Cooling

1. Chapter 1
I will start this air conditioning basics tutorial on a very simple and non-technical level with layman’s terms, and then discuss
technical details later to avoid intimidating or confusing you.
Snowy Air Conditioner Condensing Unit. Image obtained with thanks from siette on Flickr:
http://www.flickr.com/photos/siette/
Table of Contents
1. Understanding Cooling
2. Basics of Typical Residential Air Conditioner Operation
3. – Condensed Explanation
4. – Full Explanation
5. Basics of Air Conditioner Parts and the Purpose they Serve (little technical detail) (I will provide pictures of all my parts)
Diagnostics and Repair (coming soon).
Understanding Cooling
First, you must understand what cooling actually is and how it’s done. Cooling is the removal of heat from a substance.
There are many different cooling methods, but most of them are based on the same principle, which is expansion.
Alcohol feels cool in your hand because it is evaporating. Evaporation is when the particles of alcohol move further away
from each other (this is called expansion) until they turn into a gas (vapour). This is not to be confused with the fact that
cooling a substance with a refrigerator, for example actually does the opposite, which causes particles to move closer to
each other.
If you don’t understand particles, then all substances and objects are made of millions of tiny particles that you cannot see
which appear to be one large solid object to you.
As the alcohol gradually turns into a gas, it absorbs heat from your hand. Cold is simply a lack of heat, cold is not
“produced”.
All substances contain at least a little heat, even if they are cold. They only feel cold to you because they are colder than
your hands. Ice feels cold in your hand because it is absorbing heat from it. A physics rule is that heat moves to cooler
places. If you put your finger which is 98 °F on a light post hich is 8 °F cooler than your hand, then some heat from your
hand will automatically move into the light post. This tip will be helpful later in the tutorial.
Basics of Typical Air Conditioner Operation
You probably realized by now that A/C cools air by removing heat from it. This is why air conditioners are sometimes
referred to as heat pumps. Their evaporators (indoor unit) remove heat from the air, and that heat is then transferred to the
condensing unit outside. A picture of a condensing unit is at the very top of this page.

2. Condensed
An air conditioner contains many parts, but I will discuss the three parts that actually remove heat from the air, and the fans:
They are the evaporator, compressor, and condensing unit. Please visualize only those three parts until I start discussing
the others, for the sake of simplicity.
Step 1: The compressor continually forces more and more of the refrigerant in gas form into the condenser, and as it does
that, the particles of the gas are forced to move closer and closer to each other until it condenses into a liquid. During the
compression process, heat is radiated from the refrigerant by the condenser coil and the fins attached to it which make it
easier for the air to absorb heat from the refrigerant, also helping to condense the refrigerant because cooler gases
condense more easily.
The condenser fan accelerates the cooling process by blowing cool (room temperature) air over the condenser, because
cooler air is capable of absorbing more heat than hot air. As the particles of the refrigerant gas move closer and closer to
each other, that causes the refrigerant to release heat.
Step 2: After being condensed in the condenser, the compressor still forces refrigerant into it continuously and that forces it
out of the condenser through what is called the capillary tube (not all designs are like this). The capillary tube is a very
narrow tube which leads into the evaporator and restricts the flow of refrigerant. As refrigerant enters the evaporator, which
is under low pressure (refrigerant evaporates faster in low pressure areas) due to the fact that the compressor is sucking
from it, the refrigerant evaporates in it very quickly, and that evaporation process causes the refrigerant to absorb heat. The
faster it evaporates, the colder it becomes.
The cold refrigerant gas then absorbs heat from the evaporator coils (because the gas is cold) and it enters the compressor
afterwards, still cold, and absorbs heat from the compressor, cooling it and extending its life. The evaporator or blower fan
draws air from the room and blows it over the coil evaporator, which cools it, and then step 1 is repeated.
Full Explanation
The compressor continually forces refrigerant through a continuous loop called the vapour compression cycle.
Coloured Diagram of the Vapour Compression Cycle.