‘London in Summer’ by ThisParticularGreg, licensed under CC BY 2.0
So how does you air conditioning system work to help through the hot times?
Many of us take our air conditioning for granted and indeed why should we worry all the while we are being kept cool in the summer and warm in the winter. It is an interesting subject and the principles also apply to your home refrigerator too.
The Basics
An air conditioning unit is in simple terms is a mechanism that shifts heat from one place to another. The unit will extract warm air from the environment in a home or office and shift it to the outside of the building. Strangely while you may stand close to a vent and feel as though you are being cooled, in fact it is the heat energy being removed that causes the temperature drop and not the other way round of cool air being pumped into the space.
Refrigeration
The central core of an air conditioning unit is the refrigeration cycle. This cycle is a sequence of changes to temperature, state (liquid to vapour) and pressure that the important refrigerant is going through as your air conditioning system works away extracting warm air from the atmosphere in the building. Refrigerant is a fluid that deviates between liquid and vapour at the right temperature for extracting hot air and pushing it through to the outside air. The refrigerant travels through copper pipes; one is insulated and one is not and it is these pipes that connect the indoor part of your air conditioning system to the outdoor part.
Most homes and offices use the common type of system – the split system, also known as an air source system as it removes heated air. It is known as a split system as there is an outdoor unit and an indoor unit. The refrigeration cycle is common to many kinds of air conditioning system.
There are 4 different stages to the refrigeration cycle from start to finish and it can be clearly seen how essential it is to have a well maintained system.
Heat Extraction
The interior part of the air conditioning system contains a blower that extracts air from the building and pushes it over an extremely cold coil. The coil is so cold because of the refrigerant running through it, so the air moving over the coil also becomes very cold. After the air has passed over the cold coil, the air temperature will drop markedly. If the room thermostat is set to 24 C, the air will be around 12 C if the system is working optimally.
The simple physics are that heat flows from warmer to cooler, we all know heat rises in a home and a similar principle applies. Once the warm but cooled air reaches the outdoor unit, it flows into the compressor which raises the temperature of the refrigerant so that it will flow out into the atmosphere. Unless the temperature was raised, the air would not be expelled from the air conditioning unit as cooler air will not flow into warmer air.
Obviously, if outdoor temperatures are exceedingly hot, the compressor has to work even harder to raise the temperature of the air until it exceeds the outside temperature. You will often hear air conditioning unit’s compressors working overtime in extreme conditions, the same way you can hear the compressor on your domestic refrigerator working, especially in hot weather.
There is another step in raising the temperature of the air to be expelled after the compressor has done its job. The air passes over another coil, this time increasing the temperature further and finally expelling the air that was originally extracted from the building.
Once the heat flows out of the refrigerant it condenses back to liquid and rapidly drops down to a low temperature again and the process repeats itself.
This is just a simple explanation of how an air conditioning unit and system works. It applies the laws of simple physics and as can be seen from the process, it is essential to keep the air conditioning system well maintained so that it can perform the job it is designed for in an optimum way.
Make sure you get the sun cream out and be sure to carry water with you this week as the heat wave arrives in London!
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