Heat Gain Lights

Overview

Engineering reference data for Heat Gain Lights in thermodynamics.

Key Formulas

First Law

$\Delta U = Q - W$

Energy is conserved — heat added minus work done.

Ideal Gas Law

$PV = nRT$

Relates pressure, volume, and temperature of an ideal gas.

Heat Transfer

$Q = mc\Delta T$

Sensible heat transfer.

Carnot Efficiency

$\eta = 1 - T_C/T_H$

Maximum efficiency between two temperatures.

Variables

Formula for Required Electric Power

The heat gain from lighting in a space can be estimated by calculating the required electric power. This power, unless cooled separately, converts entirely into heat added to the room.

The formula to calculate the installed electric power per unit floor area is:

$P = \frac{b}{\eta_e \cdot \eta_r \cdot l_s}$

Where:

• $P$ is the installed electric power (W/m² floor area),
• $b$ is the recommended light level (lux),
• $\eta_e$ is the light equipment efficiency,
• $\eta_r$ is the room lighting efficiency, and
• $l_s$ is the emitted light from the source (lm/W).

The product $\eta_e \cdot \eta_r$ typically ranges from 0.3 to 0.6.

Lamp Efficiency Data

References

• Original Source