Ski in NC
Technical Guru
I think most ship engines are the same way. Dry exhaust, but engine coolant is cooled by a heat exchanger internal to the ship, supplied with sea water through electric driven pumps.
I think most ship engines are the same way. Dry exhaust, but engine coolant is cooled by a heat exchanger internal to the ship, supplied with sea water through electric driven pumps.
Many ships being steel use skin coolers which are simply an internal version of keel cooling. The amount of water needed for a heat exchanger on 10,000hp would take a very large pump indeed. The last trawler I ran had 2400hp and skin cooling.
"I agree, attempting to convert a wet exhaust production boat with cabin and accommodations intact would be quite a project."
It is a load easier these days with fireplace SS double wall smoke pipe that can slip over the exhaust pipe as great insulation.
Finding space for the run is difficult.
The keel kooler can be very simple , we have the Mainiac work boat version which is 2 20ft lengths of 1 1/2 galvanized pipe .
Works grand , even in Florida.
Maybe it was a reference to gas/air separated exhaust. BTW I sure like the keel cooling on my NL. It also has a gas/air separater and wet exhaust.Paul,
Not sure where you heard this info but it's inaccurate, NL actually delivers very few KC gensets, a few commercial units and mega yachts, but most MY's prefer HX models. I work very closely with NL, have been to their Seattle facility many times, and am now in the midst of writing a profile article about them. I've reviewed their production line a number of times, rare to see a KC unit.
I've never seen a genset with a dry underwater exhaust (it would have to be wet by default, you can't route dry exhaust underwater, at least not on an FRP hull), not sure how that would even work, it would make a lot of bubbles, rumbling, too much back pressure unless it had a relief port, in which case why make it underwater exhaust?
Perhaps this was a typo?
There have been several comments here about soot problems with dry stacks: blowing all over the boat; coating electronic gear and antennas, etc. But this seems to me to be mostly a poor design issue, especially with the Nordies, because the stack is center-mounted and to make things worse, is combined with the nav-stack.
Just looking at the photo you can see how there would be air turbulence and vortices coming off that mast. It's not even streamlined in shape. Plus the pilothouse/deckhouse below causes all sorts of vortices and eddies, thus likely sucking soot down. If one is sailing downwind then you can imagine the problem is even worse.
Look at the example fishing boat photo where the dry stack muffler is mounted at the side of the deckhouse, thus allowing the exhaust to extend all the way to the widest beam, to the gunnel, perhaps even extending slightly beyond that. Honestly I would recommend the exhaust in the photo be a couple of feet higher and wider to the gunnel. This allows the exhaust to exit into clean air. If the wind comes from astern, then likely the exhaust smell and soot will (mostly) miss the rest of the boat's structure.
One suggestion I would make to anyone wanting to build a Nordy with the centerline stack as shown, would be to have the engineers design those two side platforms (which support the TV and satellite domes) as NACA airfoils, upside down, of very high lift design for airflows of 10-30 knots. The air as it leaves the airfoils will naturally be drawn upward (updraft). For all you airline pilots you're familiar with the downdraft caused by air exiting your wings. This will in effect help to pull the exhaust upward and away from the boat.
Of course it won't help when the boat is sitting at mooring, no wind, and you first startup and then the dry soot blows out. But it would be better than doing nothing.
BTW, yes, I did test this in wind tunnels when I was studying for my aero engineering degree many many moons ago
When citing workboats as validation for dry exhaust, I think it's important to keep in mind that dirt and grime is much less of a concern on such a boat.
The primary reason for smaller commercial vessel dry stack applications is the challenge a wet exhaust faces with highly variable water lines due to cargo weight variations. Add to that an intentional side or stern flooding situation as loads are lifted on and off when at sea, wet exhaust simply won't work.
As an aside I've been plowing through a backlog of boating magazines left over from 2018. In the dozens of magazines I've discarded containing more than probably 200 boat reviews and tech articles, none have had dry stack nor even discuss it. Including several new Nordhavns. It would appear in the recreational world, dry stack is a non subject.
Where I live most fishing boats with dry exhaust is to keep the fumes away from the work deck and to avoid freezing. There are some lobster boats with wet that primarily operate in the warmer seasons but loading isn't an issue as they carry full loads of traps and a full lobster tank with no problem.
Steve,
It was an East Coast NL dealer in reply to a query I had about the number of NOS NL heat exchanger cores available. Maybe I misunderstood was he was telling me. He was referring to workboats.
Regards
Paul