water un-chiller

Discussion in 'Darkroom Equipment' started by David Brown, Jan 3, 2014.

  1. David Brown

    David Brown Subscriber

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    In a recent thread on another forum, I posted this about the low-tech water chiller:

    You can basically copy a keg chiller.

    1) Picnic cooler
    2) A copper coil placed inside the cooler
    (such as: http://www.amazon.com/Copper-Immersi...ersion+chiller)
    3) Fittings at both ends of the coil

    Fill the cooler with ice water. The temp of the water coming out of the coil will depend on the flow rate. Run the water slow enough and it'll come out pretty close to freezing. Run it faster for less chilling. You'll need to add ice every so often. Instead of adding ice cubes use plastic bottles full of water that you freeze. Easy to replace when they've melted and they can then go back into the freezer to refreeze.


    The question at this time is: Can this work backwards, i.e., can the ice be replaced by say, an aquarium heater, and the water warmed up a bit?

    We have had a very cold December here in Norte Tejas, and currently, the ground water is coming out at 50F or lower. I would love to get it up to at least 60F for print washing. What does the collective think?
     
  2. Roger Cole

    Roger Cole Member

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    You don't have a water heater and hot water tap you can just mix with the cold?
     
  3. Mark_S

    Mark_S Member

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    I have a small water heater (6 gal?) dedicated to the darkroom, was quick and easy to install.
     
  4. Truzi

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    It is theoretically possible, no reason it should not work. I was going to say this should not be an issue for B&W, but I see you are talking washing prints, not developing. On the rare occasion I've had to warm my developer, I simply filled a plastic basin with hot water from the tap, placed bottle of chemicals in it, and waited for them to reach the temperature required.

    I will be doing C-41 soon and will use aquarium heaters to maintain the correct temps of the water baths (and indirectly heat the chemicals) - I've already tested without chemicals and it is doable. However, this is not running water. I've found a couple aquarium heaters work slowly, so you may need many, or a different source of heating, since you are presumably running the warmed water.

    Still, I'd think you could simply get the temps you want from the tap, unless you do not have hot water running to your darkroom, or don't want to involve the house's water heater (expense, or not wanting to wait for recovery). You may need more copper (larger coil) than with the chilling, but I could be wrong. Also, the materials and your time are an expense too - so make sure you put that into the equation.
     
  5. David Brown

    David Brown Subscriber

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    Thanks for the replies so far.

    Let me clarify:

    The question was a fairly straight forward yes or no (or so I thought).

    Yes, I could install a water heater. (The darkroom is not in the house) I plumbed for one, but have yet to feel the need for the expense of installation and operation. It would only be needed here in Texas for a small part of the year, and then only intermittently during that time. I have experience with this, and have chosen not to go with a conventional water heater.

    It's also not necessary, I'm just wondering.

    I am aware of materials and my time in the equation. But it is minimal. I guess what I assumed from my OP, but perhaps is not obvious, is that - given - that there is already a chiller installed and operating, would replacing the cold source (ice) with a heat source provide warmer water at a low flow rate for print washing? ( Maybe 3 time a year ...) :smile:
     
  6. wildbill

    wildbill Member

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    switch the ice cubes with hot lava or coals:smile:
    sorry, my 4yr old is always talking about hot lava. I don't see why something you could heat up in a microwave wouldn't work. like those hot/cold packs?
     
  7. bdial

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    What about some sort of solar rig, with an insulated storage tank? If your requirement is modest, it probably wouldn't need a very big collector.
     
  8. Truzi

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    It should work, though I don't know if a few aquarium heaters would be up for the job. I'd think you may need something a bit more robust. Would the size of your coil allow you to place it in something like a large pot that could be put on an hotplate?
     
  9. David Brown

    David Brown Subscriber

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    Yes, and I thought of that. However, I would not feel comfortable without monitoring water heating over a hot plate. Even inside the darkroom, working under safelights and getting "in the zone" could lead to a mishap ... :blink:

    An aquarium heater that will heat up 5 gallons to about 80-85 degrees would be safe enough in an insulated container (one leaves them in the fish tank 24/7). The real variable is whether the cold water running through the coils would collect enough heat - and - NOT dissipate too much heat from the water jacket. Maybe two heaters? Looking at prices, it appears that it will cost me less than $30 to find out. Whereas a full grown water heater, installation, and plumbing fittings will be hundreds!

    :laugh:

    Yeah, the hot coals problem is what I'm trying to avoid. The hot packs heated in a microwave (and my darkroom has one) would probably lose heat too fast, where the aquarium heater would at least keep heating.

    I still have my heating element that I used to use for E6 processing. With it, I got about two gallons for a water jacket up to the required 100 degrees or so (IIRC).

    Hey, other people are buying more cameras or testing 14 different films, I'm doing this! :tongue:
     
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  10. Roger Cole

    Roger Cole Member

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    Got it now. Sorry, but the idea of a darkroom that is not part of the house and connected to the house plumbing never even occurred to me, so neither did the need for such a thing. Good luck with it, I see now!
     
  11. Truzi

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    With the aquarium heaters, you can often pull off the adjustment knob and reposition it. I did this to see if I could get C-41 temps - though you're not going that high. My only thought is they are not "fast." I'd get a few (depending on the size of your container). I bought some cheap ones at Walmart.

    For the hot-plate idea, if the unit is in a place you won't accidentally knock over or touch, you can dial it in at the flow-rate you want. It would take some time, but you'd not have to worry about the temp getting out of hand. Of course, I'm assuming an adjustable hot-plate, not one that is all-or-nothing temperature-wise. If your coils never touched chemicals, you might even make some soup while your washing prints.
     
  12. ME Super

    ME Super Member

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    IIRC most heat tapes are set to kick on around 40*F, if the water temp in the pipe is 50*, the heat tapes will never kick on. Nice thought though!
     
  13. Mr Bill

    Mr Bill Member

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    I'd say it would sort of work, if you size things right. If you know 1) the required flow rate for wash water, and 2) the temperature rise needed, you should be able to estimate how much wattage you need on the heaters.

    Working out a set of numbers, I'd say that a single 300W heating element would be able to raise your water temperature about 15 degrees F (from ~ 50 deg to 65 deg) with a flow rate of about 500 ml per minute (0.14 US gallon per minute, or alternately, 1 gallon every 7 minutes).

    While the heater is running full out (300 watts), it doesn't really matter what the temp of your "reverse-chiller" is; all of that 300 W is getting dumped into your system, and the only thing that removes it is the wash water. (Your water bath will eventually rise to the temperature it needs in order for the wash water flow to extract the 300 W equivalent.)

    ps. I didn't verify my calcs, so it would be smart to verify with a real test. Based on the numbers I got, 300W should heat a half-liter (500ml) by 15 deg F in about a minute. (Let me be more clear - it would not only be smart to verify, but you would have to be nuts to not do so.)

    pps. If you want to calc it yourself, use the old rule that a BTU raises the temp of 1 lb water by 1 deg F. In more modern times, a BTU is equivalent to about 1,055 joules, where a joule is equivalent to 1 watt for 1 second. So you can get your BTU by any combination of watts x seconds; 1 watt for 1,055 seconds, or 1,055 watts for 1 second, or 300 watts for 3.5 seconds.
     
  14. polyglot

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    Your simple answer is yes, it will work exactly as effectively to warm water as to cool water. Its performance will depend heavily on getting some motion in the bucket otherwise you will have lots of warm water with pockets of cold surrounding the coils and only convection to move things along. You want your heat exchanger pipe to be as long, narrow and as thin-walled as possible, and to be made of copper.

    Heat transfer at a point is symmetric with respect to the sign of temperature difference, all that matters is the thermal resistance sigma (kelvins per watt, K/W) and the temperature difference (dT) between the warm and cold water. The power flow rate is just P = dT / sigma, is in watts, and from that number you can compute the temperature rise of your water using its specific heat (4.2 J/g-K). The thermal resistance of your pipe you need to calculate from its wall thickness and surface area.

    An aquarium heater is much too low in power (40W?) to be of value here, you will want a powerful submersible heater like those from an electric kettle. By the time you add a temperature controller though, you've basically built a water heater and I'd rather buy one than make one. At 1L/minute and equilibrium, a 40W heater gives you a temperature rise of only half a degree! Sure you could preheat a large quantity of well-insulated water, but this means you're very limited in the amount of washing you can do because you will rapidly cool down your tub of warm water.

    I don't know if you have a Jobo, but I've seen them modified by putting a coil of copper tubing in the bottom bath and you run tap water through the tubing to get process-temperature fresh wash water on demand. A Jobo heater can be as much as 1kW (at least, my CPP2 has a 1kW element, the CPE is probably smaller), and with many litres of water in there, you can get a lot of warm wash-water out of it without perturbing the bath temperature too badly. With this approach, you can have basically unlimited wash water with no additional heater.
     
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  15. David Brown

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    OK, now. This is getting interesting.

    Mr. Bill: I am using a Versalab which specifies a range of .3 to 2.0 GPM, with .3 to .6 GPM as "should be satisfactory". I only need (want) 10 degrees, but that still probably leaves 300 watts a bit short.

    Poly: I don't have a Jobo, but the idea you propose using the Jobo with a coil of copper is more or less what I'm talking about: a 50 foot coil of 3/8" copper tubing immersed in a heated water bath. I still have my old Phototherm immersion heater from my color days (back in the 1970s), but it is only 500 watts.

    I may experiment with this down the line. For now, though, I suppose I might leave well enough alone. Ilford's data sheets on their papers states that anything above 5C/41F will wash both RC and FB papers. If I have the washer full of water at room temp, about 66-68 degrees these days, then the wash temp will start there and gradually decrease as the flow goes through the washer. Really, that should be fine. I've never really monitored it (wash water temperature IN in washer) but that's probably the next step.

    Interesting discussion. Thanks everybody. :smile:
     
  16. David Brown

    David Brown Subscriber

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    When we bought this house, it had 3 full baths and a powder room (still does, duh). Four chairs, no waiting. Since I am used to a dedicated darkroom, (and there is certainly room) and not working in a bath, I suggested gutting one of the baths and refitting it as the darkroom. My wife looked at me, well, you know ... :whistling:

    Anyway, we have a detached garage/shop building that the prior owner had built to work on his cars - his hobby. In the large attic space above the shop, he had built a gym, and had partially finished out the space. I completed what he started and it is 12x18, fully insulated, heated and cooled, etc. But, no native plumbing. I ran a cold water line, and actually plumbed for a water heater, but then decided against installing one based on prior experience. It isn't needed in the darkroom in this climate except rarely, and so sits unused most of the time. It's just not good for them in the long run. Yes, one can turn them off and drain them, but then starting them up when they are needed is a job in itself, and it got to be a cost/benefit decision, admittedly subjective on my part.

    The same wife referenced above has told me to just get over it and install a heater, but what does she know? :D

    http://newdr.blogspot.com/2010/07/drained.html
     
  17. Mr Bill

    Mr Bill Member

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    That's a good point. On the other hand, you don't need tight temperature control on wash water, especially with a low flow rate into a larger tank/tray, so I dunno. If I didn't have a submersible pump for circulation, I'd just try it and see how it works.

    I don't think it's necessary to figure the efficiency of the heat transfer because the water bath will eventually reach whatever equilibrium temperature it needs to do the job.

    That was also my initial thought until I looked them up. Then I found that 300 watt heaters are pretty readily available.
     
  18. polyglot

    polyglot Member

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    300W is a start and probably good enough to get a nice store of water up to temp while processing film/paper, but not enough in the steady state. 0.3GPM is 1.15L/min at 300W is only 4C of temp rise. Good enough to wash film, but not really enough power for FB washing.

    Doing a hypo clear step will obviously reduce the quantity of warm water you need.

    Or a proper heater - it sounds like you have permission from Management for that :wink:
     
  19. Mr Bill

    Mr Bill Member

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    To be clear, I didn't mean to imply that 300 watts is enough heat.(Based on David's stated specs for his Versalab, 0.3 to 0.6 gal/min "should be satisfactory.") But it seems fairly easy to use a pair of them. Whereas if you only had 40 watt heaters, you'd need fifteen of them.
     
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  20. MattKing

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    Is your air temperature appropriate (around 68F/20C)?

    If so, can you put in a largish tank and then let the air warm it to what you need, with maybe a little help from a downstream aquarium heater?
     
  21. Ronald Moravec

    Ronald Moravec Member

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    It is called a heat exchanger and works both ways although industrial ones are made for more efficient use and unidirectional
     
  22. Luis-F-S

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    May not be needed in North Tejas, but here is South Luisiana which BTW is a whole lot warmer than N. Tejas, I have a dedicated 12 gal water heater for the darkroom. Water heaters are frigging cheap. A whole lot cheaper than an "industrial heat exchanger." If mine is unused, I have an "on/off" switch and I just turn it off. If sporadic use is bad for them, get a new one in 10 years when it craps out. You'll also be able to wash your hands with "warm" water for those 10 years during the winter in the darkroom and then be able to get off the computer and actually spend the time printing. That's what I did today, water was coming in at 62 Deg, and the "dedicated water heater" warmed it up to 70 through the control valve.

    I have a similar setup inside an RV garage that the previous owner used to store race cars. I ran off the well pump line and split to the water heater and then the chiller. I have the setup shown in the LLF Forum darkroom portraits around page 51-52, and here in the Darkroom Portraits II, and also under a thread for Intellifaucet Installation:

    http://www.largeformatphotography.info/forum/showthread.php?109688-Hass-Intellifaucet-Installation

    If I may, I suggest that you listen to your wife. I do mine and it's made for a better marriage. :tongue:

    L
     
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