Sunday, July 13, 2008

Principles of basic Refrigeration

In this post I will not be explaining on how to fix anything or go into any Handyman how to’s, but just very briefly go over the principles and laws of refrigeration. Learning these laws of refrigeration will not repair a refrigerator or air conditioner but understanding the basic principles of refrigeration will be a great assistant if you want to take HVAC type jobs seriously. The basic information I am going to give you could fill many books on many shelves but I am not here to get technical. Just simply the basics.

First Law: Cold

The word “cold” is used in everyday discussion, you here it on the radio, you here it when the news is on, and when it starts snowing or whenever people will be like “damn its cold”! But in scientific law “cold” does not exist until the temperature is - 460 degrees Fahrenheit, or also know as absolute zero. So when we say it is “cold” out today it really isn’t true, it just means there is less heat then the Sahara. I am not in any way supporting that everyone should stop using the word “cold” unless its absolute zero or below, that would be bonkers. I use the term cold everyday and so will everyone as long as we exist. Since I am talking about refrigeration this is why we must understand this and the term “cold”. Scientist’s in labs have tried to achieve “cold” or absolute zero but have not gotten there yet. Scientists can get close but not quite there. Basically absolute zero or “cold” is when there is no energy left and molecules cease to move.

Most people think that because their refrigerator is blowing “cool” air that it is doing just that. It’s not, the refrigerator is just simply taking the heat that is inside and getting rid of it outside. The refrigerator is highly insulated to keep heat from coming back in but the heat will get back in eventually, I will explain this more in law no. 2. But that is all that’s going on. The refrigerator will pull heat out of the inside of the box and everything in it until the desired temperature is reached then the motor will stop. Heat will slowly travel back into the refrigerator until it rises a little bit in temperature then the process of heat removal will begin again, it will continue over and over. So in one simple sentence you can describe the first law. Refrigeration means to remove heat. Now let us go to the next one.

Law Two: Heat

Heat will always flow towards something that has less heat. This is very similar to the law of gravity. Similar to how a boulder will roll down a hill. Heat will travel to where there is less heat. Although enough force and energy could stop a boulder from rolling down hill, nothing will stop heat from moving to where there is less heat. But we can slow down this process on refrigerators with insulation, just so the compressor can keep up with the heat trying to get back inside the refrigerator. We can slow this process down in our home by having insulation put into the walls, or tint on all the windows, or even trees that are shading the house.
Think about it, if we get the freezer box down to 12 degrees Fahrenheit, then we shut it off, eventually the heat will get through the insulation and equal out the temperature outside even if it takes five years ! Heat does not care it will reach its destination no matter how long it takes.

Another example is if we heated a steel beam up to 150 degrees then placed another steel beam that was 70 degrees next to it eventually the two would equal out. The steel beam with the lesser amount of heat would be getting heat from the hotter beam until they equal in temperature. It’s a common law of refrigeration that we don’t think about every day. So remember that heat will always travel to where there is less heat.

Third Law: Heat in Vapor

This law will explain where the refrigerants come into play in the refrigeration cycle. Any liquid that is capable of turning into gas or steam will give off its heat in the steam. For instance if we have to buckets of water that are sitting out in the sun, one of the buckets has a lid on it the other bucket doesn’t. The water in the bucket that doesn’t have a lid on it is going to be much cooler then the bucket of water that has a lid on it. Why is this? As I just said the lidless bucket of water will start evaporating into steam and the heat will be pulled out of the water with the steam. The same thing would happen if we used gas instead of water, but gasoline boils at a much lower temperature the water does. Basically any liquid that can turn to vapor and back into liquid is known as a refrigerant.

Every single refrigerator and air conditioner in our modern world use these three principles to keep things cool. But we aren’t going to use water as a refrigerant because it has such a high boiling point. That’s why we use gases such as FREON. The R-22 FREON boils at 40 degrees below zero, making it a great choice as a refrigerant to get rid of heat.

That’s all for today I really hope that you learned a little bit and understand a little better on what the refrigeration cycle is doing when its removing heat. Next topic I will get into will be the basic refrigeration cycle. Until next time, Tampa Bay Handyman.

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