﻿ Firetube Flux
Example 8.13: Firetube Flux
 Fire Tube Heat Duty(Q, MMBtu/hr): Pipe Outside Temperature (To, oF) Fluid Temperature(Tf, oF) Excess Air(%): Flue Gas Rate(r,lb/MMBtu): Pipe ID(ID, ft): Flue Gas Specific Heat(Cp, Btu/(lb.oF) Flue Gas Thermal Conductivity (k, Btu/[(hr. sq ft.oF)/ft]) Flue Gas Bulk Viscosity (μb, cp) Flue Gas Viscosity at Pipe Wall (μw, cp) Convective Heat Flux(Hfc, Btu/(hr.ft2)) Refer Example 8-6 Result Flue Gas Mass Flow(Ma, lb/hr) ΔT(oF) Reynolds Number(Re) Prandtl Number(Pr) C per Fig 8-5 m per Fig 8-5 Result Heat Transfer Coefficient (hi, Btu/(hr.ft2.oF)) Convective Heat Flux(Hfc, Btu/(hr.ft2)) Total Heat Flux(Hf, Btu/(hr.ft2)) Example 8-3; Heat transfer coefficient for forced convection Step 1: Calculate Re, Pr, select C and M for Fig 8-5 Re = 1488*D*V*ρ / μ = 0.5263 * M / D * μ          Eq8-9a Pr = 2.419*Cp*μ / k          Eq 8-7 Fig 8-5 from GPSA Section 8 Step 2: Calculate ho Nu = C * Rem * Pr0.33 * (μb/μw)0.14 = hi * di / 12 * k          Eq8-5b Convective Heat Flux = Q / Ac = hi * ΔT Total Heat Flux = Convective Heat Flux + Radiant Heat Flux

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