|
|
|
|
|||||
|
||||||
(no email)
Date: Mon Oct 25 2004 - 10:44:35 EDT
Gee Jeff,
You want the long or short version?
The long version goes into things like gas laws and fact that there is no
such thing as "cold".
The short version is, "How does it work?" Answer -"Good!"
I'll try to do a condensed long version and then let someone else fill in
the things I leave out.
The gas law says that when a gas expands and losses pressure it absorbs
heat. So what happens is that the refrigeration compressor puts a gas, Freon
or some of the newer stuff, under pressure and pushes it thru a tube into
what is called an evaporator. In the evaporator the gas expands and losses
pressure. In doing so it absorbs heat so the evaporator feels cold. (Cold is
the absence of heat.)
A fan or blower pushes air thru/over/around the evaporator thereby "cooling"
it and blowing the cooled air into the room, cabin, saloon, etc.
Presto! Air conditioning.
But the unit has to get rid of the heat it absorbed in the evaporator so the
gas goes from the evap to another component called a condenser. Here it is
put back under pressure and gives up the heat it absorbed in the evaporator.
In the condenser the heat is expelled either by another fan blowing more air
over it or in the case of most marine units, water being pumped around it to
take the heat away. IE. "cooling" the condenser.
Both the evaporator and the condenser are what are commonly called "heat
exchangers". There gas to gas (AC units), liquid to gas (auto radiators) and
liquid to liquid (most boat main engine) heat exchangers.
The above describes the unit in air conditioning mode.
When the air conditioner is in the heating mode the evaporator becomes the
condenser and the condenser, the evaporator. This is commonly called reverse
cycle and a lot of folks mistakenly believe that the compressor reverses its
direction of rotation. Not so.
What happens is that a valve changes the direction of the refrigerant flow.
The blower now pushes the cabin air passed the condenser which is warm
because it giving up heat as the refrigerant comes under pressure. The air
picks up the heat and warms the room.
Now over in the evaporator, which was the condenser in the air conditioning
mode, the refrigerant expands and absorbs heat. The heat it gets is either
coming from the air or water that is being circulated around it. In most
household units its from the air, in marine units its from the water.
Theoretically this would work as long as there was any heat for the
evaporator to pick up. Right on down to absolute zero which is somewhere
about - 459 degrees F. I believe. Practically with most of the units we use
it quits being of much help with heating at around 40 degrees F.
I hope this helps. I know that I've left some important stuff out (like most
refrigerants change from a liquid to a gas in the cycle) but maybe this is
enough to get you confused.
Bill
_______________________________________________
http://lists.samurai.com/mailman/listinfo/trawlers-and-trawlering
To Unsubscribe send email to
Include the word Unsubscribe (and nothing else) in the subject or body of the message.
|