Most Stable and Quantifiable Heat Source

[MaxxxRacer]

LOL i figured that out real fast after i read what u said. i feel totaly nubbed right now.

welll a high amperage shunt it is then. btw how much do these things cost?

ive seen that thing that joe has.. i about shat myself when i saw it.. pretty amazing i must say. sadly i have no room for such a contraption, nor the money to purchase such a thing.

as to the ariflow throug the rads Ill be testing it with fans ranging from weak 25mm fans to ultra powerful 140cfm delta triblaes. I prefer this method as it shows readers what kind of performance they can expect for a given noise level and fan. show the pros and cons of the thin vs thick radiators and when you should choose one over another based on your needs. This was my plan from the begining and personally I really think that its mores usefull to the end user than pretty much any other type of airflow tests through the radiator.

EDIT: In response to jaydee, I realize that the res will loose alot of heat to secondary losses and this is why i will insulate it and seal the top up so that teh water doesnt have even more secondary cooling through evaporation (which is an amazing cooler btw). anyway i will probably have to put neoprene around the tubining throughout the setup so i dont loose even more heat through that. I will also put neoprene around the res or just make a insulating res out of something.

[bigben2k]

As we pointed out, you can get them cheap on eBay. The trick is to check how accurate they really are. The best way would be to find someone who can test it for you.

Otherwise, I have to say that I'm concerned that you might not be able to repeat the same airflow each time, but that assumes that the fans are going to go through some wear and tear. Maybe you'd be able to at least measure the voltage feeding them?

[MaxxxRacer]

oh no worries on the voltages of the fans. I will be powering them with an ocz 600 watt most likely or a 520 watt and will adjust the 12volt line to give me 12 volts and will have the dmm attached.

[bigben2k]

(sorry, been out for the past 3 days).

All right then, so where do we stand? Any more questions? Care to recap?

Would you like your own forum on the WBTA to present your test bench?

[MaxxxRacer]

hmm... so DC powered heater cartridge directly touching water in insulated reservoir.

shunt to measure the amperage of the heater. (woudl this be better than the clampmeter)

anything else im missting?

yah i would most certianly like to be a WBTA member. I think its a VERY good idea.

[bigben2k]

Ok. Goto http://forums.wbta.us/ and register. I'll have your forum up and ready in no time. You have the choice of allowing replies or not.

As long as the cartridge is meant to be used immersed, that's good. JD had an excellent idea of using one specifically made for that. Otherwise I'd tend to go with some kind of block, be it copper or otherwise (stainless steel?!?).

The clampmeter only works for AC; it's useless in DC (since it measures fluctuations, and DC has none).

[MaxxxRacer]

ahh ic.. so the shunt is the only way to measure high amperage? getting a psu for this thing is gonna be the hard part.

if i cant find a waterproof one then i can make a block for it relaitvely easy that will just have a bunch of fins on it (widely spaced) and a hole in the middle for the shunt.. stick that in the res and insulate the hell out of it.

ill go sign up now

[bigben2k]

Welcome!

http://wbta.us/forums/index.php?showtopic=62

Yeah, the shunt is the most reliable, cost effective way to do it. You can get really fancy with this stuff, but it's all basically the same; a good shunt, who's output is measured in millivolt.

Good luck on the DC power supply hunt. I'll let you know if I come across something that might fit.

In the mean time, you might want to post the specs for various heaters that you're considering, so that we can determine your voltage requirements.

[jaydee]

Originally Posted by MaxxxRacer

hmm... so DC powered heater cartridge directly touching water in insulated reservoir.

An "Immersion" cartridge heater. They are designed for liquid submersion. Good luck finding a DC one. I have searched for hours trying to find a DC spacific heater cartridge to little avail. If what they say in this thread is true I guess it doesn't have to be DC spacific to run DC?

[redleader]

Originally Posted by bigben2k

Ok. Goto http://forums.wbta.us/ and register. I'll have your forum up and ready in no time. You have the choice of allowing replies or not.

As long as the cartridge is meant to be used immersed, that's good. JD had an excellent idea of using one specifically made for that. Otherwise I'd tend to go with some kind of block, be it copper or otherwise (stainless steel?!?).

The clampmeter only works for AC; it's useless in DC (since it measures fluctuations, and DC has none).

You can measure DC with a clamp meter. Its not induction based, rather the movement of charge through the metal induces a field which can be measured. IIRC its the same principle used in emergency breaks in subways. I forget what its called though (Hall Effect maybe?). Either way, remotely measuring a field seems a lot less accurate and more expensive then actually measureing the current itself.

[MaxxxRacer]

I will post some shunts that I find. I will try looking for some immersion ones.

red leader, are you sure i can measure it with a clamp meter, and will it be as accurate as the shunt??

looking at the immersion heaters on mcmaster im quickly comign to the conclusion that they are not the way to go. making my own coper block that seals a normal heater cartridge from the water seems a more sensible way of going about things.

Ben, dont most of the DC psus go up to like 36volts max? if that is the case that would need almost 10 amps to get to 350watts of load..

check out this mcmaster part. at 120volts its 1200watts. so its 10watts per volt.. at 35volts thats 350watts... perfect for waht I need and most of the psu's on ebay are of the 35 volt variety...

4877K466
(Same as 3618K287)
Cartridge Heater With SS Lead Covering High Temp, 120 Volts, 3/4" Dia, 6" L, 1200 Watts

[bigben2k]

Ok.

1200W and 120 volts, that means 10 amps max.

You're shooting for 350 Watts.

Using:
P = V * I
and V = R * I

we get P = R * I * I (or P = R * I^2)

P=1200
I=10
so R is going to be 12 Ohm.

using:
P=350
and R=12
we get 5.4 amps.

The voltage would be 65 VDC.


If you could find a heater that would be less resistive, you could lower that voltage.

[MaxxxRacer]

any suggestions on the specs i will be needing??

at this point im kinda thinking i should reduce my 350watt requirement to 250watts. It would be alot more feasable no?

[bigben2k]

using:
P=250
and R=12

I=4.56
and V=54

No big difference.

That heater above is fine. The only thing is that if you could find one with a lower resistance, you could pump more power into it, with a lower voltage. You might just want to stick with that one, and concentrate on finding the PSU.

I think I've got other heater cartridge manufacturers in the WBTA WebLinks, if you really want to check it out.

[MaxxxRacer]

hmm... well i guess i will have to find one with lower resistance.. fun fun fun in the sun..

well i found one that is 2000watts at 120volts..
R=7.5Ohms..

not sure on the calculations that i will need otherwise.. can you show me the foruma to calcualte the amperate and volage needed.

[bigben2k]

Sure.

The equations are:
P = V * I
and
V = R * I

Where:
P = power (Watts)
V = voltage (volts)
R = resistance (Ohm)
I = amperage (amps)

With a substitution, you can get P=VI to be P=R*I^2.

What we know is:
P=2000 W
and
V=120

so I resolves to 16.7 amps.

then swapping V=RI to read as V / I = R, you get R = 7.2 Ohm.

Now for the target power. What we know is that R=7.2 Ohm, and that P should be 350 W.
P = 350 W
R = 7.2 Ohm

so using the substitution above, where P=R*I^2, and a little swapping around, we get I = sqrt (P / R). I resolves to 6.97 amps.

Then, we go back to V=R*I, and we get V = 50 volts.

So now your task is to find a DC power supply, capable of outputting at least 50 volts DC and at least 7 amps. tip: if the PSU is capable of more, it'll last you longer; there's no sense in taxing a power supply to its limit, all the time. Also, look out for voltage drifts as the unit warms up.

[MaxxxRacer]

hmm thanks

btw I'm gonna ask my electrician friend if he can find an autotransformer for AC that willl stablalize the voltage so that it will give constant voltage.