Gas Engine Ventilation Calculation

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chowdhuryakik Member Join Date: Sep 2009 Posts: 5	Gas Engine Ventilation Calculation 09/22/2009 3:52 AM
	can any one tell me how to calculate air ventilation system for gas generators? for combustion engine need 18000cum/hr heat radiation=334KW(Generator + Engine) we have 6 engines, 18 inlet fans and 12 exhaust fan. What should be the rating of the fan? Engine room should be positve pressure and temperature should be min 40 c or same temp as ambient.
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#1 "Re: Gas Engine Ventilation Calculation" by dac1267 on 09/22/2009 2:30 PM (score 3)

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#6 "Re: Gas Engine Ventilation Calculation" by dac1267 on 09/23/2009 12:07 PM (score 1)

dac1267 Power-User Join Date: Jun 2009 Location: California Posts: 106 Good Answers: 19	#1 Re: Gas Engine Ventilation Calculation 09/22/2009 2:30 PM
	There are several issues that you need to consider for an effective design. Some of these are: Ambient conditions – are you in a hot, cold or moderate climate? If you are in a hot climate, you will need to ventilate at a higher rate than in a cold climate. In a cold climate you may need to consider heating for when mechanics need to work in the room. Zoning – are you in a commercial or industrial area? You will have large intake and exhaust air openings into the generator room and noise regulations may require abatement such as sound traps, which will add external static pressure to the fan performance requirements. The extent to which noise abatement is required will determine (in part) the fan selection. What is your acceptable max temperature in the room? You stated min 40°C, but this doesn't make much sense. In SI units, your heat equation is Q = 2970.4 (H_s) / (ΔT) where Q is air flow in m³/hr, H_s is sensible heat in kW and ΔT is the temperature rise across the room in °C. Thus if the outside air is 40°C and you allow a 10°C rise across the room, the air flow for one generator would be 99211 m³/hr. In the above example, you would need to size your supply fans for a total of 703200 m³/hr (6 x (99200 + 18000)) or 18 @ 39067 m³/hr each at whatever external static pressure (ESP) your room requires for the supply openings (including louvers, dampers, sound traps, etc.) plus an allowance for pressurization (if you really need positive pressure). Exhaust fans should be sized for a total of 595200 m³/hr (6 x 99200) or 12 @ 49600 m³/hr each at the ESP for the exhaust openings. Put the exhaust fans on VFD's to control pressurization, and make sure your room and doors are tight. Also, supply and exhaust fans should be zoned and interlocked to operate with an associated generator. Air distribution within the room is also very important. Vanes or baffles should be used to direct air flow across the engines to maximize effectiveness. I would suggest contacting an HVAC consultant that has experience designing such facilities. Be sure to consider noise issues as well, and use an acoustic consultant if noise will be critical. There's more to it than this, but this will give you an idea of fan sizing and what you should consider.
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Anonymous Poster

#3
In reply to #1

Re: Gas Engine Ventilation Calculation

09/23/2009 12:52 AM

thanks.we have 6 louver. one louver is connected to 3 inlet fans .

louver

length=16'1"

Height=14' 3'

width=14'3"

in the louver we have two filter.

First filter is near to fan which is secondary filter distance from fan 4'.

Second filter whuch is primary filter distance from primary to secondary is 1' 10".

specification for filter

Secondary filter (10 micon)

Initial pressure drop=5 mm of w.c.

Final pressure drop=25 mm of w.c.

Efficincy=90%

Primary filter (15 micron)

Initial pressure drop=3 mm of w.c.

Final preuuse drop=18 mm of w.c.

Efficency=85%

waiting for u r reply

dac1267 Power-User Join Date: Jun 2009 Location: California Posts: 106 Good Answers: 19	#6 In reply to #3 Re: Gas Engine Ventilation Calculation 09/23/2009 12:07 PM
	Your mixing of SI and IP units is a bit confusing, but I will stick with SI. The pressure drop (PD) across louvers can vary drastically depending on type (storm, acoustic, etc.). The manufacturer will usually publish a PD curve, which is based on air velocity through the face area or mostly likely the net free area (you will have to look and figure it out). Based on the louver size you have provided, the face velocity is about 1.5 m/s for the air flow I calculated (3 x 39067 m3/hr) / ((21.3 m2) x (3600 s/hr)). The free area velocity will be much higher depending on the louver net free area. However, I wouldn't expect the louver PD to be more than about 5 mm WC at this face velocity unless you have some specialty louvers or the net free area is very small. Other than the louver drop, you need an allowance for room PD and pressurization. Room PD might be up to 10 mm WC and pressurization should be no more than 5 mm WC. So, your total ESP for the supply fan would be the PD for the louvers, filters, room & pressurization, or 5 + (25 + 18) + 10 + 5 = 63 mm WC (no safety allowance). For this flow and ESP, you are probably looking at about 25 to 30 hp motors on each supply fan, but these numbers are very rough. A proper design will take into account the actual equipment and configuration, rather that just the ballpark numbers here, and could save a substantial amount in first cost and operating cost. Or it could identify problem areas that might drive up the fan performance requirements. The generator field installation tech's will usually have some valuable input that you should consider as well. You need to be careful how you approach the design, because the generator manufacturer typically will not warranty a failure if it is determined that improper or insufficient air flow was provided.
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Anonymous Poster	#2 Re: Gas Engine Ventilation Calculation 09/23/2009 12:49 AM
	thanks.we have 6 louver. one louver is connected to 3 inlet fans . louver length=16'1" Height=14' 3' width=14'3" in the louver we have two filter. First filter is near to fan which is secondary filter distance from fan 4'. Second filter whuch is primary filter distance from primary to secondary is 1' 10". specification for filter Secondary filter (10 micon) Initial pressure drop=5 mm of w.c. Final pressure drop=25 mm of w.c. Efficincy=90% Primary filter (15 micron) Initial pressure drop=3 mm of w.c. Final preuuse drop=18 mm of w.c. Efficency=85%
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bioramani Guru Join Date: Jun 2009 Location: Bangalore, India Posts: 725 Good Answers: 24	#4 Re: Gas Engine Ventilation Calculation 09/23/2009 1:51 AM
	About 72000 m³/hr for a 15°C rise in temperature above ambient assuming all the 334 KW is delivered uniformly to the air stream and that there is no channeling. __________________ bioramani
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chowdhuryakik Member Join Date: Sep 2009 Posts: 5	#5 In reply to #4 Re: Gas Engine Ventilation Calculation 09/23/2009 3:26 AM
	may i know how u calculate.and what should be the pressure rating of the fan?
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babloobarjinder Member Join Date: Jun 2009 Posts: 6	#7 In reply to #5 Re: Gas Engine Ventilation Calculation 09/28/2009 12:17 PM
	for detailed calculations for gas -engine room ventilation calculations,pls. contact some profetional in this specific field.i know one m/s ludhiana proof insulation co. and you may contact them at www.lpic1791@yahoo.com .
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