Evaporation Rate by Radiation Calculator

Calculate radiation driven evaporation from heat and surface settings. Download clean results with tables easily. See energy use, mass loss and water depth changes.

Calculator Inputs

Calculation Mode

Surface Area m²

Exposure Time hours

Evaporation Efficiency % of radiation used for evaporation

Latent Heat kJ/kg

Liquid Density kg/m³

Initial Volume L, optional

Direct Net Radiation Flux W/m²

Incoming Radiation W/m²

Albedo % reflected

Emissivity %

Surface Temperature °C

Sky or Surrounding Temperature °C

Extra Radiation Gain or Loss W/m²

Formula Used

Direct mode:

Net radiation flux = entered direct radiation flux

Balance mode:

Shortwave absorbed = incoming radiation × (1 − albedo)

Longwave exchange = emissivity × σ × (sky temperature⁴ − surface temperature⁴)

Net radiation flux = shortwave absorbed + longwave exchange + extra flux

Evaporation:

Usable flux = positive net radiation flux × efficiency

Energy = usable flux × surface area × time

Evaporated mass = energy ÷ latent heat of vaporization

Evaporated volume = mass ÷ liquid density

Depth loss = evaporated volume ÷ surface area

How to Use This Calculator

Select direct mode when net radiation heat flux is already known.
Select balance mode when incoming radiation and surface data are known.
Enter the exposed liquid surface area.
Enter the radiation exposure time in hours.
Set evaporation efficiency for real losses.
Use the correct latent heat for your liquid and temperature.
Click calculate to view results above the form.
Use CSV or PDF buttons to save the result.

Example Data Table

Case	Area	Net Flux	Time	Efficiency	Latent Heat	Estimated Result
Small tray	2 m²	450 W/m²	3 h	65%	2450 kJ/kg	About 8.6 kg
Open tank	10 m²	500 W/m²	1 h	70%	2450 kJ/kg	About 5.1 kg
Drying pan	5 m²	800 W/m²	2 h	80%	2257 kJ/kg	About 12.8 kg

Evaporation Rate by Radiation in Physics

Radiation can supply energy to a liquid surface. That energy may warm the liquid, heat nearby material, or change water into vapor. This calculator focuses on the evaporation part. It estimates how much liquid can evaporate when useful radiation energy reaches the surface.

Why Radiation Matters

Sunlight, heaters, lamps, and thermal exchange can all affect evaporation. A black shallow tray often evaporates faster than a shiny surface. The difference comes from absorbed heat. Albedo, emissivity, surface temperature, and sky temperature also matter. These values control the net radiation balance.

What the Calculator Measures

The tool converts radiation heat flux into usable evaporation energy. It then divides that energy by latent heat of vaporization. The result is mass loss in kilograms. It also shows liters, depth loss, energy, power, and hourly rate. These outputs help with ponds, trays, dryers, cooling tests, and laboratory estimates.

Direct Flux and Balance Modes

Direct mode is best when you already know the net radiation heat flux. Balance mode is useful when you know incoming radiation and surface properties. The balance option subtracts reflected shortwave energy. It also estimates longwave thermal exchange between the surface and the sky. A positive net value can support evaporation.

Important Assumptions

The calculation assumes the entered efficiency already accounts for wind, humidity, convection, shading, and heat storage losses. Real evaporation can be lower when air is humid. It can be higher when air movement removes vapor quickly. For accurate field work, compare the estimate with measured water depth changes.

Using the Results

Use depth loss when checking tanks or ponds. Use mass loss when sizing dryers or heat sources. Use liters per hour for practical water planning. Review the percentage volume loss when the initial water volume is known. Downloaded CSV and PDF files help save each scenario for reports.

Practical Tips

Enter realistic latent heat values. Water near room temperature often uses about 2450 kJ per kilogram. Water near boiling uses about 2257 kJ per kilogram. Keep all units consistent. Repeat the estimate with high and low assumptions. That gives a useful range instead of one fragile number.

This approach supports quick comparison before detailed experiments or site measurements are arranged by teams.

FAQs

What is evaporation by radiation?

It is evaporation caused by radiant energy reaching a liquid surface. The energy may come from sunlight, lamps, heaters, or thermal surroundings. Only the useful part of that energy changes liquid into vapor.

What unit is radiation flux measured in?

Radiation flux is usually measured in watts per square meter. It describes how much radiant power reaches each square meter of surface area.

Why does latent heat matter?

Latent heat tells how much energy is needed to evaporate one kilogram of liquid. Higher latent heat means less mass evaporates from the same radiation energy.

What is evaporation efficiency?

Evaporation efficiency is the share of radiation energy actually used for phase change. It accounts for losses to heating, reflection, convection, storage, and surroundings.

Can this calculator be used for liquids other than water?

Yes. Enter the correct latent heat and density for the selected liquid. Results depend strongly on those two properties, so use reliable data.

What does negative net radiation mean?

Negative net radiation means the surface is losing radiant energy. In that case, this calculator reports zero radiation driven evaporation for that condition.

Why is real evaporation sometimes different?

Real evaporation also depends on humidity, wind speed, pressure, liquid mixing, salinity, and heat stored in the surface. Field checks improve accuracy.

Which mode should I choose?

Use direct mode when net radiation flux is already known. Use balance mode when you have incoming radiation, albedo, emissivity, and temperature values.