Indoor Temperature Humidity

Overview

Engineering reference data for Indoor Temperature Humidity in air psychrometrics.

Key Formulas

Humidity Ratio

$\omega = 0.622 \frac{P_v}{P_a}$

Mass of water vapor per mass of dry air.

Relative Humidity

$\phi = \frac{P_v}{P_{vs}} \times 100\%$

Ratio of actual to saturation vapor pressure.

Wet Bulb Temperature

$T_{wb} = T_{db} - \frac{P_{vs} - P_v}{\gamma}$

Temperature measured by wet-bulb thermometer.

Enthalpy of Moist Air

$h = c_p T + \omega h_g$

Sensible + latent heat per unit mass of dry air.

Variables

Symbol	Description	Unit
$\omega$	Humidity ratio	kg/kg
$\phi$	Relative humidity	%
$P_v$	Vapor pressure	Pa
$P_{vs}$	Saturation vapor pressure	Pa
$T_{db}$	Dry bulb temperature	°C
$T_{wb}$	Wet bulb temperature	°C

Calculation Equations

Sensible Heat from Lights: $H_l = P_{inst} K_1 K_2$

Sensible Heat from Electric Equipment: $H_{eq} = P_{eq} K_1 K_2$

Sensible Heat from Machines:

• Motor inside, machine outside: $H_m = \frac{P_m}{\eta_m} - P_m$
• Motor and belt inside, machine outside: $H_m = \frac{P_m}{\eta_m} - P_m \eta_b$
• Both motor and machine inside: $H_m = \frac{P_m}{\eta_m}$
• Motor outside, machine inside: $H_m = P_m$
• Motor and belt outside, machine inside: $H_m = P_m \eta_b$

Evaporation from Water Surfaces:

• Mass flow rate of evaporated water: $\dot{m}_q = A (x_1 - x_2) \alpha_e$
• Evaporation constant: $\alpha_e = \frac{25 + 19 v}{3600}$
• Water surface temperature: $t_1 = t_2 - \frac{t_2 - t_3}{8}$
• Heat for evaporation: $H_e = \frac{\dot{m}_q}{x_1 - x_2} (h_1 - h_2)$

Flow of Polluting Fluid: $q_f = \frac{22.4 q_e}{M} \cdot \frac{T}{273}$

Indoor Climate Sources Summary

The primary sources of heat and pollutants affecting indoor climate are:

• Sensible and latent heat from persons
• Sensible heat from lights
• Sensible heat from electric equipment
• Sensible heat from machines
• Latent heat from evaporation from water surfaces
• Evaporation from polluting fluids
• Carbon dioxide (CO₂) and other pollutants from persons, materials, and processes

Interactive Charts

References

• Original Source