5 Gallon Air Conditioner - Does it work? YES!! Evap Model

5 Gallon Air Conditioner - Does it work? YES!! Evap Model


Here is a short video uploaded today, demonstrating the 5gallonairconditioner.com evap model on a hot summer day.

For the non-techie types, just watch the video, and the answer to the question of does it work, is an astounding YES!!

For you guys that like to dig into the dirt a little bit, here is some of the explanation and the engineering and physics behind what you are seeing in the video.

To understand what is going on, one must understand a field of science called psychrometry.  That is just a fancy word for weather phenomenon.   You will also need to understand phrases like dry bulb temperature and wet bulb temperature, dew point, relative humidity, and a whole host of other factors.

I will try my best to simplify this field of study the best I can for you.

Dry Bulb temperature is the temperature that a thermometer reads "normally."  When you look at an outside thermometer, you are seeing the "dry bulb" temperature.

Wet Bulb temperature is the temperature that a thermometer reads if the "bulb" of the thermometer was wrapped in a wet rag, and wind was blowing on the wet rag.  Wet bulb temperature is the "theoretical lowest temperature" that evaporative cooling can achieve.

These are the two main things to know to have a basic understanding of traditional evaporative cooling.

So, there are charts that scientists use called psychrometric charts, and it's from these charts that the scientists calculate relative humidity and a whole host of other weather physical properties.

For our discussion today, and for the purpose of this video, we will only concern ourselves with dry bulb temperature (dbT) and wet bulb temperature (wbT) and relative humidity (RH).

So, in order for anyone to make an accurate assessment on evaporative cooling performance, a very critical number that is rarely mentioned, but is absolutely critical in evaluating performance is humidity, or more specifically relative humidity.

Once you have the relative humidity, and the dry bulb temperature, then you can look at the psychrometric charts and figure out the wet bulb temperature and all of the other important factors. But, for our purposes, the key factor is the wet bulb temperature.

So, to obtain the RH, the easiest way is to log into the local weather station closest to your location and pull up the real time weather data.  Temperature can vary a few degress, but RH is very accurate from these data sources.

So, then once you have the RH, then use a local, meaning, in your hand thermometer to measure the exact dry bulb temperature of your exact location.

As you can see from the video, getting a dead solid dbT is difficult because of the solar affect (mentioned in another blog) of surrounding objects.  So, it's easiest to just average all of those dbT's that you get in your immediate area.  So, even though in the video, the weather station temperature when the video was made was 101 degF, but due to solar affects from the concrete, and the steel of the table, and the 'cooling' of the trees etc, the average dbT was approximately 104 degF.

So, as mentioned in the video, the RH at the time of the video was 16%.

So, armed with that data, dbT of 104 degF and 16% RH, also the barometric pressure was 30.02 for those super technical guys.  So, according to the psychrometric charts, the wbT (theoretical lowest temperature possible) is 67 degF.

So, when determining the performance of the AC unit, you can see, that you need to know all of those factors, before you can accurately answer the question, of "does it work"

As can be seen in the video, the output air temperature also bounces around, so an average needs to be taken there as well.  

I averaged the output air temperature at 70 degF for the following calculations, where you can see depending on the exact location of the pointer, it ranged from 60degF up to about 74 degF.  So, 70 is a pretty good average.

To calculate efficiency, simply divide out the average measured temperature difference by the maximum possible temperature difference.

So, the calculation is as follows:

Efficiency = (104-70)/(104-67) = 34/37 = .919 = 91.9% efficient.

Now, what if you think that the 104 is on the high side, and you just take the weather station data of 101 degF.

In that case, the wbT is 66 degF.

So, then the efficiency calculates out as follows:

Efficiency = (101-70)/(101-66) = 31/35 = .886 = 88.6% efficient.

As a means of reference, most house/home swamp coolers sold at big box hardware stores like Home Depot or Lowes etc.  Those swamp coolers using the best pads achieve around 75-80% efficiency.  Large industrial swamp coolers typically achieve about 85-90% efficiency. Most "old school" swamp coolers from the 70s and 80s had efficiency in the 60-65% range.

So, to answer the question, of "Does it work?"

The answer is YES!