Custom Cooling System Modification Question

[ianfotheringham]

Hey there cooling system gurus...

i have an 81 45 troopie that i am nearing the end of preparing for a trip through africa and beyond...and its only taken me an effin year working on it everyday...ugh...

i have made and installed a custom water tank [about 130 liters] where the spare tire would have normally been [just behind and above the rear axle]...but before completing the build i had decided that i would like to heat the water as it will only be used for washing/showering...my plan on doing this was to run and coil a length of 5/8" copper tubing across the floor of the tank, entering and exiting it at the top, front facing side...this was accomplished nicely, and 5/8" hosing was ran from the inlet and outlet pipes, and the i attached the inlet pipe to the outlet pipe of the oil cooler [i have the 2F with the oil cooler] and then the return from the water tank was routed back into the pipe to the water pump that would have normally been connected to the outlet for the oil cooler....does that make sense to you? i understand it a little confusing....

anyway, the other day after i took a little spin to test it all out - i found that it worked like a dream! almost even 'too well' as the water coming from the tap of the water tank after an hours drive was too hot to even use...however, the more important issue was that my engine temp, which i had expected to decrease due to the water tank cooling down the coolant, rose from 80 to 100 Celsius....apparently the resistance of all that hosing to the back coupled with the coiled copper tubing, was a little much for the water pump and was not cooling the engine efficiently....

so im looking for your thoughts on a better way of heating my shower water, while not negatively effecting my engine cooling...i would prefer to utilize my little copper tubing system since its already made- but i suppose my options are open.

one of my mechanics suggested welding on a new inlet to the top of my rad, and an outlet to the bottom...but i dont really feel comfortable cutting it up and whatnot,,,maybe an couple inline electric water pumps?

let me know what you think and f you need further details,

thanks,

ian

 

[joeyg1973]

I am making a guess here but logic is telling me that once that water in the tank is heated up it is acting like a heat battery. It is collecting heat and getting over saturated then putting that heat back into the system is the best place it can release the heat. Why not put a ball valve on the hoses going to the water tank, open it up to heat it up to your liking, then close it off as it will hold that heat for quite a while if you have a lot of water in it.

I don't think it has anything to do with the pump having to push too much.

You could also try this. Disconnect it from the cooling system, get some copper pipe and bend it up into a coil and put it in a box painted black on the inside with piece of plexiglass over the top. Basically a heat exchanger. Put that on your roof and hook it up to your water tank with a small electric pump to keep things circulating during the day. Unfortunately you will still have to re-plumb you tank with an inlet on the bottom and an outlet on the top with a flexible hose on a float so that the pump will pull from the highest level of the water. You could get really trick and put a light sensor on the pump so that it only runs during the day and even power it off of a small solar panel.

If you could get the tank above the heat exchanger you wouldn't even need the electric pump as it would work as a heat pump then.

I blew up my box that everybody is still thinking in a long time ago.

 

[Bret]

If the flow isn't too restricted why not just run the oil through a cooler in front of the radiator before you return it to the motor?

Would it be feasible to run a bypass from the inside heater core to the "core " you have in the H2O tank. Then only heat it when you need to?

 

[HopLite]

I have to agree with joey but the thermodynamics/heat transfer problem you have created is possibly due to the increased volume of the coolant in your system without a corresponding increase in your ability to dump heat.

Let's think of the extremes of heat dumping ability. Reality will be somewhere in between:

(1) your cooling system is nearly stock: stock pump, stock coolant volume, but you have installed a gigantic humongous radiator...the larger the radiator the more heat it can transfer from the hot coolant to the cool air. The radiator is way oversize for the fluid volume (don't think bubbles...just think cooling capacity); the radiator can handle all the heat from the coolant and you should have no problems dumping the heat and keeping the system cool.

(2) your cooling system is nearly stock: stock pump, stock radiator, but you are cooling a humongous pool of hot coolant. Forget the size of the pump, no matter how hard you pump the fluid, your stock radiator has a fixed surface area and therefore the stock radiator can only transfer so much heat to the air. There is simply too much hot coolant and it is overwhelming the heat transferring capacity of the radiator. The heat-dumping ability of the radiator is the limiting factor (yes, you can increase the heat dumping ability by increasing the radiator size, by increasing the air flow over the radiator, or even by adding a second radiator...which could essentially a transmission cooler).

I do not know how much (by percent) the copper tubing to/from/and within the tank increased your volume of hot coolant, but it appears to have been enough to increase your engine temp by 25%. By increasing the amount of hot coolant in your system without increasing your capacity to dump heat, you are effectively approaching condition (2) above.

Possible plan "B": 12V water tank heating element with in cab switch (this is my pipe dream plan). Might also look at a farming supply store as many outdoor livestock water tanks are heated to prevent winter freezing. These supply stores might carry repair parts so you could just pick up the heating element. For safety, you could also put a temperature switch to turn on/off the element to prevent freezing/overheating. You also might look into a safety pressure relief valve to prevent a mythbuster-esque water heater explosion.

Possible plan "C": use a self priming 12v pump strong enough to pump water up to the engine compartment. Use a small heat exchanger (make your own or buy a commercially available one) in the engine compartment to heat the water. You could heat the water on demand or plumb a recirculating line back to the water tank to warm up the whole tank while you drive. This small heat exchanger close to the engine adds very little volume of hot coolant to the system and would negligibly affect the need to dump additional heat at the radiator thereby keeping you away from extreme (2) above.

Sorry for the novel...I hope this makes sense. I might forget to check this thread as I usually loiter in the 60's section. I am by no means an expert when it comes to vehicles or heat mas transfer, but the theory and science behind your problem reminds me of some heat mass transfer problems I had in college. PM me if this is unclear.

-Hoplite

 

[antFJ]

i tend to agree with hoplite... also could you just have an inline shut off valve like the heating system? you wouldn't need your shower water heated ALL day just maybe a few min before you stop to do your business. This way you could run the engine normally.. but open the circuit when you want to.

make sense? maybe it was already explored and i just missed it

 

[joeyg1973]

i tend to agree with hoplite... also could you just have an inline shut off valve like the heating system? you wouldn't need your shower water heated ALL day just maybe a few min before you stop to do your business. This way you could run the engine normally.. but open the circuit when you want to.

make sense? maybe it was already explored and i just missed it

Yeap I mentioned the ball valve option.

 

[antFJ]

then i should have just wrote x2.

 

[cruiserbrett]

Option C for sure. get a camp shower or marine heat exchanger, mount in engine bay. find a pump to circulate water from tank to heat exchanger through the existing copper tubing? that way your not forcing coolant to have to suffer the pumping losses all the way back to the tank.

Seakamp makes nice heat exhcangers that are meant for freshwater cooled boats, that pass saltwater through it to cool the coolant...

 

[cruiserbrett]

Seakamp