Radiator water flow question.

Don_196

Radiator water flow question.


Please advise me as to the most efficient way to plumb the flow of the water flow through cast iron radiators in a pump circulating system.


I assume, to help avoid air being captured in the top of the radiator, that the most trouble free water flow, would be to plumb the hot water in at the bottom and out the top at the opposite end (assuming that the flow rate in the return down pipe from the top of the radiator is over two feet per second, in order to entrain any air embolism that maybe present).


But, to maximize the output of the radiator (due to the relatively low water temperature available), I am planning to plumb the hot water into the top of the radiator, and out the bottom at the opposite end: My thinking is, due to the higher buoyancy, the hottest water would remain in the top of the radiator, and as the water cools, it would migrate to the bottom of the radiator would be returned to the boiler. (If one were to plumb them in this way, I am assuming that it may be prudent to install an automatic float type air vent on each radiator (?))


===> Please advise me if plumbing the water flow in this "in-the-top/out-the-bottom" manner has been demonstrated to be extremely troublesome; and also, if the efficiency gains are so marginal that it is not even worth considering <===


And second: (Again, to maximize the output of the radiator) I plan to have the flow velocity as high as possible to minimize the temperature drop ("Delta T"), and to also reduce the recovery time. (My target velocity is just below the noise producing velocity of 4 ft/sec in the 3/4'' supply and return piping)


This leads me to another question: I have read (Dan H.), that when retrofitting gravity systems to a pumped circulating system (wherein both the supply and return water are plumbed in and out of the bottom of the radiator) you can have too high a water velocity through the radiator; thereby not giving the hot water enough time to migrate up to the top of the radiator: i.e. the bottom is hot, but the top is cold.


===> Please advise me if there any possible problems related to high flow velocity; when plumbed in either of the above two ways (i.e. "in-the-bottom /out-the-top" --- or --- "in-the-top/out-the-bottom"). <===



==> "The fool wonders, but the wise man asks." (~ Benjamin Disraeli)


I shall thank you in advance for you expert advice.


Don~

Mark Biro

Don, you may want to see on this site:

http://www.heatinghelp.com/newsletter.cfm?Id=148

and the discussion:

http://forums.invision.net/Thread.cfm?CFApp=2&Thread_ID=49753&mc=10

In general: bottom-to-bottom, though you can also go top-to-bottom (from one end to the other), and our neighbor even proves that you can live with connections at SAME end, in at the top, and out at bottom -- I guess things work out.

Like you say, do not pump fast.

The Burnham web site also has helpful illustrated documentation for such things... pdfs