Flow meters/Rotameters

[Brendan]

We have discussed these a little on Blondy's thread HERE, after Blondy showed his in action.

Why don't you get the 0.1-2 and the 1-7, then run them in series. You'd get the best of both worlds.

For my still (running 2.4kW), I recon I'll be sitting between 0.5 and 1Lpm for the majority of the time. My problem when I ordered was that I had no idea how fast the flow was (hence the need for the thing). I'd say if you've got 2.4kW you should be fine with the 0.1-2Lpm.

I have 6kW in my boiler, but will run about 3.6kW by the sounds of it, so maybe need a little more.

I figured you'd only be exceeding 2Lp/m when in full reflux, which you're not overly worried about the flow rate...just pump it with water.

My concern is that with a setup like mine where the RC is fed from the PC, the temperature will slowly rise over the run...which alters the run much like a constant temp with a varying flow rate, and that this may be more of an issue than worrying about a measurable flow rate...then again, if you are after replication, if you stick with the flow rate, the temp will probably rise about the same rate as previous runs... :think:

edit: I like your idea Blondy of the two in series, which is what I was thinking...might have to do 2 rotameters and a temp guage all in line on the output water line 8-}

[blond.chap]

Yes I've thought about that as well, which is why I put a thermometer into the cooling line before the RC at the same time as the flowmeter.

My guess (without having run it), is that it will more or less reach a steady state once you're collecting hearts and will sit at a reasonably constant temperature. What you're actually trying to control is the cooling load provided to the RC, which you can work out by: (T[out] - T[in])*flow rate*Cp, where the temperatures are on the coolant lines, and Cp is the heat capacity of water. So for perfect control, you would also measure the temperature of coolant out.

But I'm not quite that die hard (though I might measure the temp out once or twice for fun), I figure temp in and flow will be enough to control pretty accurately.

[blond.chap]

edit: I like your idea Blondy of the two in series, which is what I was thinking...might have to do 2 rotameters and a temp gauge all in line on the output water line 8-}

The rotameter should probably go before the RC, otherwise the heat will eventually wear out the plastic (unless you meant output of the PC, in which case please proceed)

[Brendan]

Yeah, I think you're probably spot on there Blondy (except for the equation, takes the fun out of the hobby...I study engineering all day :handgestures-thumbdown: ). I'll feel like a bit of a wanker with two flow meters and the temp guage, but it sure would be interesting.

I know you said 0.5-1Lp/min usually...so at a minimum when you're collecting hearts, you find you're at about 500ml/min through the RC? If I'll be running 3.6kW, might not need to read any lower to 100ml/min then...?

edit: yeah, would put between PC and RC :D

[blond.chap]

Unfortunately I can't tell you exactly, I've only tried in on a test run with the coolant running. Just from memory of the coolant flow, I think it is between 0.5 and 1.5Lpm.