heat exchanger

[epion2985]

I was wondering what would work better for the "heat exchange" -evap in a chiller. Coiled up tubing or a condenser. Form a physics point of view the condenser would only be better if the fins had a better heat transfer coeficient then the water, provided the element between the fins and the condenser piping is not a thermal bottle nek. Then the fins would work as effective heat spredders and dispersers, like the fins on a heat sink. I guess the question is now one, what are fins normaly made form on ac condensers (aluminum?) and two, does that material as well as the braze/weld material used to attach the pipe to the fins conducts heat better then water?

[epion2985]

:stick:

[RussC]

I don't know the answer to this, I bet alot of others dont either.

RussC

[ilkkahy]

If you want as effective hx as possible then youll propably need to get plate type heat exchanger like this: http://www.apiheattransfer.com/en/Products/HeatExchangers/PlateHeatExchanger/BrazedPHE.htm
Bad thing is that those are pretty expensive. If you are going to build hx yourself then coaxial type (smaller pipe inside bigger pipe) is propably most efficient compared to work and materials. Simple pipe coil under liquid will have warm spots where there isnt proper flow so the coaxial type will get the used copper surface area work more efficiently.

Same goes to using condenser as evaporator (if i understood the question right). Also if you put some big condenser under liquid the result will take a lot of space which means much bigger thermal loss and unnecessary load to compressor.

[epion2985]

thanks, that helped alot. :)

[Holst]

Can anybody explain HOW one of those plate type exchangers works internally.

[epion2985]

I think the site linked is pretty self explanatory

look at the half section picture. Its borderline honeycomb constructon :)

[wdrzal]

The fins are usually aluminium but they do make copper finned condensors. the fins are tightly press fit on the tube, the tube itself is also thinner than the standerd M thickness. The thinner tube allows for faster transfer.

[epion2985]

I wonder how much those cost...

[RussC]

Where do we get thinner walled copper? I looked at McMaster Carr, the thinest was ~ the same as everything else. :confused:

RussC

[jinu117]

Maybe look at those finned tubing instead of plain tubing. They basically have finned inside and outside to increase surface area dramatically. Lemme see if I can dig out some links... it's rather new development in heat exchanger AFAIK.