[time-nuts] Cheap Rubidium (heatpipe cooling for)

Mon Dec 28 18:05:00 UTC 2009

Thanks   Bert

In a message dated 12/28/2009 12:48:20 P.M. Eastern Standard Time,  
lists at cq.nu writes:

Hi

The short term stability *may* improve with temperature  stabilization, 
even if the static temperature performance is fairly good.  

Since all of the rubidium guys sell parts with many different options.  
Trying to find out exactly what the rubidium you have in your hand does can be  
difficult. I suspect that testing the actual device may be the only sure 
way  to do it.

Bob

On Dec 28, 2009, at 10:52 AM, ewkehren at aol.com  wrote:

> Hi
> With all the dialog on controlling temperature  of the Rb unit I decided 
to  
> take my Frequency Electronics Inc.  5062B apart since the Oven Controlled 

> Oscillator and Rb Physics  Package are separate and I may want to replace 
the  
> oscillator  with a HP 10811 that Corby has tested to be better than 1 E 
12 
> from  1  to 100 sec.
> In order to proceed it would help if any one out  there has any 
information  
> on the circuitry, the unit has two  modules and two PC boards. The boards 
> are  power supply and  synthesizer and the modules are Rb unit and 
oscillator. 
> I have   opened the Rb unit and I am convinced that it can be a candidate 
for 
>  heat pipe  cooling. Since it can be operated separate from the rest of  
the 
> unit it will be  possible to measure heat rise. 
> The  published  plot of a 5600 shows a temp performance of +- 3 E -11   
from 
> -5 to +45 C. I am not sure if there is room for improvement.  
> Any help would be greatly appreciated.  
> 
>  
> Bert Kehren    WB5MZJ    Miami
> 
>  
> 
> In a message dated 12/27/2009 2:18:14 P.M. Eastern Standard  Time,  
> lists at cq.nu writes:
> 
> Hi
> 
>  The tip it and listen to it slam test is a standard way  of checking out 
 a 
> triple point of water cell for basically the same reason  (you  check the 
> vacuum. Of course since a TWP cell is thin glass and not a  nice  metal 
pipe, 
> you *may* break the seal by testing it   ....
> 
> Bob
> 
> 
> On Dec 27, 2009, at 9:33  AM, Joe Gwinn  wrote:
> 
>> At 12:00 PM +0000 12/27/09,  time-nuts-request at febo.com  wrote:
>>> 
>>> Date:  Sat, 26 Dec 2009 17:04:46  -0700
>>> From: Robert  Darlington  <rdarlington at gmail.com>
>>> Subject: Re:  [time-nuts] Cheap  Rubidium (heatpipe cooling for)
>>> To:  Discussion of precise time and  frequency  measurement
>>>      <time-nuts at febo.com>
>>> 
>>> My comments are  in-line,  below....
>>> 
>>> On Fri, Dec 25, 2009  at 4:38 PM, Joe Gwinn  <joegwinn at comcast.net>  
wrote:
>>> 
>>>> At 12:45 AM  +0000 12/25/09,  time-nuts-request at febo.com wrote:
>>>> 
>>>>>  
>>>>> Date: Thu, 24 Dec 2009 17:14:38   -0700
>>>>> From: Robert Darlington   <rdarlington at gmail.com>
>>>>> Subject: Re:  [time-nuts]  Cheap Rubidium (heatpipe cooling  for)
>>>>> To: Discussion of  precise time and  frequency measurement
>>>>>       <time-nuts at febo.com>
>>>>> 
>>>>>  
>>>>> On Thu, Dec 24, 2009 at 1:32 PM, Bob Camp   <lists at cq.nu> wrote:
>>>>>  
>>>>>  Hi
>>>>>>  
>>>>>> A heat pipe might work if the fluid had a   sufficiently low boiling
>>>>>>  point.
>>>>>> 
>>>>>  
>>>>> 
>>>>> The working fluid in a heat  pipe will boil at every  temperature 
above 
>  its
>>>>> melting point.
>>>>>  
>>>> 
>>>> Well, I've been thinking about this,  and I  used the term "heat pipe" 
> too
>>>>  loosely.  Both the one- and  two-pipe systems mentioned here have no  
> wicks,
>>>> and so  technically are two-phase  thermosyphons, which depend on 
> gravity  to
>>>>  circulate vapor and condensate.  A true heat pipe has  a wick, and  
will 
> work
>>>> in zero gravity.
>>>>  
>>>> One gets significant heat transfer by phase change so  long as  the 
vapor
>>>> pressure in the heat input end is  high enough to  generate enough 
vapor 
> to
>>>>  carry the thermal power flow, and  this makes the pipe isothermal.   
> However
>>>> the temperature  (although constant  along the pipe) varies with the 
> thermal
>>>> power  flow (in thermal watts) being carried.
>>>>  
>>>> What I'm looking for is related but different:  A  device where the  
> heat
>>>> transfer capacity  varies sharply with temperature, so  that there is 
a 
>  range
>>>> of heat transfer rates over which the   input-end temperature will be
>>>> substantially  constant.   This is why I envision the fluid boiling 
>  (versus
>>>> evaporating),  which is actually out of the  operating regime of a 
true 
> heat
>>>>  pipe.
>>>> 
>>>> 
>>>>> I tend  to use  water because it's cheap, but have made  them
>>>>> with 3M  "engineered fluids", Fluorinert,  and denatured alcohol.
>>>> 
>>>>  Fluorinert.  I think that's what the expensive  commercial  
CPU-cooling
>>>> heatpipes use.
>>>>  
>>> $1000 a gallon!  Or $5 a drum when you buy it at a  salvage  auction.
>> 
>> That explains why low-end  heatpipes use alcohol or  acetone.
>> 
>> Actually, one  ought to be able to use the freon  intended for 
automobile 
> air  conditioners, for a whole lot less money, even  new.
>>  
>> 
>>>>> I've  found
>>>>>  that ordinary solder works just fine.  A trick  to make these things 

> easy
>>>>> to build is to use a ball valve  at  the top (I'm assuming there is a 
> top and
>>>>>  we're going  with gravity return because it's simple).  I've got a  
few 
> that
>>>>> are still under vacuum for several  years now in this  configuration. 

>  My
>>>>> giant heat pipe of doom is a 10  foot stick of  1/2" copper with a 
ball 
> valve
>>>>> at one end  and  an end cap at the other.  There is perhaps 100ml 
water 
>  in
>>>>> there total, and no air.  You can either boil  the  liquid until it 
> builds up
>>>>> a nice  head of steam, or go the  easy way and pull a vacuum with a 
> pump  and
>>>>> just close the  valve.
>>>>  
>>>> I wouldn't have thought that an  ordinary ball valve  would be tight 
> enough,
>>>> allowing the water   to escape and the air enter, slowly, although I 
>  suppose
>>>> one  can replace the water if it comes to  that.
>>>> 
>>> Mine  have been running for a  few years with no sign of needing to be  
> pumped
>>>  down again.  They just work.
>>> 
>>>> But I  think people want to build this exactly once, so I   followed
>>>> refrigeration practice.  A properly  made  hermetically sealed 
> refrigeration
>>>>  system keeps its working  fluid essentially forever.  I suppose one  
can 
> use a
>>>> refrigeration fill valve, say from an  automobile air conditioning  
> system,
>>>> but  these all leak to some degree.
>>>> 
>>>> Is the  ball valve anything special?
>>>> 
>>> Nope, just  whatever was on the shelf at the local hardware  store.
>>>  Stainless ball with brass valve body.  Teflon bearing   surface.
>> 
>> Ahh.  A quarter-turn ball valve, used  as a  cutoff.  The term "ball 
> valve" isn't quite precise in  plumbing  parlance.
>> 
>> These are very good, but  still they are not  hermetic, and will over 
> decades (if not a  few years) lose their working  fluid.  I bet that 
while water  
> will be contained, freon will diffuse  right through the teflon  seal of 
the 
> ball valve.  So, there's the   tradeoff.
>> 
>> 
>>>>> These things  are  incredible.  If you pack snow around
>>>>>  the end of this  thing, the other end that is ten feet away gets  
cold  
> almost
>>>>> immediately.  They  want to stay isothermal and  the heat transfer is 
> at  the
>>>>> speed of sound through the  working  fluid.  Delays are introduced 
> because
>>>>>  you're  dealing with a thermal mass of copper pipe that needs to  
change
>>>>> temperature along with the working fluid so  it's not quite instant,  
> but
>>>>> still about  10,000 times faster heat transfer than  copper by 
itself.  
>  They
>>>>> are certainly handy for  getting heat out of  confined spaces.
>>>>> 
>>>>  
>>>> What is the purpose of the heatpipe of doom?    Education?
>>>> 
>>> Education, fun, and then later  a  demonstration piece.  It's fun to 
>  rapidly
>>> move the thing  along its axis, upward and then  stop.  The slug of 
water
>>> moves up and then slams back  down to the bottom and sounds like a 
steel 
> ball
>>> in  the pipe.  It makes a satisfying clang  sound.   A couple  of years 
> back
>>> when I did a demo,  people were  convinced I had a metal part in there 
> that
>>> was   loose.  I opened the valve and out came a 100ml water and   
nothing
>>> else.   Too cool, and you can make them at  home  for next to nothing.
>> 
>> This definitely  sounds like a good  physics demo for school use.
>> 
>>  
>>> Before
>>> I started using vacuum pumps to pump  them down, I'd use a blowtorch to 

> boil
>>> the  water and use the valve to throttle the steam coming  out.  Once  
the
>>> steam is coming out really fast you basically  just  quickly close the 
> valve
>>> and remove from the  heat  source.   That's it!  For smaller diameter 
>  pipes I
>>> use other methods and other working fluids because  heating tends to  
> just
>>> eject the sometimes very  expensive fluid.
>> 
>> What sizes, what fluids, what  purposes?
>> 
>> 
>> Joe
>> 
>>  _______________________________________________
>> time-nuts   mailing list -- time-nuts at febo.com
>> To unsubscribe, go to   
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>  and follow the  instructions there.
>> 
> 
>  
> _______________________________________________
>  time-nuts  mailing list -- time-nuts at febo.com
> To unsubscribe, go  to  
>  https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow  the  instructions there.
> 
> 
>  _______________________________________________
> time-nuts mailing list  -- time-nuts at febo.com
> To unsubscribe, go to  
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the  instructions there.
>  

_______________________________________________
time-nuts  mailing list -- time-nuts at febo.com
To unsubscribe, go to  
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the  instructions there.