Principles

To have a crystal clear understanding on how the process of removing heat is being perfected, we need to know all the underlying principles of refrigeration. As defined, refrigeration is the process of removing heat by absorption and extraction. This produces cooling effect on the place where heat is being taken away. To complete that process, it involves some principles or natural laws to be able to handle heat and make it move into the place where it is not wanted.

If we look at it more deeply, refrigeration deals more on handling heat and its effect rather than producing low temperatures. The latter is just the end product when heat is properly handled and controlled.  This means that, to better understand principles of refrigeration and air conditioning, it is required to have a deeper understanding on things related to heat and its effect on matters in a molecular level.

Heat and its Effect on Liquid Substance

Heat is something that is present in all substances. It is considered to be the internal energy that affects the molecular composition and atomic activity of any given matter. The amount of heat that is present in any matter identifies its atomic behavior. If altered, it may cause chemical changes or change of state.

The best way to understand the effect of heat in a substance is to pay attention to our naturally available liquid matter, called water. Water is in liquid state by default at the temperature where most of the living organisms may exist under tolerable or extreme temperature condition. Beyond this point, water changes phase that could be observable with our bare eyes.

The above image shows the molecular activity of  liquid substance with the presence of heat on it and the changes of molecular motion when  heat is being removed.  This is what happens on water when  heated  and when refrigerated.

By chemical composition, water is composed of 2 atoms of hydrogen and 1 atom of oxygen (H2O). These gaseous elements bind together and take a form of liquid at a certain atmospheric condition, which involves the temperature and pressure. At 14.7 psi, which is the normal pressure of air above sea level, water stays liquid at temperature above O⁰ C and below 100 ⁰ C.

This bonding between 2 hydrogen atoms and 1 oxygen atom that makes water as it is, which appears to be a liquid substance in our real life, is heavily dependent on the amount of heat within that atmospheric temperature and pressure condition.  The absence of heat will make the water solidify when temperature decreases to O⁰ C and below. When more heat is added, that molecular bonding may be broken.

It means, the absence of heat tightens the bonding of hydrogen and oxygen atoms. This reaches to the point that it loses its internal energy (thermal energy) and no longer moves (freezing point). This time, water turns into solid substance also known as ice.

If heat is added on ice, or just simply exposing it to open air, the atmospheric heat penetrates into the body of ice. This causes the ice to  melt and return to its original state, which is liquid  at temperature above freezing point.  If more amount of heat is added on the body of water at its normal state, it will evaporate and turn into gas. This is when the temperature reaches 100 ⁰ C (boiling point) at the same pressure condition.

When water turns into vapor, the amount of heat breaks the bonding that holds the hydrogen and oxygen atom together. Since hydrogen and oxygen are originally gaseous elements, it will become invisible and mix with other gasses in the air.

This is the reason why water will disappear when left boiling within certain amount of time. If we pay attention closely, the reason why water turns to ice, return to liquid and changes to vapor, is just due to the presence or absence of heat. To understand this better, it is also required to read know the 2 kinds of heat.

Naturally, this is how heat affects all matters but it may vary to some degree how and when chemical changes occur on some substance. For solids, the amount of heat required to change the chemical composition is quite high. It means the tighter the atomic bonding, the higher the amount of heat required.

 

Refrigeration and Natural Water Cycle

In the study of refrigeration fundamental principles, the natural phenomenon that occurs on water (water cycle) in our ecosystem is an interesting fact that must be understood for deeper understanding how refrigeration process works. This is because what happens to water during this process is very much similar to what occurred on the refrigerant inside any refrigerating  or air conditioning system.

As we all know, the body of water occupies larger portion in our planet.  As heat from the sun hits through the body of water, water evaporates and turns into vapor that makes some earth’s surface dry or decrease on water level on some springs, rivers and lakes. This process is called evaporation of water that occurred naturally.

At this point, more hydrogen and oxygen atoms are collected in the atmosphere, mixed with other gasses. Due to the amount of heat that is present in the atmosphere, hydrogen and oxygen atoms still have no way to bind together during the initial period.

But when the amount of heat in the atmosphere decreases, to the point where it can no longer separate the hydrogen and oxygen atoms, water vapor will return into its original state again and fall to the ground as liquid substance known as rain. This process is called condensation of water vapor. Or due to the absence of heat that holds the vapor body in the atmosphere, vapor will turn into liquid as hydrogen and oxygen combines again.

The reason why heat maybe altered in the atmosphere is also due to natural processes. It occurs when dark clouds blocks the sun rays that gives heat to the water vapor in the atmosphere. Heat transfer may also occur in the atmosphere when there is a new air coming with less heat content.

When heat that holds water vapor in the atmosphere is altered (reduced)  the 2 hydrogen atoms capture 1 oxygen atom and form water in the air. Since liquid has its own density and mass, by gravitational force, it should fall into the ground.

In refrigeration and air conditioning, the fact that water behaves differently at varying amount of heat is very much alike with refrigerant in the system.  The condensation and evaporation process that occurs on water in our ecosystem are the basic idea that heat can be absorbed, transferred and can be rejected somewhere else.

The water cycle in our ecosystem opens the door to the theory that when liquid substance evaporates, it holds some amount of heat. And when rain falls (condensation), the heat that holds the vapor body in the atmosphere is gone or released. This is one of the fundamental theories that lead to the creation of mechanical refrigeration system.
 
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