Generator Ventilation - acceptable temperature rise 1

[KesTheHammer]

I am doing a project in the GCC - so ambient temperatures are seen as 55°C as per specification document.

So I get the heat rejection from the manufacturer - Q = X kW.

and I want to do a Q= m·c·dT calculation, but I don't know what an acceptable final temperature is for these high ambient generators.

Do any of you guys know?

Address a problem when it shows up, not when it blows up.

 

[GT-EGR]

Are you taking about the airflow and delta T required to cool the generator radiator? Or just to cool the space/mechanical room around the generator?

The radiator airflow is a number you should get from generator manufacturer, I wouldn’t take it on to decide that yourself

For the delta T, a very typical delta is 10 degrees F above ambient. So unless the equipment physically can’t handle that number, that is the reasonable trade off between not having an extreme amount of airflow and understanding that the generator area is not going to be the most comfortable space year round. Unless you are adding refrigeration, there isn’t anything you can really do, that room will just be hot in the summer months.

 

[berkshire]

Kes the hammer,
Here is what one manufacturer has to say about it.

http://www.macallisterpowersystems.com/solutions/engineering-toolbox/generator-set-cooling-systems/

B.E.

You are judged not by what you know, but by what you can do.

 

[GroovyGuy]

Howdy Kes,
55C is a really high ambient temperature. Note that most generators are rated for a max ambient temperature of only 40C (without a serious derate of the generator's output power rating). Although I'm sure that the engine can handle an ambient temperature of > 40C.
Will these units have remote rads?
Are they prime power or standby power?
What is the fuel source (ie n-gas or diesel)?
What size (ie in kW) are we talking about here?
Is 55C the outdoor ambient temperature, correct? I would think that delta T of 5C would be achievable. (Note this will require a fair amount of mechanical ventilation.) That would bring the interior temperature up to 60C.
Will the engines have their air intake piped in from outside of the enclosure?
GG
ps I have lots of experience in packaging of gen-sets, but not in a 55C ambient environment. What do the gen-set OEMS have to say wrt this high ambient temperature. I'm sure that most OEMs can provide you with all of the information that you require.


"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 

[KesTheHammer]

Guys, thanks for the response.

It is assumed that the room will be unoccupied while the generator is running - the noise is so high that even with hearing protection it cannot be used.

The units are standby, diesel generators, 1250 kW, 1600 kW and 2750 kW - so pretty massive.

The airflow requirements for ΔT of around 10 °C is stupidly high (about twice the radiator airflow) - so I was hoping to push the ΔT to 15 or 20 - to bring it more in line with the radiator fan flow - but that would mean the generator and alternator etc is operating in a 75°C environment.

I am trying to contact the manufacturer, but it is not as fruitful as one would hope.





Address a problem when it shows up, not when it blows up.

 

[lukaiENG]

What GroovyGuy said.
Occupant comfort is not the issue, the operating requirements of the generator (and radiator) itself are the limitations.
I would persevere with getting manufacturer data. If they don't give information move onto a new supplier and cut the other one from the specification.

I have also never seen gens designed for that high of an ambient condition, but it's not the first project in the M.E. so I'm sure the manufacturers have a solution.

 

[MintJulep]

So I get the heat rejection from the manufacturer

Make sure that you are getting the right answer for the question that you should be asking.

That is to say, if you (and I hope you do) have a remote radiator then you don't want the jacket water heat rejection included in the answer.

Exhaust is going outside, so you don't want exhaust heat rejection in the answer.

 

[GroovyGuy]

Howdy Kes;
FYI I just completed a project where we installed three (3) CAT G3612 engine-gen-sets, each in it's own bldg and c/w remote radiators. Each unit is (prime power) rated 2600kWE output. Outside ambient ranged from -40C to +32.5C. Fuel supply: N-gas.
Summer ventilation requirements include 92,000 cfm to remove a max of 373kW of heat produced by the engine and alternator.
This was provided by four (4) 5hp fans, each rated 30,000cfm and vfd driven (ie in n+1 configuration). ΔT was limited to 7.5C in order not to exceed the 40C rating of the alternator (ie no de-rate of the alternator).
Combustion air was piped in from outside.

Again, I strongly suggest that you discuss the de-rating of your units with your OEM (in light of the high ambient temperature). I offer the above only as a solution that we applied to a similar project, albeit with a much lower ambient temperature.

Good luck.

GG


"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 

[chicopee]

Reading your OP, I would first inquire from the generator supplier if it is possible to provide specially build generators to withstand 55dC ambient temperatures. It will cost a lot more money if it is possible to do so.

 

[ScottyUK]

It's certainly possible to build generators capable of operating at 55°C ambient, but they are de-rated versions of much larger sets. Over-sized radiators / fin-fan banks mounted externally to the generator room, and a howling gale of cooling air through the engine enclosure to handle the heat rejection from the engine itself. Insulate the exhaust within the enclosure to minimise the heat rejected into the room.

All the big manufacturers have supplied into the gulf states - 55°C ambient won't come as a surprise.