Dry It

Which Method Will Evaporate The Water Out Of The Pot Faster!

Boiling the Water or Putting it in the oven at 500 degrees?

The Winner?

Boiling the Water!

Boiling The Water

 Then asked, most people assume that the water in the pot on top of the stove would take longer to evaporate, but it doesn’t.  In our tests, it took 22-25 minutes to evaporate the water on the stove top.  Why is this? Because the vapor pressure of the water is higher than the vapor pressure of the air. Basically, in this example, the temperature of the boiling water is higher than the temperature of of the surrounding air, and this causes faster evaporation. 

The Oven Example

Most people assume that, because the temperature in the oven reached 500 degrees, that the water would evaporate faster than on the stovetop. Makes sense, right?  In our tests, the pot of water took 2 hours to evaporate at 500 degrees. How could that be? Because the vapor pressure of the water was close to the vapor pressure of the air.  You see, in this example, the temperate of the air and the temperatures of the water were about equal, causing a similar “vapor pressure.” As a result, the water evaporated slowly.

How Does Evaporation Occur? Now that we know that the vapor pressure of the water was higher than the air and that is what caused the faster evaporation, let’s now understand when evaporation occurs.

In the IICRC S500, Chapter 5, page 122;

“Psychometric by definition” = evaporation occurs if the vapor pressure of the air is lower than the surface vapor pressure of the material.”

So let’s go back to that illustration.  The vapor pressure of the air was lower than the vapor pressure of the boiling water and that is why the evaporation rate was fast.

Now, what is the definition of vapor pressure?

“Vapor Pressure = A measure of a substance’s propensity (a natural inclination or tendency) to evaporate…It increases exponentially with an increase in temperature.” – U.S. Environmental Protection Agency.

What Does All This Mean To A Restorer?

According to the EPA, the ONLY way to increase the vapor pressure exponentially is by adding HEAT.

Have you ever asked yourself “Why does it take 3-5 days to dry out wet structures?  When we are drying a wet structure aren’t the wet materials cooler when it is wet?” YES! So, when we are using in place drying and we have air movers moving the air in a room, the vapor pressure of the wet materials is CLOSE to the vapor pressure of the air. To make it even easier to understand, the temperature of the wet materials is close to the temperature of the ambient air, which means SLOWER evaporation.  That is why it takes 3-5 days to dry out wet structures.

Therefore, if we can get the vapor pressure of the wet materials higher compared to the vapor pressure of the air, the FASTER the evaporation.  In simplistic terms, the higher the temperature of the wet materials compared to the surrounding air, the faster the evaporation rate.

However, if we are just heating the air, the temperature of the wet materials is close to the temperature of the air which means slower evaporation, regardless of the temperature of the materials.  So how do we speed up the evaporation rate in the wet materials? By directing, floating, tenting, or containing the heat to the water.

Doesn’t Heat Naturally Rise?

If we just heat the air like a lot of other heat drying equipment does, where does the heat naturally go? You’re right – the ceiling.  Now, MOST of the flood jobs that restorers do start from the floor, and end about 2 feet up the wall.  The sill plates are the hardest and usually the last parts to dry in a wet structure.     

So, instead of just heating the air and wasting all our BTU’s, we should float, tent, contain or direct heat to the wet materials.  

So if we float the carpet as you see here, where is all the HEAT? Right at the water and when you heat water it evaporates

 Now what does the IICRC say about Heat?12.1.22    & 12.1. 23  (Page 52)  Heat accelerates evaporation, heat should be applied directly to materials

Now the IICRC did NOT say to heat the air, it stated to DIRECT the heat right to the materials and this will accelerate evaporation.
 

12.3.1.1        Partial (or soft) floating of carpet. Carpet acts as an insulator and holds heat close to the materials being dried. (Page 55)

So if floating of carpet was so bad for carpet then why does it say that by soft floating of carpet (we do not want the carpet flapping, this WILL cause delamination) this will act as basically an insulation blanket and keep the heat close to the materials being dried. Therefore, because the vapor pressure of the wet materials is HIGHER than the vapor pressure of the air, this means is that you will create FASTER evaporation or to understand in simplistic terms the temperature of the wet materials is hotter than the surrounding air which will cause faster evaporation.
 
12.3.2.10.4 Drying walls, solid wood floors, the underside of sub floors, etc. can be accelerated by applying heat to the materials.
Here it states that if you again apply HEAT to the materials you will dry faster. Do you notice it didn’t say to use warm air, no it stated to use heat and this will accelerate to evaporation rate.

And The Take Away Is… 

So after all this information we have come to realize that Heat Drying and Direct Heat Drying have two different categories. Now with TES/ETES if you just want to heat the air you can. But, if you can direct, contain, direct or tent the heat – this is what will help you create faster evaporation and then you can dry out wet structures faster.

 The only equipment out there that does all this is TES – the leader in Direct Heat Drying.

Tags: dry, dryit.ca, fire damage, flood, restoration, systems, water, water damage

This entry was posted on Monday, December 28th, 2009 at 1:22 pm and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.