Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Moist Air - Water Vapor and Saturation Pressure

Saturation pressure of water vapor in moist air vs. temperature.

Sponsored Links

Water vapor is almost always present in the surrounding air.

Note! - the equations below is for pure water vapor - not moist air.

Saturation Pressure of Water Vapor

The maximum saturation pressure of the water vapor in moist air varies with the temperature of the air vapor mixture and can be expressed as:

p_ws = e^{(77.3450 + 0.0057 T - 7235 / T)} / T ^8.2 (1)

where

p_ws = water vapor saturation pressure (Pa)

e = the constant 2.718.......

T = dry bulb temperature of the moist air (K)

Density of Water Vapor

The density of water vapor can be expressed as:

ρ_w = 0.0022 p_w / T (2)

where

p_w = partial pressure water vapor (Pa, N/m²)

ρ_w = density water vapor (kg/m³)

T = absolute dry bulb temperature (K)

Saturation pressure and density of water vapor for common temperatures

Water vapor - temperature saturation pressure diagram

Water vapor - temperature saturation pressure diagram

Temperature		Saturation Pressure				Density
(^oC)	(^oF)	(Pa)	(mmHg)	(psia)	(inHg)	(kg/m³)	10^-3 (lb/ft³)
0	32	603	4.6	0.09	0.18	0.005	0.30
10	50	1212	9.2	0.18	0.36	0.009	0.59
20	68	2310	17.4	0.33	0.68	0.017	1.08
30	86	4195	31.7	0.61	1.24	0.030	1.90
40	104	7297	55.1	1.06	2.15	0.051	3.20
50	122	12210	92.2	1.8	3.60	0.083	5.19
60	140	19724	149	2.9	5.82	0.13	8.13
70	158	30866	233	4.5	9.11	0.20	12.3
80	176	46925	354	6.8	13.8	0.29	18.2
90	194	69485	525	10.1	20.5	0.42	26.3
100	212	100446	758	14.6	29.6	0.59	36.9
120	248	196849	1486	28.6	58.1	1.10	68.7
140	284	358137	2704	51.9	105.7	1.91	119
160	320	611728	4619	88.7	180.5	3.11	194
180	356	990022	7475	144	292.1	4.80	300
200	392	1529627	11549	222	451.2	7.11	444

1 lb/ft³ = 16.018 kg/m³
1 kg/m³ = 0.0624 lb/ft³

Example - Saturation Pressure Water Vapor

The Saturation pressure of water vapor in moist air at dry bulb temperature 25^oC can be calculated:

First, convertion from °C to K:

(25 °C) + 273 = 298 (K)

Then Eq. (1) is used:

p_ws= e^{(77.3450 + 0.0057 (298 K) - 7235 / (298 K) )} / 298 [K]^8.2

= 3130 (Pa)

Sponsored Links

Related Topics

Air Psychrometrics - Moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content.

Related Documents

Air - Humidity Measurement from Dry and Wet Bulb Temperature - Relative humidity in moist air can estimated by measuring the dry and wet bulb temperature.
Air - Maximum Moisture Carrying Capacity - Maximum water content in humid air vs. temperature.
Air - Moisture Holding Capacity vs. Temperature - The moisture holding capacity of air increases with temperature.
Air Drying Force - The drying force of air depends on the air moisture holding capacity and the water surface to air evaporation capacity.
Dry Air - Thermodynamic and Physical Properties - Thermodynamic properties of dry air - specific heat, ratio of specific heats, dynamic viscosity, thermal conductivity, Prandtl number, density and kinematic viscosity at temperatures ranging 175 - 1900 K.
Humid Air vs. the Ideal Gas Law - Pressure, temperature and volume in a perfect ideal gas like moist air (air with water vapor).
Liquids - Vapor Pressures - Vapor and saturation pressure for some common liquids.
Moist Air - Daltons Law of Partial Pressure - The pressure in a mixture of dry air and water vapor - humid or moist air - can be estimated by using Daltons Law of partial pressures.
Moist Air - Degree of Saturation - Humidity ratio of moist air to humidity ratio of saturated moist air.
Moist Air - Density vs. Pressure - Density of moist air vs. pressure ranging 75 - 1000 mmHg.
Moist Air - Density vs. Water Content and Temperature - Density of the mix of dry air and water vapor - moist humid air.
Moist Air - Mole Fraction of Water Vapor - Mole fraction of water vapor is the ratio of water molecules to air and water molecules.
Moist Air - Psychrometric Table for Pressure 29.92 inHg. - Dry and wet bulb temperatures, saturation pressure, water vapor weight, specific volume, heat and more.
Moist Air - Vapor Pressure - Vapor pressures vs. dry and wet bulb temperatures in moist air.
Removing Heat with Air - Calculating heat removed with air by measuring the wet bulb temperature.
Water - Boiling Points at Vacuum Pressure - Online calculator, figures and tables giving the boiling temperatures of water in varying vacuum, SI and Imperial units.
Water - Saturation Pressure and Specific Weight vs. Temperature - Vapor pressure and specific weight of water at temperatures ranging 32 to 212 ^oF - Imperial Units.
Water - Saturation Pressure vs. Temperature - Online calculator, figures and tables with water saturation (vapor) pressure at temperatures ranging 0 to 370 °C (32 to 700°F) - in Imperial and SI Units.
Wet Bulb Globe Temperature (WBGT) - The Wet Bulb Globe Temperature can be used to measure the general Heat-Stress index.

Sponsored Links

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse!

Translate

About the Engineering ToolBox!

Privacy

We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.

Advertise in the ToolBox

If you want to promote your products or services in the Engineering ToolBox - please use Google Adwords. You can target the Engineering ToolBox by using AdWords Managed Placements.

Citation

This page can be cited as

Engineering ToolBox, (2004). Moist Air - Water Vapor and Saturation Pressure. [online] Available at: https://www.engineeringtoolbox.com/water-vapor-saturation-pressure-air-d_689.html [Accessed Day Mo. Year].

Modify access date.

close

3D Engineering ToolBox - draw and model technical applications!

2D Engineering ToolBox - create and share online diagram drawing templates!

Engineering ToolBox Apps - mobile online and offline engineering applications!

Scientific Online Calculator

Scientific Calculator

3 10

Sponsored Links