Water Evaporation Rates

This cannot be calculated or measured from the sets you have posed. You do not include any information about atmospheric conditions at all. In all of your scenarios posed it could be raining and thus no net evaporation happening at all or a bright sunshiny day with humidity levels as low as one can get on the water.

Hi redfred,

When it rains................. Is that what they mean by 'reverse osmosis'?

Just a thought, you know?

Good luck.

Ask your instructor to provide sufficient information to allow a reasoned answer.

The evaporation rate during heavy rainfall might be considered to be negative.

There is no answer to this question. Atmospheric conditions have a profound effect and salinity a negligible one.

The "pan evaporation rate" is considered to be more directly affected by direct sunlight than by temperature increase alone, the photon's flying in knock water molecules off their matrix of surface tension, thus on days of equal temperature, clear skies spell more evaporation.

Not another blooming guesser?

Factors influencing the rate of evaporation

Concentration of the substance evaporating in the air If the air already has a high concentration of the substance evaporating, then the given substance will evaporate more slowly. Concentration of other substances in the air If the air is already saturated with other substances, it can have a lower capacity for the substance evaporating. Concentration of other substances in the liquid (impurities) If the liquid contains other substances, it will have a lower capacity for evaporation. Flow rate of air This is in part related to the concentration points above. If fresh air is moving over the substance all the time, then the concentration of the substance in the air is less likely to go up with time, thus encouraging faster evaporation. This is the result of the boundary layer at the evaporation surface decreasing with flow velocity, decreasing the diffusion distance in the stagnant layer. Inter-molecular forces The stronger the forces keeping the molecules together in the liquid state, the more energy one must get to escape. Pressure In an area of less pressure, evaporation happens faster because there is less exertion on the surface keeping the molecules from launching themselves. Surface area A substance which has a larger surface area will evaporate faster as there are more surface molecules which are able to escape. Temperature of the substance If the substance is hotter, then evaporation will be faster. Density The higher the density, the slower a liquid evaporates.

In the US, the National Weather Service measures the actual rate of evaporation from a standardized "pan" open water surface outdoors, at various locations nationwide. Others do likewise around the world. The US data is collected and compiled into an annual evaporation map.^[2] The measurements range from under 30 to over the120 inches (3,000 mm) per year.

The above is some hints for you. Hope you like it.

Steve To

Hong Kong.

Hi KC wuu,

This is obviously a set question that is set to trip you up. The question itself does not make sense. Why would you want to know the evaporation of salt and fresh water, and evaporation that it seems involves just about any other water can interact with any land.

There is no Country ref', or temps? What is going on here. Why not type your request for each sub-section into Google and see what comes back? Is that too obvious?

It is called research. Try doing some and you may even find the details you require. Any of us could possible find any answer to a specific request but this quest is just silly and unintelligent and nonsense. Nothing to be gained that can be usefully be included in any scientific work.

A real honest sensible request may be what is the evaporation per m² of fresh water at 80 °C. That is not what you ask, though.

How about telling me the 'evaporation' of icy sea water crashing over a ships prow? The wave was estimated to have been 50 tons.

It makes about as much if not sense as the several questions posed in your thread.

Me thinks you is pullin our plonkers here?

Bye Bye.

Dear Wuu,

In my opinion, your question makes sense.

Certainly, the answer is not easy because there are many parameters involved.

The fact that there are public information regarding the evaporation rate shows that it is an interesting figure.

I can not help you.

Only several replies to your question give you hints.

The others, only show the ignorance of the senders

ARTURO,

In my opinion, your opinion conclusively demonstrates your ignorance.

"the answer is not easy because there are many parameters involved."

That should read, "the answer is not easy possible because there are many UNKNOWN parameters involved."

Why bother to respond at all?

I suspect a reasonable answer to your question is that assuming everything else remains constant (i.e. temperature, humidity, etc.) the water evaporation rate will be determined by the water surface area available to the atmosphere. When the water is smooth (no waves) there will be a certain surface area closely represented by the area of the water body. Under wave conditions the water surface area will be many times the plain surface area. The surface area includes the area of drops resulting from crashing waves. The actual problem is more complicated because I have assumed that the water vapor pressure above the liquid water remains constant. This is probably a reasonable first assumption.

is this homework?

For a cooling tower evaporation rate I was told about 2%.

The calm versus rough water, rough water increases the surface area and thus should have more evaporation, but the other factors mentioned leading up to relative humidity above the surface (i.e. more evaporation on a sunny day with calm surface, then on a cloudy, stormy day with rough surface).

Dear Mr. CoronaCameraMan,

Evaporation NEED NOT NECESSARILY be 2 Percent, the wet-bulb temp. is nearer to Saturation Temp. EVAPORATION mainly depends upon RELATIVE HUMIDITY - which has a direct link to WET-BULB Temperature. Lower the wet-bulb temp, higher will be the evaporation. Pl. refer PSYCHROMETRIC CHART.

DHAYANANDHAN.S

Maximum evaporation rate is achieved in the wet bulb of a sling psychrometer because of the difference of partial pressure of water vapor. Knowing this, I would go about measuring the dew point (perhaps with a condensation dew pointer) under the conditions you specified. The difference in dew points should be related to the difference in partial pressure and therefore evaporation rate.

As pointed out by other friends in their posts, there are several factors that influence the evaporation rate. These factors does not remain constant even for a short period of time. They keep changing every minute, every hour, throughout the day and all through the year. These factors vary even within short distance from place to place. Therefore it is highly impossible to predict evaporation rate to a precise level. Estimation of annual precipitation through rainfall and snow etc. throughout the world help us calculate the evaporation rate.

Dear Mr.KC Wuu,

There are several factors, RELATIVE HUMIDITY OF AIR, WIND VELOCITY, Temp. at SURFACE, INTERNAL CIRCULATION etc. It is a complex aspect.

DHAYANANDHAN.S