Refrigeration and CoolBot 101

Have you ever considered what a summertime trip to the supermarket would be like without refrigeration? You jump into your air conditioned car, a brief respite from the afternoon’s blistering temperatures. Your hair curls as soon as you step out into the parking lot (thanks humidity!), until you cross the threshold of the supermarket’s automatic sliding doors and — whoosh! — you are back in a crisp and comfortable 74°F climate. You find yourself surrounded by aisles of fresh produce, meat and dairy, thanks in part to the walk-in cooler that the farmer built, the refrigerated trailer that transported the harvest, and the refrigerated display case housing all of those colorful crops. None of this would have been possible without refrigeration.

For many years, these farmers, hobbyists, brewers, wine enthusiasts, and DIY-ers have tinkered with window A/C units to harness the power contained in these small but capable devices, attempting to use them as proper refrigeration systems. Combining some electrical knowledge with a bit of grit, these guys could bypass the original thermostat controls to allow the units to keep cooling. One of the problems that typically arises when attempting to rig this system is that you will eventually freeze the evaporator coil if you don’t stop your unit from cooling, so it is difficult to obtain a good balance in between defrost and desired room temperature — since you could not monitor both with the same control. Plus, let’s be honest: Most people lack the electrical skills and/or the know-how to tackle this kind of project, nor do they feel comfortable doing electrical modifications to their appliances. Then the CoolBot showed up and revolutionized everything.

And we’ll soon get to that. But first, let’s give you a quick refresher course on how refrigeration systems work.

Whether it’s a refrigerator, a walk-in cooler, a 3-ton home central A/C or just a small window A/C unit, these machines all share the same basic components and work under the same principle. These devices are removing heat from a desired space and transferring it into another space. Seems simple, right?

The main basic components of ANY refrigeration system are:

  1. Compressor
  2. Condenser Coil (the warm part)
  3. Expansion device (also called metering device)
  4. Evaporator Coil (the cold part)
  5. The Fans

In order to understand what is going on inside a refrigeration system, let’s step back into our elementary school science lab for a minute. Listen up, kids:

  • Heat always transfers from a warmer surface to a cooler surface.
  • Water changes from liquid to vapor at around 212°F, when it reaches its boiling point. When that hot water vapor hits the cold window, it turns back into drops of liquid water (condenses).
  • The boiling temperature of water changes when the atmospheric pressure is different. Grandma used to insist that water would boil faster in our cabin in the Rocky Mountains than it would at the beach house in Florida at sea level. And she was right! Water will boil at a lower temperature at a higher altitude because there is less air pressure on the surface of the liquid to make it start bubbling and, therefore, to boil it.

Now for some more cool science stuff: Certain substances were discovered to have very curious properties when they are changed from liquid to vapor, then back into liquid (boiled and condensed). When these substances are forced to go from a high pressure-warm temperature liquid state (in the condenser coil), into a low pressure environment (in the evaporator coil), they will boil (vaporize) at VERY low temperatures. By harnessing this trait inside a closed loop system, we can change the state of this substance over and over again, using it to cool a space.

  • A fan blowing air OUT of a condenser coil allows the coil to lose heat, since the coil is hotter than the air. This causes the coil to cool, making the hot vapor inside (refrigerant) turn to liquid  (condensate). This is why we call it a condensing coil.
  • A fan sucking air IN through the evaporator coil will allow the coil to gain heat from the air that circulates over it since the air is hotter than the coil. This makes the air colder and the coil warmer. G’bye heat! Hello, cooling! This all takes place within the evaporator coil.

Check out this diagram of a refrigeration cycle in a window A/C working its magic:

 

Window A/C Diagram
© Refrigeration and Air Conditioning Technology.
Bill Whitman, Bill Johnson, John Tomczyk, Eugene Silverstein. 5th Edition. Page 26

 

 

A window A/C or Mini Split system has all the same basic components as a refrigeration system, but is limited by its own temperature control due to its native application. In order to control this refrigeration cycle, the room temperature and other variables, the CoolBot introduces some new components to this basic system to control it and achieve the desired results.

The CoolBot uses a heater cable to fool the A/C sensor, utilizing two temperature sensors that simultaneously monitor both the room and the A/C fins’ temperature. This allows the user to use a window or Mini Split A/C to refrigerate a room without ANY electrical connections.

Some FAQs related to the CoolBot: Is this is good for an A/C unit? Is the A/C working continuously? How efficient is this system? Can the A/C unit really run under these conditions?

Both the New York State Energy Research and Development Authority and UC Davis have done extensive trials and research on the use of the CoolBot, helping us to answer all of these looming questions. No, the A/C does not run continuously. Once the room has reached the desired temperature, in most cases the A/C will actually cycle less than if it was working in a regular home (since it has less insulation, windows, and constant air infiltration), as opposed to the same A/C installed in to a much smaller, airtight, and highly insulated “walk-in cooler” type room. These studies also verified the benefits of a lower initial investment, plus the energy savings of the system. CoolBot could be up to 40% more energy efficient than a conventional system in a properly designed cooler. According to these studies, most A/C manufacturers have been proven to take precautions in their A/C’s design, using accumulators and U-shaped vapor return lines, to avoid the possibility of flooding the compressor if liquid refrigerant was coming from the evaporator.

 

Thousands of satisfied customers are living proof that the CoolBot system is both an economic and efficient solution for small refrigeration applications. Ten years and 45,000 happy customers could not be wrong about this!

 

References:

NYSERDA. Evaluation of the CoolBot Low -Cost Walk-In Cooler concept. CDH Energy Corp.May 2009

Ref. Page 16- CoolBot Economics.

 

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