🚀 go-pugleaf

In article <1992Dec11.192622.6719@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>In article <1992Dec11.171454.3158@magnus.acs.ohio-state.edu> kpearce@magnus.acs.ohio-state.edu (BULLDAWG) writes:
>
>[discussion of boiling in nitrogen deleted]
>>
>>But at this point, the metal makes a phase transition from one kind of
>>metal crystal to another (bcc to alpha).  Whenever a substance under goes
>>a phase trnsition it gives up heat.  So what was happining was that the
>>metal was bubbling away as it cooled down giving up heat in a straight-
>>forward way and then at a centain temperature, the metal says "hey, I'm in the
>>wrong shape, and I have too much energy" and then gives up that excess energy
>>_in_addition_ to the heat energy it was giving up to begin with and then
>>as soon as it makes the phase transition, the copper goes to cooling down as
>>before (the bubbles slow down).
>
>     So all metals have discrete phase transitions near the boiling point of
>     nitrogen?   And these phase transitions involve increased cooling
>     /increased heat transfer?

Of course not.


>
>     I think you'll find that it is just changes in the heat 
>     transfer characteristics of the metal/fluid interface down near 
>     the boiling incipience point that are the real cause.  
>
>     See my earlier posting for details.
>

I saw the earlier post.  The data shown is over a range of temperatures.
All LN2 that is found in an open dewar will be 77K.  Refering to his chart, 
the LN2 should be boiling furiously (and is not, I just took a look to 
make sure).  The data that you show in your chart just doesn't apply to this
process (since it is all taking place at 77K).



>                             dale bass
>-- 
>C. R. Bass                                          crb7q@virginia.edu        
>Department of Mechanical, 
>     Aerospace and Nuclear Engineering
>University of Virginia                              (804) 924-7926