Cooling water with Nitrogen

The apparatus seems to be a method of aerating the water in a fish tank.

1) Why use nitrogen? If there are fish living in the water then having little oxygen in the water will eventually cause asphyxiation. If the purpose is to introduce turbulence then air is cheaper than nitrogen, as the purification step to generate nitrogen is avoided.

2) The back-pressure is determined by the depth of the diffuser below the water surface. You can only regulate the flowrate.

3) The temperature of the tank contents, in the absence of any heat sources, will be determined by the wet-bulb temperature of the surrounding air. Evaporation is taking place into the bubbles and at the turbulent surface of the fish tank. In the limit, the water tank temperature will approach that of the wet-bulb temperature of the surrounding air, over time. It is behaving like a cooling tower.

4) Asphyxiation of the fish and people in the room, due to the low levels or absence of oxygen, because it has been displaced by nitrogen.

5) Using air, yes: most fish tanks do this. Using nitrogen, only if there is sufficient ventilation taking place to sweep the nitrogen-rich air out of the building so that oxygen levels remain tolerable, though why would anyone want to kill those lovely little fish swimming around?

DON'T MESS ABOUT WITH NITROGEN. IT'LL HAVE YOU!

Good morning.

What you are telling me is that this method of cooling down water is NOT a good idea and is DANGEROUS?

I need to find a way to lower temperature to the 10-20 C to transport these small fish over long distances for several hours in 35-38C air temp. At present they are dying. We already have an Oxygen line in the tanks and that works fine from about November through March. But for APRIL to October it is so hot many fish are dying.

What would you suggest to cool the water? I need something simple........

Thank you.

netmaker

Ah! Some additional information - the tanks are now mobile in low latitudes and intended for transporting the fish.

Given the likely range of ambient air temperatures and humidity levels, insulating both the vehicle and the tank used during transport would be a good first step. Installing some form of refrigeration system to chill the water to the required temperatures would be a second, and the resilience and size of the fish would determine those parameters needed for the correct design and operation of the system. Monitoring oxygen levels in the water would also be of value, as bubbling nitrogen would be a good way of displacing oxygen from the water and asphyxiating the fish - it could be that they are dying from lack of oxygen, not lack of coolth!

Hi,

It seems to me that you are trying to utilise the cooling effect of expanding gas to cool the water (don't quote me but I think this is called the Joule-Thompson effect). If this is so, and you don't want the Nitrogen to contact the water, could you rig a coiled copper tube, similar to the condensing coil in an alcohol still, in the water and allow the Nitrogen to expand within that. The water in contact with the coil would cool and so on... You might want some kind of circulation device also.

Just a thought.

Drew

Keep adding some ice to the water. Slip in chunk of ice and it will take time for it to melt down fully. You may also have to remove the over flowing water. Ice can also be outside the fish tank to cool the fish tank water.

You said;

"You may also have to remove the over flowing water."

Fill a glass with water and ice.

Let the ice melt.

Notice that the level in the glass lowered slightly.

Here are some alternative ideas.

1. Can you direct your air conditioner flow by the tank?

2. Could you have ice above the tank and let the melting cool down the main tank?

3. or just drop some ice in every half hour.

good luck

yes.

regulator.

heat trace, for one.

few. pressure. killing fish.

yes.

The ice idea works but it gets real cold then it gets warmer very quick. This stresses the fingerlings.

I like the idea of a cooling coil of sorts. We haev access to a 110V power source during transport and storing........ any ideas of how to make something SIMPLE AND SAFE?

Thank you all......

netmaker

Netmaker,

Greetings from your neighbor in Texas!

Since you have 110 at your disposal, why couldn't you take a window unit airconditioner, plumb the evaporator into the tank and then recharge? You would have to do something with the fan on the evaporator side, but it would be cheap and effective. Furthermore, you would already have a thermostat (may have to modify the thermostat for your desired temperature range) and could keep the temperature within a few degrees of your desired range. A window AC at the local discount store is < $100. You would have to find a creative AC man, or do the modification yourself. Just from previous postings, I would imagine you have the creativity and expertise to handle such a modification. In the long run, this would be far cheaper and safer (for you and the fish) than liquid nitrogen, or nitrogen in general.

B.T.W. What kind of fish are you transporting?

Good Luck!

DAG

How about a 100V water chiller??

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I try to keep things simple. Go to Home Depot (Building supply store) buy some cans of "Great Stuff" it is an aerosol can full of polyurethane foam. Build up a layer on the outside of the fiberglass tank 2 to 3 inches thick. Place blocks of ice in the tank. Perhaps increase the circulation rate to even out the temperature of the water in the tank.

Now the hard way: Take apart a small window mount air conditioner and submerge the evaporator coil (the one inside the house that gets cold) and the thermostat probe into the water. Make sure the cooling fan on the condensor coil still circulates air to dissipate the heat. try different settings on the Thermostat until the desired water temp is maintained. It would not hurt to insulate the tank with this approach as well. Good luck!

Pretty straight forward I feel.

Run the Nitrogen through an exchanger/coil of some kind and run the tanks water through the other side of the exchanger/coil. If this is for profit then I would like to know if the 75 gallon tank is the max size because there are many vechicles that have "dual air conditioning" systems built in and the "rear system" could more then handle your needs.

Mike

How about packing the tank in dry ice and regulating temp UP with heater?

Just a thought.

The air stone is probably still an great idea - but hook it up to a low voltage air compressor driven by the vehicle electrical supply. That should take care of the oxygenation of the water and help the fish survive the trip.

Insulate the tank. Is the vehicle open? Can you screen the top of the tank from the sun? Could you surround the tank with a few laters of hessian and keep it wet? The airflow would chill the hessian by ten-fifteen degrees and help keep the tank cool.

How about aerating the water with compressed air, then covering your bags with damp cloth. The evaporation should keep the bags cool.

I think nitrogen is out. Expanding gaseous N2 from a high pressure cylinder through a cooling coil of sorts would require too much N2 to make it cost effective. It would also be hard to control. Here is a simple, mechanical system concept based on using liquid CO2. All commercial CO2 cylinders contain CO2 as a liquid. Turning the cylinder upside down allows liquid withdrawal (you may also be able to get what is known as a siphon cylinder which uses a dip tube to withdraw liquid with the cylinder right side up). Put a liquid CO2 regulator on the CO2 cylinder and adjust the pressure to 5 psig. using small diameter copper tubing, run the CO2 from the output of the regulator to an internally equalized thermostatic expansion valve feeding about 25 feet of 3/8 inch coiled copper tubing which is submerged in the water and has the end opposite the expansion valve out of the tank. Run some cheap plastic pipe or tubing from this end to somplace where you can safely vent the used CO2 to the atmosphere. Locate the sensing bulb of the expansion valve underwater on the copper tubing just before the copper tubing exits the water. Adjust the expansion valve to maintain a coil temperature a few degrees below the water temperature desired. Once everything is hooked up and the tank is full of water, just turn on the CO2 and the rest is automatic. Hope I've given you enough information to get you started and to take it from here. Depending on the transport or holding time required, I'd consider about 4 inches of poly foam insulation on the outside of the tank and some method to agitate the water to prevent stratification. Don't forget to not crowd the tank with fish or their excrement will eventually build up to poisonous levels and kill them off. Activated carbon filtration will extend this time significantly.

Just noticed a typo in my earlier post. Adjust pressure regulator to 50 psig not 5 psig and insulate the copper line between the regulator and the expansion valve.

CO2 is deadly, undetectable, and an accumulated level of 5% is toxic to both people and fish. The nitrogen would work on this same principle, andd is just as readily available in cryogenic, relatively low pressure portable cylinders, of I believe about 400 pound capacity. BN2 would need to accumulate to over 50% to be at risk of anoxia from diluted o2, and 75% to approach fatal "altitude sickness" levels. The N2 is not toxic, as CO2 is, merely oxygen displacing.

Keep oxygenating with compressed air bubbling, and blow large volumes of air accross the surface, sufficient to ensure agitation, and use the evaporative effect to drop the temperature to the wet bulb temperature. If that isn't low enough, air conditioning could be used, perhaps by bubbling the cooled air through a manifold of perferated pipes, adding the evaporative cooling to the lowered air temperature.

Insulated sidewall panels and tank covers, reflective and radiant finishes, (white paint rather than aluminum or stainless finish), and don't forget to set the tanks on an insulated base to keep the road heat away. Provide some stilling baffles with extensive bubbling to keep from "drowning" the fish. Air bubbles rather than O2 bubbles to prevent burning of the fish gills,

Are these fish for stocking a lake/pond/stream, or farming? Maximum and minimum water temperature for fish survival? Netted removal or flow out? How many tanks on the vehicle? Single point delivery or multiple drops?

Lots of help if we know the available resources.

Then we might really be able to offer the most suitable aid.

RichH.

hmm alot of references to copper tubing above. Keep in mind cuprous and cupric salts are extremely toxic to fish. Also, with regard to CO2, it will displace oxygen like nitrogen (maybe even worse, since it is heavier) and will acidify the water if directly injected. So the venting away from the water and the breathable atmosphere is a must. To stabilize the water from rapid temperature changes you need a insulative covering. The polyurethane foam mention previously would be a good idea. Also cover the tank during transport and insulate the top if possible. Keep some access port in the top with a lid to close it. Since Air needs to be circulated through the tank to maintain the oxygen levels for the fish, you might precool the air lines before injection into the tank. Maybe multiple copper tubings in an ice chest in the air intake line, and keep ice in the chest. Control the air flow based on the temperature in the tank. If there is adequate insulation and the air inflow is cool enough, there should be adequate cooling capacity (and a little extra air flow will not kill the fish, though alot might). Alternately, a heat exchanger on the air intake connected to a electric refrigeration device.

I know others have already answered these questions but here's my 2 bobs worth

1. Yes, there are fittings available to adapt to any size. Industrial gas suppliers will point you to a local supplier

2. Usually you'd use a pressure reducing valve followed by a flow reducer. Fittings and reg's for nitrogen will be unusual and hence expensive.

3. The temperature drop from expansion will depend on the amount of gas used, so not much (PV=nRT), the temp drop from agitating the water will depend upon the wet-dry bulb thingy ie the humidity. Ice/dry ice etc are expensive ways to cool. If you want to cool the tank buy a commercial cooling system (yes, it's expensive but it'll work properly).

4. Nitrogen isn't poisionous, but will displace the normal air from a room if there isn't sufficent ventilation. Jeff

The bulk of your cooling capacity in an expansion/cooling coil system is going to occur at the point of pressure drop (the pressure regulator), which generally, not being submersible, will condense ice and waste your primary cooling. A better bet would be to us a higher pressure (maybe 250 psi) and an air conditioner capillary style expansion valve in the start of the cooling coil under the water, to produce cold gas where you need it, not out in the open air.

The 250 psi figure is within the range of many freon-based coolant systems, and many expansion capillaries have the temperature controls built in. See if a local AC repair shop can help you chose the right equipment for your needs.

I just wanted to politely disagree on point #2. fittings can be obtained at a relatively low cost. Contact an outfit that uses them regularly and ask about surplus or contact a compression fitting distributor such as your local Industrial supply co or Swagelock^tm.

We've used similar 'total loss' systems for cooling detectors in the past because it's a cheap & easy solution. You would have to rig up some piping to get from the gas bottle to the air stone, we use ¼" stainless pipe to route bottled gas then flexible hoses to individual blow guns. You can regulate the pressure with a standard regulator on the bottle then use a needle valve near the operating end to control flow. Temperature control would be trial & error but be careful, we use total loss systems to get to -20°C. Nitrogen is ok indoors as long as you have reasonable ventilation, we use nitrogen blow guns all over our factory & have guys walking round with open polystyrene dewars holding liquid nitrogen for our leak checkers and cryo pumps, it looks like a scene from Frankenstein with a low nitrogen fog over the floor.

If you have in fact n2 in clouds on the floor and not cold air condensate then that really is scary. Nitrogen can kill you two times with one breath. let me tell you how. you breathe in when sensors in your lungs tell you that there is to much co2. if you breathe in excessive nitrogen it displaces the co2 and o2. sensors not seeing any co2 say don't breathe, you die. Then since o2 travels from high consentration to low, o2 normaly goes from lung to blood as co2 goes fron blood to lung, now we have n2 in lung so the O2 in the blood having been transfered during our LAST breath now flows from blood back to lung, no o2 to brain, heart, etc. dam we die again. Has anyone ever tripped and fell on the floor an died? maybe soon.....

Hmm, I always assumed the fog was nitrogen boiling off but perhaps it is condensate. We have had dewars dropped so that all of the liquid nitrogen spilled out but no one has suffered any ill effects that I know of. They hold about a litre of liquid nitrogen.

It's the super cold N2 condensing the water vapor in the air. By the way, how long do you hold a litre of LN2 in a dewar?

We only hold the N2 long enough to walk from the large dewar to the where it's poured into the cryo pump or leak checker, just a few minutes.

A droplet of liquid nitrogen will boil where it is in contact with a floor at ambient temperature. The droplet will skid along supported upon the nitrogen vapour below it, like a hovercraft. Listen for the fizz!

Be aware that nitrogen-rich air is oxygen-depleted air. DON'T MESS ABOUT WITH NITROGEN - IT'LL HAVE YOU! (With apologies to Crabtree above)

So 'recycling' (gutting) an old fridge from the dump wont work then?

Now that I've seen your full description of the problem, how large a tank are we talking about? Have you seen the portable drink coolers you can get for camping etc., they work off of a 12V car accessory socket. The one I have cost about £15 & the lid containing the cooler is removeable so that you can swap it for the standard cool box lid that came with it. It keeps my beer cool for hours on a long trip & I can imagine mounting that cooler lid over a medium size fish tank.

do you have a supply of block ice? circulate you water through a heat exchanger, in a tank filled with block ice and water or maybe salt water. Use a length of tube and a small pump. That is simple and keep you tank water cool enough for your fish.

Mike

I would like to share a little bit of my knowhow with you gentlemen/ladies...

When tropical fish is transported normally they are packed in polythene bags with small amount of water and a lot of oxygen. (20% of space water 80% oxygen). Typically medicinal grade O2 is used (small cylinders with a regulater).

Forgot to mention .. before filling O2 the bag is kept inside a rigidfoam box so that when O2 is introduced the bag takes square shape. Then the bag is sealed and box also is closed with the lid.. Now you are ready to transport.

Once the boxes reach the destination bag is taken out and put in a tank so that once the temperatues get equal slowly new water is added to the bag.

( I rear and breed fish as a hobby and if you are interested to share my know how in this area I will be very happy to oblige -you may contact me on sisiraa@gmail.com)

In fact in case of some varities of fish (like Siamese fighting fish) water is not used at all, but fish are packed in wet cotton and oxygenated.

One more advice, try to keep bags flat so that surafce area increases and it will mean more oxygen will dissolve in water.

Get an old freezer.

Put water in it.

Cold water for transport will be the result.

You could super-aerate the water.

The ice cube in each bag is not a bad idea.

Do a test.

Pack a fish in a bag and see how long it lives using different packaging methods.

You can take a drinking fountain (Wall mount or Floor style) and remove the valve that you push to get a drink. You can then connect a pump to either the inlet or the outlet whichever is easier to circulate the actual water in the tank. The tank in the water fountains we use are stainless steel, not copper, so it won't poison the fish. Connect a thermostat to turn the pump on and off to circulate the water. Adjust the water fountain thermostat to cool the water to a temperature that won't shock the fish when the water is circulating. You can leave the water fountain powered all the time to keep the water reserve cool and power the pump to control the tank temperature. This would be very easy to build and very little modification would be required. If you need more details let me know.

Using bone-dry nitrogen would be a great way to cool the water down, but it would be due to evaporation of the water into the gaseous stream that would cause the cooling. Industrial gas manufacturers utilize this process with their waste nitrogen stream in an air separation unit. It becomes sort of a super cooling tower that they use to cool compressed air to drop a lot of the water out of the gas before going to the drier system.

You could regulate the pressure to a couple of psig with a regulator that you can buy at a welding store probably and then the temperature would be a function of the flow rate of the bubbles (maybe even get a rotameter downstream of the regulator). This may or may not be too expensive, considering that nitrogen is not free.

However it is always a bad idea to use nitrogen in a confined space. An alarming number of deaths in confined spaces are due to the presence of an inert gas that people were unaware was hanging around. Several breaths of a nitrogen atmosphere are usually fatal and you don't even get a chance to scream that something is wrong. See this month's Process Safety Beacon for a good example. I would not recommend letting it just bubble through the water, it'll probably kill the fish and then you.

You say you want to keep it simple, I would recommend the air conditioner coil or something similar. Stay away from nitrogen in a confined space if at all possible.

I am very interested on your topic using waste nitrogen to cooldown the water. The cool water will be used as chilled water for air before entering air drier. I would say, the Nitrogen as a direct contact aftercooler. The waste nitrogen flows from bottom of vessel and water showering on top getting direct contact and adorbed heat fom water and vented on top stack. I like to use this as experiment in our plant(ASU), we were having 1,500m3/hr waste nitrogen vented. I need help for vessel design and calculation to get cool water of 15deg.C, waste N2 temp. is 32deg.C

Just put some ice in big ziplock plastic bags and float them in the tank. When the ice melts it won't raise the water level much because you just remove a bag of water each time you put in a bag of ice. Increase the circulation enough to keep the water temp fairly even. Monitor it close and experiment a little - you will get it down pat so you will just know how much ice you need and how often it needs changing. It will be easy and cheap. If automation is required you have recieved many worthwhile response but I wold avoid any gases that would contaminate the water and possibly kill the fish. I think that was what you were trying to avoid.

So many ideas.........

I have decided to call in an AC guy that I know and we will look at using an old 110v unit and re-adpating the coils to pass through the water.

The Nitrogen system can work as someone I spoke with in California used it to prep his produce ( he would ship fresh live prawns). He said he would NOT use inside of building. I am very leary of things I do not know much about and this gaseous thing might cause a problem later.

I want to thank all of my friends old and new on CR4 for their comments on this. As usual, listening to other's advice gives me ideas of what to do or even NOT to do .

Looking at everything posted here I can see i might wnat to stick with my expertsie which is net design and manufacture and let an AC expert rig me something safe and simple.

If the fish have to be left somewhere at a location, I do not want someone from OSHA or EPA being called out to investigate my contraption.

This is just a part time thing we are doing as a favor for a good customer moving

some fish frommpoint A to point B .

Thank you all.

netmaker

Hi,,

I just read most of thist thread...it's all been said....

But...

If you are putting in an AC rig...Why modify the coils to go in the water?

If the water starts off cool and you AC the air inside the van...the water won't warm up! So you don't need to waste time money etc modifying it!

What you are doing is removing the problem...rather than solving it..

e.g. don't let the water warm up...then you don't need to cool it!

Good luck..say Hi to the fishes ....mmmmm fishes...prrrrr

A critical issue that I have not seen mentioned is that bubbling nitrogen through the water will purge the oxygen from the water. I am sure you would have 100% mortality doing that.

I have transported tropical salt water fish. My method is to put fish in a large plastic bag with a small amount of water. Then I inflate the bag with oxygen and tie it off like a ballon. The bag is then placed in a cooler to prevent rapid temperature swings. Fish have survived in this way for days.

I carry a lecture bottle of oxygen (1 ft long by 3 inch diameter compressed gas cylinder) with a small regulator fitted with a length of metal tube to insert into the bag. Fully charged, the cylinder holds 57 liters of oxygen. Way more than I ever needed.

If you insulate your tank well, add a little ice when necessary, and keep an oxygen cap over the water, the fish should do fine.

Bill Morrow

OK 10 yrs aquaculture should help you with this problem.

1. fish are dying from lack of oxygen crossing the gill membrane. This is by 2 causes: it gets warmer and the fish increases respiration; using more oxygen and absorbing less efficiently

2. why pump flatulence into the water? when bad gas enters your proximity it causes a reaction. I.e. gasping, choking, bloated face, vomiting and laughter!

Nitrogen is bad! 70% of the atmospheric composition and some 60% of all food/nutrient make up. The mouth is the single largest excretory organ.

Suggestion:

1.stick fish in a bag and sit them on ice for masses up to 300gm per bag/litre

2. use the truck/car heat-pump as per a water cooler. These are commonly capable of taking some 15 degrees celcius off a 300kg mass per hour. Pity we make heat or drivers would freeze.

3. look up Australian fish transporters, or Swiss. Swiss technology is best and used in 25 tonne masses very frequently in Scotland.

Australia exports live Prawns/shrimp to Japan at 4 degrees celcius and masses of 5kg per package. I am designing a system to transport 300kg per cubic metre of Scallop from Oz to Greece. These will go in a plane onto tarmacs through any number of stupid places. Nothing hard just challenging.

Cliff

Cliff,

In essence, I might just back out of this entirely. the liability associated with possibly killing off several thousand dollars of potential brood stock sturgeon is now scaring me.

I have build seines, holding pens and and assortment of barrier net for aquaculture ponds for 20 years plus......I never have tried moving fish.

I do believe I am going to just pass along my AC guy to the customer and let them decide. This is sounding more and more like an accident waiting to happen for me.....

Thank you for the input tough. all of these ideas may just come in handy later on down the line.

Regards,

netmaker

You say your pushing air in the tanks now?

Try a vortex to remove the heat from the air. It's so small you can place it in your hand. Install it outside the tank and it will blow the heat out into the air and push cold air into the tanks.

It works, I've used them many times, but not on fish.

Labguy,

CAn you describe this vortex and where they can be found or how they install?

Thank you.

netmaker

Mcmaster Carr handles them or you can get them straight from Exair. They work with compressed air and are great for cooling cabinets. They would be very inefficient for your application. They also are used to cool tooling on mills and saws.

Pebbles,

Thank you.

I am reasonably certain I am going to set up the customer with my AC guy and let them settle it out. This is starting to look like a liability case if these fish turn belly up. My expertsie is in the nets and seines to catch , hold and carry the little critters.

Thank you for your input.

netmaker

The cooling effects of hydrogen would be little. As it would have all ready evaporated before getting to the water. Don't know what the excessive dissolve nitrogen in the water would do to the fish

A mist spray over the tanks would drop the temp some.

Evaporative cooler- Set up sides like the evaporative coolers drawing air through with fan letting water run back into tank. would oxygenate the water too

A bath of dry ice with your circulation line ran through it. With temperature switch to regulate flow can't shut it off water would freeze in the line.

Insulate the out side of tank.

What is this tank being transported in? I would think that transporting your current arrangement, as is, in a properly refrigerated truck (forget about coils etc. in the water) would take care of the problem. Insulating the tank is a good idea, to avoid rapid temperature fluctuations, but I believe that introducing cooling directly to the water is a potential disaster waiting to happen, in the event of a malfunction.

If you want to use a pickup truck, install an insulated white (polished stainless would be ideal) truck cap (just foam up the inside surfaces of an old one). Double glaze and mirror tint the back window (auto-zone tint film and lexan sheet siliconed to the inside of the window frame) You might even consider a second layer of (polished stainess?) sheet metal on the roof, mounted with stand-offs about an inch high, and open at the edges, or at least front and back. Mount 2 small refrigeration units on it (for reliability, in case one conks out, see your AC guy for sizing). When not transporting, the cap could be placed on top of 4 short walls around a tank in a building (in effect, a small refrigerated building within a building).

And as an added bonus, you could deliver meat in your spare time!

Ammonia refrigerant in your existing A/C would be the best, but the fine would be hefty by DOT. Might do some time when they catch on. Plus if it leaks... you'll want your gas mask. R-134 will not overcome the extended heat load through a standard A/C system, with piping to the truck bed. Not in New Orleans heat. Physically impossible over 93 degrees, sitting at a stop light. Your exchanger will not be effective using SUVA.

Why not use more insulation and stick with ice? Use 10 inch thick Expanded Polly Styrene foam with fiberglass re-enforcing panel (FRP) glued to the foam, inside and out. It's R-50. Make a big beer cooler in your pickup and place the DRY ICE away from actually contacting the fish on either side. Use a blow through box and some PVC piping to circulate the chilled air around your fish, either tanked or bagged.

Do a test run with your 80% Oxygen filled baggies, (get a cylinder from the welding shop, the oxygen is purer than from the hospital;) Just blow a little into each bag as you seal them for shipping. Thermometer to your cab will read an electronic sending unit. One for water temp and one for air temp. If you build a water tank within the cooler instead, just leave a surrounding circulating area for the ice blower to cool the tank on all four sides. Might have to place the ice in there the night before the move, is all.

Your ambient air temp will make a huge difference with how much DRY ICE you will need to keep the baggies cool, not frozen, so keep a record and use a blow off vent in case of over cooling. Baffles in a water tank will be required for slosh at stops. drill small holes, a bit larger than the fish, but not too many. Bag the fish, just like the pro up ^^above^^ does and you'll be fine. Just pull a permit before you cross state lines, so you and your fish don't rot in jail.

Agricultural boys will wreck your day, if they catch you.

EPS is PCB Free, mildew resistant and inexpensive. FRP can be sealed with Silicone. You can also shoot the truck cap with Tiger Foam. It is a brand name insulation which comes in a cylinder like refrigerant, that you shoot from a cheap gun and hose. 50 bucks a can and it sticks to anything. Don't forget the drain plug and by all means use an explosion proof fan and recirculating pump around pure oxygen!

Thank you Moto, I am very conscious of the laws involving this and would never try to run afoul of the Agg guys or the EPA.......and I am not foolish enough to try anything that would endanger anyone either.

I learned a great deal with this discussion, but mostly that I am out of my league .

I'll leave the refrigeration to the AC guys and the customer. All I need to do is round up the little critters and hold them in a nice, soft polyester net pen until they are ready to travel.

However, i did learn a whole lot about cooling water with gases.

Once again CR4 has an unlimited supply of knowledgable folks ready to lend a hand.

In my experience fish are best transported in either batter or breadcrumbs, this also makes them easier to handle as you move them into the fryer.

.........along with some batter fries, a side order of big ol' Gulf shrimp, some fresh tomatoes and an ice cold glass of sweet tea and lemon..........

ca se bon mon amis !!!!!!!

South Louisiana --- Blessed by Gods own hand -- just got thru munchin some mudbug etouffee.

Mmmmmm....etouffee...Do any of you guys have a good recipe for etouffee? The real kind like you find in Louisiana, not this mess they try to pass off for etouffee in Texas.

recipe

Thanks! I'll try it out and report back.

Texas and Louisiana got hit hard this year with the Whitehead virus. It kills crawfish right in the pond.

However it is harmless to humans.

My wife refuses to cook with the Chinese imported crawfish. I can't tell the difference but she says she can and that is that!

As for La. being blessed by God's own hand.........hmmmmmmmm it might have been but the politicians have sure messed it up something awful.

bon soir

netmaker

I sure liked that idea using the old freezer. Is that really a no-go on the idea list?

Post #20 from wrenched.

CR3

Hey C,

Actually when I got into it with my customer, he was very adamant about ME being liable for his fish load. At that point I backed out.

I build nets...........I am not an AC guy or anything close to that. The old frezer was actually a good idea.

Keep in touch.

netmaker

If it was me doing it, and the vehicle could carry the extra weight, I'd simply use 2 tanks of 75 gal each with the same amount of fish as you'd carry in 1. Then I'd use your bubbler connected to an aquarium pump, in order to maintain oxygen levels in the water (1 in each tank). This could be augmented with a single block of ice in each tank to moderate temperature rise.

Tanks should not be exposed to road wind, so if they are traveling exposed, a removable insulation should be employed.

Now this is most important! ... Care should be taken at the end of the fingerling's journey to match temperature to the receiving water. As long as they have oxygen, the fish are not as sensitive to the changing temperature if it takes place slowly. Sudden changes in temperature will throw them into shock. So, it may be necessary to plan your tanks heat gain to achieve the desired temperature matching the receiving pond by the time of arrival, rather than trying to maintain 15 degrees C for the trip.

I realize you have already decided to pass on the opportunity, but I thought the information might be helpful anyway.

All the information is useful........if not now for later. We generally do not handle any fish except to provide the nets and pens. This was just an after thought , until I realized i was going to be liable for the fish.

Once again, thank you all for the ideas. No knowledge is ever wasted as there will always come a time when it might just be needed. I kept this file for future references.

as for the etouffe, my wife's secret ingredient is that she uses fresh crawfish tails and then chops up shrimp tails into little bitty pieces to act a filler of sorts. You don't know the shrimp are there but it makes the etouffe taste very rich.

Etouffe is an art over here just like good chili is an art in Texas.

Shrimp season starts Monday and that means I'm fixing on going off my cholesterol diet again.......and again...........and again..........

see you all around. Thank you all for the ideas and I thnak you for the information. It will come in handy one day when we have to do this...... however, this time I am opting out.

Try this. Get a vortex tube, a thermostat and a solenoid valve. Use compressed air (no need for nitrogen).

The vortex tube generates both hot and cold air from compressed air. Hot air comes out from one end and cold air comes out of the other end. The model you get determines how low a temperature you can generate (even below 0ºC!). The thermostat controls the cycling of the system. If you can get a model that generates the exact temperature you need, you won't need the solenoid valve and thermostat.

Google "vortex tube" for companies that sell these things. Actually, if you're up to it, you might even try building one yourself! They're fairly simple in construction.

Looks like a nice concept. How did you plan to control the hot and cold air temperatures?

Vortex tubes are curious things. You inject compressed air in the middle, and cold air comes out one end and hot air comes out the other end. We use them for cooling the remote cameras in our spray dryer. The ambient temperature inside the tower is around 50 deg. C so the cameras need to be cooled to keep them from getting damaged by the heat.

In some models, the temperature can't be adjusted. In others, the temperature is adjusted by controlling the quantity of hot air that comes out of the hot end.

It's a fascinating device. Depending on how cold you want to go, the only cost for operating these things is the compressed air. No moving parts, simple construction, zero maintenance.

I just saw this drawing.

It looks really simple.

I might have a use for this in my Condenser Cooler fan in the shop. Chilled water would make for chilled air flow.

Thank you. Hope your Typhoon season is as calm as our hurricane season........so far nothing active....I still have damage not fixed from 2005.

Thank you

netmaker

You're welcome.

Where I live, we don't get hit by typhoons. The city lies outside of what we call the "typhoon belt". Right now, we get afternoon showers but no wind. In Manila, they're having a dry spell. The dam levels are actually getting very low at this time.

I've been telling my siblings to move here. Almost no traffic, air's fresh, cheaper produce, and no storms (at least not the kind they know).

Er, provided the bonding of the material is non toxic and not water soluble, an open grain sintered carborundum stone may work for you.

Cooling would probably work better with a thermoelectric device attatched to a heatsink into a comparitively fast flowing circulation to avoid freezing and exiting to a high/low set point thermistor conected to an amplifier and solenoid relay circuit. Bear in mind that if the tank is well insulated, the ammount of heat pumping will be low with respect to the ambient surroundings. Try looking for MELCOR as a device and consultation supplier.

You may get some behavioural indicators if the fish begin to crowd around the cooler outlet vent... or if they begin to stay away from it!

Seasonal variations in temperature may be critical to their growth and lifecycle.

very very cool (pun intended) I had never even heard of such untiil this thread.

That is the beauty of this forum. And might I dare say, This forum more than others.