Evaporation Rate Calculator
Calculate water loss from pools, tanks, or open surfaces based on environmental conditions.
Humidity must be between 0 and 100.
Hourly Evaporation Mass:
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Daily Volume Loss:
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Daily Level Drop:
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Water Vapor Pressure Differential:
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About Evaporation Rate Calculation
Evaporation is the process by which liquid turns into vapor. Accurately calculating the evaporation rate is critical for managing swimming pools, industrial cooling ponds, reservoirs, and chemical processing tanks. This calculator uses empirical formulas based on Dalton's Law of Partial Pressures to estimate the rate of water loss.
How It Works
The calculation is primarily driven by the difference between the saturation vapor pressure at the water's surface and the actual vapor pressure of the surrounding air. The formula used accounts for:
- Water Temperature: Warmer water has higher kinetic energy, leading to higher vapor pressure and faster evaporation.
- Air Temperature & Humidity: These determine the moisture holding capacity of the air. Dry air absorbs moisture faster than humid air.
- Wind Speed (Air Velocity): Air movement removes the saturated boundary layer just above the water surface, significantly accelerating evaporation.
- Surface Area: A larger surface area provides more space for water molecules to escape.
The Math Behind It
This calculator utilizes a standard engineering formula often used for estimating evaporation from open water surfaces (simplified formulation):
E = (0.089 + 0.0782 × V) × A × (P_sat – P_air)
Where:
- E: Evaporation rate (kg/hour)
- V: Wind speed over the surface (m/s)
- A: Surface area (m²)
- P_sat: Saturation vapor pressure at water temperature (kPa)
- P_air: Actual vapor pressure of the air (kPa)
Why Monitor Evaporation?
Swimming Pools: High evaporation rates lead to significant water loss, requiring frequent refilling and chemical re-balancing. It also causes immense heat loss, increasing heating costs.
Industrial Tanks: In chemical engineering, knowing the evaporation rate is vital for concentration control and safety management of volatile liquids.
Reservoirs: In water resource management, estimating evaporative loss helps in planning water supply during droughts.