another source of heat

[mobile_bob]

is that from the lubrication system of an engine

i found a reference this weekend to the typical heat available from the hot oil in a diesel engine, being approx
2.5% of the btu value of the fuel burned

so in a typical changfa 195 where we are burning ~1 gallon per hour at rated load,

135000 btu/gal x 2.5% = 3375btu's

because of the design of the engine, the vast majority of this heat must be dissipated via radiation rather than
through the coolant, allowing us the ability to tap into and harvest this heat.

aside from the obvious benefits to oil cooling for this type of engine, the added 3375 btu's of recovered heat raises the
overall efficiency of a well designed cogenerator by nearly 4%. in a well shielded and insulated engine this number seems likely.

3375 btu's is a bit less than  1 kwatt of heat. (988watts) that alone equates to about 5-6 gallons of domestic hot water per hour
which is enough to wash dishes with, or take a quick shower... not bad for a heat source that is generally not considered by most
of us.

certainly seems like something that warrants investigation to me.

this is probably most appropriate for those engine's that make enough heat into the oil to even make it worthwhile, my thinking
is that most lister/oid types don't fit this catagory as the crankcase never really warms up much in service.

bob g

[mobile_bob]

my 195 based trigen is going to also be fully enclosed, because it has a compressor
and i have the valving to covert it into a heat pump as well, in the winter months the enclosure
will be closed and all heat will be pulled out of that enclosure.

the heat in the lube oil is a high quality heat that for most of the year needs to be disposed of anyway
so the idea is "why not put it to good use"

because the changfa has an oil pump, and i will be incorporating a full flow and bypass filter system,
the ability to insert a small exchanger would be quite easy.

also it is fair to note that i plan on the reintroduction of the cooled oil to be fed directly into the gear train
in an effort to quiet those notoriously noisy gears that changfa type engines are known for.

bob g

[veggie]

Hi Bob,

IMHO.....
When a water cooled engine is running, the heat from the oil is already dissipating (and mostly captured) somewhere.
Typically the oil heat is conducted through the engine parts/block and ends up in the cooling system.
So in effect the heat from the oil is already being recovered by a water cooled engine.

If you add an oil cooler of sufficient size to capture the 3K btu's that you mentioned, you may actually reduce the btu's captured by your cooling system by that same amount.

Perhaps the only additional oil heat that one might capture is the heat that would have been dissipated from the none-cooled part of the engine block which normally heats the ambient air. I your case, a complete enclosure would capture that heat.

veggie

[mobile_bob]

Veggie:

i would both agree, and respectfully disagree with your assessment

i would agree that a significant amount of heat is taken up by the cooling systems in most designs, however

the changfa or other chinese variants separate the oil from the cooling system fairly effectively, in that the oil is returned
via the drainback passages which does not allow for close contact to the water jacket.

also when you operate the engine up to near max rating, or in my case beyond that rating there is a large amount of heat
being transferred to the oil and the only way for it to be dissipated is largely through the castings and steel oil pan.

i don't think there would be much if any benefit of heat available at low or part load, but there is a significant amount of heat
a full load, and if we are to abate geartrain noise i for one will be fitting the engine with closely fitted insulated shields, effectively
cutting off most of the radiant heat transfer as well.

my little toyota 2 liter diesel pickup even has an oil cooler, it is non turbo and still the oem engineers figured it needed to have one
likely to remove heat from the oil under heavily loaded conditions.

i would also like to point out, the oil heat if it is to be transferred to the coolant, must have coolant with a lower temperature
if i am to try to get the oil down to 180 degree's F, i certainly cannot expect the cooling system that is running at 207-215 degree's F
to do anything toward that goal.

my opinion only

bob g

[Ronmar]

You would want the coolant returning from the radiator/heat exchanger to pass thru the oil cooler first.  My coolant returns from my heatex at sub 100F temps.  My only concern would be with not allowing the oil to get warm enough.  On an engine that is ran daily, this is not a big issue.  But on an engine that is in backup service, moisture drawn in thru the crankcase breathing is an issue.  When ran, you need to maintain oil temp at a high enough point to allow that moisture to evaporate out of the oil and be exhausted from the case.  In the case of my lister, it takes a lot of running to get all that oil down low up to temp.  I have contemplated a small cappilary line off the end of the bearing oil feed pipe that runs up to the rocker arms and drips oil into those oil holes.  this would be accompanied by a second small oil line drilled into the side of the head to take the dripped oil away from the head when it reaches the top of the valve spring cups.  this oil could be returned to the camshaft end bearings.  This would serve several  purposes.  One would be an easilly identifiable way to see that the oil is pumping.  No drip drip into the rockers means the pump has quit.  Another would be consistant a consistent rocker lube oil film.  And last, but not least would be to add some heat from the head to the oil as it passes thru...

Even with an oil cooler in the loop, I think there is still a significant ammount of oil heat lost thru the pan and non cooled portions of the case as Veggie points out. An insulated enclosure with a radiant plate type loop or perhaps something like a A/C condenser or oil cooler panel in the vicinity of the oil pan might be an effective capture device.  Cast Iron oil pan?  Braze a copper coolant loop to the oil pan...   Heat flows to cold.  With an insulated enclosure, the coolest place for the heat to flow to then becomes the 195F coolant loop and the oil cooler being fed with lower temp return coolant, instead of 70F room air...    

[mobile_bob]

i have been considering soldering a copper tube loop to the oil pan and then cover it with the insulated shield

this particular application s195 trigen is slated to run a minimum of two one hour runs per day, it takes less than 5 minutes to be at full
operating temperature under full rated load, at which it will be running 90% of the time.

as for a lister/oid, i would concur re the issues of overcooling and not allowing the oil to heat up enough to boil off moisture, most of
those engine's don't generally run long enough or hot enough as it is to keep things dry down below, at least not enough so that i would
feel comfortable taking any btu's away from the oil.

bob g

[Ian]

There are a couple of people on this forum running their engines in an enclosed space (Jens is one). After a reasonable amount of running the engine vapours and general crud build up and coat everything with a dirty, oily film.

This is not a good environment for a heat exchanger. A radiator style system would clog up in no time. A coarse, coiled loop of tubing system might fare better but will still need frequent cleaning to keep the already reduced efficiency up (relative to higher surface area designs).

Consider maintenance too – an enclosure and other bits of kit in the vicinity of the engine just get in the way of servicing and repairs. If you do install heat reclamation from within the enclosure, think about how you can easily remove it for servicing and maintenance work. They also tend to be a little bit fragile (easy to bend / break) and so should be away from anything that might hit it.

Temperatures inside my acoustic hood are fairly consistent (no heat reclamation intended from inside the enclosure) at about 50 – 70 C. the oil runs at about 70 C so even without heat extraction, the oil will not evaporate off any water  in the sump. The water thermostat operates at about 90 C and temperature measurement of the head shows the temperature does not go much above this – even at the end of a 48 hour continuous run.

I am not convinced there is much to be gained from enclosure (or oil) heat extraction but this is just my 2p worth and YMMV.

Regards,
Ian

[Henry W]

i have been considering soldering a copper tube loop to the oil pan and then cover it with the insulated shield

this particular application s195 trigen is slated to run a minimum of two one hour runs per day, it takes less than 5 minutes to be at full
operating temperature under full rated load, at which it will be running 90% of the time.

as for a lister/oid, i would concur re the issues of overcooling and not allowing the oil to heat up enough to boil off moisture, most of
those engine's don't generally run long enough or hot enough as it is to keep things dry down below, at least not enough so that i would
feel comfortable taking any btu's away from the oil.

bob g

Hello Bob,

That idea would work. When the S195 is loaded it oil gets ot a pretty good temp. When I was doing some load tests on my gen-set a while back I did take some temp readings and I wish I recorded them. The oil temp was brought up very quickly. With my S195 being hopper cooled I did notice the oil temp rising much quicker much quicker than the water temp. I also know the oil does get hot enough to boil off moisture. Which is a good thing. It would not be that hard to wrap a coil around the S195 oil pan and have it soilered on. If people don't have the experiance to solder that much copper on steel I bet a good radiator shop could do it for a reasonable price.

I feel a fair amount of heat could be extracted from a setup you are desribing.


Henry

[mobile_bob]

i think it gets lost in the verbiage that i am referring only to the changfa style engines, and not the lister/oid engine

as far as i can tell the difference's between the two are more numerous than are the similarities, very much
and apples to oranges thing when it comes to just about anything one wants to discuss.

on a changfa style engine one can control the vast majority of the fumes that would serve only to clog up air/air or air/water
exchangers that might be included in a containment system, however Ian makes a good point that accessibility should be
a forethought and not an afterthought with such a design.

maybe in order to mitigate confusion, i should move this topic to the changfa board?

bob g

[WGB]

From what I'm following, we want to keep the temp up on diesels using WVO & alternative oils.
So would pulling the heat out of the crankcase oil be counterproductive?

[WGB]

From what I'm following, we want to keep the temp up on diesels using WVO & alternative oils.
So would pulling the heat out of the crankcase oil be counterproductive?

I think you could pull all the heat you want out of the oil without affecting what happens in the combustion chamber.

You are only generating X amount of heat, the heat you are pulling out of the oil has to come from somewhere?
Oil coolers on other engines drop operating temps?

[mobile_bob]

i got no problem making all the heat necessary to burn whatever fuel i want to burn
the engine has a closed and pressurized cooling system and runs over 207 degree's F, with the coolant in the
head being well over 220 degree's F, all the while with a radiator and fan to control the heat at this level.

and the fan runs with some consistency as well.

if there is 3000 btu's available in the oil, i suspect i could harvest 75% of it and not effect the fan cycling by much at all.

we have to remember the engine will be running at over 7kwatts electrical load continuously or a bit over 10kwatt mechanical

making heat is not an issue with a 195 working hard

bob g

[mobile_bob]

Lloyd:

i am kicking around something along these lines

bob g

[vdubnut62]

Bob, what's the agribed?
Ron

[billswan]

bob

Got to ask you about the particulate filter? Where would you find such an animal to match your changfa?

Could you please give a quick explaination of how it will be kept clean? Are you talking of the modern ones that burn them selves out when they get restrictive?

What kind of catalytic converter? what are they used for on diesels? are they for oxides of n or other?

So many questions so little time

Billswan