My work environment has been a bit noisy lately. The school is having the roof renovated. The building’s air-conditioning units have been disconnected during the time of this refurbishment.
It being summer, there’s a need to open windows and to bring in industrial air-conditioning units to maintain a workable atmosphere within the building. At the beginning of this week, contractors wheeled two of these units into the space close to my office area, plugged them into the mains and switched them on.
Other units were similarly introduced at points throughout the building. The Science teachers who worked in the areas, including myself, viewed this activity with amusement. It was evident that the contractors knew nothing about thermodynamics.
The heat exchange part of an air-conditioning unit operates in a way similar to a refrigerator. In normal use, the unit sucks warm air from the room through a cooling unit and filter. Fresh air from outside the building is drawn in through windows and other openings to replace the heated air expelled during the process.
The resulting chilled air is blown back into the room while the removed heat is air-pumped to the exterior, usually through a duct in a window.
In the case of the units that we observed, there was no such venting. Instead, the hot air from the action of the cooling unit was being pumped back into the room. It was as if a fridge had been turned on and its door had been left wide open. In such a circumstance, the fridge does nothing more than make a noise and heat the room.
The overall effect of the air-conditioning units being used in this way was not unlike that of using large blow heaters. In no time, people started to complain about the rising temperature.
A little learning
Science is a wonderful thing. Its principles are being utilised in just about every piece of technology that contributes to our lives today. Of course, an understanding of scientific principles isn’t always necessary to use or install the equipment that puts these principles into effect.
There are at least three levels of understanding that can allow one to realise the significance of a scientific idea, such as the thermodynamic principles that were put to use in the construction of the air-conditioning units:
- It works provided certain conditions are met according to a recipe for installation. For the air-conditioning unit to be effective, it has to be functioning and have its required vents clear, one of which has to be ducted to the exterior.
- It works as it follows the thermodynamic idea that heat can be pumped by using a small amount of energy that is eventually released as heat (which is why the fridge with its door open does nothing more than heat up the room).
- It works, and its function can be explained by thermodynamic principles:
a) energy can neither be created nor destroyed,
b) heat energy is released when a gas is compressed so that it condenses to a liquid and this same heat is taken in when the liquid is allowed to evaporate – this is what happens in the heat exchange unit of a fridge,
c) some energy will always be wasted when heat energy is pumped using mechanical means – entropy is always increased as a consequence.
Understanding at level 3 can be achieved by senior secondary school Physics students.
Level 2 can be understood by able students of Junior Science.
Working recipes that define the factors that are important in level 1 need only be followed when it comes to the correct and appropriate installation of a piece of technology in general circumstances.
The example that I unpack here shows how related learning can apply at various levels to the curriculum. What is significant is that the most elementary levels of learning are still important to the correct use of technologies that involve sophisticated principles in their design and construction.
As it happens, the contractors were notified by Science teachers about the correct use of the air-conditioning units which were immediately switched off. Appropriate locations near windows were then found. Necessary ducts to the outside of the building were fitted correctly to the machines within 24 hours.
Through all this, the cicadas continued their sibilant summer chorus.