Radiant With Shield Section Heat Transfer Calculator

This calculator performs the heat balance between the total heat absorbed in a radiant box, including the radiation to the shield tubes, and the exit temperature, Tg(bridgewall) that will support that heat transfer. Additionally, the calculator computes the balance between the burner release and the heat exiting the radiant section. Since, we are not performing convection heat transfer in this excercise, the convection heat transfer per ft2 of the shield tubes, must be input. The heat in the exit flue gas is from the radiant section and does not account for the convection heat transfer in the shield.

qR = qr + qc
Where,
 qr = saAcpF(Tg4 - Tw4) qc = hcAt(Tg - Tw) qr = Radiant heat transfer, Btu/hr qc = Convection heat transfer, Btu/hr s = Stefan-Boltzman constant, 0.173E-8 Btu/ft2-hr-R4 a = Relative effectiveness factor of the tube bank Acp = Cold plane area of the tube bank, ft2 F = Exchange factor Tg = Effective gas temperature in firebox, °R Tw = Average tube wall temperature, °R hc = Film heat transfer coefficient, Btu/hr-ft2- °R At = Total outside area of the tubes, ft2

Then,

qrls + qair + qother = qR + qS + qloss + qout

For this calculator, the combustion air is at 60 °F, so the qair factor drops out of the equation. The fuel is gas, so there is no atomization and we are assuming it to be at 60 °F, so the qother factor also drops out of the left hand side. The equation can now be stated as,

qrls = qR + qS + qloss + qout
Where,
 qrls = Burner release, Btu/hr qS = Radiation heat transfer in shield section, Btu/hr qloss = Setting loss as % of Release, % qout = Heat leaving radiant section, Btu/hr

Combustion Air & Fuel Gas Inputs
 Air Composition, mole% Fuel Composition, mole % N2 = CH4 = C6H14 = C2H4 = O2 = C2H6 = CO = C3H6 = CO2 = C3H8 = H2 = N-C4H8 = H2O = N-C4H10 = N2 = C6H6 = Ar = I-C4H10 = CO2 = H2O = SO2 = N-C5H12 = C = O2 = CO = I-C5H12 = S = H2S =

 Process Data Duty, Btu/hr: Tube Wall Temp, F: Setting Loss, %: Excess Air, %: Firebox Data Width or Dia., ft: Height, ft: Length(0 for Cyl), ft: FG Exit Area(shld not expd), ft: Film Coef.(hc), Btu/hr-ft2- °R: Beam Length Correction: Radiant Tube Data Number Tubes: Tube Od, in: Tube Spacing, in: Eff. Tube Length, ft: Tube Arrangement: Single row of tubes next to refractory wall Double row of tubes next to refractory wall Single row of tubes fired both sides Double row of tubes fired both sides Shield Tube Data Number Tubes: Tube Od, in: Tube Spacing, in: Tubes Per Row: Eff. Tube Length, ft: Uo*LMTD, Btu/hr-ft2: Plenum Height(if in-direct): Location: Exposed to radiant Not exposed to radiant