Resurrection of a CFEI 100 KVA Induction Furnace

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awemawson:
At last, a useful reference to required cooling from:

https://www.tct-tesic.com/wp-content/themes/tct/assets/documents/induction-furnace-handbook.pdf

"Cooling water volume
is determined mainly by the electrical output. One can say roughly that approx.
27% of the furnace output and the heat losses from the crucible wall will have to
be dissipated. In rough terms, one can reckon on approx. 35% of the furnace output as the total loss performance that must be dissipated."

So for my 100 KW furnace 35 KW cooling, which is right on the money for my original 39 WK chiller :thumbup:

awemawson:

--- Quote from: Pete. on April 18, 2020, 07:49:07 AM ---I've been thinking about this and comparing it to the kit we use at work, a lot of which is water cooled.

Our most powerful concrete saw uses a 27kw motor, and the drive electronics and motor are both cooled by the (same) water feed, which is usually just fed from a 1/2" hose up to 25metres long off a domestic water supply. The motor is just a cooling jacket. Very often the supply is quite marginal and you can get away with surprisingly little flow without tripping the thermal protection.

--- End quote ---

Presumably the motor being sizable will be fairly efficient? The cooling I assume only has to lose the energy lost by inefficiency so if it is 75% efficient it's only having to carry away 6.75 kW

RussellT:
Hi Andrew

You do have interesting problems don't you. :clap:

I've been thinking about this at odd moments. Presumably the main argument against a total loss system is that it would scale up quickly and even a thin layer of scale would reduce heat transfer significantly. Can the pipework be descaled with acid? I don't know if citric acid would dissolve scale - I expect it would.

I'm intrigued by the idea of using the stream. That would give the possibility of a counter current heat exchanger which would potentially be more efficient. My usual interest in trying to do jobs for little or no expenditure is imagining a series of old domestic radiators lying in the stream. :scratch: :loco:

I'm sure there are design guides for heat exchangers, but without having consulted any :bugeye: I recall from physics lessons that heat transfer is proportional to wall thickness, surface area, temperature difference, etc and I wondered whether this might help in some ball park calculations. :smart:

I had in mind if you know the area extracting heat from the furnace and the temperature difference and you know the temperature difference you are aiming for in the cooling section then you can calculate the area needed - and similarly for different materials.

I'm not sure whether to mention this, but even though the borehole is there already, do you need some sort of abstraction license?

That enough rambling thoughts for today. I look forward to seeing your progress.

Russell

awemawson:
Russell,

From what I've recently discovered about 'welded plate' heat exchangers they seem pretty efficient in terms of heat transfer so I don't think there is any need to use direct cooling, in that any cold water source can be isolated from the furnace plumbing by the heat exchanger. This is really needed anyway as the water needs to be low conductivity and with added glycol.

Although the stream sounds an attractive proposition, it's a long way from the foundry both for laying pipe and pumping the water, whereas the bore hole is only 15 yards away.

The bore hole water will undoubtedly be heavily laden with iron, as that's why it ceased being used for public supply, so my heat exchanger will presumably eventually clog up with it, but as Seadog said, it can be acid flushed, and frankly they are fairly cheap for what they are. (A 50 plate welded one rated at 90-100 kW is less than £100 from Poland or Czech including postage). I would err on the large size for the H.E. as I can easily throttle the cooling side if it proves excessive.

As far as I can tell an abstraction licence is only required if drawing more than 20 cu M per day which I wont be.

awemawson:
Today I managed to open up the Bore Hole :thumbup:

My friend Andy came with his big Kango clone and in a matter of 20 minutes freed the man hole cover frame from it's flaunching. Whoever did it originally used soft sand (should be sharp sand) so it came away remarkably easily having been given a seeing to with the breaker.

I slid the forks of the fork lift truck under the assembly and carried it away for dealing with at a later time - it's a blooming heavy lump of iron !

So this exposed a 24" pool of water - again I slid my fibreglass duct pulling rod down it and it went down to 174 foot :bugeye:

I rigged up my petrol 2" water pump, with a foot valve and rigid pipe into the bore hole, and flat pipe out to a reasonably convenient 'rodding eye' on my roof and surface drain network that leads about 60 metres to the stream. Starting the pump water fairly gushed out down at stream level and the bore hole level started falling.

As the level went down, man steps were revealed set into the side of the bore hole - it's a brave man that goes down those :bugeye:

It was my intention to carry on pumping until I got to the limit of the suction hose to see what was revealed, but at this point the engine died on the pump - would briefly start on choke but immediately dies. So pumping operations had to cease until I find the pump problem.

A quick tidy up and a temporary cover put over the hole was enough excitement for one day :clap:

(Pete. will recognise the cover :thumbup: )

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