AC cooling in summer
What’s the best way to cool down your kitchen on a hot summer’s day? If your immediate answer is “Open the refrigerator door,” you’re way off target! Every bit of heat a refrigerator sucks in through its cool box is pumped straight out of the metal fins at the back. If anything, because of the sheer inefficiency of the machine, you’ll make the room even hotter. But using a refrigerator to cool a home isn’t such a mad idea as it might seem: with a few slight modifications, it’s almost exactly how an air conditioner works. Let’s take a closer look!How not to cool your kitchen
Refrigerator with the door open just seen here o general ac
Photo: Physics tells us you can’t cool your kitchen by leaving the refrigerator door open!
A basic law of physics called the conservation of energy says you can’t make or destroy energy: if you have some energy you don’t want (such as heat in your kitchen), you can’t get rid of it completely. All you can do is change it into another form or move it to another place. If you open your refrigerator door in the hope that you’ll cool the kitchen, all the heat that gets drawn in has to go somewhere else. The only place it can go is out of the back of the machine. You may have noticed that the grid of fins on the back of a refrigerator gets pretty hot—and that’s why: they’re giving off all the heat that would normally be inside. You can find out more in our article on how refrigerators work.
How to build an air conditioner
But all’s not lost! Instead of letting the power of science defeat us, we just have to use it the right way.
Suppose you take a refrigerator and build your house around it, so half the machine (the chiller cabinet) is inside your home and the other half (the grid of hot fins at the back) is outside. Now if you leave the door open, what you have in effect is a fully fledged air conditioner. It draws in heat from inside your home and belches it out again outside, gradually cooling your home in the process.
The simplest air conditioner units work in almost exactly this way, except they have fans on both sides to circulate air more rapidly. They also have a heating element in them so they can warm the air in a room on cold days as well as cool it down on warm days. Machines like this are sometimes called HVACs (heating and ventilation air conditioning units). More elaborate air conditioners use long ducts to pipe the warmed or cooled air throughout an entire building, but they still work in essentially the same way.