Humidity Ratio Calculator

Humidity Ratio Calculator:

Enter the values of vapor pressure, P_w(kPa)and total pressure, P_(kPa)to determine the value of Humidity Ratio, x.

Enter Vapor Pressure :		kPa
Enter Total Pressure:		kPa
Result – Humidity Ratio:

Humidity Ratio :

The humidity ratio, also known as specific humidity, refers to the amount of water vapor contained in a given mass of dry air. It indicates the air’s moisture level and is essential in psychrometric analyses and HVAC system design.

This ratio helps in understanding how much water vapor the air contains, which is essential for air-conditioning, drying, and environmental control processes.

Humidity ratio is dimensionless but usually expressed in units of kg of water vapor per kg of dry air (kg/kg da) or grams per kg (g/kg).It does not change with pressure (unlike relative humidity) and is a reliable indicator of actual moisture in air.

Humidity ratio is useful in designing air-conditioning systems, especially when cooling and dehumidifying moist air.It plays a major role in energy calculations where latent heat (heat required to remove or add moisture) is considered.Humidity ratio remains constant in an adiabatic saturation process (evaporative cooling without heat loss).Dry air is a mixture of gases, primarily nitrogen and oxygen, and the water vapor is considered a separate component.

Humidity ratio increases with higher water vapor pressure and decreases with higher atmospheric pressure.It is often determined from wet-bulb temperature and dry-bulb temperature using psychrometric charts or equations.A greater humidity ratio indicates a higher concentration of water vapor in the air.It is essential in processes such as drying clothes, food processing, greenhouses, and indoor air quality control.

Humidity Ratio, x equals 0.622 multiplied by the vapor pressure, P_w(kPa)in kiloPascals divided by the difference between total pressure, P_(kPa)in kiloPascals and vapor pressure, P_w(kPa).

Humidity Ratio, x= (0.622 *P_w(kPa)) / (P_(kPa)– P_w(kPa))

x= humidity ratio.

P_w(kPa)= vapor pressure in kiloPascals, kPa.

P_(kPa)= total pressure in kiloPascals, kPa.

Humidity Ratio Calculation:

1. Given: P_w(kPa)= 2.5kPa, P_(kPa)= 101.325kPa.

Humidity Ratio, x= (0.622 *P_w(kPa)) / (P_(kPa)– P_w(kPa))

x= (0.622 * 2.5) / (101.325 – 2.5)

x= 1.555 / 98.825

x= 0.01574.

2. Given: P_w(kPa)= 2.2kPa, x= 012.

Humidity Ratio, x= (0.622 *P_w(kPa)) / (P_(kPa)– P_w(kPa))

0.012 = (0.622 * 2.2) / (P_(kPa) – 2.2)

0.012 = (0.622 * 2.2) / (P_(kPa) – 2.2)

0.012 = (1.3684) / (P_(kPa) – 2.2)

0.012(P_(kPa) – 2.2) = 1.3684

0.012 * P_(kPa) – 0.0264 = 1.3684

0.012* P_(kPa)=1.3684+0.0264

P_(kPa)= 1.3948 / 0.012

P_(kPa)= 116.233kPa.