I need to "shock cool" a 200 litre drum of hot wax (with around an 80%
white spirit cutback)

I need to get the whole of the wax cooled very quickly.  I will be
doing this on a very small scale - cooling a batch of 5 drums about
once a month at the most.  So I need something fairly easy and cheap
to put together.

How do I do this?

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Clarification of Question by chrissyboy-ga on 22 Mar 2006 06:45 PST

Just to clarifiy:  the wax will be cut back with about 80% white
spirit.  The whole mixture will be hot.  (The original question could
have been understood to mean that the wax was being cooled with the
white spirit - this is not the case).

I need to get the whole hot wax/white spirit mixture very cool, very quickly.

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Request for Question Clarification by pafalafa-ga on 22 Mar 2006 06:51 PST

chrissyboy-ga,

You're the only one who really knows all the parameters of the job --
cost constraints, equipment availability, speed of cool-down, etc --
so I doubt anyone here can offer a full-fledged solution guaranteed to
do the trick.

Water is the obvious starting point, though -- either a large-volume
hose-down, or an actual immersion into a tank of water.


You can also add something cold-but-intert into the wax -- dry ice and
liquid nitrogen come to mind.

A combination of water on the outside, ice/nitrogen on the inside
might be the fastest way to go.

Do these sound feasible to you?  

If so, what additional information do you need?

If not, please give us a bit more context for the sort of constraints
you're working with.

Thanks,

pafalafa-ga

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Clarification of Question by chrissyboy-ga on 22 Mar 2006 09:26 PST

Hi pafalafa,

Costs need to be kept to less than $2000.00 if possible.   (A lot less
than this would be good!)  I already have a stainless steel tank which
I can use to immerse the drums in water.  I also have a gantry and a
drum hook and a winch.  How can I get the water really cold?  I guess
the dry ice or nitrogen could be put in a container to put in the wax.
  How cold is the dry ice going to be?  I guess dry ice is the same
thing as nitrogen?  What equipment do I need for handling it.   Speed
of cool down is not known exactly at this point.  I need to do some
more lab work.  I am trying to get the wax in a sort of super
saturated solution in the white spirit where it will be in a
dispersion rather than in solution.   The cool down will have to be
pretty fast I reckon.   From hot to cold in minutes if not seconds.

---

Request for Question Clarification by pafalafa-ga on 22 Mar 2006 11:19 PST

chrissyboy-ga,

Thanks for the update...that helps quite a bit.

I'm still struggling with how to best answer your question, though. 
No matter what the eventual solution is, you can't escape having to do
some trial-and-error tests of different sorts of cooling to see how
well they work for you.

The simplest is to hose down the outside of the drum, and possibly,
even hose the top of an open drum, if you don't mind your mixture
getting exposed directly to water.

Placing the drum on a pallet -- or hoisting the drum a bit -- would
allow you to hose the bottom as well, which would cool it even faster.

Next in line would be to pick up a drum, and immerse it in a simple
ice-water bath.  You could also make it a salt-water, ice-water bath,
which is colder, and would cool the drum even faster.

SAFETY NOTES:  (1) don't seal the drum, as it could shatter or
explode, and (2) any sort of rapid cooling will make the mixture
bubble and splatter, so be careful about this.  (3) white spirits
fumes aren't that good for you...make sure your site is well
ventilated.


If the water-approach doesn't do the trick, then you may need to move
to colder materials, like dry ice ( -109.3 degrees F) or -- much
colder -- liquid nitrogen (-321 deg F).

I suspect you can add these directly to the mixture (without having to
package either materials) as they quickly turn into gas and evaporate.
 But here too, you would need to do trial-and-error tests to see what
works for you.

Again, these are dangerous materials, and need to be handled quite carefully. 


Let me know what sort of additional details you would like to have to
make for a complete answer to your question.

paf

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Clarification of Question by chrissyboy-ga on 22 Mar 2006 11:39 PST

Hi pafalafa, 

I don't think hosing is going to do it.  I am trying to copy a
manufacturer (I don't want to say too much about that).  I know they
use "shock cooling" during the process.  If the hot wax/white spirit
mixture cools down slowly it is not going to work.  So it has to be
cooled really quickly.  I am going to have to do quite a lot of trial
and error I suspect.

Dry ice and nitrogen sound like the way to go.  I could immerse the
drum in my water tank and put some dry ice or nitrogen in the water.

I think if you can find out what equipment  (available in the UK with
prices) I will need and what the procedure would be to handle it and
also how I can use dry ice and/or nitrogen to do some laboratory type
tests fairly cheaply and safely you will have earned the money.

---

Request for Question Clarification by denco-ga on 22 Mar 2006 15:24 PST

Howdy chrissyboy-ga,

To hopefully add to pafalafa-ga's great ideas, you might think about
circulating the coolant through a copper coil.  Think copper pipes
bent into a "screw" (helix) shape that could placed into the drums,
and then "turned" to remove from the cooled wax.

The pipe would have to be shaped so that the coolant would circulate
through it.  Slightly warm water could be circulated through it in
order to remove the coil in the post cooling stage.

Looking Forward, denco-ga - Google Answers Researcher

Proces of solidification depends on


1) Latent heat of melting (which is the heat generated as the molten
was solidifies) and which needs to be carried away.

While the heat exchange depends on the temperature difference between
the coolant and the solid, temperatures are not critical.
 Meaning, cold water is sufficient
(naturally,it has to be a stream of water or refrigerator coolant).

You are limited by the thermal conductivity of wax 
(which you should know - measure it, or get it from manufacturer)

and by 'geometry of the process' - the arangement of the cooling tank.

Pipes have been suggested, and that is a step in the right direction.
However, mining the solid wax from the vessel with pipes may be dificult.

More practical method is to extrude the wax into the coolant.

To put it simply -  making noodles out of your wax.
 The noodles, by the way, cook well and fast for the same reason:
  Efficient heat transfer due to 'good' geometry.
 
The alternative is to drip-drop the hot vax into the coolant. In both cases
you can easily separate the solid wax from coolant for further processing.

Cooling of melts into the solid, or inverse problem - melting of an icecube
in a glass of water are known in physics as 'the Stefan problem'

named after:

Josef Stefan was born in St. Peter near Klagenfurt, Austria on 24
March 1835 and died a century ago on 7 January 1893. He enrolled at
the University of Vienna in
 http://ta.twi.tudelft.nl/nw/users/vuik/wi1605/opgave1/stefan.pdf

The processes described by his equations are dominated by the conductivity of
the solid phase - in this case conductivity of wax, which is low and by the
latent heat of wax, which is high 
(sohigh that paraffin is used for 'heat storage').


Paraffin Wax -conductivity	             0.25  - (W/m.K)
http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

 Paraffin Wax  - latent heat                70-91   - (kJ/kg)
 http://www.fskab.com/Annex17/Materialdata/PCMProdukte.xls.

During solidification (freezing) crust forms at the surface,  which is
in contact with coolant, which insulates the molten center from direct
contact and further heat transfer.

Extrusion into the coolant produces thin 'noodles' and that eliminates
 this problem

Alternative is to have to melt circulate - as described here, by
cooling it inside copper spheres:
 
Heat Transfer During Phase Change of Paraffin Wax Stored in Spherical Shells
http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000127000003000357000001&idtype=cvips&gifs=yes


Another alternative is to add aluminium thermal conductivity promoters
of various designs into the body of the wax as described here:

	
"Latent heat storage systems especially those employing organic
materials have been reported to exhibit a rather slow thermal
response. This is mainly due to the relatively low thermal
conductivities of organic latent heat materials. This paper reports
experiments carried out to investigate methods of enhancing the
thermal response of paraffin wax heat storage tubes by incorporation
of aluminium thermal conductivity promoters of various designs into
the body of the wax. Heating and cooling runs were carried out and
phase change times determined. It was found that the phase change time
reduced significantly by orders of up to 2·2 in energy storage
(heating) and 4·2 in energy recovery (cooling). Internal fins
performed much better than the star matrices and expanded aluminium
performed better than promoters made from aluminium sheet metal in
both storage and recovery of heat"

http://www3.interscience.wiley.com/cgi-bin/abstract/10150/ABSTRACT?CRETRY=1&SRETRY=0

This article (dealing with heat storage) has numerical values of the parafin
properties (latent heat, conductivity, viscosity .)
(Paraffin wax is an attractive material for heat storage applications.
 due to high latent heat ...)
http://72.14.203.104/search?q=cache:Cvxk2hpZRNAJ:www.fskab.com/Annex17/Workshops/EM3%2520Tokyo%25202002-09-30--1002/Presentations/13%2520Full%2520Paper%2520of%2520Buddhi.pdf+conductivity+latent+heat+wax&hl=en&ct=clnk&cd=10&lr=lang_en


More details on Extrusion (most recommended method)
 
There is a variety of extrusion machines on the market. Extrusion of
the wax into coolant may require considerable presure which 'kitchen
robot' is unlikely to provide. Textile spinining machine may work, but
would not fit a $2000 budget. Here is a description of wax extrusion device:

"This communication describes the construction of a simple and very
inexpensive wax injector from commercially available parts"

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8184903&dopt=Abstract

This company " offers several types of amorphous polyolefins under the
proprietary name  .. " for extrusion into candles.
http://www.igiwax.com/microcrystalline.shtml

Candles are made by extrusion and here is an industry forum 
http://www.feedscrewdesigns.com/cgi-bin/forums/Ultimate.cgi

Depending on your volume and budget, you can go from a simple tool

"The Matt Gun An affordable, simple-to-use tool which enables you to
take full advantage of the extrusion technique, transforming hard wax
pellets into wires of different shapes and thicknesses. An important
advantage of the Matt Gun lies in the fact that the extruded wax wire
can vary in thickness..."
http://www.lacytools.ca/catalog/product_info.php/products_id/12886


To industrial eqipment

http://flitetech.com/products.htm

Melt extrusion technology has proven to be a suitable method for the
... impact on the properties of wax matrix granules prepared by this
extrusion process. ...
www.pharmainfo.net/exclusive/reviews/ melt_granulation_technique_:_a_review/3/

 producer of feed screws
http://flitetech.com/products.htm


...


Hedgie

Maybe it is obvious to you guys, but what is the temperature range?
Starting temperature, cooled temperature?

Is it possible to pour the mixture into a pre-cooled container?

Does it have to be cooled in 200 ltr. batches, or is it possible to do so in 
smaller amounts?

True enough Myoarin.  Pour the wax mixture into a bunch of tubes that are
sitting in a coolant bath.  Might be able to get away with iced saltwater.

Just a little suggestion off the top of my screwy head... someone did
use fire extinguishers to cool cans of beer. It might be feasible for
cooling a vat of wax (spray the sides of the vat).

It is theoretically ossible to chill the drums in a combimnation on
slat watyer slush, with a dewar of Liquid Nitrogen poured in, however
this can be "destructive", so be EXTREMELY CAREFUL. As people have
said, DO NOT seal the drum. BTW, techtor, it was the Mythbusters who
chilled beer on TV, but salt/water/ice one hands down for cost vs.
temp. decrease.

I honestly feel really stupid right now. My last comment has so many
spelling mistakes it is almost incomprehensible. The reason: My
keyboard battery is dying, and I type wasy to fast. One last thought:
denco recommended a coil on the inside- it may be slightly more
effective in the vat, but if the vat is thermo-conductive, it will
work just as well on the outside, and will become more reusable.

Regards,
Alex Miller

Hmmm?  The "answer":  for some reason I got the impression that the
idea was to cool the mixture so fast that the wax did not clump,
perhaps because this seems like the obvious and normal result, hence
the question.
But this is not stated anywhere.

Chrissyboy,
If my impression is correct, please have patience and ask for a clarification.

Regards, Myoarin

As to the dry ice, frozen co2 has nowhere near enough heat capacity
for the job. I tried to use it as a refrigeration system once... no
good.  Liquid nitrogen running through pipes going through your wax is
feasible in efficacy but is not good to work with and will exceed your
budget to use it safely.

Best solution is probably water, fully saturated with salt with a ton
of ice in it. It'll work fast.

You could also use a full fledged refrigeration system, running freon
or ammonia. I'm sure someone produces an industrial version like what
you'd need. Potential problems of these methods, you'd need a hell of
a lot of water and ice for 5 55gal drums.  And a custom refrigeration
system with a real coolant and evaporators and such, could most likely
be expensive, but more reusable than the water.