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Non-Circular Duct & Annulus Convection
Core Numerical Engine in Fortran 90 • 26 total downloads
noncircular_duct.f90
! =========================================================================
! Source File: noncircular_duct.f90
! =========================================================================
program noncircular_duct
implicit none
integer :: gtype,ftype,hcfg,i
double precision :: W,H,Di,Do,V,Tin,Tw,Lp
double precision :: rho,mu,kf,Pr,cp
double precision :: Dh,Ac,Pw,ar,Re,Nu,Nu_lam,f_d,h_c,Q,Tout,Le,mdot
double precision :: Vs,Res,Nus,hs,fs
double precision, parameter :: pi=3.14159265358979d0
read(*,*) gtype; read(*,*) W; read(*,*) H
read(*,*) Di; read(*,*) Do
read(*,*) V; read(*,*) Tin; read(*,*) Tw; read(*,*) Lp
read(*,*) ftype; read(*,*) rho; read(*,*) mu
read(*,*) kf; read(*,*) Pr; read(*,*) cp; read(*,*) hcfg
if(ftype==1) then; rho=1.177d0;mu=1.85d-5;kf=0.0263d0;Pr=0.71d0;cp=1007d0
elseif(ftype==2) then; rho=997d0;mu=8.9d-4;kf=0.613d0;Pr=6.13d0;cp=4180d0
elseif(ftype==3) then; rho=870d0;mu=0.05d0;kf=0.14d0;Pr=500d0;cp=2000d0
endif
W=W/1000d0; H=H/1000d0; Di=Di/1000d0; Do=Do/1000d0
select case(gtype)
case(1)
Ac=W*H; Pw=2d0*(W+H); Dh=4d0*Ac/Pw
ar=max(W,H)/max(min(W,H),1d-6)
if(hcfg==1) then
if(ar<=1.5d0) then; Nu_lam=2.98d0
elseif(ar<=2.5d0) then; Nu_lam=3.39d0
elseif(ar<=3.5d0) then; Nu_lam=3.96d0
elseif(ar<=6d0) then; Nu_lam=4.44d0
elseif(ar<=10d0) then; Nu_lam=5.60d0
else; Nu_lam=7.54d0; endif
else
if(ar<=1.5d0) then; Nu_lam=3.61d0
elseif(ar<=2.5d0) then; Nu_lam=4.12d0
elseif(ar<=3.5d0) then; Nu_lam=4.79d0
elseif(ar<=6d0) then; Nu_lam=5.33d0
elseif(ar<=10d0) then; Nu_lam=6.49d0
else; Nu_lam=8.24d0; endif
endif
case(2)
Ac=sqrt(3d0)/4d0*W*W; Pw=3d0*W; Dh=4d0*Ac/Pw; ar=1d0
if(hcfg==1) then; Nu_lam=2.47d0; else; Nu_lam=3.11d0; endif
case default
Dh=Do-Di; Ac=pi/4d0*(Do*Do-Di*Di); Pw=pi*(Do+Di)
ar=Di/max(Do,1d-6)
if(hcfg==1) then
if(ar<0.08d0) then; Nu_lam=17.46d0
elseif(ar<0.15d0) then; Nu_lam=11.56d0
elseif(ar<0.35d0) then; Nu_lam=7.37d0
elseif(ar<0.7d0) then; Nu_lam=5.74d0
else; Nu_lam=4.86d0; endif
else
if(ar<0.08d0) then; Nu_lam=0d0
elseif(ar<0.15d0) then; Nu_lam=11.91d0
elseif(ar<0.35d0) then; Nu_lam=7.54d0
elseif(ar<0.7d0) then; Nu_lam=6.14d0
else; Nu_lam=5.39d0; endif
endif
end select
Re=rho*V*Dh/mu
Nu=Nu_lam
f_d=64d0/max(Re,1d0)
if(Re>2300d0) then
f_d=(0.790d0*log(Re)-1.64d0)**(-2)
Nu=(f_d/8d0)*(Re-1000d0)*Pr/(1d0+12.7d0*sqrt(f_d/8d0)*(Pr**(2d0/3d0)-1d0))
endif
h_c=Nu*kf/Dh
mdot=rho*V*Ac
Q=h_c*Pw*Lp*abs(Tw-Tin)
if(mdot*cp>0d0) then; Tout=Tin+Q/(mdot*cp); else; Tout=Tin; endif
if(Re<2300d0) then; Le=0.05d0*Re*Dh; else; Le=10d0*Dh; endif
write(*,'(A)') '============================================'
write(*,'(A)') ' NON-CIRCULAR DUCT & ANNULUS CONVECTION'
write(*,'(A)') '============================================'
write(*,'(A)') ''
write(*,'(A)') '--- INPUTS ---'
if(gtype==1) write(*,'(A)') ' Geometry = Rectangular'
if(gtype==2) write(*,'(A)') ' Geometry = Equilateral Triangle'
if(gtype==3) write(*,'(A)') ' Geometry = Annulus'
if(hcfg==1) write(*,'(A)') ' Boundary Condition = Uniform Wall Temp (T)'
if(hcfg==2) write(*,'(A)') ' Boundary Condition = Uniform Heat Flux (H)'
write(*,'(A,F10.4,A)') ' Velocity V = ',V,' m/s'
write(*,'(A,F10.2,A)') ' Inlet Temp T_in = ',Tin,' C'
write(*,'(A,F10.2,A)') ' Wall Temp T_wall = ',Tw,' C'
write(*,'(A,F10.2,A)') ' Pipe Length L = ',Lp,' m'
write(*,'(A)') ''
write(*,'(A)') '--- GEOMETRY ---'
write(*,'(A,F12.6,A)') ' Hydraulic Diameter D_h = ',Dh,' m'
write(*,'(A,ES12.4,A)') ' Cross Section Area A = ',Ac,' m2'
write(*,'(A,F12.6,A)') ' Wetted Perimeter P = ',Pw,' m'
write(*,'(A,F10.3)') ' Aspect / Radius Ratio = ',ar
write(*,'(A)') ''
write(*,'(A)') '--- FLUID PROPERTIES ---'
write(*,'(A,F12.4,A)') ' Density rho = ',rho,' kg/m3'
write(*,'(A,ES12.4,A)') ' Viscosity mu = ',mu,' Pa.s'
write(*,'(A,F12.6,A)') ' Conductivity k = ',kf,' W/mK'
write(*,'(A,F12.4)') ' Prandtl Pr = ',Pr
write(*,'(A)') ''
write(*,'(A)') '--- RESULTS ---'
write(*,'(A,ES14.4)') ' Reynolds Number Re = ',Re
if(Re<2300d0) then
write(*,'(A)') ' Flow Regime = Laminar'
else
write(*,'(A)') ' Flow Regime = Turbulent'
endif
write(*,'(A,F10.6)') ' Friction Factor f = ',f_d
write(*,'(A,F12.2)') ' Nusselt Number Nu = ',Nu
write(*,'(A,F12.4,A)') ' Convection Coeff h = ',h_c,' W/m2K'
write(*,'(A,F12.2,A)') ' Heat Transfer Q = ',Q,' W'
write(*,'(A,F10.2,A)') ' Outlet Temperature T_out= ',Tout,' C'
write(*,'(A,F10.4,A)') ' Entry Length Le = ',Le,' m'
write(*,'(A,ES12.4,A)') ' Mass Flow Rate = ',mdot,' kg/s'
write(*,'(A)') ''
write(*,'(A)') '--- VELOCITY SWEEP ---'
write(*,'(A)') ' V[m/s] Re Nu h[W/m2K] Regime'
write(*,'(A)') ' --------------------------------------------------------'
do i=1,25
Vs=0.1d0+(V*4d0-0.1d0)*dble(i-1)/24d0
Res=rho*Vs*Dh/mu
if(Res>2300d0) then
fs=(0.790d0*log(Res)-1.64d0)**(-2)
Nus=(fs/8d0)*(Res-1000d0)*Pr/(1d0+12.7d0*sqrt(fs/8d0)*(Pr**(2d0/3d0)-1d0))
else
Nus=Nu_lam
endif
hs=Nus*kf/Dh
if(Res>2300d0) then
write(*,'(2X,F8.3,2X,ES10.3,2X,F9.2,2X,F10.3,2X,A)') Vs,Res,Nus,hs,'Turbulent'
else
write(*,'(2X,F8.3,2X,ES10.3,2X,F9.2,2X,F10.3,2X,A)') Vs,Res,Nus,hs,'Laminar'
endif
enddo
write(*,'(A)') ''
write(*,'(A)') '--- CORRELATIONS ---'
write(*,'(A)') ' Laminar: Nu from geometry tables (Incropera Table 8.1)'
write(*,'(A)') ' Turbulent: Gnielinski Nu=(f/8)(Re-1000)Pr/[1+12.7sqrt(f/8)(Pr^2/3-1)]'
write(*,'(A)') ' f = (0.790 ln Re - 1.64)^-2'
write(*,'(A)') ' Ref: Incropera Ch.8 Sec.8.6, Kothandaraman Ch.9 Sec.9.6'
end program noncircular_duct
Solver Description
Calculates convection in rectangular ducts, triangular ducts, and concentric annuli. Utilizes hydraulic diameter concept ($D_h = 4A/P$) and geometry-specific laminar Nusselt limits, combined with Gnielinski correlation for turbulent regimes.
Key Numerical Methods & Architecture
- Input Redirection: Reads parameters sequentially from standard input (`stdin`) using Fortran sequential read (`read(*,*)`), ensuring modular integration.
- Modular Design: Formulated using pure mathematical routines, separation of equations from output formatting, and precise numerical solvers (e.g. bisection, Newton-Raphson).
- Standard Compliant: Written in clean, standards-compliant Fortran 90 to ensure cross-compiler compatibility.
🛠️ Local Compilation
To test this code on your machine, compile the source code file(s) using a standard Fortran compiler (e.g., `gfortran`).
Compilation Command:
gfortran -O3 noncircular_duct.f90 -o noncircular_duct
Execution Command:
Execute the program by feeding the sample input file into the program using stdin redirection:
noncircular_duct < input.txt
📥 Downloads & Local Files
Preview of the required input file (input.txt):
! Geometry type (1=Rectangular, 2=Equil. Triangle, 3=Annulus)
1
! Duct width W [mm]
100.0
! Duct height H [mm]
50.0
! Annulus inner diameter Di [mm]
0.0
! Annulus outer diameter Do [mm]
0.0
! Mean velocity V [m/s]
3.0
! Inlet temperature Tin [C]
25.0
! Wall temperature Tw [C]
80.0
! Duct length L [m]
2.0
! Fluid type (1=Air, 2=Water, 3=Oil)
1
! Boundary condition (1=Uniform Wall Temp, 2=Uniform Heat Flux)
1
1
! Duct width W [mm]
100.0
! Duct height H [mm]
50.0
! Annulus inner diameter Di [mm]
0.0
! Annulus outer diameter Do [mm]
0.0
! Mean velocity V [m/s]
3.0
! Inlet temperature Tin [C]
25.0
! Wall temperature Tw [C]
80.0
! Duct length L [m]
2.0
! Fluid type (1=Air, 2=Water, 3=Oil)
1
! Boundary condition (1=Uniform Wall Temp, 2=Uniform Heat Flux)
1