The Vespiary

The Hive => Chemicals & Equipment => Topic started by: wyndowlicker on October 26, 2002, 08:11:00 PM

Title: Build your own refrig. recirculator!No more ice.
Post by: wyndowlicker on October 26, 2002, 08:11:00 PM (

Check out the plans for this puppy!Im tired of ice hows about ya'll?

You can tell the queen of diamonds,by the way that she shines.-GD
Title: For the water pump, just buy a drill pump for ~$5 ...
Post by: hCiLdOdUeDn on October 26, 2002, 08:17:00 PM
For the water pump, just buy a drill pump for ~$5 at hardware store. Use a 1/4hp horsepower motor. This will save money instead of buying a ~$70 water pump.

Looks like a good way to save from buying some ice  ;)

Sink or SWIM
Title: wow!
Post by: wyndowlicker on October 26, 2002, 08:42:00 PM
This may just bee my first contribution.I havent seen alot on this subject.Im all over this.bringing multiple bags of ice inside someplace may cause someone to wonder why you need so much ice,when most homes today are equipt with a freezer. :P maybee if Im real lucky somemod will rate this! :P  ;D  ;D    :P

You can tell the queen of diamonds,by the way that she shines.-GD
Title: read it again -
Post by: jimwig on October 26, 2002, 09:31:00 PM
this is just a very nice recirculation device with temp sensing------ it doesn't cool per se.
like i said it just recirculates water - or coolant - if you want ice temps you gotta lower the molecular movement and pumping it around doesn't do that. in fact it probably raises the temp by way of friction in the system.

got me all excited for a second.  this finnish dude has a nice site with some neat techno.

while i'm on the subject - ammonia absorptive refrigeration seems the way to go. unless of course your freezer compartment is large enough - like mine isn't.
Title: I don't get what the trouble with dry ice is.
Post by: El_Zorro on October 27, 2002, 02:31:00 AM
I don't get what the trouble with dry ice is.  Just get a dry ice generating bag, and head down to your local paintball shop and pick up a big old honkin' tank of CO2.  Nobody gives a fuck.  You can even get a tank of nitrogen, for that souped up model you have laying aound for tournaments.

Who is that masked man?
Title: And how much is that dry ice generating bag?
Post by: Rhodium on October 27, 2002, 02:05:00 AM
And how much is that dry ice generating bag? How much is a tank of CO2? How many kilos of dry ice do you get from each kilo of gas in that tank? It is a cost issue.
Title: What about glycol?
Post by: Beeman on October 27, 2002, 05:29:00 AM
cryogenic refrigeration

I read where adding naptha to ice , or dry ice lowered the temperature, possibly maintaining it also??  what is that called?

Swim wonders about the ice machine out back of Maw-n-laws shop, that "needed to bee replaced" because it was producing out of sequence with the other 3 machines.
Is there something that can bee added to glycol to lower its temperature?
I will get actual glycol temperatures in the AM!
Ammonia Generation is something Swim has been interested in!

That old machine and how the glycol, or the cooler, freezes the water in the SS tube, ,  from the inside out!
Thats just 2 interestings!!

Title: Baal has an 'immersion cooler' that was picked up ...
Post by: baalchemist on October 27, 2002, 02:21:00 PM
Baal has an 'immersion cooler' that was picked up cheaply($50)used and it cools liquids to -100c, very handy super-cooling device to have around. Just stick the cooling probe in the shit your chilling,and away you go. Its also a great quick way for freezing up 5 gal buckets of H2O into big ice blocks when needed, and freezer space is lacking.

Shoot Narcs, Not Drugs
Title: thermo - bee king.........
Post by: jimwig on October 27, 2002, 07:50:00 PM
the dry ice bag is the most expeditious way. however the quantity produced  is small- get the big bag ye say - so say ye all-    well better get the big --------- that's BIG CO2 bottle.

I don't think your return for those economical ("yields") bees out there is gonna cut it.

Oh the reason the ammonia cycle kinda appeals to me IS because it is:

LOWTECH - no moving parts and the consumable fuel for the heat source can me any controllable power - propane (my favorite) or electricity or whatever.   Even solar !!!           available everywhere.

AVAILABLE - most cab-over RV's are equipped with ammonia refrigerators. they run duel power sources - both electricity and propane. Round and round the interstate they flew - and flew - and flew.
and these units are around used and new. current technology.

EFFICIENT - meaning they produce on a low maintenance schedule - pound for pound they probably suck but you gotta figure what's more important. Achievability or fantasy.   (Now there's a topic for another time) the refrigerator [RV] i have had experience with worked just fine.both stationary and remote.

 and i do believe that the freezer unit could expanded to a larger more useful capacity with a little effort.

seeya and write if you get cool.

Title: I have a suggestion for a simpler and cheeper ...
Post by: TrickEMethod on October 30, 2002, 08:15:00 AM
I have a suggestion for a simpler and cheeper options to achieve the equivelant or better results.  This coolant supply works particularly well to precool your dried NH3 vapor to speed final condensation.  With my current setup I can produces 2-3 cups of anhydrous ammonia in about 30-40 min, not counting cleanup.  I still have a few things that I still hope to improve, but it produces a product that SWIM has used in solvated electron reactions without a hitch.  And other than a whiff when the setup is taken apart for cleaning, there is no fumes or odor released, period.

The reason I bring this up in this thread is the "cooling" unit I used is cheep, easy and is near perfect for any bee's needs.

What you need...
   $20 - Round plastic insulated drink ice cooler with spiggot
   $10 - 500 GPH 12v bilge pump
   $10 - two 10' long plastic coated ice maker hoses
   $10 - misc brass fittings and some teflon tape
   $50 - total

Go pick up one of those "gatorade coolers" like coach used to bring to socker practice.  Not the squared off kind that never holds enough beer, but the round and tall kind with the spigot near the bottom.  These are available all over, but I'd recomend the camo green kind from the camping and killing isle instead of the electric orange kind in the sporting trash section(duh).

The bilge pump can be found in the boating section at wally world.  Don't get the submergable kind, get the small pump that has the 4" long 3/4" outder diameter pipe threaded input port intended to extend through a water tight bulkhead.  The pump is packaged with the necessary threaded flange and rubber grommet to affect a water tight seal without complicated tools, techniques or solvents. 

You will need a wrench to loosen the plastic holder nut that seats the spiggot into the molded recess in the bottom of the cooler.  Once you remove the button thing that is aways too hard to press, you will need to slightly widen the opening by about 1/16th of an inch all the way around before the suction port will fit.  I just stuck an old bit in a drill and churned it round the rim for 90 seconds, but no doubt dremmel sells the perfect cutting tool for those more style concious.

Since the cooler will most likely be filled with ICE, some sort of effort should be made to avoid pulling ice into the pump.  What seems to work the best is drill a good number of 1/4in holes in the last inch and a half of the treaded suction pipe which will extend into the cooler.  To keep out the smallest pieces of ice or undesolved CaCl/NaCl, secure a piece of fabric or hand towl over the suction holes using a rubberband or wiretie.  If you have plenty of holes your coolant flow will hardly be affected by the filter profallactic.

To get the coolent to and from whatever device you wish to cool, pick up a couple of those 10' long white polymer protected water hoses sold at the hardware stores for your refrigerators ice maker.  The small diameter of the hose does restrict the flow of the coolant a bit, but more importantly it limits the amount of time the coolant spends in the poorly insulated hose. 

The coolant supply hose is attached to the 3/4" NTP threaded ejection port using one of four 3/4" NTP female to 5/16" male compression fittings you should aquire wherever you get the ice maker hose.  While you have your drill out, you need to drill a half inch or so hole in the center of the fitted platic lid to alow the returing coolant to complete the cycle.  A couple of 1/2" brass washers can be screwed into place by using a brass compression fitting to extend through the lid and using the compression nut to hold the washer down.  Looks nice too, until the water, CH3OH, CaCl or NaCl turn the shiney brass finish - lime green. Teflon plumbers tape and a bit of care are advisable to keep the sharp brass threads from 'cross threading' the softer plastic threads and soaking the suroundings in MeOh or worse.

To pull it all together I would recomend securing both coolant hoses together using wireties every 6" or so, and then wrapping them both using a single section of the split foam insulation sold for the hot water plumbing in your home.  This cuts down on clutter and saves heat loss and wasted ice.  Style points are awarded for those who invest in few garden hose quick connects.  This minimal upfront investment will be particularly helpfull when it comes time to fit the somewhat ungainly device into an evidence locker.

Also, by picking up a few extra male adapters you can connect the coolant system to several different devices in an instant witout dragging around wrenches, extra adapters or teflon tape.

Any 6v-12v transformer / regulator from the shack will drive the pump, as will a motorcycle or car battery if you are roughing it.  Since the pump is DC, simple rate control can be affected by placing a light dimmer between the power supply and the wall, or using a simple PWM circuit available all over the net.

What you load the cooler with will depend on what you wish to cool, for how long and how cold. 

Here's some coolant combinations that have worked for me...

   condenser for solvent reflux
      - straight water with a few plastic 'cold packs' from the freezer

   Solvent recovery
      - dilute CaCl/water solution and a 10lb bag of ready ice.
      - make sure CaCl is well disolved to avoid cloging pump

   precooling NH3 vapor to speed condensation
      - strong MeOh/water solution and a 20lb bag of ready ice

I will try to add pictures of the cooler setup into a DOC here shortly, because it really is an easy and cheap solution that works near perfectly.

Let me know if you have any suggestions...

And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
Title: Tip: Post a link to the picture only, in its ...
Post by: Rhodium on October 30, 2002, 09:26:00 PM
Tip: Post a link to the picture only, in its original location. The URL will be hidden.
Title: I have a cryo dewer, several in fact.
Post by: TrickEMethod on October 30, 2002, 09:38:00 PM
I have a cryo dewer, several in fact.  I also have two of the 5' tall tanks of CO2 and one with Helium.  But I found working with liquid CO2 to be VERY hazardous.  The minimum pressure you will have to contain is 800psi, and that is if the tank is at room temp.  Also, since different material have different coeficients of expansion you have many problems with using brass fittings with stainless etc...

I had a stainless tube blow out of a brass compression fitting and go through the sheetrock over my garage and dent the underside of my roof with no warning long after it was under pressure.  So if you go stainless, you have to go stainless all the way, do not connect brass to stainless with a threaded or compression fitting.  I thought I would be ok by having the metal that would shrink slower on the outside, but I forgot that as it warmed up later the outside metal would then expand quicker.  Even worse, being on the outside it heated up faster than the inner compression fitting.  And it became a spear gun driven by 800psi and you can not imagine what a deafening roar 800psi makes as it rockets out of a small diameter compression fitting.

also to get efficient cooling you must invert the tank and lead liquid through a high pressure line to your coil and affect an expansion control valve at the beginning of your coil.  You will also need a cooperating retarding control valve at the terminus of the coil or you will be venting high volumes of CO2 and the vast majority of your detlaT out into the atmosphere....

I am fairly competent and more than willing to take on tricky shit.  And I have and can use a MIG welder.  I also have high pressure hoses and tanks already, but I have satisfied myself that dry ice from the grocery store half a mile away KICKS ASS on liquid CO2.

I can get -20deg(REAL WORLD) using ice/MeOh, and have two $25 CPU heat exchangers and a 170watt peltier sandwiched between them.  I have a 8 channel A/D and a quad output PWM regulated 400 watt dc supply on my lab PC that I intend to hook up to track the temp at both sides of the peltier and at the in and out of both heat exchangers.  I will drive two bilge pumps with one channel each and double up the last two for the peltier.  After I fuck around with pump speed, peltier load vs. deltaT, etc. I will let you know.  But I already tried just hooking the shit up to a supply does not work.  If you do not balance the load of the peltier and exceed the heat ejection rate the result is a produce deltaT instead of negative.  If you underdrive the peltier, you get no additional cooling affect and the peltier acts as an additional thermal barrier between your secondard coolant and your target.

Once I can play around with the setup on a metered system it is likely that some simplifying rules of thumb can be made.  Such as matching two 500GPM pumps off of a single supply to a 170WATT peltier driven by a single supply and never letting your secondary coolant get above -20deg Celcius. 

Once I figure out a combination that works together I think an additional $50-60 will take the cooling system I have a make it capable of delivering ~100watts of -50 to -60deg celcius cooling using MeOh as the primary loop coolant and MeOh/H2O in the secondary.

Until then I have been using a thin glass vase caped off with a rubber plumbing flange dropped into a mixture of dryice and acetone.  When the dry precooled NH3 hits the -78deg glass it condenses as fast as I can produce it.  I get 2-3 cups of NH3 on $9 of dryice and still have plenty left to maintain cooling for 24hrs if I don't use it right away.

I will try to writeup construction notes(w/ pictures) on the NH3 generator, precooler and dryice condensation rig today.  I think most bee's will just stick with the dryice option, if so you can build the entire setup for about $125 in a single afternoon from 100% wally world and depot parts.


And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
Title: Peltier!
Post by: Rhodium on October 30, 2002, 10:22:00 PM
That was a VERY interesting post!

What kind of peltier element would you need to get enough cooling capacity to drive a regular reflux/distillation condenser? Would you need a cooling water reservoir on both the primary and secondary circulation circuit?

How do you modulate the effect of a peltier element? Do you cycle it on/off or do you vary the voltage supplied to it? To ensure that the cooling water to the condenser stays at 0-10°C, how cold does the cooling water to the peltier need to be? Would it be enough to cycle 20-40°C water through it from a 5-10L reservoir (starting at room temp, and allowing for gradual heating of it, without affecting the temperature in the condenser circuit too much)?
Title: 100% stainless is the way to go, wish I had known ...
Post by: TrickEMethod on October 30, 2002, 10:25:00 PM
100% stainless is the way to go, wish I had known that before.  I didn't want to wait for special ordered stainless parts that cost $25(and up) per fitting, so I tried brass and could have very easily killed myself or someone else.  FYI, all the fittings and hoses I used were at least 2500psi burst pressure rating.  But those ratings are based on room temp containment of none corrosive gasses, and usually excluse H2.  The H2 exclusion is due to H2's ability to escape because of its small size.

As for liquid ref. not getting to 800psi, you should recheck that assumption.  Any liquid CO2 tank will float around 800psi at room temp.

Maybe you were talking about some other gas, but be really sure before you fuck around because if you get hit by a fitting launched by 800psi it wount leave a wound, it leaves pieces!

And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
Title: The answer to all your questions is "yes, but...
Post by: TrickEMethod on October 30, 2002, 10:58:00 PM
The answer to all your questions is "yes, but..."

A 170watt peltier with a max detlaT of 70deg celcius can do just that, but only at a friendly high side temp.  At you follow the output curve either direction from a given devices peek(these rating are always based on the peek), they fall off 30% or so fairly quickly.  So I just mentally derate the device by 40% and forget about it.

If you wish to drive a condenser using peltier you get two potential benefits, not having to supply ice to a cooler(pretty minimal benifit) and extended period, digitally controlled temperature control that can follow a timed curve.  By purchasing a $99 device that hooks to your computer you can sample the temp of the coolant and drive a PWM(pulse width modulated) adjusted voltage or current to the peltier.  Temp control with feedback, using a visual basic program. 

By sampling other cheep sensors such as conductivity, ph, or various ion sensors, you could even add inteligence to allow the system to determine when to trigger the next transition or to shutdown or trigger an alarm. 

Way off the subject...
I had an automatic panic and flush setup on one reaction that used a $13 X10 controller to turn on an external blower and another to trigger a 24v AC voltage water valve(sprinkler system) to flush the contents of an plexiglass containment chamber with NaOH.  I was fucking around with H2S, and wanted to live to tell.

I built an h2s sensor using a piece of chemically treated paper and a USB webcam.  VB can aquire a BMP from the cam each second and I read the RGB color values all using an activeX control from from the internet.  If the RGB values shifted more than 15%, I flushed everything with NaOH and went to see a movie.  The only real trick was suppplying a consistant light source.  finally I built a box around a testtube with the light a camera mounted inside.

If anyone is interested in an H2S sensor, I will start a new thread.

And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
Title: High-tech fractional distillation
Post by: Rhodium on October 31, 2002, 12:07:00 AM
One really nifty thing you could build with a peltier-cooled condenser would be a fractional distillation column, where the temperature of the cooling water gradually increases to allow for a REALLY slow distillation head temperature increase (the thermometer being electronic, sending feedback to the control circuit).
Title: Peltiers...
Post by: ClearLight on October 31, 2002, 02:20:00 AM
Hey guys, all the specs you need for peltier construction are around the laser guys on the net... we use them to cool the frequency doubled crystals that get sam's laser faq I believe I saw specs and schematics there to drive them... I've looked into them on a laser project but chem come first ;) ,  anyway they work well, and these guys are all about surplus P's at 5.00 a pop... great tech.. you can drive it with a basic stamp controller for the control, no prblm, to reg the power for it...

Infinite Radiant Light - THKRA
Title: I checked out the link, but it contradicts your ...
Post by: TrickEMethod on October 31, 2002, 05:05:00 AM
I checked out the link, but it contradicts your statements about pressure tanks.  It doesn't give any pressure/enthalpy information about CO2 at all.  If you think that O2 or N2O data gives any indication of how CO2 behaves, then you need to do some reading.  Here is what your link said about pressure tanks...

3. Cylinders
AS 2030 1977. ChromeMoly Alloy steel or now Aluminium. Aluminium cylinders are extruded from bar stock, neck pressed at 400deg.C, heat slowly to 525deg.C, quenched in water, and finally aged at 175deg.C for 8 hours. All screw threads are the same (1:8 taper Whitworth 55deg. curved ends 14 tpi) but the pin indexing on the valve body and colour of the cylinders vary (AS 1944, 2471). Pressure tested to 24,000 Kpa (240 Atmospheres) with water for 30 seconds; if the cylinder stretches more than 0.02% it is rejected. Wall thickness 3mm.

So tanks are tested to 240 atm which is over 3400 psi.

Here is another link that gives more information (

Here is a quote from that page, which I stongly urge you to read...

A CO2 cylinder filled with liquid CO2 at room temperature has a gas pressure of about 800 psi. above the liquid. The enthalpy available to the cylinder contents are those values in the liquid-gas two phase region at about 800 psi., in the spots labeled "A" for the gaseous CO2 and "B" for liquid CO2. As the gas or liquid enters the orifice, the pressure drops from these two points with constant enthalpy values (under ideal conditions) into the two phase liquid-gas region

And here is a hard print reference...

   Perry's handbook for chemical engineer's 6th Ed
   page 3-111 table 3-161
   Critical constants of Elements and Org & Inorg Compounds
   CO2 -  Te  31.1 deg C
          Pe  73 atm (~1050 psi)
          De  0.460 g/cc

And your comments about the peltier not being able to achieve the temperatures you are targeting, that is not true either.  The peltier can operate well below -100 deg celcius.  This would require a two stage peltier combination that is efficiently cooled by ice/MeOH, but it is not overly difficult.

What I wonder is why you think you need that low a temperature.  You don't need it for condensing NH3, I can promise you that.  I can do that all day long without anything near that.

I surely hope you do some more research before you hurt yourself or someelse.  I am not overly proud to admit it, but I could have easily killed myself or any one of a number of people around me fucking around with liquid CO2 and I understood the danger much better than you seem to.


And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
Title: Peltiers to cool circulating cooling water
Post by: TrickEMethod on October 31, 2002, 06:19:00 AM
I think we should start a new thread on peltiers and their uses, but to answer your question about fractional distilation...

They work quite well for distilation of low boiling substances, I have done this with a very quickly rigged setup.  I didn'nt continue with the device however because it was unlikely to be able to handle distilations requiring 130 deg Celcius.  Most peltiers are destroyed by temps as low as 70 deg Celcius.  Marlow has a couple of devices rated for high heat, here is a link to their web site. (

They discuss PWM control and have extensive informtion on matching specific devices against heat load.

In the distilations I was doing, I was using the Peltier to heat the flask, instead of cooling it.  This would all depend on what you were distilling of course.  What is nice about Peltiers is you can switch from heating to cooling by reversing the direction of current flow.  So you could transition from 50 deg Celcius above room temperature to 50 deg below all with a single stage device and a heat sink.

If you push the device to hard however, small fractures can develop between the small internall elements stopping current flow and killing the device.  I have done this to several devices. 

By stacking a smaller device on top of a larger one, you can increase the temperatur difference you can achieve.  So if your first stage device drops the temp by 50-60 deg Celcius, a second one could start there and shoot for another 50-60.  The efficiency does however drop off.

What makes Peltiers somewhat TrickE, is the parasitic heat produced interal to the device.  The device 'pumps' heat from one side to the other side, but it also adds waste heat as a byproduct which must be ejected or removed by the heat exchanger.  If heat is not removed at the required rate, the chip will quickly exceed its operating temperature and destroy itself.  This can happen in 60 seconds, I have done it myself. 

The key with Peltiers is heat ejection, if you can keep the 'hot' side cool, the cold side will be, as much as 70 deg cooler.  So if you are cooling the 'hot' side with ice/MeOH to -20 deg Celcius, you will easily get -60 deg Celcius on the cold side even under a 50 watt heat load.  But your cooling system will need to remove maybe 80 watts of heat from the hot side of the peltier, 50 that is being pumped and 30 or so added by the device itself. 

To exchange that amount of heat and still remain at -20 deg, the coolant will have to be at least 20 deg colder.  I need to site down and calculate the exact numbers again, but I have sketched it out several times before.  The difference in temp and the conductivity and surface area determine the amount of BTU's per second which limits everything else.

When you over drive your Peltier and pump more heat than can be removed from the device, the 'hot' side gradually rises and the cool side follows it.  Before long, seconds in some cases, the 'cool' side can go above room temperature becomming a heater and soon after becomming trash.

Meaning that a poorly cooled device might produce a maximum cooling result of only 30 deg below room temp when powered by 25% of its full power rating.  And if driven by 50% of its full power rating cease to cool at all and actually start to heat the 'cool' side above room temperature.

That is why you need tempurature sensors on the hot and cold sides of the device to adjust the supply current dynamically.  A simple control program can make the necessary adjustments to account for variations of heat extracted from the reaction, variations in the coolant temperature and changes in the desired target temperature for things like extended crystalizations or distilations.


And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
Title: It could very possibly be that I don't understand ...
Post by: TrickEMethod on October 31, 2002, 06:33:00 AM
It could very possibly be that I don't understand what you meant to say.  I have never dealt with a CO2 tank that was only filled with gas.  I wouldn't know what one would be used for even, but it sure wouldn't be usefull for cooling.

The gas would cool down somewhat when it exited the tank and expanded, but nowhere near the temperature drop seen when a liquid evaporates.  And without the volume/mass advantage of a liquid, the tank wouldn't hold enough to matter.  You would have a much smaller mass, that provided a lower cooling potential per unit mass.  A poor combination for cooling all around.

BTW, did you even look at the link I posted?  It is one of the best I have found on the subject.

And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
Title: What's wrong with immersion coolers?
Post by: Triton on October 31, 2002, 06:40:00 AM
Would'nt it be much easier and safer to just use an immersion cooler instead of messing around with CO2 and all thats required to use it?
Used ones aren't very expensive at all.
Title: thermocouples are cheap
Post by: goiterjoe on October 31, 2002, 07:25:00 AM
It's easy to attach a thermocouple to each side of the peltier device to get temperature readings to use for closed loop feedback control.  PWM modulation would be a lot easier than PAM, since you could just use relaying circuits to regulate temperature instead of having to use amplifying circuits.  You could pick up a programmable controller board for under $100 to automate your cooling device; this would also make the setup extremely portable.  You could write different programs to load onto the controller board for different setups and reactions.

I've started a couple of threads on peltier devices in the past.  If you're going to open a thread on them, we ought to talk about everything from power relaying to PID controllers.  That way we can talk about the complete electrical design of the system.

If at first you don't succeed, try, try again. Then give up. There's no use being a fool about it.
Title: Yes please, this was hugely interesting.
Post by: Rhodium on October 31, 2002, 07:43:00 AM
Yes please, this was hugely interesting.
Title: lets see if the ambient coolant temperature is ...
Post by: jimwig on November 01, 2002, 07:18:00 PM
lets see if the ambient coolant temperature is 20C
and the high side of returned coolant is 100C
the required ideal drop (high efficiency) would be -80C
that's a lot --especially for continuous use

though it is a small volume and a small area-- hmmm?

can a peltier or a series of peltiers be counted on for that sort of use?

two conventional compressors such as in lab freezers (the minus zero variety) seems more likely - hooked up in series so as to have an intial drop on one and then a secondary drop to the desired level on two.

Title: ya know the volumes here are really the problem.
Post by: jimwig on November 01, 2002, 07:27:00 PM
ya know the volumes here are really the problem.
i mean if you have say a ten thousand gallon coolant tank and you are lowering the temp 80C at a flow rate of 2gmp then you are considerably along the way.

i don't have a lake handy and using that kind of flow would make me feel wasteful. recirculation and cooling has always been the desired method.

something along the way of a precooler before return to the coolant pool and then letting the adsorptive recycling coils be submerged in the vast ==== nevermind.

i still really like the solar ammonia collector. its just a fantasy but who knows....
Title: I am not entirely sure I understand you ...
Post by: TrickEMethod on November 03, 2002, 06:46:00 AM
I am not entirely sure I understand you statments/questions.  But on a hunch, let me offer some comments...

If you are trying to 'drive' a condenser, you have to do two things.

1) Have enough heat ejection capacity to keep pace with the 'load' caused by: 

  a) vapor condensation
  b) super-cooling of the condensate before it exits the condenser
  c) heat exchange with the surounding environment

2) Deliver accurate temperature control through real-time current adjustment based on sensor feedback from the system.

I like the strategy of using a secondary coolant reservior filled with anything from water at room temp to MeOH/ice at -20deg Celcius to deliver the real heavy lifting and use the Peltier as more of a controling device or when necessary, range booster.

Depending on a Peltier to deliver a 30deg Celcius temp drop is practical, anything greater is most likely going to require multiple stages.  And even with multiple stages, going above 45deg Celcius is pretty tough.

This means that a Peltier only system working from Ambient (22 deg Celcius) might get you down to -20 or so.  And achieving this will absolutly require a liquid-air heat exchanger.  You just can't get enough heat ejection from forced air heat-sink dissipation from a 1.5" x 1.5" surface coupling. 

Believe me.  I tried, and tried, and tried... and never even got 10% of what I needed.  If you arn't willing to back a Peltier with a surface/liquid exchanger, pump and secondary coolant, then you should not bother with the device.  It's just took fucking lightweight without it.


And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!