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In the summer, perhaps you have gotten out of a swimming pool and then felt cold standing in sunlight? That's since the water in your skin is evaporating. The air carries off the water vapor, and with it some of the heat will be recinded from your own skin.

That is similar to what happens inside older refrigerators. In place of water, though, the fridge uses chemicals to accomplish the cooling.

You will find a few things that need to be known for refrigeration.

1. A gasoline cools on expansion.

2. If you have a couple of things that are different conditions that touch or are near one another, the hotter surface cools and the colder surface warms up. This can be a law of physics called the 2nd Law of Thermodynamics.

Old Refrigerators

If you consider the back or bottom of an older ice box, you'll see a long thin tube that curls back and forth. This tube is linked to a pump, that is operated by an electrical motor.

Within the tube is Freon, a type of gas. Freon may be the manufacturer of the gas. That gas, chemically is called Chloro-Flouro-Carbon or CFC. This fuel was found to hurt the environment if it escapes from appliances. So now, other substances are used in a somewhat different approach (see next section below).

CFC begins as a fluid. The pump forces the CFC through a large amount of circles in the freezer area. There the substance turns to a vapor. When it does, it soaks up a few of the temperature which may be in the freezer compartment. Since it does this, the coils get colder and the freezer starts to obtain colder.

In the regular part of your ice box, you can find fewer rings and a larger area. Therefore, less heat is soaked up by the circles and the CFC vapor.

The pump then sucks the CFC as a vapor and pushes it through finer pipes which are on the outside the fridge. By compressing it, the CFC turns back to a liquid and heat is given off and is consumed by the air around it. That's why it may be just a little warmer behind or under your refrigerator.

Once the CFC passes through the outside circles, the fluid is ready to return back through the freezer and refrigerator over and over.

Today's Appliances

Contemporary appliances do not use CFC. Instead they use ammonia gas. Ammonia gas turns into a fluid when it's cooled to -27 degrees Fahrenheit (-6.5 degrees Celsius).

A motor and compressor pushes the ammonia gas. As it is condensed when it is compressed, a gas gets hotter. When you go the compressed gas through the rings on the back or base of a modern fridge, the hot ammonia gas can lose its warmth to the air in the area.

Remember the law of thermodynamics.

As it cools, the ammonia gas can transform into ammonia fluid because it's under a high pressure.

The ammonia liquid flows through what's called an expansion valve, a tiny little gap that the liquid needs to fit through. Involving the valve and the compressor, there is a area since the compressor is pulling the ammonia gas out of this side.

If the liquid ammonia gets a low pressure region it boils and changes into a gas. This really is called vaporizing.

The rings then proceed through the freezer and normal part of the refrigerator where the ammonia in the coil pulls the heat out of the chambers. This makes the inside of the fridge and whole refrigerator cold.

The cold ammonia gas is sucked up by the compressor, and the gas goes back through the exact same procedure over and over.

How Can the Heat Remain the Exact Same Inside?

A computer device called a thermocouple (it's basically a can sense if the temperature in the ice box is as cool as you would like it to be. When it reaches that temperature, the electricity is shut off by the device to the compressor.

Nevertheless the icebox is not completely closed. You will find places, like around the doors and where the pipes undergo, a little bit can be leaked by that.

Then when the cold from inside the refrigerator begins to flow out and the heat leaks in, the thermocouple turns the compressor back on to cool the refrigerator off again.

That is why you'll hear your ice box compressor engine coming on, working for a while and then turning it self off.

Today's refrigerators, but, have become energy efficient. Ones sold today use about one-tenth the total amount of energy of ones that were built 20 years ago. Therefore, if you have an old, old icebox, it's better to buy a new one because you'll spend less (and energy) over a lengthy time period.

To find out more go to:

Argone National Laboratory - Ask A Scientist ( Hand's 8th Grade Science Site (www.mansfieldct.org/schools/mms/staff/hand/heatrefrig.htm)

How Stuff Works - Fridge (www.howstuffworks.com/refrigerator.htm)

Science Treasure Trove - fridge site (www.education.eth.net/acads/treasure_trove/refrigerator.htm)