Monday, June 11, 2012

Like Iceland in a Box

by Drew Martin
As a kid, I learned from a CHiPs episode that refrigerators are dangerous because you can get trapped in them, but I did not know how fiery they are. Do you know how a self-defrosting fridge works? Every six to eight hours an electric heater under the freezer coils blasts the icy mass with extreme heat. Pictured here is the inside of my own freezer going through the cycle. The photo with the grid is a picture of the heater coil in a glass tube. It is amazing to witness the defrost because it is like some kind of Icelandic paradox of volcanic fissures in a frozen landscape. This cycle happens behind a metal panel in the back of the freezer. The temperature in the freezer may jump up 20 degrees Fahrenheit, which is why the typical setting for the freezer/refrigerator is 0/37 (degrees Fahrenheit, respectively). I would think we could have a better system considering all of our technological advances. This apparatus has been consuming my thoughts since my refrigerator broke down a couple weeks ago. An instructional YouTube video on the subject guided me away from having my own meltdown. After watching the video a couple times, I pulled the big refrigerator out from the alcove in the wall, took out all the food and beverages, then defrosted it. Later that day I was back in business and was relieved when the temperature sank to 0/37. But two weeks later, as I had read it might, the shutdown occurred again. I knew it meant the heating coil was not working so I defrosted the refrigerator again and tried to pull out the coil but it would not unclip. With the refrigerator unplugged, I cut the insulated copper wires that feed it and removed the glass-encased coil. The coil had burned out, much like a spent light bulb. I snipped off the burned-out section and twisted together the thin coil wires. I put the heating unit back in and joined the copper wires. The freezer unit quickly frosted up like wintry pine trees and I got quite worried, but the heating unit eventually kicked in and melted away the ice. What I found most interesting was how the heater coil works. Electricity flows really well through copper. Copper is extremely conductive. The thinner wire in the heater coil is Nichrome (80% Nickel and 20% Chrome), which not as conductive but lets electricity pass with great resistance, which is converted into heat. The heater coil in the refrigerator is not unlike the coils in toasters and space heaters, which are like really inefficient light bulbs. The difference is that light bulbs use an even thinner wire made of tungsten, which has even greater resistance. Tungsten completely burns up at high temperatures in the presence of oxygen, which is why it is encased in a bulb that is filled with an inert gas or is evacuated.