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cast rad heating up, infrared pic

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hot_rod
hot_rod Member Posts: 22,394
I've been meaning to try flowing a radiator at various gpm and see what it looks like.
The 1st run at a 1 gpm flow rate.

I can get to about 4.3 gpm with the current circ, 3/4" tube connection, for the second run after it cools back down to 65F shop temperature.

I snapped a shot every 4 minutes for 20 minute run period.

A nice match up for a mod con as return stayed low throughout the 20 minute run.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
PC7060kcopp

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  • Steamhead
    Steamhead Member Posts: 16,950
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    I'll be interested to see at what flow rate the water just shoots across the bottom of the radiator without circulating to the top.

    Also, that looks like a column rad- are you going to try this with a large-tube and small-tube type to see how they differ?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • hot_rod
    hot_rod Member Posts: 22,394
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    This is the only radiator I have right now. Do you recognize the brand?
    Steve Minnick got it for me out of a Chicago building.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Steamhead
    Steamhead Member Posts: 16,950
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    It's a "flue" radiator. I think it's an Italian Flue model, made by American Radiator Co. See page 59 of "E.D.R.".
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • axeyal
    axeyal Member Posts: 8
    edited December 2022
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    hot_rod said:

    I've been meaning to try flowing a radiator at various gpm and see what it looks like.
    The 1st run at a 1 gpm flow rate.

    I can get to about 4.3 gpm with the current circ, 3/4" tube connection, for the second run after it cools back down to 65F shop temperature.

    I snapped a shot every 4 minutes for 20 minute run period.

    A nice match up for a mod con as return stayed low throughout the 20 minute run.

    Rob,
    I looked at the picture you uploaded. I'm not sure I understand the description on it. What is the stable state delta T between the SWT and RWT at the end of the 20 minutes?

    How high can you get the Delta T between SWT and RWT across the radiator by reducing the flow even further?
  • hot_rod
    hot_rod Member Posts: 22,394
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    So in this test, with this specific radiator, here are the results of the two flow conditions.

    The first pics are about 20 seconds after I got the pump and boiler fired, camera in position.

    As expected the ∆T is tighter on the 4 gpm flow, and the radiator ended up about 33° warmer after 20- minutes. Look at temperature numbers on the bar, as the color bar keeps adjusting up.

    Circ power consumption went from 6W- 40W to get the higher flow rate. BTU/hr output was about 4,000 btu/hr higher on the 4 gpm test at the 20 minute point.

    With these numbers I could supply 140F and warmer and still be returning condensing temperature to a mod con. Even with 180F supply on the 1 gpm I could maintain condensing return temperature. For how long? Depends on the load of the room to some degree, I suppose.

    Next test is at 6 gpm.

    Unfortunately I had to leave two other radiators behind when we moved last year. A pantry shelf type and a large L shape one :(

    I'd like to flow a few other versions, send radiators!

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • hot_rod
    hot_rod Member Posts: 22,394
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    Here is a 1.1, 4 and 7 gpm flow test.

    Using the Stelrad derate chart. These column rads measure 36" tall 8" wide, call it 3.5ft/ section X 8 = 28 sq ft.

    So output at the AWT 1120 at 1.1, 1960 at 4 gpm, 2520 at 7 gpm.
    Heat up time increased with flow rate also.

    Interesting footnote about 140F is typical. I suppose on the larger ∆ operation the drop would be considerable in series radiators, so even with 180 SWT the AWT could be realistic at 140F?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream