First off you can't make cold. Cold is the absence of heat, so if you are hot you want to take some of that heat away. The term heat pump is generally used for an air conditioner that can also be used to heat your home, but basically any type of refrigeration is a heat pump. What we are doing with refrigeration (this includes air conditioning) is removing heat from a location where we don't want it to an unobjectionable location.
How is this accomplished? Well that is where the refrigeration cycle come in. The first step is compression of the refrigerant vapour. Once the compressed vapour leaves the compressor it enters the condenser. The condenser is a coil of copper tubing that is finned that acts as a heat sink, a fan helps pull air through it. As the refrigerant vapour cools is condenses into a liquid the pressure remains the same. One thing you may not know is that this change in state actually requires lots of energy, much more than a simple change in temperature. This liquid now goes through a metering device for this discussion we will only cover the fixed orifice. This is basically a restriction in the system, this is where the refrigerant enters the evaporator pretty much the same thing ans the condenser, at this point the pressure drops. This pressure drop changes the boiling point of the refrigerant, just like if you are high in a mountain water boils at a much lower temperature. As mentioned earlier changing state requires lots of energy. This is where the magic happens. As the refrigerant boils it requires this energy where does it get it? From the hot air in the conditioned space, as this hot air gives up some of it's energy it cools down. Now the refrigerant is a vapour again and returns to the compressor, to start the cycle again. The energy it picked up inside ready to be released outside through the condenser.
If you noticed something I have yet to mention Freon, well Freon is actually Dupont's brand name for their line of refrigerants. The name is no longer used because of the bad press because of the ozone depleting characteristics of some refrigerants, they now call it Puron. Refrigerant comes in many types for different applications, Your home AC likely has R22, older cars and refrigerators had R12(the first refrigerant to be banned) newer fridges and cars use R134A.
Contrary to popular belief refrigerant does not need to be topped up regularly, yes it can leak out but if there is a leak it should be repaired before adding more refrigerant. One of the most important and easy maintenance requirements for any refrigeration system is to keep both the condenser and evaporator clean, the condenser (the part outside) by hosing it off with water, be sure not to bend the fins over, and the evaporator by regularly replacing the filter.
The secret Life of Machines did a great episode on the refrigerator check it out http://www.techno-fandom.org/slom.shtml actually all their shows are great.
Feel free to ask questions I will do my best to answer them.
3 comments:
Good post Jabz! Good for people to get a reminder that nothing "creates" cold. Some simple science that we should all know, even if too few of us remember it.
Freon is Dupont trade name for it refrigerants and Puron is carrier trade name for it refrigerants.
Puron is actually R-410a.
Dupont and Carrier are to different company.
I bet you...
My mistake, I thought all Dupont refrigerants were now under the Puron name.
Yeas Carrier and Dupont are two different companies, although I am sure they worked together to make R410 the new standard.
Bruce welcome to my blog, mind if I ask how you found it?
Post a Comment