To take a glance at all pocketEngineer software and OS requirements, click Software List.

For Android OS, see aRhoAIR free. 

ALERT! The original copy of rhoAIR is only available on this site. If you have downloaded it from other sites, you may have downloaded a fake/spam one. The original copy does not require setup installation, and there is no ads, no bundle, etc. 

Need to plot points and lines on digital psychrometric chart, see Psychro Visual (Windows OS program).

rhoAIR is a state point psychrometric air properties calculator to find air density, vapour pressure, dew point temperature, moisture content, enthalpy, etc. It is specially designed by a professional engineer to replace the psychrometric chart. rhoAIR will change the way you normally find air properties and air density by using conventional psychrometric chart.

Aim: creating a mobile design environment (ShowMe!) for the practising engineers & designers in today's mobile world.

Results: Instant solutions at your fingertips.

Highlights:

• calculate Air Density, DewPoint Temperature, various Vapour Pressure, Moisture Content, Specific Volume, Enthalpy, etc.

• input options for RH or Wetbulb Temperature.

• calculation formulation to ASHRAE guidelines.

• alternative method to using conventional Psychrometric Chart.

• mobile & independent program for Windows PC.

• in SI & IP units.

• save results function for printing.

Did you know? . . .about Enthalpy Units 

It is incorrect to directly convert Enthalpy from SI unit (kJ/kg) to IP unit (Btu/lb), and vice versa. Hard to believe! Test it yourself.

 [Answer: This is because the reference temperature point of the (latent) heat of vaporization (hfg) in metric and imperial units are different.] 

Did you know? . . .the definition of Standard air density = 1.204 kg/m3?  

The value is of course valid only for what is termed standard air conditions.

Dry air refers to air that does not contain water vapour, i.e. RH = 0%. Note that moist air is lighter than dry air.

• In the International Standard Atmosphere (ISA), standard temperature and pressure is 15 oC and 101325 Pa respectively. This gives the air density of 1.225 kg/m3 at sea level and the air does not contain water vapour, i.e. dry air.

• At 20 oC, the dry air has a density of 1.204 kg/m3. At 20 oC and 101325 Pa, it may be referred to as Normal temperature and pressure conditions.

• In AMCA 210 Standard for fan performance testing, standard air is defined as air with a density of 1.2 kg/m3 (at 20 oC, 50% RH and 101325 Pa approximately). see calculation example below.

• ASHRAE 37 Standard for unitary air-conditioning testing defines standard air as dry air having a mass density of 1.204 kg/m3  (at 20 oC and 101325 Pa).

• SMACNA 126 Standard for HVAC duct testing defines density of standard air equals 1.204 kg/m3.

Note that there are many definitions of standard temperature and pressure. To avoid confusion, it is  often necessary to state the standard reference conditions.

What is the DewPoint temperature when RH = 0%? . . .

At RH = 0% (completely dry air), there will be no DewPoint temperature as completely dry air will not reach a state of saturation.

Calculation Example 

At 20 oC , 50% RH and sea level, find air density, dewpoint temperature, moisture content, enthalphy, etc?

Altitude, Z = 0 m

DryBulb, Tdb = 20 °C

Relative humidity, RH = 50 %

WetBulb, Twb = 13.8 °C

Air density, rho = 1.199  kg/m³

DewPoint, Tdp = 9.3 °C

Details . . .

(1) Atmospheric pressure, P = 101,325 Pa

(2) Saturation vapour pressure, Pws = 2,338.8 Pa

(3) Partial water vapour pressure, Pw = 1,169.4 Pa

(5) Humidity ratio (Moisture content), W = 7.262 g(water)/kg(dry air)

(6) Specific volume, v = 0.8402 m³/kg(dry air)

(7) Enthalpy, h = 38.55 kJ/kg

Calculation Exercise 

A sling psychrometer reads 44 oC dry bulb temperature and 30 oC wet bulb temperature. Calculate air density and other psychrometric properties.

Air Mixing Problems? 

rhoAIR is not designed to calculate mixing air psychrometric properties. If you need mixing air calculation, see  Qcondensate.