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Compact Heat Exchanger Sizing
Core Numerical Engine in Fortran 90 • 34 total downloads
compact_hx.f90
! =========================================================================
! Source File: compact_hx.f90
! =========================================================================
program compact_hx
implicit none
integer :: i,stype
double precision :: Re_Dh,Dh,sigma,alpha_d,Atot,Lf
double precision :: Thi,Tci,Ch,Cc,Pr_h,Pr_c
double precision :: j,ff,h_air,Nu,Cmin,Cmax,Cr,NTU,eps,Q
double precision :: Res,js,fs,Nus
read(*,*) stype; read(*,*) Re_Dh; read(*,*) Dh
read(*,*) sigma; read(*,*) alpha_d; read(*,*) Atot
read(*,*) Lf; read(*,*) Thi; read(*,*) Tci
read(*,*) Ch; read(*,*) Cc; read(*,*) Pr_h; read(*,*) Pr_c
if(stype==1) then; j=0.233d0*Re_Dh**(-0.48d0); ff=0.292d0*Re_Dh**(-0.25d0); endif
if(stype==2) then; j=0.249d0*Re_Dh**(-0.42d0); ff=0.583d0*Re_Dh**(-0.28d0); endif
if(stype==3) then; j=0.652d0*Re_Dh**(-0.54d0); ff=1.12d0*Re_Dh**(-0.36d0); endif
if(stype==4) then; j=0.394d0*Re_Dh**(-0.49d0); ff=0.564d0*Re_Dh**(-0.29d0); endif
Nu=j*Re_Dh*Pr_c**(1d0/3d0)
h_air=Nu*0.026d0/Dh
if(Ch<Cc) then; Cmin=Ch; Cmax=Cc; else; Cmin=Cc; Cmax=Ch; endif
Cr=Cmin/Cmax
NTU=h_air*Atot/Cmin
eps=1d0-exp(NTU**0.78d0*Cr/(-1d0)*(exp(-Cr*NTU**0.22d0)-1d0))
if(eps>1d0) eps=1d0; if(eps<0d0) eps=0d0
Q=eps*Cmin*(Thi-Tci)
write(*,'(A)') '============================================'
write(*,'(A)') ' COMPACT HEAT EXCHANGER (KAYS & LONDON)'
write(*,'(A)') '============================================'
write(*,'(A)') ''
write(*,'(A)') '--- INPUTS ---'
if(stype==1) write(*,'(A)') ' Surface = Plain fin'
if(stype==2) write(*,'(A)') ' Surface = Louvered fin'
if(stype==3) write(*,'(A)') ' Surface = Offset strip fin'
if(stype==4) write(*,'(A)') ' Surface = Wavy fin'
write(*,'(A,F10.1)') ' Re_Dh = ',Re_Dh
write(*,'(A,F10.6,A)') ' Dh = ',Dh,' m'
write(*,'(A,F10.4)') ' sigma (Ac/Afr) = ',sigma
write(*,'(A,F10.1,A)') ' Surface density alpha = ',alpha_d,' m2/m3'
write(*,'(A,F10.2,A)') ' Total surface A = ',Atot,' m2'
write(*,'(A,F10.4,A)') ' Flow length L = ',Lf,' m'
write(*,'(A,F10.2,A)') ' T_hot_in = ',Thi,' C'
write(*,'(A,F10.2,A)') ' T_cold_in = ',Tci,' C'
write(*,'(A)') ''
write(*,'(A)') '--- j AND f FACTORS ---'
write(*,'(A,ES12.4)') ' Colburn j-factor = ',j
write(*,'(A,ES12.4)') ' Fanning f-factor = ',ff
write(*,'(A,F10.4)') ' j/f ratio = ',j/ff
write(*,'(A,F10.2)') ' Nusselt Nu = ',Nu
write(*,'(A,F10.2,A)') ' h_air = ',h_air,' W/m2K'
write(*,'(A)') ''
write(*,'(A)') '--- THERMAL RESULTS ---'
write(*,'(A,F10.4)') ' Cr = ',Cr
write(*,'(A,F10.4)') ' NTU = ',NTU
write(*,'(A,F10.4)') ' Effectiveness = ',eps
write(*,'(A,F12.2,A)') ' Heat transfer Q = ',Q,' W'
write(*,'(A,F10.2,A)') ' T_hot_out = ',Thi-Q/Ch,' C'
write(*,'(A,F10.2,A)') ' T_cold_out = ',Tci+Q/Cc,' C'
write(*,'(A)') ''
write(*,'(A)') '--- Re SWEEP (j & f factors) ---'
write(*,'(A)') ' Re j f j/f Nu'
write(*,'(A)') ' --------------------------------------------------'
do i=1,25
Res=100d0*10d0**(2d0*dble(i-1)/24d0)
if(stype==1) then; js=0.233d0*Res**(-0.48d0); fs=0.292d0*Res**(-0.25d0); endif
if(stype==2) then; js=0.249d0*Res**(-0.42d0); fs=0.583d0*Res**(-0.28d0); endif
if(stype==3) then; js=0.652d0*Res**(-0.54d0); fs=1.12d0*Res**(-0.36d0); endif
if(stype==4) then; js=0.394d0*Res**(-0.49d0); fs=0.564d0*Res**(-0.29d0); endif
Nus=js*Res*Pr_c**(1d0/3d0)
write(*,'(2X,F8.0,2X,ES10.3,2X,ES10.3,2X,F8.4,2X,F8.2)') Res,js,fs,js/fs,Nus
enddo
write(*,'(A)') ''
write(*,'(A)') '--- CORRELATIONS ---'
write(*,'(A)') ' Plain fin: j=0.233*Re^-0.48 f=0.292*Re^-0.25'
write(*,'(A)') ' Louvered: j=0.249*Re^-0.42 f=0.583*Re^-0.28'
write(*,'(A)') ' Offset strip: j=0.652*Re^-0.54 f=1.12*Re^-0.36 (Manglik-Bergles)'
write(*,'(A)') ' Wavy fin: j=0.394*Re^-0.49 f=0.564*Re^-0.29'
write(*,'(A)') ' Cross-flow unmixed: eps=1-exp((NTU^0.78/Cr)(exp(-Cr*NTU^0.22)-1))'
write(*,'(A)') ' Ref: Kays & London, Compact Heat Exchangers (1984)'
write(*,'(A)') ' Manglik & Bergles, J Heat Transf (1995)'
end program compact_hx
Solver Description
Thermal analysis and sizing of compact heat exchangers using Kays and London performance correlations. Supports plain, louvered, offset strip, and wavy fin geometry configurations. Evaluates Colburn j-factors, friction f-factors, Nusselt numbers, exchanger effectiveness, and total heat transfer duty.
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 compact_hx.f90 -o compact_hx
Execution Command:
Execute the program by feeding the sample input file into the program using stdin redirection:
compact_hx < input.txt
📥 Downloads & Local Files
Preview of the required input file (input.txt):
! Surface type (1=Plain fin, 2=Louvered, 3=Offset strip, 4=Wavy)
1
! Reynolds number Re_Dh
800
! Hydraulic diameter Dh [m]
0.003
! Frontal area ratio sigma (Ac/Afr)
0.534
! Surface density alpha [m2/m3]
886
! Total surface area A_tot [m2]
10
! Flow length Lf [m]
0.05
! Inlet hot temperature Thi [°C]
90
! Inlet cold temperature Tci [°C]
25
! Hot fluid capacity rate Ch [W/K]
2000
! Cold fluid capacity rate Cc [W/K]
1500
! Hot fluid Prandtl number Pr_h
0.71
! Cold fluid Prandtl number Pr_c
0.71
1
! Reynolds number Re_Dh
800
! Hydraulic diameter Dh [m]
0.003
! Frontal area ratio sigma (Ac/Afr)
0.534
! Surface density alpha [m2/m3]
886
! Total surface area A_tot [m2]
10
! Flow length Lf [m]
0.05
! Inlet hot temperature Thi [°C]
90
! Inlet cold temperature Tci [°C]
25
! Hot fluid capacity rate Ch [W/K]
2000
! Cold fluid capacity rate Cc [W/K]
1500
! Hot fluid Prandtl number Pr_h
0.71
! Cold fluid Prandtl number Pr_c
0.71