Why no radiators in boats?
 

"Chris" wrote in message
om...

[snip]

Air and water are both fluids.

[snip]

Didn't this guy say he's an engineer?

--
-Netsock

"It's just about going fast...that's all..."
http://home.insight.rr.com/cgreen/

Why no radiators in boats?
 

"Netsock" wrote in message
...
"Chris" wrote in message
om...

[snip]

Air and water are both fluids.

[snip]

Didn't this guy say he's an engineer?


Air and water *are* both fluids.

Why no radiators in boats?
 

Chris,
I believe that you are correct in your assessment, but common usage
would indicate otherwise. No car company I know of calls the finned cooling
device a heat exchanger nor have I heard of a boat manufacturer referring to
a radiator in their vessel. As you say they could call them either way but
that would just be confusing. IMHO
Paul

"Chris" wrote in message
om...
(Gould 0738) wrote in message
...
Thats a lame argument. Think about it.

KH

You're right. There's no difference between a cow and a horse, either.
Both are
mammals, walk on four legs, eat grass, and are commonly domesticated.
Just as
devices designed to transfer heat to the atmosphere and devices designed
to
transfer heat from one liquid to another are not different in concept
and one
term is properly interchangeable with the other, so it is also a waste
of time
to nitpick whether an animal is a cow or a horse. (At least until you
want to
go for a ride or get some milk to make butter and cheese).

I gotta come to KH's defense. As an engineer let me explain that
there is no difference at all between a "radiator" and heat exchanger.
They are both heat exchangers. The physical principles that govern
their operation are identical. One is a water to air heat exchanger
and one is a water to water heat exchanger. They just use different
fluids. This distinction only alters a few of the variables in a
machine designers calculations. The principal means of heat transfer
in both is conduction and convection. Radiation plays such an
insignificant part that it would be ignored by all but the most anal
engineers. It's not the difference between a horse and cow, it's the
difference between an arabian and a quarter horse. Same basic animal,
different applications. If a radiator actually radiated energy away
as the sun radiates energy to earth, why must it be put in front of
the car with air forced through it? www.howstuffworks.com will back
me up on this. Look up "car cooling system" and click on the radiator
link. In the first sentence it calls it a heat exchanger. You can
prove it to yourself on your car by blocking the grille with cardboard
and disabling your radiator fan, get on the highway and watch the
temperature gauge.

Why no radiators in boats?
 

OK, Radiators, heat exchangers, air to fluid, fluid to fluid, air to air,
blah, blah blah. They all get rid of heat or absorb it, whatever - there's
a transfer of heat from something "hot" to something less hot. or vice
versa.

The original question was really asking why are there not car type
"radiators" on boats. This semantical stuff, while interesting (NOT), is
irrelevant, imho.

Has anyone yet pointed out that it simply works better to exchange motor
heat with an unlimited supply of cool liquid rather than air? Cars first
take the heat from the block with liquid for this very reason. Air cooled
engines are generally very small in comparison.

In a car, however, the liquid is limited because it's a closed system and
therefore the next step is to transfer to the only unlimited cool thing
around, the air.

Boats goe through an unlimited supply of cool liquid which is better at
taking away the heat than an air-based "radiator". Therefore, the use of a
small fluid-fluid heat exchanger rather than a large fluid-air heat
exchanger. Some bypass this also with lake or ocean water cooling through
the block w/o exchanger.

Air boats, being the main exception to this use car type heat exchangers,
aka "radiators" because (1) they *can* (space and air movement allows them)
and (2) they don't have an outboard or outdrive leg, or jet intake to
easily suck in the water. Sure they could have a water inlet like a
straight inboard, but because of (1) above, they don't have to.

Just mho,

Cam

Why no radiators in boats?
 

flu·id (flu'id)
n.
A continuous, amorphous substance whose molecules move freely past one
another and that has the tendency to assume the shape of its container; a
liquid or gas.

"Netsock" wrote in message
...
"Chris" wrote in message
om...

[snip]

Air and water are both fluids.

[snip]

Didn't this guy say he's an engineer?

--
-Netsock

"It's just about going fast...that's all..."
http://home.insight.rr.com/cgreen/

Why no radiators in boats?
 

"Netsock" wrote in message ...
"Chris" wrote in message
om...

[snip]

Air and water are both fluids.

[snip]

Didn't this guy say he's an engineer?

They are both fluids. Water is a liquid and air is a gas but they are
both fluid. Fluid does not equal liquid. Look it up.

Why no radiators in boats?
 

Of course, I'm not suggesting that we all change the way we refer to
our car parts. I was responding to and correcting the guy who said
that heat exchangers and radiators are different not only in name but
in how they work.
He made a statement that was incorrect based on a misconception of the
physics of how radiators work so I had to respond in the same vein.
As far as the issues of this thread are concerned here is my take:

The reason we don't see radiators on boats is that air is an
inefficient cooling fluid. It is a very poor conductor of heat and
has low heat capacity. On the other hand, water is an excellent
conductor of heat and has huge heat capacity. So if a huge supply of
cold water is available near the engine, it is an easy decision. As
an engineer, I'd dump all of that heat in the water rather than try to
force it into the air.

One way to understand the heat conducting properties of water is to
think about how comfortable 72 degree air is vs. 72 degree water. 72
degree water feels alot colder simply because it is carrying your body
heat away very quickly. The lake does the same thing with your engine
heat. Carries it away very quickly.

I'm new to boating and as such have never even seen a heat exchanger
on a boat (my cooling system is open) but I'd bet that they are alot
smaller than radiators in cars. This is further illustration of how
efficent water is as a cooling fluid.

Chris



(Gould 0738) wrote in message ...
A heat exchanger, as the term is commonly applied, transfers heat between
liquids.



Technically, a "radiator" is not a radiator. A real radiator is what
you see on the floor of an old apartment building with no forced air
flow through it.

"As the term is commonly applied........"

Walk into your nearest auto shop this fall and ask to have your heat exchanger
serviced. You'll get more than a few strange looks.

Send a marine mechaninc down to your boat to change the zincs on your
"radiator"
and the wrench might sense this is a perfect time (and you're the perfect
client)
to recommend servicing the framus and the diogenator as long as he's aboard- it
will only run an extra $200.

If it takes a physics lecture to shore up a theory that "radiators and heat
exchangers are really the same thing" it doesn't, in the real world, address
the issues of this thread.

Those seem to have been:

1. Why don't we see radiators in boats?

schools of thought in response

a. Of course we do. I can show you hundreds of inboards with radiators

b. boats use a liquid to liquid heat exchanger rather than an automotive type
radiator to cool the engine.

c. There is no difference between an automobile radiator and a heat exchanger
on a boat.


If this were a multiple choice exam, I'd go with B. Thanks anyway, though.