio of solar heat gain through a shaded window to the gain through the same window without any shading. A value of 1.00 indicates no reduction, while lower values indicate greater shading effectiveness.

Key relationships from the data:

• External shading (awnings, solar screens) is generally more effective than internal shading.
• The effectiveness of external solar screens increases with solar altitude, meaning they perform better when the sun is higher in the sky.
• Internal venetian blinds transmit nearly zero direct solar energy but still allow significant heat gain through absorption and re-radiation.

References

• Original Source