another small breakthrough on our NERD technology.

[Rosemary Ainslie]

And TK,  Can I impose on you now to please open your own thread.  Then you can use whatever argument you want - and it won't then interrupt this. 

You'll be able to propagandise to your heart's content.  I promise you I won't post there. 

Kindest regards,
Rosie Pose.

[TinselKoala]

You are still claiming a lie, Rosemary. Until this is dealt with... you will have to deal with me on this thread. Or not... that's your continuing choice. But I'll keep pointing out your calculation errors and your false claim of 25.6 MILLION JOULES, equivalent to over 4100 Watts continuous power, until you correct and retract it --- or PROVE ME WRONG with solid evidence. I am not afraid of being proven wrong. Let's see you do it.

What's wrong with the test that I proposed? Take six batteries, charge them fully with a battery charger, randomly select three and set them aside. Make your oxtail soup for a couple of days or hours or whatever using the other three. Then take both sets, hook them up to identical ordinary light bulb loads, and watch, using a time-lapse webcam, to see which set of batteries runs out first. Repeat a few times, charging all with a charger and then randomly selecting the batteries each time, just to be sure. This could be done within two weeks, easily.

Is that simple enough for you? Why can't your circuit be tested fairly that way?

Another brief calculation reveals that, for your claim to be true, since I = P / V, your mosfets would have to be carrying a CONTINUOUS current of (4100 Watts/(5 batteries x 12 v per battery)) == over 68 Amps. Pretty remarkable, since that's way over the rating of the miracle magic IRFPG50 , I think. I'll have to check the data sheet....

[eatenbyagrue]

So Guys,

Here's what TK is hoping you'll believe.  Provided we get water to boil - then it matters not how long we keep it boiling you never again reference the amount of joules other than the amount required to reach boiling point in the first instance.  So.  If you want to calculate how much energy it takes to keep a pot boiling for 6 hours or so - to cook some ox tail say - then don't worry.  The actual amount of energy in joules - is only applicable to taking that water to boil.  Would that our electrical suppliers saw sense in this.  Our utility bills would not then be quite so onerous.

Unfortunately our utility suppliers are also not that idiotic.
Kindest as ever,

Rosemary

Now you know I am a supporter, but you cannot use the formulas you have posited.  You made a simple transposition.  A watt is one joule per second, but a joule is not one watt per second.


When you talk about keeping water at a certain temperature, you cannot use the function for raising the temperature of water.  Keeping water at a certain temperature is a calculation that depends on the joules of energy going out of the container of water that you have.  This in turn will depend on ambient temperatures and also the insulation of the container.


As far as boiling, that is actually a different calculation too.  I believe it takes about 2260 joules to vaporize one gram of water (without changing temperature).


But anyway, I think you are very close, Rosemary.  Just fix these simple typos and I think you will be done!

[TinselKoala]

@eaten:
It's not a simple transposition or a typo. Note that she tries to add the same energy twice, as well as multiplying the energy times the TIME. This is not a transposition or a typo, it's a fundamental conceptual error.

When you answered my example question, you did not make this error. Why are you accepting it from Rosemary now?

In the data she gave, she did not talk about "keeping" the water at a certain temperature. Any replacement of lost heat from her probably not-well-insulated container would indeed add to the energy required. Let's say it doubles it. Fine. Now let's say that she boiled away all of the 900 grams of water into steam in the last 10 minutes of the test. So that's about 330000 Joules to raise the temperature, another 330000 Joules to compensate for heat losses, and 900 x 2260 Joules for the phase change. 660000 + (900 x 2260) == a bit over 2.6 million Joules. Is this coincidentally about one tenth of her 25.6 MILLION joules claim? Note that she didn't claim to have boiled off all the water.
If I had done so, I would certainly have pointed it out. But that's just me.

Got any more of them coffin nails? That was a good one. Thanks for bringing it up.

[TinselKoala]

And TK,  Can I impose on you now to please open your own thread.  Then you can use whatever argument you want - and it won't then interrupt this. 

You'll be able to propagandise to your heart's content.  I promise you I won't post there. 

Kindest regards,
Rosie Pose.

I note, once again, the attempt to silence your critics rather than deal honestly and openly with their criticism. What's the matter, isn't Stefan responding to your PM requests to have me blocked or banned?

http://www.irf.com/product-info/datasheets/data/irfpg50.pdf

Note the maximum continous drain current. Compare to the current necessary to provide 4100 Watts at 60 volts. Now count your mosfets. DO THE MATH. If you have six mosfets in parallel, carrying 68 Amps, and each mosfet is rated at maximum 6.1 amps _when cold_, what do you suppose is gonna happen? What's going to happen, very rapidly, when the _first_ one fails? I'll tell you... by the time the sixth one fails it will be like a shotgun going off on your table top.
Is it going to matter very much where the current is coming from or whether it's pulsed rapidly or not? I don't think so.