On Oct 12, 2011, at 6:38 AM, Jed Rothwell wrote:
Jouni Valkonen <[email protected]> wrote:
Water inflow rate was calibrated and it was 13 kg/h.
For this test? Where does it say that? Anyway, that comes to 3.6 g/
s which is enough to sustain the highest power without having the
reservoir run dry.
It could be the reservoir was overflowing during most of the test.
That would make no difference to the readings in the heat
exchanger. The flow could be steam, or a mixture of steam and hot
water; the heat exchanger will read it the same way.
I think that Hefner said that there may be intermittent bursts of
hot water entering the heat exchanger and this might explain some
of the outlet thermocouple variations. I do not think so:
1. We have very few data points from the thermocouples. You would
have to have readings taken every few seconds to see a momentary
heat burst.
Groups of slugs can last a while - until the water level drops.
3. Hot water coming through the pipe would lower the temperature
not raise it.
Wrong! Even if the steam were hotter, the high specific heat of
water means the heat transfer will be greater at that point.
However, because T2 readings can not be trusted, we don't even know
if the steam temperature is 120°C.
3. Putting the outlet thermocouple on the pipe is a good way to
blur out momentary variations and heat bursts. It is a recommended
technique.
Its baloney. The thermocouples should have been located in wells in
the water flow a few cm down the rubber tubing.
The NRL went to a lot of trouble to make sure their pipes are good
heat sinks in their test bed system. However, I think installation
instructions recommend you put the thermocouple about 2 feet from
the boiler or heat exchanger on a straight segment of pipe.
I read somewhere that you are supposed put at strap on pipe
thermocouple about 2 feet away.
This is different. Rubber tubing is used.
I cannot find that document. I think that is what it said. If that
is true, the readings may be a little bit high because of the steam
pipe. As I said before, the thermal mass of the cooling water is so
much larger than that of the steam that even if the thermocouple is
picking up the average temperature right between them -- which is
highly unlikely given its position -- the temperature would still
be pretty close to the correct value.
There are many strap on thermometers available that are intended to
be used on the outside of pipes. This one is a general-purpose
thermocouple. However, this technique will work fine as long as the
thermocouple is wrapped in insulation.
- Jed
More arm waving.
Your voice recognition system needs to be adapted to sense arm waves
and footnote the text with reader warnings. 8^)
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
