In childhood, I used to think that the only way to get ice was through hailstones. Whenever I used to eat ice cream, the only thing that would come to my mind is that someone might have collected hailstones to make this ice cream. When I saw the Refrigerator for the first time, I was in real confusion because I used to think about who placed the ice in the Refrigerator. However, when I started getting older, I realized how the Refrigerator works, and with time, the thrill of childhood imagination faded away.
If you have ever gotten puzzled in your childhood about how refrigerator work, and wants to understand how a refrigerator works and also learn about its working principles, stay put with this post. We are going to talk about the basic principles step by step.
Components of Refrigerator
Before we start learning about how a refrigerator works, you should know about its basic principles. You might say that a refrigerator works by taking heat from the inside of the box and getting rid of it on the outside. Well, that’s not correct.
Refrigeration is the transfer of heat from a place where it is not wanted to a place where it is unobjectionable. To do this, a refrigerator uses a unit inside the box(evaporator) that takes up the heat at a unit outside the box(condenser) that gets rid of it.
Evaporator and the Condenser are tied together by connecting lines referred to as the suction line and the liquid line. There are few more components in the system called compressor(which is a pump), the expansion valve, and the receiver(a kind of storage tank).
A chemical substance called refrigerant flows through the system. It’s a refrigerant that picks up BTUs of heat from inside the box(Evaporator) and discards them outside. In the process, the refrigerant changes from a liquid to gas, then in the condenser, it changes back to a liquid. At the same time, the pressure increases in the compressor and decreases in the expansion valve.
Basic Principles of How a Refrigerator Works?
Before you understand how the system works, you must learn why and how these changes occur. That means learning some basic principles concerning heat.
To begin with, take a swimming pool and Kathy, who was swimming in the cold water after she has dried off she finds the air warm, but Helen has just come from the steam room, and she thinks the air is cold.
The terms hot and cold are relative; they are used to compare one thing to another. As the girls gossip, Kathy gets warmer as the heat from the air passes to her body and warms her; however, Helen gets more relaxed as heat passes from her body to the atmosphere.
Heat always passes from a warmer substance to a cooler one. For example, if you put an ice cube into the water, it is cold, but the ice is even colder.
By comparison, the water is warm so that heat will flow from the water to the ice, and this changes the ice from solid to water. If you heat the water, it turns into vapor, and this vapor is a gas. These three solid, liquid, and gas are called the three states of matter, and all matter around us exists in one of these three states.
Now let’s see what happens to the temperature; if you apply heat to the ice, the thermometer reads 32 degrees Fahrenheit and the ice changes to water; the temperature stays constant at 32 degrees.
The heat is causing the state’s change from solid to liquid; then, as you continue to heat the water, the temperature increases until it reaches 212 degrees. The water starts to boil; the temperature remains at 212 degrees. The heat from the flame is now being used not for a change of temperature but the change of state.
Remember, heat is taken in for the change from solid to liquid, then the heat is taken in for the change from liquid to gas. Now a change of state is always accompanied by a gain or loss of heat. It is critical that any substance takes in heat when it boils or changes from a liquid to a gas and that any substance gives off heat when it condenses or changes from a gas to a liquid.
Suppose we have a container filled with gas, and we add a thermometer to measure the temperature of the gas and a pressure gauge to measure its pressure. if you push in on the piston, the pressure increases, and the temperature increases.
Now let the piston out, the pressure goes down, and the temperature goes down. The rule is when a gas is compressed, the pressure goes up, and the temperature goes up when a gas is allowed to expand, the pressure goes down, and the temperature goes down. It’s true for any gas.
How a refrigerator work?
We’ll begin at the receiver where the excess refrigerant is stored. It is in a liquid state, and under high pressure, the high pressure forces the refrigerant through the liquid line to the expansion valve. This valve causes pressure to drop, and the high-pressure liquid becomes a low-pressure liquid.
It is like letting air slowly out of a balloon. The air in the balloon is still under high pressure, but the air that gets through expands and pressure drops. In the same way, a refrigerant that passes through the expansion valve expands, and it’s pressure drops. The low-pressure refrigerant flows into the evaporator.
Now, if any of the food in the box is warmer than the refrigerant heat will flow from the food to the evaporator, so in the evaporator, the refrigerant takes in heat and begins to boil. Remember, any substance takes in heat when it changes from a liquid to a gas, and the gas is sucked through the connecting line into the compressor as the piston moves down.
The suction valve opens, and the gas is sucked into the compressor as the distance starts again; the suction valve is forced shut, and the discharge valve is pushed open. At this stroke, the gas is compressed. Remember what happens when the gas is compressed, the pressure goes up, and the temperature goes up.
The gas is now at high pressure, and high temperature flows into the condenser. The gas is hot hotter than the surrounding air, so it gives up heat to the air as the refrigerant loses heat it starts changing back into a liquid. The liquid refrigerant returns to the receiver to complete the above cycle.
Review of Refrigeration Process
Now let’s review the whole thing: How a refrigerator works?
- Receiver to Expansion Valve: Refrigerant under high pressure flows from the receiver to the expansion valve.
- Valve to Evaporator: The valve causes a pressure drop, and the evaporator takes in heat from the box.
- Evaporator to Refrigerant: If anything in the box is hotter than the refrigerant, it gives up its heat to the refrigerant as the refrigerant takes in heat, it changes from a liquid to a gas. Remember, any substance must take in the weather to change from a liquid to a gas.
- Refrigerant to Compressor: The compressor sucks the vapor out of the evaporator and compresses it. It increases the pressure and temperature.
- Compressor to Condensor: The vapor is now hotter than the surrounding air, so in the condenser, heat has been given to the atmosphere.
- Condensor to Receiver: As the refrigerant loses its heat, it changes from a gas to liquid and flows into the receiver.
Final Verdict of How a Refrigerator works
Now let’s consider some additional points that many refrigeration students have trouble understanding.
In the evaporator, the temperature may be shallow, perhaps 21 degrees below zero, and yet the refrigerant is boiling. How can anything boil at such low-temperature water boil at 212 degrees, but other substances boil at different temperatures, some higher than water, some lower.
The refrigerant known as r12 boils at minus 21 degrees, and there’s no mystery about it. It is merely a property of the substance. The refrigerant in the suction line is carrying all the heat it picked up in the box, but its temperature is only about five degrees above zero. If you touch the line it feels cold, how can something cold be carrying a lot of heat?
Remember that hot and cold are relative terms you know when water boils, but refrigerant boils at a much lower temperature. So all the coolant can take on heat change to a gas and still seem cold. Again the reason is that the two substances have different boiling points.
Also See: How refrigeration Works?
You’ve seen the basic principles of refrigeration. I suggest you study the system until you understand it thoroughly memorizing isn’t enough. You must understand what happens and why? The rest of your work will be based on these same principles of how a refrigerator works.