Eclipse ThermJet Burners for Preheated Combustion Air - Power ...

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Step 5: Combustion AirSystem: Blower and airpressure switch (continued)Table 3.1Required calculation informationTotal system heat input Btu/hr QNumber of burners - -Type of fuel - -Gross heating value of fuel Btu/ft 3 qDesired excess air percentage(typical excess air percentage@ high fire is 15%)Air/Gas ratio(Fuel specific, see table below)Air flowGas flowDESCRIPTION UNIT OF MEASURE FORMULA SYMBOLpercent %- ?scfhscfhV airV gasTable 3.2FUEL GASFuel gas heating valuesSTOICHIOMETRIC*GROSS HEATINGAIR/GAS RATIO? (ft 3 air /ft3 ) VALUEgasq (Btu/ft 3 )Natural gas(Birmingham, AL)9.41 1,002Propane 23.82 2,572Butane 30.47 3,225* Stoichiometric: No excess air. The precise amount of air and gas are present forcomplete combustion.Example BlowerCalculationApplication example:A batch furnace requires a gross heat input of 2,900,000 btu/hr.(based on anticipated 60% efficiency with preheated air). Thedesigner decides to provide the required heat input with fourburners operating on natural gas using 15% excess air.Calculation example:a. Decide which ThermJet PCA burner model is appropriate:Q (total heat input) of 2,900,000 btu/hr4 burners = 725,000 Btu/hr/burner• Select 4 Model TJ0075 ThermJet PCA burners based on therequired heat input of 725,000 Btu/hr for each burner.b. Calculate required gas flow:QV gas= q=2,9000,000 btu/hr1,002 Btu/ft 3 = 2,894 ft 3 /hr• Gas flow of 2,894 ft 3 /hr is required16 Eclipse ThermJet PCA Design Guide No. 206, 3/5/07
Example BlowerCalculation(Continued)Calculation example (Continued):c. Calculate required stoichiometric air flow:V air-Stoichiometric= α (air/gas ratio) x V gas= 9.41 x 2,894 ft 3 /hr= 27,235 ft 3 /hr• Stoichiometric air flow of 27,235 scfh requiredd. Calculate blower air flow requirement based on thedesired amout of excess air:V air= (1 V airexcess air %) x V air-Stoichiometric= (1 + 0.15 ) x 27,235 ft 3 /hr = 31,320 ft 3 /hre. Calculate eductor flow. For this example, eductor flow is40% of combustion air flow:V eductor= .4 x 31,320 ft 3 /hr = 12,528 ft 3 /hr• Final blower air flow requirement is the sum ofV air+ V eductor= 43,848 ft 3 /hr at 15% excess air.Note:It is common practice to add an additional 10% to the finalblower air flow requirement as a safety margin.2. Find the blower model number and motor horsepower (hp).With the output pressure and the specific flow, you can find theblower catalog number and the motor hp in Bulletin/Info Guide610.4. Eclipse Combustion recommends that you select a TotallyEnclosed Fan Cooled (TEFC) motor.5. Select the other parameters:• inlet filter or inlet grille• inlet size (frame size)• voltage, number of phases, frequency• blower outlet location, and rotation direction Clockwise(CW) or Counter Clockwise (CCW).Eclipse ThermJet PCA Design Guide No. 206, 3/5/0717
Page 1 and 2: Design Guide 2063/5/07Eclipse Therm
Page 4: DocumentConventionsThere are severa
Page 7 and 8: Safety2IntroductionSafetyImportant
Page 9 and 10: System Design3DesignDesign structur
Page 11 and 12: Step 2: Control Methodology(continu
Page 13 and 14: Step 3: Ignition SystemFor the igni
Page 15: Step 5: CombustionAir System: Blowe
Page 19 and 20: AppendixConversionFactorsMetric to
Page 21: Key to System Schematics (Continued

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