Heat Exchangers, Types and explainations.

ben2go · Nov 17, 2019

For those that aren't familiar with heat exchangers, and those that are, I encourage you to have a look at these two videos. I've worked with heat exchangers since I was in school in my teens to learn industrial maintenance mechanics. I learned so new stuff about these heat exchangers and they are the two predominate heat exchangers found on our boats. The videos can also help pin point problems, make adjustments, and repairs.

Most common, tube type.

Second most common, plate type. This one is really good.

DavidM · Nov 17, 2019

Very nice tutorials. Wish I had them when I was starting out my career. I learned how they are built the hard way by cleaning them early in my career.

I worked with heat exchangers most of my life as a chemical engineer working in the engineering and construction industry maintaining, designing and building refineries, chemical plants, etc.

Plate exchangers were relatively rare in that industry and are also rare in boats as well. They are sometimes used in water heating systems for boats.

The video discusses single pass and multi pass shell and tube heat exchangers. For boat engines, the main heat exchanger is often mult ipass. It was a three pass heat exchanger on my Yanmar 6LY engine. All others: the transmission, lube oil and air coolers were all single pass.

Fouling and leaking are the two concerns we have with marine engine heat exchangers. Fouling usually occurs on the raw water side (always the tube side) and consists of calcium and magnesium compounds that precipitate out of sea water. These are cleaned mechanically by rodding the ID of the tubes or circulating an acid through the tubes.

The shell side is usually not cleaned for two reasons: it has relatively clean stuff on it like lube oil and coolant and the lube/coolant heat exchangers cannot be disassembled to get to the shell side to clean them. If they are fouled on the shell side (rare) or leak, then they must be replaced.

The only heat exchanger that can be disassembled for cleaning the shell side is the air cooler. You remove the end caps and then slide the tube bundle out (easier said than done). The shell side of the tube bundle can then be cleaned with a cleaning solution in an ultrasonic bath or with a pressure washer.

These heat exchangers develop leaks at the shell to tube bundle joint due to corrosion. These can sometimes be cleaned up and machined and reassembled with new gaskets and o-rings. But if too bad they must be replaced.

Dealing with the various heat exchangers on marine engines is a big part of routine engine maintenance.

David

ben2go · Nov 17, 2019

Pretty cool, David. I've been messing around with boats for a while. Mostly freshwater fishing and ski boats around 16 to 25 feet. Some heat exchangers can be big pains to diagnose without the tools to pressurize the unit. I'm planning to keel cool my boat. That should eliminate the heat exchanger problems.

Sanjv9473 · Sep 8, 2021

Heat Exchanger, types and explanation

A heat exchanger is a system used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact.

Types

What Are The Different Types Of Heat Exchanger?

Finned Tube Heat Exchanger Or Air Cooled Heat Exchanger. Suitable for: air/gas to fluid. ...

Shell And Tube Heat Exchanger. Suitable for: fluid to fluid / fluid to gas. ...

Plate Heat Exchanger Or Gasket Plate Heat Exchanger. Suitable for: fluid to fluid / fluid to vapour.

ben2go · Sep 8, 2021

Sanjv9473 said:
A heat exchanger is a system used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact.

Types

What Are The Different Types Of Heat Exchanger?

Finned Tube Heat Exchanger Or Air Cooled Heat Exchanger. Suitable for: air/gas to fluid. ...

Shell And Tube Heat Exchanger. Suitable for: fluid to fluid / fluid to gas. ...

Plate Heat Exchanger Or Gasket Plate Heat Exchanger. Suitable for: fluid to fluid / fluid to vapour.

twistedtree · Sep 9, 2021

ben2go said:
Pretty cool, David. I've been messing around with boats for a while. Mostly freshwater fishing and ski boats around 16 to 25 feet. Some heat exchangers can be big pains to diagnose without the tools to pressurize the unit. I'm planning to keel cool my boat. That should eliminate the heat exchanger problems.

Keep in mind that with keel cooling you are really just moving the heat exchanger to the outside of the boat. Cleaning is still required similar to other heat exchangers, especially with respect to the salt water side.

Scrib · Sep 9, 2021

Hmmh, always thought an advantage of keel coolers is that there is no saltwater in the system; the saltwater being outside the pipes and still in the ocean. Am I adrift?

ben2go · Sep 9, 2021

twistedtree said:
Keep in mind that with keel cooling you are really just moving the heat exchanger to the outside of the boat. Cleaning is still required similar to other heat exchangers, especially with respect to the salt water side.

That was two years ago. I have moved away from motor to sail. After three suppliers I was working with to obtain materials to build my boat went under due to covid, and not being able to get products, I threw in the towel for good. Old fiberglass sailboats from the 60s and 70s are selling off pretty cheap. I just can't seem to get there in time with my cash when I find one I like.

twistedtree · Sep 9, 2021

Scrib said:
Hmmh, always thought an advantage of keel coolers is that there is no saltwater in the system; the saltwater being outside the pipes and still in the ocean. Am I adrift?

The salt water stays outside the boat - that's true. But your heat exchanger, aka keep cooler is still in contact with the sea water, and will still suffer from marine growth and corrosion. Maintenance is still required. You are essentially taking the heat exchanger to the sea water instead of bringing the sea water to the heat exchanger.

OldDan1943 · Sep 9, 2021

The walls of the keel cooler are very very thin. I would take my keel cooler to a radiator shop every 2 years to be cleaned and pressure tested. When I had a bottom job.

ben2go · Sep 9, 2021

twistedtree said:
The salt water stays outside the boat - that's true. But your heat exchanger, aka keep cooler is still in contact with the sea water, and will still suffer from marine growth and corrosion. Maintenance is still required. You are essentially taking the heat exchanger to the sea water instead of bringing the sea water to the heat exchanger.

Most keel coolers made from cupronickle don't have growth issues quite as bad at stainless or aluminum units. Copper, I'm told, will fatique and crack. This was told to me by a rep for Duramax marine. A lot of the New England fishermen make theirs out out of copper piping. Steel boats use a split pipe welded to the hull as the cooler and anti foul over it but those are nearly as long as the boat and tucked up next to the keel.

Conall, I think is on here and he has welded coolers.
Conall's Boat Build: Keel Coolers

DIY copper keel cooler.

FF · Sep 10, 2021

Some keel coolers are totally internal in metal boats .
A chase is welded into the hull with a gasket cover .
The warm water section of the hull does require more scrubbing , as the higher temps attract fouling.

But scrubbing the hull is way less skilled work than overhauling a heat exchanger.

ben2go · Sep 10, 2021

FF said:
Some keel coolers are totally internal in metal boats .
A chase is welded into the hull with a gasket cover .
The warm water section of the hull does require more scrubbing , as the higher temps attract fouling.

But scrubbing the hull is way less skilled work than overhauling a heat exchanger.

Those are common on canal boats in EU and Russia. It's like a baffled tank welded to the inside of the hull that redirects water through it to cool the engine. There was a video about them on youtube but I couldn't find it.

psneeld · Sep 10, 2021

From a marine engineerr....

https://www.alfalaval.us/microsites/gasketed-plate-heat-exchangers/tools/gphe-vs-shell-and-tube/

A general rule says plate exchangers are about 5 times more efficient than shell and tube. They are the HX of choice on most ships for systems where size and performance are important. There are few larger engines that are not delivered with plate HXs

Marco Flamingo · Sep 10, 2021

I first came across the plate type heat exchangers when researching home heating for my house. I installed hydronic floor heat and needed a heat exchanger to transfer heat from the domestic hot water to the radiant floor hot water. My SS plate heat exchanger is about the size of a football. I was really sceptical that it could do the job, but numbers don't lie.

My hot water heater is demand electric the size of a brief case and fits between two studs in the utility room. The plate heat exchanger and two circulating pumps sit on a small shelf. That's the entire domestic hot water and heat for the house. Tiny, silent, no air blowing.

I don't know if they make a plate heat exchanger small enough to replace the tube exchangers on my old Lehman. The other issue would be that the plate exchanger's efficiency is probably because of very close tolerances. I'm not sure how it would handle little bits of seaweed and seagull poop.

twistedtree · Sep 10, 2021

ben2go said:
Those are common on canal boats in EU and Russia. It's like a baffled tank welded to the inside of the hull that redirects water through it to cool the engine. There was a video about them on youtube but I couldn't find it.

This is a great solution when designed into a steel hull boat. Just not one available to most pleasure boats.

twistedtree · Sep 10, 2021

Marco Flamingo said:
I first came across the plate type heat exchangers when researching home heating for my house. I installed hydronic floor heat and needed a heat exchanger to transfer heat from the domestic hot water to the radiant floor hot water. My SS plate heat exchanger is about the size of a football. I was really sceptical that it could do the job, but numbers don't lie.

My hot water heater is demand electric the size of a brief case and fits between two studs in the utility room. The plate heat exchanger and two circulating pumps sit on a small shelf. That's the entire domestic hot water and heat for the house. Tiny, silent, no air blowing.

I don't know if they make a plate heat exchanger small enough to replace the tube exchangers on my old Lehman. The other issue would be that the plate exchanger's efficiency is probably because of very close tolerances. I'm not sure how it would handle little bits of seaweed and seagull poop.

I suspect serviceability is the big reason we see tube heat exchangers anywhere sea water is one of the fluids.

I’m using a plate heat exchanger for the first time, coupling engine heat to my house hydronic heating system. It’s MUCH more compact than an equivalent tube exchanger.

FF · Sep 12, 2021

" . I installed hydronic floor heat and needed a heat exchanger to transfer heat from the domestic hot water to the radiant floor hot water".

How did you solve the problem of a leak in the unit from contaminating the domestic water?

The floor tubing is usual filled with 50% antifreeze which can be poison.

sunchaser · Sep 12, 2021

twistedtree said:
I suspect serviceability is the big reason we see tube heat exchangers anywhere sea water is one of the fluids.

I’m using a plate heat exchanger for the first time, coupling engine heat to my house hydronic heating system. It’s MUCH more compact than an equivalent tube exchanger.

We too use a plate heat exchanger for tying the hydronic heating system into the engine coolant loop. It is about the size of a cigar box.

Each of our engines have plate heat exchangers for coolant to oil. This facilitates proper oil temperatures when engines are lightly loaded or working hard.

Marco Flamingo · Sep 12, 2021

FF said:
How did you solve the problem of a leak in the unit from contaminating the domestic water?

The floor tubing is usual filled with 50% antifreeze which can be poison.

No antifreeze. My hydronic heat is in concrete slab on grade. Even when I'm gone for a month in the winter, the slab only cools down to the mid-50's. Because of the thermal mass in the house, we don't even drain the potable water when gone for months in the winter. Thermometer recorded the lowest temp in the house was mid-40's after three days below freezing (which is unusual for us). Hell would have to freeze over before I'd need to worry about antifreeze, but I'm keeping my eye on climate change.

twistedtree · Sep 12, 2021

Marco Flamingo said:
No antifreeze. My hydronic heat is in concrete slab on grade. Even when I'm gone for a month in the winter, the slab only cools down to the mid-50's. Because of the thermal mass in the house, we don't even drain the potable water when gone for months in the winter. Thermometer recorded the lowest temp in the house was mid-40's after three days below freezing (which is unusual for us). Hell would have to freeze over before I'd need to worry about antifreeze, but I'm keeping my eye on climate change.

You might want to check whether your boiler requires glycol. Most do for corrosion inhibiting, in addition to freeze protection.

GoneDiving · Sep 12, 2021

Marco Flamingo said:
I don't know if they make a plate heat exchanger small enough to replace the tube exchangers on my old Lehman. The other issue would be that the plate exchanger's efficiency is probably because of very close tolerances. I'm not sure how it would handle little bits of seaweed and seagull poop.

Single piece plate heat exchangers (that cannot be disassembled) can be tiny, almost palm sized. They are commonly used in home brewing or 4WD water heating.

I've used modular models for oil heating down to tissue box sized. Obviously these can be made smaller by simply using less plates.

Heat Exchangers, Types and explainations.

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