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Application Manual – Liquid Cooled Generator Sets

936 MECHANICAL DESIGN

Engine Cooling

Liquid–cooled engines are cooled by pumping acoolant mixture through passages in the enginecylinder block and head(s) by means of anengine–driven pump. The most common genera-

tor set configuration has a mounted radiator andan engine–driven fan to cool the coolant and ven-tilate the generator room. Alternative methods forcooling the coolant include skid–mounted liquid– to–liquid heat exchangers, remote radiator, aremote liquid–to–liquid heat exchanger, and cool-ing tower configurations.

Cooling systems for reciprocating engine–drivengenerator sets have the following common char-acteristics, regardless of the heat exchangerused, to remove heat from the engine. These

include:

• The engine portion of the cooling system is aclosed, pressurized (10–14 psi/69.0–96.6kPa) system that is filled with a mixture ofclean, soft (demineralized) water, ethyleneor propylene glycol, and other additives.Engines should not be directly cooled byuntreated water, since this will cause corro-sion in the engine and potentially impropercooling. The “cold” side of the cooling sys-tem can be served by a radiator, heatexchanger, or cooling tower.

• The engine cooling system must be properlysized for the ambient and components cho-sen. Typically the top tank temperature of thesystem (temperature at the inlet to theengine) will not exceed 220° F (104° C) forstandby applications, and 200° F (93° C) forprime power installations.

• The cooling system must include deaerationand venting provisions to prevent buildup ofentrained air in the engine due to turbulentcoolant flow, and to allow proper filling of theengine cooling system. This means that in

addition to the primary coolant inlet and out-let connections, there are likely to be at leastone set of vent lines terminated at the “top” ofthe cooling system. Consult the enginemanufacturer’s recommendations for thespecific engine used for detailed require-ments8. See Figure 6–14 for a schematic

8 Requirements for venting and deaeration of specific Cummins

engines are found in Cummins documents AEB.

representation of the cooling and vent lineson a typical engine.

• A thermostat on the engine typically is usedto allow the engine to warm up and to regu-late engine temperature on the “hot” side ofthe cooling system.

• The cooling system design should accountfor expansion in the volume of coolant as theengine temperature increases. Coolantexpansion provisions for 6% over normal vol-ume is required.

• The system must be designed so that there isalways a positive head on the engine coolantpump.

• Proper flows for cooling depend on minimiz-ing the static and friction head on the enginecoolant pump. The generator set will not coolproperly if either the static or friction head lim-

itations of the coolant pump are exceeded.Consult the engine manufacturer for infor-mation on these factors for the specific gen-erator set selected. See Cooling Pipe SizingCalculations in this section for specificinstruction on sizing coolant piping and cal-culating static and friction head.

• Engine and remote cooling systems shouldbe provided with drain and isolation provi-sions to allow convenient service and repairof the engine. See example drawings in thissection for locations of drains and valves typ-

ically used in various applications.

Skid–Mounted Radiator

A generator set with a skid–mounted radiator(Figure 6–15) is an integral skid–mounted cool-ing and ventilating system. The skid–mountedradiator cooling system is often considered to bethe most reliable and lowest cost cooling systemfor generator sets, because it requires the leastamount of auxiliary equipment, piping, controlwiring, and coolant, and minimizes work to bedone at the jobsite on the generator set cooling

system. The radiator fan is usually mechanicallydriven by the engine, further simplifying thedesign. Electric fans are used in some applica-tions to allow more convenient control of theradiator fan based on the temperature of theengine coolant. This is particularly useful inseverely cold environments.

© 2004 Cummins Power Generation All copies are uncontrolled





FILL/PRESSURECAP

RADIATORVENT TUBE

FROM ENGINE VENT LINE(5% OF COOLANT FLOW)

FILL NECK WITH VENTHOLE TO CREATE

THERMAL EXPANSIONSPACE

TOP TANK VOLUMEMUST EQUAL 10% OFTOTAL SYSTEM VOL-

UME (DRAWDOWNCAPACITY) PLUS 5%

FORTHERMAL EXPANSION

DEAERATED/FILL/MAKEUPCOOLANT FROM FROM TOP TANK

(ABOVE BAFFLE PLATE) TOLOWEST POINT IN SYSTEM

HOT COOLANT FROM

ENGINE TO RADIATOR(BELOW BAFFLEPLATE)

SEALEDBAFFLEPLATE

Figure 6–14. Deaeration Type of Radiator Top Tank

COOLAIR

HOTAIR

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AIR INLET

RADIATOR

FLEXIBLE DUCT CONNECTOR WIND/NOISE BARRIER

ENGINE-DRIVEN FAN

PREVAILING WINDS

ENGINE-DRIVENCOOLANT PUMP

Figure 6–15. Factory-Mounted Radiator Cooling





Since the genset manufacturer typically designsskid–mounted cooling systems, the system canbe prototype tested to verify the overall perfor-mance of the system in a laboratory environment.An instrumented, controlled, laboratory environ-ment is useful in easily verifying the performance

of a cooling system. Often physical limitations ata project site can limit the accuracy or practicalityof design verification testing.

The major disadvantage of the skid–mountedradiator is the requirement to move a relativelylarge volume of air through the generator room,since the air flow through the room must be suffi-cient for evacuating heat radiated from the gener-ator set and for removing heat from the enginecoolant. See Ventilation in this section for detailsof ventilation system design and calculations

related to ventilation system design. The enginefan will often provide sufficient ventilation for theequipment room, eliminating the need for otherventilating devices and systems.

Remote Radiator

Remote radiator systems are often used whensufficient ventilation air for a skid–mounting cool-ing system can not be provided in an application.Remote radiators do not eliminate the need for generator set room ventilation, but they will reduce it. If a remote radiator cooling system is

required, the first step is to determine what type ofremote system is required. This will be deter-mined by calculation of the static and friction headthat will be applied to the engine based on itsphysical location.

If calculations reveal that the generator set cho-sen for the application can be plumbed to aremote radiator without exceeding its static andfriction head limitations, a simple remote radiatorsystem can be used. See Figure 6–16.

If the friction head is exceeded, but static head isnot, a remote radiator system with auxiliary cool-ant pump can be used. See Figure 6–14 andRemote Radiator With Auxiliary Coolant Pump, inthis section.

If both the static and friction head limitations of theengine are exceeded, an isolated cooling systemis needed for the generator set. This mightinclude a remote radiator with hot well, or a liquid– to–liquid heat exchanger–based system.

Whichever system is used, application of aremote radiator to cool the engine requires care-ful design. In general, all the recommendationsfor skid mounted radiators also apply to remoteradiators. For any type of remote radiator system,consider the following:

• It is recommended that the radiator and fanbe sized on the basis of a maximum radiatortop tank temperature of 200o F (93o C) and a115 percent cooling capacity to allow for foul-ing. The lower top tank temperature (lower

than described in Engine Cooling) compen-sates for the heat loss from the engine outletto the remote radiator top tank. Consult theengine manufacturer for information on heatrejected to the coolant from the engine, andcooling flow rates9.

• The radiator top tank or an auxiliary tankmust be located at the highest point in thecooling system. It must be equipped with: anappropriate fill/pressure cap, a system fill lineto the lowest point in the system (so that thesystem can be filled from the bottom up), anda vent line from the engine that does not haveany dips or traps. (Dips and overhead loopscan collect coolant and prevent air from vent-ing when the system is being filled.) Themeans for filling the system must also belocated at the highest point in the system,and a low coolant level alarm switch must belocated there.

• The capacity of the radiator top tank or auxil-iary tank must be equivalent to at least 17percent of the total volume of coolant in thesystem to provide a coolant “drawdowncapacity” (11percent) and space for thermal

expansion (6 percent). Drawdown capacityis the volume of coolant that can be lost byslow, undetected leaks and the normal reliev-ing of the pressure cap before air is drawninto the coolant pump. Space for thermalexpansion is created by the fill neck when acold system is being filled. See Figure 6–14.

9 Information on Cummins Power Generation products is pro-

vided in the Cummins Power Suite.





* – THE VENT LINE MUST NOT HAVE ANY DIPS OR TRAPS THAT WILL COLLECT COOLANT AND PREVENT AIR FROM VENTING WHEN THE SYSTEM IS BEING

FILLED WITH COOLANT.

** – THE FILL/MAKEUP LINE MUST BE ROUTED DIRECTLY TO THE LOWEST POINT IN THE PIPING SYSTEM SO THAT THE SYSTEM CAN BE FILLED FROM

THE BOTTOM UP AND NOT TRAP AIR.

VENTILATINGAIR INLET



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7–12 PSI (48-83 kPa)PRESSURE CAP

REMOTERADIATOR

VENTILATINGFAN

VENTLINE*

PREVAILING WINDS

HOT COOLANT LINETO RADIATOR

DRAIN VALVE ATLOWEST POINT

IN SYSTEM

COOLANTRETURN TO

ENGINE

SYSTEMFILL/MAKEUP

LINE**

HOT AIR

SAE 20R1 OR EQUIVALENTHOSE DOUBLE CLAMPED

AT BOTH ENDS WITH“CONSTANT-TORQUE“

HOSE CLAMPS

GATE ORBALL VALVESTO ISOLATEENGINE FORSERVICING

Figure 6–16. Remote Radiator Cooling (Deaeration Type System, See Figure 6–14)





• To reduce radiator fin fouling, radiators thathave a more open fin spacing (nine fins orless per inch) should be considered for dirtyenvironments.

• Coolant friction head external to the engine(pressure loss due to pipe, fitting, and radia-

tor friction) and coolant static head (height ofliquid column measured from crankshaftcenterline) must not exceed the maximumvalues recommended by the enginemanufacturer10. See the example calcula-tion in this section for a method of calculatingcoolant friction head. If a system configura-tion cannot be found that allows the engine tooperate within static and friction head limita-tions, another cooling system type should beused.

NOTE: Excessive coolant static head (pressure) can cause the coolant pump shaft seal to leak. Excessive coolant friction head (pressure loss) will result in insuf- ficient engine cooling.

• Radiator hose 6 to 18 inches (152 to 457mm)long, complying with SAE 20R1, or an equiv-alent standard, should be used to connectcoolant piping to the engine to take up gener-ator set movement and vibration.

• It is highly recommended that the radiatorhoses be clamped with two premium grade“constant–torque” hose clamps at each end

to reduce the risk of sudden loss of enginecoolant due to a hose slipping off under pres-sure. Major damage can occur to an engine ifit is run without coolant in the block for just afew seconds.

• A drain valve should be located at the lowestpart of the system.

• Ball or gate valves (globe valves are toorestrictive) are recommended for isolatingthe engine so that the entire system does nothave to be drained to service the engine.

• Remember that the generator set must elec-

trically drive remote radiator fan, ventilatingfans, coolant pumps, and other accessoriesrequired for operation in remote coolingapplications. So, the kW capacity gained bynot driving a mechanical fan is generally con-

10 Data for Cummins engines is in the Power Suite.

sumed by the addition of electrical devicesnecessary in the remote cooling system.Remember to add these electrical loads tothe total load requirement for the generatorset.

• See Ventilation General Guidelines and

Heat Exchanger or Remote RadiatorApplications, both in this section, concerninggenerator room ventilation when remotecooling is used.

Deaeration Type Remote Radiator System

A deaeration type of radiator top tank (also knowas a sealed top tank) or auxiliary tank must be pro-vided. In this system, a portion of the coolant flow(approximately 5 percent) is routed to the radiatortop tank, above the baffle plate. This allows airentrained in the coolant to separate from the cool-

ant before the coolant returns to the system. Con-sider the following:

• Engine and radiator vent lines must rise with-out any dips or traps that will collect coolantand prevent air from venting when the sys-tem is being filled. Rigid steel or high densitypolystyrene tubing is recommended for longruns, especially if they are horizontal, to pre-vent sagging between supports.

• The fill/makeup line should also rise withoutany dips from the lowest point in the piping

system to the connection at the radiator toptank or auxiliary tank. No other piping shouldbe connected to it. This arrangement allowsthe system to be filled from bottom up withouttrapping air and giving a false indication thatthe system is full. With proper vent and fillline connections, it should be possible to fillthe system at a rate of at least 5 gpm (19L/Min) (approximately the flow rate of a gar-den hose).

Remote Radiator with Auxiliary Coolant

PumpA remote radiator with an auxiliary coolant pump(Figure 6–17) can be used if coolant frictionexceeds the engine manufacturer’s maximumrecommended value, and static head is withinspecifications. In addition to the considerationsunder Remote Radiators, consider the following:





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AUXILIARYCOOLANT PUMP

BYPASS GATEVALVE

GATE OR BALL VALVES TO ISOLATEENGINE FOR SERVICING

RADIATORVENT LINE

7–12 PSIPRESSURE CAP

AUXILIARY TANKALTERNATIVE TO A DEAERATION-TYPE

RADIATOR. VOLUME CAPACITY MUST BE ATLEAST 15% OF SYSTEM COOLANT VOLUME

REMOTE RADIATORASSEMBLY

ENGINE VENTLINE

SYSTEM FILL/MAKEUPLINE

HOT COOLANT LINETO RADIATOR

COOLANT RETURNTO ENGINE

Figure 6–17. Remote Radiator With Auxiliary Coolant Pump and Auxiliary Tank

• An auxiliary pump and motor must be sizedfor the coolant flow recommended by theengine manufacturer and develop enoughpressure to overcome the excess coolantfriction head calculated by the method shownin the previous example.

NOTE: One foot of pump head (pump manufacturer’s data) is equivalent to 0.43 PSI of coolant friction head

(pressure loss) or one foot of coolant static head (height of liquid column).

• A bypass gate valve (globe valves are toorestrictive) must be plumbed in parallel withthe auxiliary pump, for the following reasons: – To allow adjustment of the head devel-

oped by the auxiliary pump (the valve isadjusted to a partially–open position to





recirculate some of the flow backthrough the pump).

– To allow operation of the generator setunder partial load if the auxiliary pumpfails (the valve is adjusted to a fully openposition).

• Coolant pressure at the inlet to the enginecoolant pump, measured while the engine isrunning at rated speed, must not exceed themaximum allowable static head shown onthe recommended generator set Specifica-tion Sheet. Also, for deaeration type coolingsystems (230/200 kW and larger generatorsets), auxiliary pump head must not forcecoolant through the make–up line into theradiator top tank or auxiliary tank. In eithercase, the pump bypass valve must beadjusted to reduce pump head to an accept-

able level.• Since the engine of the generator set doesnot have to mechanically drive a radiator fan,there may be additional kW capacity on theoutput of the generator set. To obtain the netpower available from the generator set, addthe fan load indicated on the generator setSpecification Sheet to the power rating of theset. Remember that the generator set mustelectrically drive the remote radiator fan, ven-tilating fans, coolant pumps, and otheraccessories required for the set to run for

remote radiator applications. So, the kWcapacity gained by not driving a mechanicalfan is generally consumed by the addition ofelectrical devices necessary in the remotecooling system.

Remote Radiator With Hot Well

A remote radiator with a hot well (Figure 6–18)can be used if the elevation of the radiator abovethe crankshaft centerline exceeds the allowablecoolant static head on the recommended genera-tor set Specification Sheet. In a hot well system,

the engine coolant pump circulates coolantbetween engine and hot well and an auxiliarypump circulates coolant between hot well andradiator. A hot well system requires carefuldesign.

In addition to the considerations under RemoteRadiator, consider the following:

• The bottom of the hot well should be abovethe engine coolant outlet.

• Coolant flow through the hot well/radiator cir-cuit should be approximately the same ascoolant flow through the engine. The radiatorand the auxiliary pump must be sized accord-

ingly. Pump head must be sufficient to over-come the sum of the static and friction headsin the hot well/radiator circuit.

NOTE: One foot of pump head (pump manufacturer’s data) is equivalent to 0.43 PSI of coolant friction head (pressure loss) or one foot of coolant static head (height of liquid column).

• The liquid holding capacity of the hot wellshould not be less than the sum of the follow-ing volumes: – of the coolant volume pumped per

minute through the engine (e.g., 25 gal-lons if the flow is 100 gpm) (100 liters ifthe flow is 400 l/min), plus

– of the coolant volume pumped perminute through the radiator (e.g., 25 gal-lons if the flow is 100 gpm) (100 liters ifthe flow is 400 l/min), plus

– Volume required to fill the radiator andpiping, plus 5 percent of total system vol-ume for thermal expansion.

• Careful design of the inlet and outlet connec-tions and baffles is required to minimize cool-

ant turbulence, allow free deaeration andmaximize blending of engine and radiatorcoolant flows.

• Coolant must be pumped to the bottom tankof the radiator and returned from the top tank,otherwise the pump will not be able to com-pletely fill the radiator.

• The auxiliary pump must be lower than thelow level of coolant in the hot well so that it willalways be primed.

• The radiator should have a vacuum reliefcheck valve to allow drain down to the hot

well.• The hot well should have a high volumebreather cap to allow the coolant level to fallas the auxiliary pump fills the radiator andpiping.





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AUXILIARY COOLANT PUMP FORHOT WELL/RADIATOR CIRCUIT

REMOTE RADIATORASSEMBLY

VACUUM BREAK

HOT WELL

BREATHER CAP

ENGINEVENT LINE

HOT ENGINECOOLANT

RETURNTO ENGINE

BAFFLES

PUMP COOLANTTO RADIATORBOTTOM TANK

Figure 6–18. Remote Radiator With Hot Well and Auxiliary Coolant Pump





• Remember that the generator set must elec-trically drive remote radiator fan, ventilatingfans, coolant pumps and other accessoriesrequired for operation in remote coolingapplications. So, the kW capacity gained bynot driving a mechanical fan is generally con-

sumed by the addition of electrical devicesnecessary in the remote cooling system.Remember to add these electrical loads tothe total load requirement for the generatorset.

Multi–Loop Engine Cooling–Remote Radia-tors

Some engine designs incorporate more than onecooling loop and therefore require more than oneremote radiator or heat exchanger circuit forremote cooling applications. These engines uti-

lize various approaches to achieve Low Tempera-ture Aftercooling (LTA) of the intake air for com-bustion. A primary reason behind the creation ofthese designs is their affect on improvement ofexhaust emissions levels. Not all of these enginedesigns however are easily adaptable for remotecooling.

Two–Pump Two–Loop: A common approach forlow temperature aftercooling is to have two com-plete and separate cooling circuits with two radia-tors, two coolant pumps and separate liquid cool-

ant for each. One circuit cools the engine water jackets, the other cools the intake combustion airafter turbocharging. For remote cooling, theseengines require two complete separate remoteradiators or heat exchangers. Each will have itsown specifications of temperatures, pressurerestrictions, heat rejection, etc. that must be metin the remote systems. This data is available fromthe engine manufacturer. Essentially, two circuitsmust be designed, each require all the consider-ations of, and must meet all the criteria of a singleremote system. See Figure 6–19.

Note: Radiator placement for the LTA circuit can be critical to achieving adequate removal of heat energy required for this circuit. When the LTA and jacket water radiators are placed back to back with a single fan, the LTA radiator should be placed upstream in the air flow so as to have the coolest air traveling over it.

One–Pump, Two–Loop : Occasionally enginedesigns accomplish low temperature aftercoolingthrough the use of two cooling circuits within theengine, two radiators but only one coolant pump.These systems are not recommended for remotecooling applications due to the difficulty of achiev-

ing balanced coolant flows and thus proper cool-ing of each circuit.

Air–to–Air Aftercooling: Another approach toachieving low temperature aftercooling is to usean air–to–air radiator cooling circuit instead of anair–to–liquid design as described above. Thesedesigns route the turbocharged air through aradiator to cool it before entering the intake man-ifold(s). These systems are not generally recom-mended for remote cooling for two reasons. First,the entire system piping and radiator are operate

under turbocharged pressure. Even the smallestpinhole leak in this system will significantlydecrease turbo charger efficiency and is unac-ceptable. Second, the length of the air tube run tothe radiator and back will create a time lag inturbocharging performance and potentially resultin pressure pulses that will impede proper perfor-mance of the engine.

Radiators for Remote Radiator Applications

Remote Radiators : Remote radiators are avail-able in a number of configurations for generator

set applications. In all cases, the remote radiatoruses an electric motor–driven fan that should befed directly from the output terminals of the gener-ator set. A surge tank must be installed at thehighest point in the cooling system. The capacityof the surge tank must be at least 5% of the totalsystem cooling capacity. The pressure capinstalled there is selected based on the radiatorsizing. Vent lines may also need to be routed tothe surge tank. A sight glass is a desirable featureto display level of coolant in the system. It shouldbe marked to show normal level cold and hot. A

coolant level switch is a desirable feature to indi-cate a potential system failure when coolant levelis low.

Some remote radiator installations operate withthermostatically controlled radiator fans. If this isthe case, the thermostat is usually mounted at theradiator inlet.





Engine RadiatorOutlet

LTA RadiatorOutlet

Side–by–Side Engine/Low Temperature Aftercooling Radiators

Figure 6–19. A Horizontal Remote Radiator and Aftercooler Radiator

Radiators may be either horizontal type (radiator

core is parallel to mounting surface) or verticaltype (radiator core is perpendicular to mountingsurface) (Figure 6–19). Horizontal radiators areoften selected because they allow the largestnoise source in the radiator (the mechanical noiseof the fan) to be directed up, where it is likely thatthere are no receivers that may be disturbed bythe noise. However, horizontal radiators can bedisabled by snow cover or ice formation, so theyare often not used in cold climates.

Remote radiators require little maintenance, but

when they are used, if they are belt driven, annualmaintenance should include inspection and tight-ening of the fan belts. Some radiators may usere–greasable bearings that require regular main-tenance. Be sure that the radiator fins are cleanand unobstructed by dirt or other contaminants.

Skid–Mounted Heat Exchanger: The engine,

pump and liquid–to–liquid heat exchanger form aclosed, pressurized cooling system (Figure6–20). The engine coolant and raw cooling water(the “cold” side of the system) do not mix. Consid-er the following:

• The generator set equipment room willrequire a powered ventilating system. SeeVentilation in this section for information onthe volume of air required for proper ventila-tion.

• Since the engine of the generator set does

not have to mechanically drive a radiator fan,there may be additional kW capacity on theoutput of the generator set. To obtain the netpower available from the generator set, addthe fan load indicated on the generator setSpecification Sheet to the power rating of the





HOT AIR

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RAW WATERSUPPLY

RAW WATERDISCHARGE

ENGINE-MOUNTEDHEAT EXCHANGER

PREVAILING WINDS

VENTILATING FANVENTILATING AIR INLET

FLEXIBLEWATER CONNECTIONS

Figure 6–20. Factory-Mounted Heat Exchanger Cooling

set. Remember that the generator set mustelectrically drive remote radiator fan, venti-lating fans, coolant pumps and other acces-sories required for the set to run for remoteradiator applications. So, the kW capacitygained by not driving a mechanical fan isgenerally consumed by the addition of elec-trical devices necessary in the remote cool-ing system.

• A pressure–reducing valve must be providedif water source pressure on the cold side ofthe system exceeds the pressure rating ofthe heat exchanger. Consult heat exchangermanufacturer for heat exchanger informa-tion11.

11 Data for heat exchangers provided on Cummins Power

Generation products that are provided with factory–mounted

heat exchangers is available in the Cummins Power Suite.

• The heat exchanger and water piping mustbe protected from freezing if the ambienttemperature can fall below 32 F (0 C).

• Recommended options include a thermo-static water valve (non–electrical) to modu-late water flow in response to coolant tem-perature and a normally closed (NC)battery–powered shut off valve to shut off thewater when the set is not running.

• There must be sufficient raw water flow toremove the Heat Rejected To Coolant indi-cated on the generator set SpecificationSheet. Note that for each 1° F rise in temper-ature, a gallon of water absorbs approxi-mately 8 BTU (specific heat). Also, it is rec-ommended that the raw water leaving theheat exchanger not exceed 140° F (60° C).Therefore:





Raw WaterRequired (gpm)

Heat Rejected

∆ T ( F) • c

Btumin

8 BtuF–Gallon

=

Where:∆ T = Temperature rise of water across core

c = Specific heat of water

If a set rejects 19,200 BTU per minute andthe raw water inlet temperature is 80° F,allowing a water temperature rise of 60° F:

Raw Water Required =19,200

60 • 8= 40 gpm

Dual Heat Exchanger Systems: Dual heatexchanger cooling systems (Figure 6–21) can bedifficult to design and implement, especially if a

secondary cooling system such as a radiator isused to cool the heat exchanger. In these situa-tions the remote device might be significantlylarger than expected, since the change in temper-ature across the heat exchanger is relativelysmall. These systems should be designed for the

REMOTERADIATOR



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PRESSURE CAPHEAT EXCHANGERHOT COOLANT OUT

TO SECONDARYEXCHANGER

DRAIN VALVE ATLOWEST POINT

IN SYSTEM

COOLANTRETURN TO

HEATEXCHANGER

Figure 6–21. Dual Heat Exchanger System (With Secondary Liquid–to–Air Cooler)





specific application, considering the require-ments of the engine, liquid to liquid heat exchang-er, and remote heat exchanger device12.

Cooling Tower Applications: Cooling tower sys-tems can be used in applications where the ambi-

ent temperature does not drop below freezing,and where the humidity level is low enough toallow efficient system operation. Typical arrange-ment of equipment is shown in Figure 6–22.

Cooling tower systems typically utilize a skid– mounted heat exchanger whose “cold” side toplumbed to the cooling tower. The balance of thesystem is composed of a “raw” water pump (theengine cooling pump circulates coolant on the“hot” side of the system) to pump the coolingwater to the top of the cooling tower, where it is

cooled by evaporation, and then returned to the12 Skid–mounted heat exchangers provided by Cummins

Power Generation are typically not suitable for use in dual

heat exchanger applications. Dual heat exchanger arrange-

ments require carefully matched components.

generator set heat exchanger. Note that the sys-tem requires make–up water provisions, sinceevaporation will continuously reduce the amountof cooling water in the system. The “hot” side ofthe heat exchanger system is similar to thatdescribed earlier under skid mounted heat

exchanger.

Fuel Cooling with Remote Radiators

Generator sets occasionally include fuel coolersto meet the requirements for specific engines. Ifan engine is equipped with a separate fuel cooler,these cooling requirements must be accommo-dated in the cooling system design. It is not oftenfeasible to, and often against code to pipe fuel to aremote location. One approach would be toinclude a radiator and fan for fuel cooling withinthe generator space and account for the heatrejection in the room ventilation design. Anothermight be a heat exchanger type fuel cooling sys-tem utilizing a remote radiator or separate watersupply for the coolant side.

ALT

ENGINE

HE

NRV

NRV

Figure 6–22. Diagram of Representative Cooling Tower Application





Cooling Pipe Sizing Calculations

The preliminary layout of piping for a remoteradiator cooling system shown in Figure 6–16calls for 60 feet of 3–inch diameter pipe, threelong sweep elbows, two gate valves to isolate theradiator for engine servicing and a tee to connectthe fill/makeup line. The recommended genera-tor set Specification Sheet indicates that coolantflow is 123 GPM and that the allowable frictionhead is 5 PSI.

This procedure involves determining the pres-sure loss (friction head) caused by each elementand then comparing the sum of the pressurelosses with the maximum allowable friction head.

1. Determine the pressure loss in the radiatorby referring to the radiator manufacturer’s

data. For this example, assume the pressureloss is 1 psi at a flow of 135 gpm.

2. Find the equivalent lengths of all fittings andvalves by using Table 6–3 and add to thetotal run of straight pipe.

Three Long Sweep Elbows–3 x 5.2 15.6

Two Gate Valves (Open)–2 x 1.7 3.4

Tee (Straight Run) 5.2

60 Feet Straight Pipe 60.0

Equivalent Length of Pipe (Feet) 84.2

3. Find the back pressure at the given flow perunit length of pipe for the nominal pipe diam-eter used in the system. In this example, 3inch nominal pipe is used. Following thedashed lines in Figure 6–23, 3 inch pipecauses a pressure loss of approximately1.65 psi per 100 foot of pipe.

4. Calculate the pressure loss in the piping asfollows:

Piping Loss = 84.2 feet x 1.65 psi = 1.39 psi100 feet

5. The total system loss is the sum of the pipingand radiator losses:

Total Pressure Loss = 1.39 psi piping + 1.00psi radiator = 2.39 psi

TYPE OF FITTING NOMINAL INCH (MILLIMETER) PIPE SIZE

1/2(15)

3/4(20)

1(25)

1–1/4(32)

1–1/2(40)

2(50)

2–1/2(65)

3(80)

4(100)

5(125)

6(150)

90Std. Elbow orRun of Tee Reduced.

1.7(0.5)

2.1(0.6)

2.6(0.8)

3.5(1.1)

4.1(1.2)

5.2(1.6)

6.2(1.9)

7.7(2.3)

10(3.0)

13(4.0)

15(4.6)

90Long SweepElbow or Straight

Run Tee

1.1(0.3)

1.4(0.4)

1.8(0.5)

2.3(0.7)

2.7(0.8)

3.5(1.1)

4.2(1.3)

5.2(1.6)

6.8(2.1)

8.5(2.6)

10(3.0)

45Elbow 0.8(0.2)

1.0(0.3)

1.2(0.4)

1.6(0.5)

1.9(0.6)

2.4(0.7)

2.9(0.9)

3.6(1.1)

4.7(1.4)

5.9(1.8)

7.1(2.2)

Close Return Bend 4.1(1.2)

5.1(1.6)

6.5(2.0)

8.5(2.6)

9.9(3.0)

13(4.0)

15(4.6)

19(5.8)

25(7.6)

31(9.4)

37(11.3)

TEE, Side Inlet orOutlet

3.3(1.0)

4.2(1.3)

5.3(1.6)

7.0(2.1)

8.1(2.5)

10(3.0)

12(3.7)

16(4.9)

20(6.1)

25(7.6)

31(9.4)

Foot Valve andStrainer

3.7(1.1)

4.9(1.5)

7.5(2.3)

8.9(2.7)

11(3.4)

15(4.6)

18(5.5)

22(6.7)

29(8.8)

36(11.0)

46(14.0)

Swing Check Valve,Fully Open

4.3(1.3)

5.3(1.6)

6.8(2.1)

8.9(2.7)

10(3.0)

13(4.0)

16(4.9)

20(6.1)

26(7.9)

33(10.1)

39(11.9)

Globe Valve, Fully

Open

19

(5.8)

23

(7.0)

29

(8.8)

39

(11.9)

45

(13.7)

58

(17.7)

69

(21.0)

86

(26.2)

113

(34.4)

142

(43.3)

170

(51.8)Angle Valve, Fully

Open9.3

(2.8)12

(3.7)15

(4.6)19

(5.8)23

(7.0)29

(8.8)35

(10.7)43

(13.1)57

(17.4)71

(21.6)85

(25.9)

Gate Valve, FullyOpen

0.8(0.2)

1.0(0.3)

1.2(0.4)

1.6(0.5)

1.9(0.6)

2.4(0.7)

2.9(0.9)

3.6(1.1)

4.7(1.4)

5.9(1.8)

7.1(2.2)

Table 6–3. Equivalent Lengths of Pipe Fittings and Valves in Feet (Meters)





COOLANT FLOW – U.S. Gallons Per Minute (liters/min)

0.1

0.5

1.0

5.0

0.2

0.3

0.4

2.0

3.0

4.0

2 (50) 2.5 (65) 3 (80) 4 (100) 5 (125)

6 (150)

1.5 (40)

P R E S S U R E L O S S (

P S I P E R

1 0 0 F O O T O F P I P E L E N G T H )

1 0

2 0

3 0

4 0

5 0

1 0 0

2 0 0

4 0 0

5 0 0

1 , 0

0 0

3 0 0

( k P a P e r

3 0 M e t e r s o f P i p e L e n g t h )

(35)

(3.5)

(7.0)

(1.4)

(2.1)

(5.9)

(14)

(21)

(28)

(0.7) ( 3 8 )

( 7 6 )

( 1 1 4 )

( 1 5 0 )

( 1 9 0 )

( 3 8 0 )

( 7 6 0 )

( 1 5 0 0 )

( 1 9 0 0 )

3 8 0 0 )

( 1 1 4 0 )

Figure 6–23. Frictional Pressure Losses for Inch (mm) Diameter Pipes

6. The calculation for this example indicatesthat the layout of the remote radiator coolingsystem is adequate in terms of coolant fric-tion head since it is not greater than theallowable friction head. If a calculation indi-cates excessive coolant friction head, repeat

the calculation using the next larger pipesize. Compare the advantages and disad-vantages of using larger pipe with that ofusing an auxiliary coolant pump.

Coolant Treatment: Antifreeze (ethylene or pro-pylene glycol base) and water are mixed to lowerthe freezing point of the cooling system and toraise the boiling point. Refer to Table 6–4 for

determining the concentration of ethylene or pro-pylene glycol necessary for protection against thecoldest ambient temperature expected. Anti-freeze/water mixture percentages in the range of30/70 to 60/40 are recommended for mostapplications.

NOTE: Propylene glycol based antifreeze is less toxic than ethylene based antifreeze, offers superior liner protection and eliminates some fluid spillage and dis- posal reporting requirements. However, it is not as effective coolant as ethylene glycol, so cooling system capacity (maximum operating temperature at full load)will be diminished somewhat by use of propylene glycol.





Cummins Power Generation generator sets,125/100 kW and larger, are equipped withreplaceable coolant filtering and treating ele-ments to minimize coolant system fouling andcorrosion. They are compatible with most anti-freeze formulations. For smaller sets, the anti-

freeze should contain a corrosion inhibitor.

Generator sets with engines that have replace-able cylinder liners require supplemental coolantadditives (SCAs) to protect against liner pittingand corrosion, as specified in the engine and gen-erator set operator’s manuals.

Ventilation

General Guidelines

Ventilation of the generator room is necessary to

remove the heat expelled from the engine, alter-nator and other heat generating equipment in thegenset room, as well as to remove potentiallydangerous exhaust fumes and to provide com-bustion air. Poor ventilation system design leads

to high ambient temperatures around the genera-tor set that can cause poor fuel efficiency, poorgenerator set performance, premature failure ofcomponents, and overheating of the engine. Italso results in poor working conditions around themachine.

Selection of the intake and exhaust ventilationlocations is critical to the proper operation of thesystem. Ideally, the inlet and exhaust allow theventilating air to be pulled across the entire gener-ator room. The effects of prevailing winds mustbe taken in to consideration when determiningexhaust air location. These effects can seriouslydegrade skid–mounted radiator performance. Ifthere is any question as to the wind speed anddirection, blocking walls can be used to preventwind blowing into the engine exhaust air outlet

(See Figure 6–24). Care should also be taken toavoid ventilation exhausting into a recirculationregion of a building that forms due to prevailingwind direction.

MIXTURE PERCENTAGES (ANTIFREEZE/WATER)

MIXTURE BASE0/100 30/70 40/60 50/50 60/40 95/5

FREEZING POINT32° F(0° C)

4° F(–16° C)

–10° F(–23° C)

–34° F(–36° C)

–65° F(–54° C)

8° F(–13° C)

ETHYLENE GLYCOL

BOILING POINT212° F

(100° C)220° F

(104° C)222° F

(106° C)226° F

(108° C)230° F

(110° C)345° F

(174° C)

FREEZING POINT32° F(0° C)

10° F(–12° C)

–6° F(–21° C)

–27° F(–33° C)

–56° F(–49° C)

–70° F(–57° C)

PROPYLENE GLYCOL

BOILING POINT212° F

(100° C)216° F

(102° C)219° F

(104° C)222° F

(106° C)225° F

(107° C)320° F

(160° C)

Table 6–4. Freezing and Boiling Points vs. Concentration of Antifreeze





Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

COOLAIR

HOTAIR


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Á Á

Á Á

Á Á

Á Á

Á Á

Á Á

Á Á

Á Á

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PREVAILING WINDS

RADIATOR WIND/NOISEBARRIER

ENGINE-DRIVENFAN

THERMOSTATICALLYCONTROLLED LOUVER

NOT LESS THANHEIGHT OF RADIATOR

OUTLET AIRDAMPER

MEASURE STATIC PRESSURE WITH-IN 6 INCHES (150 mm) OF THERADIATOR. SEE Figure NO TAG

FLEXIBLE DUCTCONNECTOR

INLET AIRDAMPER

Figure 6–24. Factory-Mounted Radiator Cooling

Ventilating air that is polluted with dust, fibers, orother materials may require special filters on theengine and/or alternator to allow proper operationand cooling, particularly in prime power applica-tions. Consult the factory for information on use ofgenerator sets in environments that includechemical contamination.

Engine crankcase ventilation systems canexhaust oil–laden air into the generator set room.The oil can then be deposited on radiators or oth-

er ventilation equipment, impeding their opera-tion. Use of crankcase ventilation breather trapsor venting of the crankcase to outdoors is bestpractice.

Attention should be give to the velocity of intakeair brought into the generator set room. If the airflow rate is too high, the generator sets will tend topull rain and snow into the generator set room

when they are running. A good design goal is tolimit air velocity to between 500–700 f/min(150–220 m/min).

In cold climates, the radiator exhaust air can berecirculated to modulate the ambient air tempera-ture in the generator set room. This will help thegenerator set warm up faster, and help to keepfuel temperatures higher than the cloud point ofthe fuel. If recirculation dampers are used, theyshould be designed to “fail closed”, with the main

exhaust dampers open, so that the generator setcan continue to operate when required. Design-ers should be aware that the generator set roomoperating temperature will be very close to theoutdoor temperature, and either not route waterpiping through the generator set room, or protectit from freezing.





As ventilating air flows through an equipmentroom, it gradually increases in temperature, par-ticularly as it moves across the generator set.See Figure 6–25. This can lead to confusion asto temperature ratings of the generator set andthe overall system. Cummins Power Generation

practice is to rate the cooling system based on theambient temperature around the alternator. Thetemperature rise in the room is the differencebetween the temperature measured at the alter-nator, and the outdoor temperature. The radiatorcore temperature does not impact the systemdesign, because radiator heat is moved directlyout of the equipment room.

A good design goal for standby applications is tokeep the equipment room at not more than 125° F(50° C). However, limiting generator set room

temperature to 100° F (40° C) will allow the gener-ator set to be provided with a smaller, less expen-sive skid–mounted radiator package, and elimi-nate the need for engine de–rating due toelevated combustion air temperatures13. Be surethat the design specifications for the generatorset fully describe the assumptions used in thedesign of the ventilation system for the generatorset.

13 .Check the engine manufacturer’s data for information

on derating practice for a specific engine. Information on

Cummins Power Generation products is on the Power

Suite.

The real question then becomes, “What is themaximum temperature of outdoor air when thegenerator set will be called to operate?” This issimply a question of the maximum ambient tem-perature in the geographic region where the gen-erator set is installed.

In some areas of the northern United States forexample, the maximum temperature is likely tonot exceed 90° F. So, a designer could select theventilation system components based on a 10° Ftemperature rise with a 100° F generator set cool-ing system, or based on a 35° F temperature risewith a 125° F generator cooling system.

The key to proper operation of the system is to besure that the maximum operating temperatureand temperature rise decisions are carefully

made, and that the generator set manufacturerdesigns the cooling system (not just the radiator)for the temperatures and ventilation required.

The result of improper system design is that thegenerator set will overheat when ambient temper-atures and load on the generator set is high. Atlower temperatures or lower load levels the sys-tem may operate properly.

Air Flow Out

Air Flow In

90F 110F

125F

Figure 6–25. Typical Air Temperature Surrounding an Operating Genset





Air Flow Calculations

The required air flow rate to maintain a specifictemperature rise in the generator room isdescribed by the formula:

m =

Q

cp T d

Where:m = Mass flow rate of air into the room;

ft3 /min (m3 /min)Q = Heat rejection into the room from the

genset and other heat sources; BTU/min(MJ/min).

cp = Specific heat at constant pressure;0.241 BTU/lb– ° F (1.01x10 –3 MJ/kg– ° C).∆T = Temperature rise in the generator setroom over outdoor ambient; ° F (° C).

d = Density of air; 0.0754 lb/ft3 (1.21 kg/m3).Which can be reduced to:

0.241 • 0.0754 • ∆ Tm =

Q 55.0Q(ft3 /min)= ∆ T

OR:

Q

(1.01 • 103) • 1.21 • ∆ Tm =

818Q(m3 /min)= ∆ T

The total airflow required in the room is the calcu-lated value from this equation, plus the combus-tion air required for the engine14.

In this calculation the major factors are obviouslythe heat radiated by the generator set (and otherequipment in the room) and the allowable maxi-mum temperature rise.

Since the heat rejection to the room is fundamen-tally related to the kW size of the generator setand that rating is controlled by building electricalload demand, the major decision to be made bythe designer regarding ventilation is what allow-

able temperature rise is acceptable in the room.

14 Data required for calculations for specific Cummins Power

Generation generator sets can be found on the Cummins Pow-

er Suite. There may be significant differences in the variables

used in these calculations for various manufacturer’s products.

Field Testing of Ventilation Systems

Since it is difficult to test for proper operation, onefactor to view in system testing is the temperaturerise in the room under actual operating condi-tions, vs. the design temperature rise. If the tem-perature rise at full load and lower ambient tem-peratures is as predicted, it is more probable thatit will operate correctly at higher ambients andload levels.

The following procedure can be used for prelimi-nary qualification of the ventilation systemdesign:

1. Run the generator set at full load (1.0 powerfactor is acceptable) long enough for theengine coolant temperature to stabilize. Thiswill take approximately 1 hour.

2. With the generator set still running at ratedload, measure the ambient air temperature ofthe generator set room at the air cleaner inlet.

3. Measure the outdoor air temperature (in theshade).

4. Calculate the temperature differencebetween the outdoor temperature and thegenerator set room.

5. Verify that the design temperature rise of thegenerator room is not exceeded, and that themaximum top tank temperature of the engineis not exceeded.

If either the design temperature rise or top tanktemperature is exceeded, more detailed testing ofthe facility or corrections in the system design willbe required to verify proper system design.

Skid–Mounted Radiator Ventilation

In this configuration (Figure 6–24), the fan drawsair through inlet air openings in the opposite walland across the generator set and pushes itthrough the radiator which has flanges for con-necting a duct to the outside of the building.

Consider the following:

• The location of the generator room must besuch that ventilating air can be drawn directly





from the outdoors and discharged directly tothe outside of the building. Ventilation airshould not be drawn from adjacent rooms.Exhaust should also discharge on the radia-tor air discharge side of the building to reducethe likelihood of exhaust gases and soot

being drawn into the generator room with theventilating air.

• Ventilating air inlet and discharge openingsshould be located or shielded to minimize fannoise and the effects of wind on airflow.When used, the discharge shield should belocated not less than the height of the radia-tor away from the ventilation opening. Betterperformance is achieved at approximately 3times the radiator height. In restricted areas,turning vanes will help to reduce the restric-tion caused by the barriers added to the sys-

tem. When these are used, make provisionsfor precipitation run–off so that it is not routedinto the generator room.

• The airflow through the radiator is usuallysufficient for generator room ventilation. Seethe example calculation (under Air Flow Cal-culations in this section) for a method ofdetermining the airflow required to meetroom air temperature rise specifications.

• Refer to the recommended generator setSpecification Sheet for the design airflowthrough the radiator and allowable airflow

restriction. The allowable air flow restric-tion must not be exceeded. The staticpressure (air flow restriction) should be mea-sured, as shown in Figures 6–24, 6–26, and6–27, to confirm, before the set is placed inservice, that the system is not too restrictiveThis is especially true when ventilating air issupplied and discharged through long ducts,restrictive grilles, screens, and louvers.

• Rules of thumb for sizing ventilation air inletsand outlets have been applied or even pub-lished in the past but have more recentlybeen largely abandoned. Due to large varia-tion in louver performance and greaterdemands on installations for space, noise,etc., these rules of thumb have proven to beunreliable at best. Generally, louvermanufacturers have charts of restriction ver-sus airflow readily available. These chartscombined with duct design and any otherrestriction can be easily compared to thepublished specifications for the generator set

for a reliable method of determing accept-able restriction levels.

• For installations in North America, refer to theASHRAE (American Society of Heating,Refrigeration and Air Conditioning Engi-neers) publications for recommendations on

duct design if air ducts are required for theapplication. Note that the inlet duct musthandle combustion airflow (see the Specifi-cation Sheet) as well as ventilating airflowand must be sized accordingly.

• Louvers and screens over air inlet and outletopenings restrict airflow and vary widely inperformance. A louver assembly with narrowvanes, for example, tends to be more restric-tive than one with wide vanes. The effectiveopen area specified by the louver or screenmanufacturer should be used.

• Because the radiator fan will cause a slightnegative pressure in the generator room, it ishighly recommended that combustion equip-ment such as the building heating boilers notbe located in the same room as the generatorset. If this is unavoidable, it will be necessaryto determine whether there will be detrimen-tal effects, such as backdraft, and to providemeans (extra large room inlet openings and/ or ducts, pressurizing fans, etc.) to reducethe negative pressure to acceptable levels.

• In colder climates, automatic dampers

should be used to close off the inlet and outletair openings to reduce heat loss from thegenerator room when the generator set is notrunning. A thermostatic damper should beused to recirculate a portion of the radiatordischarge air to reduce the volume of cold airthat is pulled through the room when the setis running. The inlet and outlet dampersmust fully open when the set starts. Therecirculating damper should close fully at 60°F (16° C).

• Other than recirculating radiator dischargeair into the generator room in colder climates,all ventilating air must be discharged directlyoutside the building. It must not be used toheat any space other than the generatorroom.

• A flexible duct connector must be provided atthe radiator to prevent exhaust air recircula-tion around the radiator, to take up generatorset movement and vibration, and preventtransmission of noise.





Note: Duct adapters or radiator shrouds may not be designed to support weight or structure beyond that of the flexible duct adatper. Avoid supporting additional weight/equipment with the duct adapter or radiator shroud without sufficient analysis of strength and vibration considerations.

• Typically a generator set with a Skid– Mounted radiator is designed for full–powercooling capability in an ambient temperatureof 40° C while working against an externalcooling air flow resistance of 0.50 inch WC(Point A, Figure 6–27). External airflow

resistance is that caused by ducts, screens,dampers, louvers, etc. Operation in ambienttemperatures higher than the design temper-ature can be considered (Point B, Figure6–27, for example) if derating is acceptableand/or resistance to cooling airflow is less

than the resistance under which the coolingcapability was tested. (Less resistancemeans greater airflow through the radiator,offsetting the effect of higher air temperatureon radiator cooling capability.) Close con-sultation with the factory is required to attainacceptable generator set cooling capabilityin an elevated ambient temperature.

INCLINEDMANOMETER

0.01 IN WCACCURACY

LEAVE THE OTHER END OFTHE MANOMETER OPEN TO

THE GENERATOR ROOM

—STATIC PRESSURE PROBE—1/4 IN (6 mm) COPPER TUBE WITH PLUGGED END

AND 1/16 IN (1.5 mm) CROSS-DRILLED HOLES

ORIENT THE TIP PARALLEL WITH THE AIRSTREAM IN RADIATOR DISCHARGE DUCT WITHIN

6 INCHES (150 mm) OF THE RADIATOR

Figure 6–26. Recommended Instrumentation for Measuring Air Flow Restriction

100%

MAX

TEMP

40° CSTANDARD RATING @

40° C & 0.50 INCH WC

PERCENT RATED POWER

A M B I E N

T T E M P E R A T U R E

POSSIBLE OPERATING POINT @ 0.00 INCH WC,

ELEVATED TEMPERATURE & REDUCED POWER

A

B

Figure 6–27. Figure Cooling Capability in Elevated Ambients





HOT AIR



Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

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Á

Á

Á Á

Á Á

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INLET AIR DAMP-ER

ENGINE-MOUNTED HEAT EXCHANGER

PREVAILING WINDS

VENTILATINGFAN

Figure 6–28. Ventilation for a Heat Exchanger Cooling System

Ventilating Heat Exchanger or RemoteRadiator Applications

A heat exchanger (Figure 6–28), or remote radia-tor cooling system might be selected because ofnoise considerations or because the air flowrestriction through long ducts would be greaterthan that allowed for the engine–driven radiatorfan. Consider the following:

• Ventilating fans must be provided for the gen-erator room. The ventilating fans must havethe capacity of moving the required flow ofventilating air against the airflow restriction.

See the following example calculation for amethod of determining the airflow requiredfor ventilation.

• A remote radiator fan must be sized primarilyto cool the radiator. Depending on its loca-tion, it might also be used to ventilate thegenerator room.

• The fan and air inlet locations must be suchthat the ventilating air is drawn forward overthe set.

In general, remote cooling systems have moreparasitic loads, so slightly less kW capacity isavailable from the generator set in those applica-tions. Remember to add the parasitic loads to thetotal load requirements for the generator set.

Example Ventilating Air Flow Calculation

The recommended generator set SpecificationSheet indicates that the heat radiated to the roomfrom the generator set (engine and generator) is4,100 BTU/min. The muffler and 10 feet of 5–inchdiameter exhaust pipe are also located inside thegenerator room. Determine the airflow required

to limit the air temperature rise to 30° F.

1. Add the heat inputs to the room from allsources. Table 6–5 indicates that the heatloss from 5–inch exhaust pipe is 132 BTU/ min per foot of pipe and 2,500 BTU/min fromthe muffler. Add the heat inputs to the roomas follows:Heat rejection from generator set 4,100Heat from Exhaust Pipe–10 x 132 1,320




Heat from Muffler 2,500Total Heat to Generator Room(BTU/Min) 7,920

2. The required airflow to account for heatrejection in the room is proportional to the

total heat input divided by the allowable roomair temperature rise (See Ventilation earlierin this section):

m =55 • 7920 = 14,520 ft3 /min

30

© 2004 Cummins Power Generation All copies are uncontrolled

cummins power generator

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