Keeping Things Cool: The Internal Workings of the Refrigerator

By Dave Donovan

Imagine where we would be without the refrigerator. Food certainly wouldn't last as long. Without leftovers, your grocery bill would be even higher than it already is. You can forget about all those delicious frozen treats in the summer, and have you ever tried room temperature milk? The refrigerator is definitely an appliance we cannot do without. We're going to take a closer look at just how today's "icebox" keeps everything nice and cold. But first, who should we thank for saving us a lifetime of rotting produce?

It's an understatement to say that refrigerators have been a long time coming. The first record of someone using artificial refrigeration came from William Cullen at the University of Glasgow in the 1700s. He began with a unit that used vapor-compression as a means to cool. Throughout the years, small advancements in technology baby-stepped this appliance into the safe household fixture we have today. It wasn't until the start of the 20th century that refrigerators were beginning to show up in homes – at least, homes of the incredibly wealthy. In 1911, a General Electric sulfur-dioxide cooled refrigerator sold for $1,000.00! With more advancements coming quickly, and the use of Freon as a cooling agent, the 1930s saw an increase in home users. But it wasn't until after World War II that the appliances went into mass production. Further advancements in the ‘50s and ‘60s, like ice makers and auto-defrosting, made the refrigerator a "must have" in the kitchen.

Now let's take a closer look at how the refrigerator works. You may be surprised to learn how much heat goes into cooling. A refrigerator uses contained gases, which continuously circulate through the coils. The coolant of choice (at one time Freon, but now it's the more environmentally friendly HFC-134a) enters the compressor. The compressor heats up the coolant and compresses it. The coolant leaves the compressor as a superheated vapor and flows to the condenser. At the condenser, the heat is removed from the compressed vapor, thus condensing it all the way to liquid form. The liquid then heads through the throttle valve, and that's where its pressure gets dramatically lowered. The sudden loss of pressure causes a flash-evaporation of some of the liquid. This causes the refrigerant to cool down significantly. Now, the partially vaporized refrigerant is cold and gets sent through the coils in the evaporator. Once there, a fan pushes air across the coils and into the refrigerator to cool your cucumbers. The vaporized refrigerant then heads on to the compressor, and the process begins anew.

Frost-free freezers are common companions to most refrigerators sold today. They keep ice buildup from forming in the freezer by adding a little heat to the coils every so often. Frost-free freezers have a timer, a temperature sensor, and a heating coil dedicated for the purpose. The timer is usually programmed to turn on the heating coils, which are wrapped around the cooling coils, about every six hours. This melts any ice that may be collecting on the coils. When the temperature sensor reads the temperature rising above 32 degrees, it turns the heating coils off. You may sometimes wonder why your ice cream bar isn't as frozen as it should be. It's probably because the heating coils were just on.

You can adjust the coldness in your refrigerator with a dial usually located either right in front or toward the rear on the inside of the refrigerator. It's basically a thermostat that tells the compressor when to turn off and on. It's important to know where to set the dial. If it's too cold, some foods will freeze. If it's not cold enough, some foods will spoil. The ideal temperature for inside a refrigerator is 37^o F, while the freezer should be 0^o F.

The last few decades brought many advancements to the refrigerator, and probably one of the most loved is the automatic ice maker. Simply by tapping into a cold water line and connecting a hose, you'll never have to worry about refilling those pesky ice trays again. Some models have ice makers inside the freezer and some have them on the door. Either way, they are convenient, although space consuming. Your freezer definitely loses some cargo room to house these units.

An inlet hose runs from the water tap, up the back of the refrigerator, and into the freezer compartment where it gets connected to the ice maker. A timer opens up a solenoid that allows the water to come in and fill the reservoir. Once filled, the solenoid closes. The water is frozen by the cold air of the freezer. There is a thermostat that meters how cold the water is getting. Once the frozen water hits a certain temperature, the thermostat kicks on a heating coil underneath the ice. This helps to separate the ice from the molds. Then the gears begin to turn, and the blades of the ice maker roll down and push the ice cubes up and out of their molds and into the ice cube holding tray. Once the blades reach their full revolution, the cycle starts again. A metal arm rises with the ice in the tray. Once it reaches a certain height, it switches the ice maker off so it won't continue churning out ice cubes.

The refrigerator, more so than any other appliance, is in constant change. From the mid-1700s to today's energy-saving models, new advancements in food preservation are always evolving. It will be interesting to see what is developed next for one of our most necessary appliances. If your refrigerator is acting up and giving you a headache, don't replace it just yet! See if you can find the answer to your problem with our handy repair guide. It's tailored to address the most common issues with everyday refrigerators. Read the guide, fix the fridge, and keep your cool.