cast iron radiator cooling

[Bottleveg]

welcome to our new member from the UK



nice to have a few more of the fine folks from over the pond joining the party

bob g

Thanks for the welcome Bob,
I've also joined the LEF. I'm new to Lister's and have just bought an 8/1 SOM with original 4.5kva genny and cast iron damper. It had been stood for ten years but I've only found stuck pump tappets and governor weights so far. The electrics worked fine but could do with a re-wire. All I need to do know is build a soundproof engine shed!
                                            Mark.

[vdubnut62]

Ok I'm way off! I had it in my head that cold water for cooling the living space was involved. Wow, sorry!
Someone here has used a cast rad in their home, I've seen pics of it posted.
Here is a formula you might find useful about heat loss from uninsulated steam pipes circa 1950ish.
I'm also 8 or 10 posts behind, so bear with me! it took a while for me to scan Machinery's handbook page and convert it to a pdf.


Ron

[Ronmar]

The 55 gallon drum surface area is not the best place to start as it is intended to be a 55 gallon drum without a top.  As the engine temp increases near 200F, the majority of the heat dissipated from a 55 gallon drum cooler is thru evaporation off of the top 452 SQ/IN of exposed water.  At 200F, the heat loss per square inch of surface area thru evap from the top of a 55 gallon drum is 8.3 times that of the same surface area of the drum skin in 60F still air.  With the top 452 SQ/IN being about 1/6 that of the remaining 2981 SQ/IN of skin, at 200F, the top will dissipate 8407 BTU/HR mainly thur evap, while the remainder of the skin will only shed 6,624 BTU/HR for a total of 15,031 BTU/HR which is a 6/1 just under full sustainable load...  Put the top on the drum and you are only going to get 7,627 BTU/HR of cooling out of that drum with 200F input in 60F still air. That would be about 1.3KW of electric load on my 6/1...

Based on my reference info from the engineers toolbox, and personal measurements on my 6/1 at various loads, you will need to dissiapte near 6,000 BTU/HR thru the cooling system, per KW of electric load to keep the engine happy.  At an engine op temp near 200F, and in 60F still air, you will get about 2.22 BTU per SQ/IN out of steel, so you will need 2,702 SQ/In of surface area per KW of electrical load, or the enhanced equivelent.  By enhanced equilivent, I am refering to the heat transfer efficiency gains that the radiator design gets you over a flat tank wall.  By design, a cast radiator shape creates convective airflow and helps breakup laminar flow which improves it's efficiency, just as the close fin spacing and fan forced airflow greatly increases the efficiency of an automotive radiator...  

I would reccomend a dual system.  One to put as much heat into the house as is needed, and a secondary/alternate loop to handle the full potential cooling load of the engine when you don't need the heat in the house.  In an ideal world, I would incorporate a storage tank into this scheme.  This would allow you to store heat for possible later, longer duration/slower rate usage by the radiators, when the generator is not running...

A variation of my avitar might work OK.  It would use a heat exchanger to cut down on the ammount of coolant required in the engine.  It also keeps the heat and engine loops separate.  The primary loop would have glycol and only contain a gallon or so of coolant.  The secondary loop would circulate heated water to the insulated storage tank, with the return to the engine being off the bottom of the tank.  The tank and heating system would NOT be pressurized.  An auto thermostat at the heat exchanger outlet would determine the water temp sent to the storage tank from the heat exchanger.  When the tank gets full of hot water, the radiator at the tank outlet back to the engine heat exchanger would dissipate any excess heat to the atmosphere(or wherever you choose).  On the right side of the tank in the drawing, a pump would draw hot water from the tank top thru a thermal regulating/tempering valve and send it to the house radiators.  The cold water returning from the house rad would either return to the tank, or be remixed with hot water and sent again to the house radiator.  I did forget to add a thermal expansion tank to the storage portion of the drawing.  The advantage of this setup is that you can set the desired temperature of the water being sent to the house radiator wherever you like, or think is safe...