Natural circulation loop design: heat exchanger

[NaturalSolar]

I am trying to design, or at least do a preliminary model, for a natural circulation loop. I will need two heat exchangers, both of which have a few criteria in my plan. But I am largely not able to just go to the local heat exchanger store and select one which will probably suffice for my preliminary investigation.

So what I am looking for is (1) a solar collector heat exchanger, which will input a certain amount of heat into the working fluid. It needs to be in the range of 5 to 25 kW. The delta-T will be around 2 to 10 C, for a working fluid around 40 C. Input and output piping will be from 2 to 6 inch ID. Assume water as the working fluid, although this has not been chosen and glycol is quite common for this. Flow rates will be from 10 to 80 gpm. (0.5 to 5 lps) Low Re number.

The matching heat exchanger (2) will need to be able to cool the working fluid by a lower amount, probably 30% of the kW rating of the first heat exchanger. It will be cooled by forced ambient air. Its delta-T and flowrate will be the same as above.

Because of the criterion of the entire system to be operating in natural circulation (no pump), there needs to be a careful selection of low friction parts, so the K and f factors will both be significant. My software (AFT) is willing to accept these values, but I don't know where to obtain such info on a standard heat exchanger.

So if someone knows of such heat exchangers, how to obtain a list of such things, perhaps even the pricing for such things, I would be grateful. I checked eBay and Wal-Mart (Just kidding).

 

[pmover]

i will presume you are referring to residential or light industry grade application. try TACO or Bell and Gossett. simply provide them the process conditions (temps, visc, pressures, fluid, etc.) for both streams and they will be able to provide you the info you request.

good luck!
-pmover