Radiant Heat Transfer Calculator

This calculator performs the heat balance between the total heat absorbed in a radiant box 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.

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. On the other side, we have no shield so the qS drops out.
The equation can now be stated as,

qrls = qR + qloss + qout
Where,
qrls = Burner release, 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: Flue Gas Exit Area, ft:
Film Coef.(hc), Btu/hr-ft2- °R: Beam Length Correction:
Tube Data
Number Tubes: Tube Od, in:
Tube Spacing, in: Eff. Tube Length, ft:
Tube Arrangement: