Little help with college work (refrigeration)

[Spazatao]

The title kind of speaks for itself, but I'd appreciate any links and tips you might have about refrigeration of ambients. Air condicioned systems, heat exchangers, etc. I already have a very good idea of what to do but I want more sources and information apart from wikipedia and the most obvious google results... BTW, I'm in a mechanical engineering graduation. Thanks!

[Magnet]

I don't have any links, but I have a lot of books on the subject. What is it you need exactly?

[cvrefugee]

They keep stuff cold?

[Blind_Io]

http://home.howstuffworks.com/refrigerator3.htm

This might be a place to start.

[Topher]

This might not help, but I made a pdf from a word document that i typed out some notes from. Mostly to do with heat exchanger. There is the name of the book and stuff it comes from in the document, it doesn't look as great as i was hoping it would but anyway.

http://www.doc2pdf.net/temp/heat_exchanger.pdf

[chaos386]

I'd suggest going to your university library and looking for thermodynamics textbooks. I'll also second what Magnet said and ask what are you looking for specifically? My chemical engineering studies also cover refrigeration and heat exchangers, but they might be handled a little differently than they would be by a mechanical engineering curriculum, so if you just ask for any info about refrigeration, you might not get what you want.

[Spazatao]

@Blind_Io: really nice! I used to have "how stuff works" books, but never thought they'd have such a good website!
@Topher: Thanks! That'll be good for a specific part of the work.
@chaos386: I've been there, and the books are right here on my desk.

Sure, I wasn't that clear when I first posted, but, here it goes:
It's a small written work (10-15 pages) about ambient refrigeration systems. Large ones. The ones you'd find in a shopping mall, supermarket, big buildings... Home refrigeration is not included. I need to tell how they work (through pure electricity, gas powered turbines, other forms), how they distribute the cold itself (I've read about very cold water being pumped on a series of pipes, that when in contact with air, would cool it) and all the technical aspects that might be relevant... As I've said, it shoudn't be something big, because on those 10 to 15 pages I still have to include environmental concerns (CFC ozone problem, for example) and a small bibliography....
Many many thanks!

[Blind_Io]

Well, if you want to get technical they don't "distribute the cold." Cold is a lack of thermal energy, refrigeration works by forcing the heat to another location, hence the terms "heat exchanger" and the sometimes-used "heat-pump." Now, I have not read through how it all works, but the physics is pretty common. Energy travels from areas of high-heat to areas of low-heat. You create a coil or heat-sink that contains a fluid that has less heat energy than the ambient air temperature. Force the air over the heat-sink, as it passes the heat moves from the air to the coil and into the liquid which is taken away to be re-cooled.

Just don't phrase it as moving the cold. You are always moving heat.

Good luck on your paper.

[chaos386]

Originally Posted by Blind_Io

Well, if you want to get technical they don't "distribute the cold." Cold is a lack of thermal energy, refrigeration works by forcing the heat to another location, hence the terms "heat exchanger" and the sometimes-used "heat-pump." Now, I have not read through how it all works, but the physics is pretty common. Energy travels from areas of high-heat to areas of low-heat. You create a coil or heat-sink that contains a fluid that has less heat energy than the ambient air temperature. Force the air over the heat-sink, as it passes the heat moves from the air to the coil and into the liquid which is taken away to be re-cooled.

Just don't phrase it as moving the cold. You are always moving heat.

Good luck on your paper.

It should be mentioned that heat exchangers, heat pumps, and refrigerators are different things.

A heat exchanger is just a device to efficiently transfer heat from a high-temperature to a low temperature. A car radiator is a good example.

A refrigerator is a device to extract heat from a cold location and eject it in a hot location. This is usually done by compressing a gas (which raises its temperature above ambient. This is usually done by an electric motor), condensing it (by cooling, usually in air), expanding it (which lowers its temperature below ambient), and then compressing it again. A refrigerator will use heat exchangers at both the compression and expansion stages. By the way, this type of refrigeration is called the "vapor-compression refrigeration cycle". There's also another type called "absorption refrigeration", which can directly use heat to run the cycle.

A heat pump works similarly to a refrigerator, but the cycle can be run in reverse, which swaps the hot and cold sides, turning it into a heater. When it's used as a heater, it's basically a reversed heat engine.

[Blind_Io]

Cool, I never knew that.

[Spazatao]

@chaos386: That was awesome! The tip you gave me about absorption refrigeration probably saved my life!
Thanks a lot to everybody. I'll post here my grades and what my professor will say. It's a shame no one understands portuguese, 'cause I'd like to share it with you guys....