Heat exchangers.. if I were to use a small diesel for my sailboat that did
not have a
heat exchanger already attached to the engine ??

How do I size the heat exchanger? Does it go by horse power, size of engine
... cyclinders ..

On Sun, 02 Dec 2007 18:38:37 GMT, "Sir Thomas of Cannondale"
wrote:

Heat exchangers.. if I were to use a small diesel for my sailboat that did
not have a
heat exchanger already attached to the engine ??

How do I size the heat exchanger? Does it go by horse power, size of engine
.. cylinders ..


Diesels are efficient thermal converters. Let's use a 40% thermal
efficiency at generating the rated horse power of the engine,
so it needs to dispose of the other 60% as heat.
Heat out of the exhaust, and heat into cooling water.

The exhaust can take care of itself, so your question amounts to this:
what factor of rated horse power should I allow for an engine cooling
heat exchanger?
Fuel thermal content = 100/40 of rated HP
That's 2.5 times rated HP
Exhaust thermal content = (say half the waste heat) =
(2.5 - 1 ) X 1/2 of rated HP = 0.75 of rated HP
leaving
Cooling heat also 0.75 of rated HP

This estimator gives the cooling requirement of a 10 HP diesel as
10 X 0.75 HP = 7.5HP or
7.5 X746 watts = 5.6 kW

It's a little bit conservative.

Brian W

Clear as mud?

Wow.. just as I thought.
===



"Brian Whatcott" wrote in message
...
On Sun, 02 Dec 2007 18:38:37 GMT, "Sir Thomas of Cannondale"
wrote:

Heat exchangers.. if I were to use a small diesel for my sailboat that
did
not have a
heat exchanger already attached to the engine ??

How do I size the heat exchanger? Does it go by horse power, size of
engine
.. cylinders ..


Diesels are efficient thermal converters. Let's use a 40% thermal
efficiency at generating the rated horse power of the engine,
so it needs to dispose of the other 60% as heat.
Heat out of the exhaust, and heat into cooling water.

The exhaust can take care of itself, so your question amounts to this:
what factor of rated horse power should I allow for an engine cooling
heat exchanger?
Fuel thermal content = 100/40 of rated HP
That's 2.5 times rated HP
Exhaust thermal content = (say half the waste heat) =
(2.5 - 1 ) X 1/2 of rated HP = 0.75 of rated HP
leaving
Cooling heat also 0.75 of rated HP

This estimator gives the cooling requirement of a 10 HP diesel as
10 X 0.75 HP = 7.5HP or
7.5 X746 watts = 5.6 kW

It's a little bit conservative.

Brian W

Clear as mud?

On Sun, 02 Dec 2007 18:38:37 GMT, "Sir Thomas of Cannondale"
wrote:

How do I size the heat exchanger? Does it go by horse power, size of engine
.. cyclinders ..

Heat to be dissipated, and therefore heat exchanger size, is directly
proportional to the fuel burned. In other words, horsepower.

Casady