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#1
03-16-2009, 11:38 AM
 btsp Guest Posts: n/a
BTU/bhp-hr

BTU/bhp-hr

Im not to sure what this means and im not sure how i can get it to M3/hr or some kind of KWH form.

any help would be great

Thanks in Advance
BTSP
#2
03-16-2009, 11:59 AM
 JohnS Double Ultimate Supreme Member Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,215 Rep Power: 18
Re: BTU/bhp-hr

Quote:
 Originally Posted by btsp BTU/bhp-hr Im not to sure what this means and im not sure how i can get it to M3/hr or some kind of KWH form. any help would be great Thanks in Advance BTSP
It is dimensionless, both units being energy units. It is some kind of "efficiency" obscured by the units conversion. Convert both numerator and denominator to joules, which will divide out.

It could either be the inverse of brake specific fuel consumption or it scould be waste heat produced per horsepower-hour. Do you have any sense of context?

BTU is a measure of thermal energy. It could be the total energy in some amount of fuel for example. The inverse, fuel used per horsepower hour is brake specific fuel consumption. The fuel is usually measured in mass or volume units, but could be measured in heat content.

On the other the BTUs could be only the waste heat and a measure of how much waste heat is produced per horsepower-hour of output from an engine. It would relate to cooling system demand.

Since engine efficiencies are around 30-35%, if the BTUs represent total heat energy (fuel) when expressed as joule/joule, you'll get a number around 3, if only the waste heat that must be cooled, around 2 (moreorless)
#3
03-16-2009, 12:27 PM
 btsp Guest Posts: n/a
Re: BTU/bhp-hr

ya the units refer to:

100% Load
Fuel Consumption (100% load) with Fan
per ISO3046/1: +5%, -0% tolerance

i just want to find out how much gas im using per H

THanks in Advance
BTSP
#4
03-16-2009, 03:19 PM
 JohnS Double Ultimate Supreme Member Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,215 Rep Power: 18
Re: BTU/bhp-hr

Quote:
 Originally Posted by btsp ya the units refer to: 100% Load Fuel Consumption (100% load) with Fan per ISO3046/1: +5%, -0% tolerance i just want to find out how much gas im using per H THanks in Advance BTSP
So, you'd have to multiply by output horse power, then divide by the energy content of your gas.
#5
03-17-2009, 06:52 AM
 btsp Guest Posts: n/a
Re: BTU/bhp-hr

SO i dont know why i cant understand this

100% Load
Fuel Consumption (100% load) with Fan
per ISO3046/1: +5%, -0% tolerance

BTU/bhp = 7899

It is a NAtural Gas generator producing 1040KWH Output

i want to find the amount of Natural gas it is using to produce this an hour.

And then from there i can get Eff. but i jsut dont know what to do with this unit of measurement above.

Sorry for the troubles

BTSP
#6
03-17-2009, 08:37 AM
 JohnS Double Ultimate Supreme Member Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,215 Rep Power: 18
Re: BTU/bhp-hr

The manufacturer has done everything possible to obscure the truth and only provide relatively useless numbers. You are missing some data you need, and I will pull numbers out of my a** which you should try to replace with actuals. They are pretty representative though.

A generator set consists of a generator and and engine which drives it. Each has an efficiency < 100%. The fuel consumption data you were given applies only to the engine. You don't know the bhp the engine has to put out to drive the generator at rated load.

A generator output is actually rated in power, kilowatts, not energy, kilowatt*hours. The kilowatt hours are the number of kilowatts it puts out times the number of hours it does so. I hope my little 4 kW generator will run (intermittantly) for at least 1000 hours total and put out a total of 4000 kWh over its useful life. I am assuming your generator is actually rated for 1040 kW. Note that it will only put out this much if that much load is plugged into it. At lower than max load, it will consume lower than max fuel

Horsepower and kilowatts are both units of power, 1 HP = 746 W, or 0.746 kW. An ideal (100% efficiency) generator could produce 1040 kW of electrical output with 1394 hp measured on the drive shaft. A 90% efficiency generator would require 1549 shaft hp to produce the output. You need a figure from the supplier for generator efficiency, or required horsepower at rated load. Reaching in my repository of handy numbers, a very good efficiency around 93% would require about 1500 shaft hp, and I will use that figure.

At rated consumption of 7899 BTU/bhp·h and engine output of 1500 hp, you need 11.85 MMBTU/h. Now, another issue for the supplier. Is that fuel number based on Higher Heating Value or Lower Heating Value? (The difference depends on whether the water vapor in the exhaust is assumed to condense and provide useful heat). Engines are normally rated on LHV and I will assume.

The energy content of natural gas supplies varies according to source. The Dept of Energy gives "typical" values of 983 BTU/ft³ LHV, 1089 BTU/ft³ HHV. You should get figures from your own gas supplier. 11.85 MMBTU/h divided by 983 BTU/ft³ is 12053 ft³/h. Natural gas is more commonly specified as hundreds (CCF) or thousand (MCF) of cubic feet, so 120.53 CCF/h or 12.053 MCF/h.

This answer is based on three SWAGS (generator efficency, LHV, and gas energy content) and one honest conversion. Depending on assumption validity, it could vary 10% or more.

Finally, the fuel consumption number is weird as ISO standards are all metric. 7899 BTU is 8.334 MJ, and 1 hp·h is 2.6845 MJ, so this number reduces to 8.334 MJ/2.6845 MJ = 3.104, and is the reciprical of engine efficiency 32.2%. This needs to be multiplied by generator efficiency for overall.
#7
02-26-2010, 11:34 AM
 Unregistered Guest Posts: n/a
Re: BTU/bhp-hr

What is the conversion formula for BTU/bhp-hr to BTU/hr?
#8
05-03-2010, 05:54 PM
 Unregistered Guest Posts: n/a
Re: BTU/bhp-hr

the long answer above gives you the more correct way to arrive at this but in ultra simple form and assuming 100% efficiency of everything, you multiply the BTU/bhp-hr times the HP of the unit. if that makes you feel like you have an answer, great - although it is wrong. thats assuming 100% efficiencies and gas with constant BTU of 1,000-1,100 BTU/CF. You also have to consider mechanical efficiencies.... If you will plug in all your specific variables into the long answer above, you will be pretty darn close to correct.
#9
11-14-2013, 01:37 PM
 Unregistered Guest Posts: n/a
Re: BTU/bhp-hr

G3516A Gas Generator Set
Emission level (NOx) mg/Nm3 500
Aftercooler SCAC Deg C 43
Package Performance (1)
Mechanical Power (with water pumps and w/o fan) bkW Continuous 1136
Power Rating @ 0.8 pf (with water pumps and w/o fan) ekW Continuous 1100
Power Rating @ 1.0 pf (with water pumps and w/o fan) ekW Continuous 1112
Electric Efficiency @ 1.0 pf (ISO 3046/1) (2) % 36.5
Thermal Efficiency (Jacket Heat+Exh-Heat to 120°C) % 45.3
Thermal Efficiency (Jacket Heat+Exh-Heat to 25°C) % 53.5
Fuel Consumption (3)
100% load with water pumps and w/o fan MJ/bkW-hr 9.51
Altitude Capability
At 25 Deg C (77 Deg F) ambient, above sea level (4) (m) 250
Cooling System-Required
Jacket water temperature ( Maximum outlet ) Deg C 110
Exhaust System at full load
Combustion air inlet flow rate (wet) Nm3/min 72.7
Exhaust stack gas temperature Deg C 502
Exhaust gas flow rate (wet) Nm3/min 83.7
Heat Rejection (6)
Heat rejection to jacket water kW 462
Heat rejection to AC and OC kW 259
Heat rejection to exhaust (LHV to 25 Deg C) kW 1032
Generator
Frame 824
Temperature rise Deg C 105
Motor starting capability @ 30% voltage dip 0.4 PF skVA 2637
Emissions (5)
NOx @ 5% O2 (dry) mg/Nm3 500
CO @ 5% O2 (dry) mg/Nm3 2252
THC @ 5% O2 (dry) mg/Nm3 1758
NMHC @ 5% O2 (dry) mg/Nm3 264
Exhaust O2 (dry) % 7.7
CONTINUOUS 1100 ekW 1375 kVA
50 Hz 1500 rpm 400 Volts
LEHE0233-02 5
RATING DEFINITIONS AND CONDITIONS
(1) Continuous --- Maximum output available for an unlimited time
Ratings are based on pipeline Low Energy gas having a Low Heat Value (LHV) of 17.7-23.6 MJ/Nm3 and minimum
Cat Methane Number of 130 at minimum fuel pressure of 10 kPag. For values in excess of altitude, ambient temperature,
inlet/exhaust restriction, or different from the conditions listed, contact your local Cat dealer.
(2) Efficiency of standard generator is used. For higher efficiency generators, contact your local Cat dealer.
(3) Ratings and fuel consumption are based on ISO3046/1 standard reference conditions of 25 deg C (77 deg F) of
ambient temperature and 100 kPa (29.61 in Hg) of total barometric pressure. 30% humidity with 0, +5% fuel tolerance.
(4) For site specific power, contact your Cat Dealer.
(5) Emissions data measurements are consistent with those described in EPA CFR 40 Part 89 Subpart D & E and
ISO8178-1 for measuring HC, CO, PM, NOx. Data shown is based on steady state engine operating conditions of 25 deg
C (77 deg F), 96.28 kPa (28.43 in Hg). Emission data is Cat “not to exceed” data and includes a tolerance factor for
engine facility and instrumentation variations.
(6) Heat Rejection – Data based on nominal tolerances.
can you tell me how much natural gas in cubic meter/hr i used to produced 1 kw/hr?

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