Enter the velocity of air above the water surface, the water surface area, the maximum humidity ratio of saturated air, and the current humidity ratio of air to determine the evaporation rate of water from a surface.

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## Evaporation Rate Formula

The following formula is used to calculate the evaporation rate of water.

gh = (25+19*v)*(A)*(Xs-X)

- Where gh is the evaporation rate (kg/h)
- v is the velocity of air above the surface (m/s)
- A is the water surface area (m^2)
- Xs is the maximum humidity ratio of saturated air (at the same temperature as the water surface)
- X is the current humidity ratio air

To calculate the evaporation rate, multiply 19 by the velocity of the air, add 25 to the result, multiply by the surface area, then multiply by the difference in current humidity ratio and maximum humidity ratio.

## Evaporation Rate Definition

An evaporation rate is defined as the speed at which water is evaporated into air typically measure in weight per unit of time.

## Evaporation Rate Example

How to calculate an evaporation rate?

**First, determine the velocity of air.**Measure the speed of the air above the surface of the water.

**Next, determine the surface area.**Calculate the total water surface area exposes to air.

**Next, determine the maximum humidity ratio.**Calculate the maximum humidity ratio of saturated air at the same temperature as the surface of the water.

**Next, determine the current humidity ratio.**Calculate the current humidity ratio of the air.

**Finally, calculate the rate of evaporation.**Calculate the water evaporation rate using the equation above.

## FAQ

**What is an evaporation rate?**

An evaporation rate is a speed at which water is evaporated from the surface of a body of water.