Heat Pump Refrigeration Cycle (I)

Now it’s time to end this section by discussing the Heat Pump Refrigeration Cycle after we have talked about the thermal theory, the difference betweenthe sensible heat and latent heat and of course the pressure enthalpy chart.  

I know you have heard it before, that your air conditioner or heat pump uses exactly the same mechanical cycle that your small refrigerator at home uses or the walk-in cooler at the close by convenient store you buy your soda from, all of these equipment are just an applications for what we call it the “refrigeration cycle” or the “Vapor compression” cycle or the “Direct expansion Cycle (DX)”

Willis Haviland Carrier

A Little bit of history ….

On July 17, 1902, Willis Carrier  (the founder of the CARRIER Company) submitted drawings for what became recognized as the world's first modern air conditioning system. However he did not invent the heat pump refrigeration cycle  himself he invented one of its many applications.

In fact  it was  the work of so many people, before him  like William Cullen of Scotland (1756)  ,  Benjamin Franklin  (1758 ) (and yes he is The hundred-dollar bill Benjamin Franklin)   and  the 1st  (at least on paper) designer of Vapor compression refrigeration cycle   Oliver Evans  (1805)  and Alexander Twining  who successfully commercialized the Idea in (1856) , and so many others ( if you really want to read about the fulldetailed history of the refrigeration cycle  here is a great article in Wikipedia you can read .

If it wasn’t for those great men, we wouldn’t be enjoying that frozen ice-cream that we take it for granted now.

The main function of the Heat Pump Refrigeration cycle. 

The refrigeration cycle has only one function and one function only, it moves the heat from one place to another, against its natural order of heat transfer and that’s why we pay money (in a form of energy), we have learned from the thermodynamics laws in the thermal theory section, that heat moves naturally form the higher temperature object to the lower temperature object.

What if you want to do the opposite of that? which is to move the  heat from the lower temperature object (to make it even colder) to the higher temperature object?  That’s to be considered against the natural order of heat movement and that’s why you pay for that, and that is the main function of the Heat Pump Refrigeration cycle

How can we do this?

The 1st step that you need do is to isolate those 2 objects from each other completely as much as you can, how? Let’s say you want to cool your home (a relativity colder object) so you want to move the heat from your home to the outside (relativity hotter object). You must isolate your home from the outside (closing the windows, better insulation , etc…) the less contact your home has with the outside is the better, because if you allow the 2 objects to contact,  a natural order of heat transfer will take place and the heat will move from the outside to the inside of your home, making  it even hotter…and that’s the last thing you want to do.

Well Insulated House

So  you isolated it, then what , okay you must bring even a colder object ( a medium ) let’s say an ice-cube and you place it inside your home , from the  latent heat and sensible heat section we have learned that when the  ice melt it absorbs latent heat   and that’s what will exactly happen, the ice-cube  will melt and absorbs  heat from the surrounding ( your home in this case ) even so that heat  is latent to the ICE cube but it will be sensible  to your home  thus it will lower its temperature or cool your house down ..

Then  you need to take that melted ice-cube water by now -  to the outside and here you have, you moved heat from your home (a relativity colder object) to the outside (relativity hotter object) , using a medium and in this case it was  the ICE Cube  or water , of course you did some work you brought the ice, you  put it into  your house then you moved  it outside and that work cost money in sense of energy, mechanical Heat Pump Refrigeration Cycle  is exactly the same but in lot more efficient way…. 

Okay that's it for Part 1 please click on part 2 to finish this subject. 


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