Cooling Diesel Fuel to Increase Efficiency

[ssreese1500]

Was told recently by an engine manufacturer that by decreasing the fuel oil temperature at the fuel oil rail to my engines by 10 degrees F will give me approximately a 1% increase in efficiency.

Has anyone heard of this?

If so, do you know where i might be able to find a 110vac operated chiller that would accomplish this? My comsumption at sea speed is about 155 gallons of diesel fuel per hour, ambient temp in the 115 degree F range, and the fuel into the engine is approx. 100 degrees F. Would really love to get the temp to the engine to about 80 degrees.

Any ideas?

 

[orenda1168]

Ssreese1500:

Before jumping into this, you might want to ask the engine manufacturer to define his "efficiency" gain!

Orenda

 

[pauljohn]

What temp. is the seawater and could you use it to cool the fuel by running both through a heat exchanger?

 

[MikeHalloran]

Around here in SoFla, the temperature of the seawater going into a boat is around 90F most days. It gets warmer as you go toward the equator.



Mike Halloran
Pembroke Pines, FL, USA

 

[ssreese1500]

Mike, exactly the issue I am facing with a water cooled system. Not enough delta T to really do me any good. Besides, my vessels have keel coolers and the last thing I want to do is introduce a new salt water cooling system. We even considered running the supply piping through one of the fuel oil storage tanks, but again the temperature differential isnt enough to make it worthwhile. I think a chiller unit is the way to go, at least to prove what the engine manufacturer is telling me.

To answer Orenda's question, you are right, i wasnt very clear. 1% fuel decrease for every 10 degrees F cooler the fuel is at the engine.

 

[zeusfaber]

Is that 1% less fuel mass, or 1% fuel volume?

10^oF cooling is going to make your fuel about 0.7% denser - which is close enough to 1% to make me ask the question.

A.

 

[ssreese1500]

good point. allegedly, it will be 1% less consumption. I have a set of fuel oil meters that measure flow and temperature, factoring in the temperature when figuring the flow in Gallons per minute. There is a meter on the supply and the return, so consumption is the difference between the two. I should be able to tell over about a month what kind of reduction I am getting.

 

[pauljohn]

Temps in open ocean are much cooler than near land. Virginia Key just south of Miami was 67 F today and Sombrero Key was 71F. Even in August ave. temps in Gulf are 85F. Data from NOAA buoys taken about 3 feet below surface.

Because of unlimited supply of cooling water and a relatively small amount of fuel I would think it wouldn't be difficult to bring the fuel down to near sea temps.

 

[orenda1168]

Ssreese1500:

I guess that I must be missing something....here are my problems with a 1% efficiency increase for each 10 degree reduction in fuel oil temperature.

First, a diesel engine knows only two things....BTU's in, power out. Ignoring the effect of temperature on fuel handling, atomization and so on, at whatever temperature the fuel is maintained, the engine will still require a given BTU input...i.e. fuel mass...for a given power output. Fuel temperature can only be related to fuel volume, not fuel mass required by the engine. If this is so, then where does the fuel consumption reduction come from? I presume that it is not a result of reduced fuel preheating.

Secondly, having run a four week at-sea trial on a homogenized water/Bunker C blend aboard a 30,000 DWT steam turbine tanker in 1985, I was able to demonstrate a fuel efficiency gain of about 1% for each 1% water emulsified into the fuel by virtue of cleaner burning, reduceable excess air and fewer fireside deposits, subsequently confirmed by others on this ship and sister vessels burning similar fuel/water blends. However, our trial fuel had an 8% water content which resulted in a nominal 8% fuel consumption reduction for a given set of ship sailing parameters. My point in bringing this up is to question anyone's ability to reasonably and accurately measure a 1% efficiency improvement when, with a diesel, you don't have the combustion variables to play with that are available on a steam boiler ship. To my knowledge, on-board fuel flow instrumentation isn't accurate enough to reliably pick up this difference, nor can consumption be easily correlated to at-sea and engine operating conditions that can and do dramatically effect fuel consumption.

As I started out with, I must be missing someting here...I will greatly appreciate whatever you can offer to set my thinking straight.

Regards,


Orenda

 

[MikeHalloran]

The little Diesel fuel that I have personally handled seemed to be about five pct water and ten pct dirt.

Boats of the modest size we're talking about don't draw water from three feet down. They get water that's been warmed by the sun. Even if they draw three feet and the seachests are on the deepest part of the hull and they're not planing, the water they're getting was just pushed down by the hull passing over.

A chiller seems like the way to go. Whether you'd gain enough engine efficiency to pay for running the chiller is another matter. You could just move to Alaska...




Mike Halloran
Pembroke Pines, FL, USA

 

[pauljohn]

Sorry Mike I disagree.

I think it would be relatively easy using mostly spare parts you would normally have on board to temporarily (i.e. not coastguard approved) rig up a system where you could pass 10,000 galls. of sea water over 155 galls. of fuel per hour on it's way to the engines and bring it down to 80F which is the temp ssreese was looking for.

I regularly sea trialed and tested boats out of Ft. Laud. Miami, Palm Beach and raw water temps coming in to the engines were never more than 1 or 2 degrees different than what NOAA meteorological. buoys were reporting. Sure water is warmer 3 feet up on the surface but only by a couple of degrees and in calm weather.

The Caribbean is almost always around 80F except in the sheltered shallower parts. The Pacific is much colder than the gulf - Hawaii never gets out of the 70's.
check this page out

http://www.nodc.noaa.gov/dsdt/cwtg/satl.html

Or you could go for a swim and let me know!! I wish I could but I'm 2,000 miles away.

ssreese

if your fuel temp is 100F then you must be getting some heating from somewhere.

If it was that simple to realise fuel savings why don't we see this method used all the time?

 

[pauljohn]

That should of been one thousand galls. not ten.

 

[ssreese1500]

Paul, the seachest suction is about 20 feet below the surface, so yes, I COULD rig something up, the thing is I dont want to introduce any sea water systems to the engine room. Right now, the only sea water system on the whole boat is the fire pump, and I am quite happy to keep it that way. I have used small industrial chillers while working with production TIG welding, and they were cheap and effective. Lastly by using a chiller, I could adjust the temperature of the fuel to whatever I wanted and document the fuel consumption at that temp, rather than try to figure it out with the additional variable of fluctuating fuel temp due to changes in sea water temp.

The fuel is definitely heated from the heat of the engine room. These are ocean going tugs, aka a floating fuel tank with an engine room. The engine room has fuel tanks on all four sides of it, including the day tanks. That is the heat source. Also, the heat of the sun on a steel deck will raise the temp of fuel in a tank a lot more than you might think.

Orenda, I remember when people were testing the fuel/water mix on steam ships, but I never actually did it myself. If I remember correctly, one of the points of this would be that the water in the fuel flashed to steam in the air box and better atomized the fuel, resulting in more complete combustion, is this correct? That being said, you in effect are decreasing the BTU per pound of your fuel by adding the water, but your boiler is burning it better and able to extract more available BTUs from the fuel, right? In effect that is what I am trying to accomplish here. While I certainly can not tweek the diesel cycle, I can certainly make changes to how the engines produce power with the fuel they are provided. One Example: we were able to document a fuel reduction of about 2% based on changing out the fuel injectors being used on the engine. These boats are on a steady run and the meters are sensitive enough to document very small changes in fuel consumption. Over a period of time all the variables you mentioned eventually come very close to evening out.

Mike, ALASKA??? sorry pal, I moved to Florida over 10 years ago and my blood is VERY thin. The only reason Im going to Alaska is to catch a Halibut or shoot a large brown woodland animal.

 

[MikeHalloran]

I'm inferring that you don't have seawater cooled aftercoolers, which might offer more bang for the buck than a fuel chiller.

I spent a few days in Seward, AK to learn how to make better exhaust parts for the tour boats. Those may have been the only sunny days that whole winter, of course. I liked it a lot. I like Florida, too.






Mike Halloran
Pembroke Pines, FL, USA

 

[orenda1168]

Ssteese1500:

I appreciate your insight. Yes, you're correct in your understanding of water-emulsified boiler fuel and how the combustion of this can result in reduced fuel consumption.

In any case, I (and I'm sure others) will be most interested in your progress with the fuel chilling concept. please let us know how you make out!

Regards,



Orenda

 

[pauljohn]

a couple of points to consider.

Cooling 155 galls. of fuel 20 degrees or more per hour is going to require lots of power.
Will you use up all your predicted fuel savings powering your chiller? This was why I thought of using seawater directly - you only pay for the pump.

Won't you need a seawater cooling flow system for your chiller anyway?

I thought you might be able to stop the fuel getting warm in the first place but that maybe impossible from what you describe, Right?

I agree it is always best to stay with the systems you are familiar with and it sounds like you have already decided to use the chiller, will be interested to hear how your project goes.

Paul

 

[frankiee]

May I ask what kind of engines?

 

[liviebudgie]

I have a deisel, steam amd boiler engineer ticket.
Twenty three years sea service on Navy vessels.
In all that time i have not seen any system to cool fuel.
In fact i have seen the reverse, fuel heating to allow pumping and transfer and for cleaning.
If the ship is so sensitive to fuel ecconomy, run at most ecconomical speed.
Do runs over a set distance at different speeds and measure the fule used. The graph plotted will show the best speed to run the hull at for fuel consumption.

 

[ssreese1500]

Thanks for all the help you guys, and I will certainly let you know what I find out regarding this project. As stated before, the challenge will be to get a chiller that is efficient enough that I dont lose my fuel savings.

to answer the last few questions.

The engines in question are EMD 645 series.

The engines burn straight diesel, not heavy fuel.

It is common knowledge that you burn a lot more fuel to increase your speed further up the fuel/speed graph. However, if we run for a year at 800 rpm as opposed to 900, we save a lot of fuel, but we make one less trip a year, and the profit from that trip exceeds the fuel savings. my challenge is to save fuel AND maintain operating speed.

 

[Compositepro]

I can not think of any reason that cooling the fuel would increase efficiency and quite a few reasons that heating the fuel would help. Perhaps there is some secondary effect that is peculiar to your engine but investigate further before you waste money on nothing.