💻 Fortran Source Code Library
Run calculations locally on your own machine. View code structure, read technical explanations, and download compilation packages including sample input files.
Double-Pipe Heat Exchanger Designer
Core Numerical Engine in Fortran 90 • 0 total downloads
double_pipe_design.f90
! =========================================================================
! Source File: double_pipe_design.f90
! =========================================================================
program double_pipe_design
implicit none
double precision :: T_hi, T_ho, T_ci, T_co
double precision :: m_h, m_c, Cp_h, Cp_c
double precision :: D_i_in, D_i_out, D_o_in
double precision :: k_w
double precision :: h_i, h_o
double precision :: R_fi, R_fo
double precision :: Q_h, Q_c, Q_avg
double precision :: dT1, dT2, LMTD
double precision :: R_clean_sum, R_fouled_sum
double precision :: U_clean, U_fouled
double precision :: A_clean, A_fouled
double precision :: L_clean, L_fouled
double precision :: overdesign
double precision :: discrepancy
integer :: config
integer :: i
character(len=40) :: config_name
double precision, parameter :: PI = 3.141592653589793d0
! Read inputs from stdin
read(*,*) config ! 1=Parallel, 2=Counter
read(*,*) T_hi ! Hot fluid inlet temp [C]
read(*,*) T_ho ! Hot fluid outlet temp [C]
read(*,*) T_ci ! Cold fluid inlet temp [C]
read(*,*) T_co ! Cold fluid outlet temp [C]
read(*,*) m_h ! Hot fluid mass flow rate [kg/s]
read(*,*) m_c ! Cold fluid mass flow rate [kg/s]
read(*,*) Cp_h ! Hot fluid specific heat [J/kg.K]
read(*,*) Cp_c ! Cold fluid specific heat [J/kg.K]
read(*,*) D_i_in ! Inner pipe inner diameter [m]
read(*,*) D_i_out ! Inner pipe outer diameter [m]
read(*,*) D_o_in ! Outer pipe inner diameter [m]
read(*,*) k_w ! Wall thermal conductivity [W/m.K]
read(*,*) h_i ! Inner pipe convection coefficient [W/m2.K]
read(*,*) h_o ! Outer annulus convection coefficient [W/m2.K]
read(*,*) R_fi ! Inner fouling factor [m2.K/W]
read(*,*) R_fo ! Outer fouling factor [m2.K/W]
! Input validation
if (config < 1 .or. config > 2) then
write(*,'(A)') 'ERROR: Invalid configuration selector.'
stop
end if
if (T_hi <= T_ci) then
write(*,'(A)') 'ERROR: Hot inlet temperature must be greater than cold inlet temperature.'
stop
end if
if (T_hi <= T_ho) then
write(*,'(A)') 'ERROR: Hot inlet temperature must be greater than hot outlet temperature.'
stop
end if
if (T_co <= T_ci) then
write(*,'(A)') 'ERROR: Cold outlet temperature must be greater than cold inlet temperature.'
stop
end if
if (m_h <= 0.0d0 .or. m_c <= 0.0d0 .or. Cp_h <= 0.0d0 .or. Cp_c <= 0.0d0) then
write(*,'(A)') 'ERROR: Mass flow rates and specific heats must be positive.'
stop
end if
if (D_i_in <= 0.0d0 .or. D_i_out <= 0.0d0 .or. D_o_in <= 0.0d0) then
write(*,'(A)') 'ERROR: Diameters must be positive.'
stop
end if
if (D_i_in >= D_i_out) then
write(*,'(A)') 'ERROR: Inner pipe inner diameter must be less than its outer diameter.'
stop
end if
if (D_i_out >= D_o_in) then
write(*,'(A)') 'ERROR: Inner pipe outer diameter must be less than outer pipe inner diameter.'
stop
end if
if (k_w <= 0.0d0 .or. h_i <= 0.0d0 .or. h_o <= 0.0d0) then
write(*,'(A)') 'ERROR: Conductivity and heat transfer coefficients must be positive.'
stop
end if
if (R_fi < 0.0d0 .or. R_fo < 0.0d0) then
write(*,'(A)') 'ERROR: Fouling factors cannot be negative.'
stop
end if
! Configuration name
if (config == 1) then
config_name = 'Parallel Flow (Concentric)'
else
config_name = 'Counter Flow (Concentric)'
end if
! Heat duties
Q_h = m_h * Cp_h * (T_hi - T_ho)
Q_c = m_c * Cp_c * (T_co - T_ci)
Q_avg = Q_h ! Use hot side duty as primary design load
discrepancy = abs(Q_h - Q_c) / Q_h * 100.0d0
! LMTD Calculation
if (config == 1) then
dT1 = T_hi - T_ci
dT2 = T_ho - T_co
else
dT1 = T_hi - T_co
dT2 = T_ho - T_ci
end if
if (dT1 <= 0.0d0 .or. dT2 <= 0.0d0) then
write(*,'(A)') 'ERROR: Temperature cross occurred. Sizing impossible for parallel flow.'
stop
else if (abs(dT1 - dT2) < 1.0d-6) then
LMTD = dT1
else
LMTD = (dT1 - dT2) / log(dT1 / dT2)
end if
! Thermal Resistances and Overall Heat Transfer Coefficients (based on outer surface of inner tube, Ao)
! R_clean = 1/ho + (D_i_out * log(D_i_out/D_i_in)) / (2*kw) + (D_i_out/D_i_in) * (1/hi)
R_clean_sum = (1.0d0 / h_o) + &
(D_i_out * log(D_i_out / D_i_in)) / (2.0d0 * k_w) + &
(D_i_out / D_i_in) * (1.0d0 / h_i)
! R_fouled = R_clean + R_fo + R_fi * (D_i_out/D_i_in)
R_fouled_sum = R_clean_sum + R_fo + R_fi * (D_i_out / D_i_in)
U_clean = 1.0d0 / R_clean_sum
U_fouled = 1.0d0 / R_fouled_sum
! Required surface areas (based on Ao)
A_clean = Q_avg / (U_clean * LMTD)
A_fouled = Q_avg / (U_fouled * LMTD)
! Required tube lengths
L_clean = A_clean / (PI * D_i_out)
L_fouled = A_fouled / (PI * D_i_out)
! Overdesign percentage
overdesign = (A_fouled - A_clean) / A_clean * 100.0d0
! ============================================
! OUTPUT
! ============================================
write(*,'(A)') '============================================================='
write(*,'(A)') ' DOUBLE-PIPE HEAT EXCHANGER SIZING & RATING'
write(*,'(A)') '============================================================='
write(*,*)
write(*,'(A)') '--- CONFIGURATION & FLOW TYPE ------------------------------'
write(*,'(A,A)') ' Flow Arrangement = ', trim(config_name)
write(*,*)
write(*,'(A)') '--- GEOMETRY SPECIFICATIONS ---------------------------------'
write(*,'(A,F12.2,A)') ' Inner Pipe Inner Dia = ', D_i_in*1000.0d0, ' mm'
write(*,'(A,F12.2,A)') ' Inner Pipe Outer Dia = ', D_i_out*1000.0d0, ' mm'
write(*,'(A,F12.2,A)') ' Outer Shell Inner Dia = ', D_o_in*1000.0d0, ' mm'
write(*,'(A,F12.2,A)') ' Wall Thermal Cond (kw) = ', k_w, ' W/m.K'
write(*,*)
write(*,'(A)') '--- HEAT TRANSFER COEFFICIENTS & FOULING ---------------------'
write(*,'(A,F12.2,A)') ' Tube Convection (hi) = ', h_i, ' W/m2.K'
write(*,'(A,F12.2,A)') ' Annulus Convection (ho) = ', h_o, ' W/m2.K'
write(*,'(A,F12.6,A)') ' Tube Fouling (Rfi) = ', R_fi, ' m2.K/W'
write(*,'(A,F12.6,A)') ' Annulus Fouling (Rfo) = ', R_fo, ' m2.K/W'
write(*,*)
write(*,'(A)') '--- THERMAL ANALYSIS & DUTY ---------------------------------'
write(*,'(A,F12.2,A)') ' Hot Fluid Inlet Temp = ', T_hi, ' C'
write(*,'(A,F12.2,A)') ' Hot Fluid Outlet Temp = ', T_ho, ' C'
write(*,'(A,F12.2,A)') ' Cold Fluid Inlet Temp = ', T_ci, ' C'
write(*,'(A,F12.2,A)') ' Cold Fluid Outlet Temp = ', T_co, ' C'
write(*,'(A,F12.2,A)') ' Calculated Heat Duty Q = ', Q_avg, ' W'
write(*,'(A,F12.2,A)') ' Cold Side Absorbed Qc = ', Q_c, ' W'
write(*,'(A,F12.3,A)') ' Energy Mismatch = ', discrepancy, ' %'
write(*,'(A,F12.2,A)') ' LMTD = ', LMTD, ' deg-C'
write(*,*)
write(*,'(A)') '--- OVERALL HEAT TRANSFER COEFFICIENTS -----------------------'
write(*,'(A,F12.2,A)') ' U_clean (based on Ao) = ', U_clean, ' W/m2.K'
write(*,'(A,F12.2,A)') ' U_fouled (based on Ao) = ', U_fouled, ' W/m2.K'
write(*,*)
write(*,'(A)') '--- SIZING RESULTS ------------------------------------------'
write(*,'(A,F12.4,A)') ' Required Clean Area = ', A_clean, ' m2'
write(*,'(A,F12.4,A)') ' Required Fouled Area = ', A_fouled, ' m2'
write(*,'(A,F12.2,A)') ' Required Clean Length = ', L_clean, ' m'
write(*,'(A,F12.2,A)') ' Required Fouled Length = ', L_fouled, ' m'
write(*,'(A,F12.2,A)') ' Overdesign Factor = ', overdesign, ' %'
write(*,*)
! Temperature profiles for chart plotting
write(*,'(A)') '--- TEMPERATURE PROFILE ALONG EXCHANGER --------------------'
write(*,'(A)') ' Position % T_hot [C] T_cold [C]'
write(*,'(A)') ' --------------------------------------------------'
do i = 0, 20
if (config == 1) then
! Parallel flow
write(*,'(F10.1,4X,F10.2,4X,F10.2)') dble(i)/20.0d0*100, &
T_hi - (T_hi - T_ho) * dble(i)/20.0d0, &
T_ci + (T_co - T_ci) * dble(i)/20.0d0
else
! Counter flow
write(*,'(F10.1,4X,F10.2,4X,F10.2)') dble(i)/20.0d0*100, &
T_hi - (T_hi - T_ho) * dble(i)/20.0d0, &
T_co - (T_co - T_ci) * dble(i)/20.0d0
end if
end do
write(*,*)
write(*,'(A)') '--- FORMULAS USED -------------------------------------------'
write(*,'(A)') ' Q = m_dot * Cp * delta_T'
write(*,'(A)') ' LMTD = (dT1 - dT2) / ln(dT1/dT2)'
write(*,'(A)') ' 1/U_clean = 1/ho + D_out*ln(D_out/D_in)/(2*kw) + (D_out/D_in)*(1/hi)'
write(*,'(A)') ' 1/U_fouled = 1/U_clean + Rfo + Rfi*(D_out/D_in)'
write(*,'(A)') ' A = Q / (U * LMTD)'
write(*,'(A)') ' L = A / (pi * D_out)'
end program double_pipe_design
Solver Description
Sizes double-pipe concentric heat exchangers by resolving convection heat transfer coefficients, fouling resistances, and tube wall conduction resistance. Computes overall heat transfer coefficient ($U_o$) and uses counterflow LMTD to determine the required tube length.
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 -ffree-line-length-none double_pipe_design.f90 -o double_pipe_design
Execution Command:
Execute the program by feeding the sample input file into the program using stdin redirection:
double_pipe_design < input.txt
📥 Downloads & Local Files
Preview of the required input file (input.txt):
! Hot Inlet Temp ($T_{hi}$) [°C]
120.0
! Hot Outlet Temp ($T_{ho}$) [°C]
80.0
! Hot Mass Flow Rate ($\dot{m}_h$) [kg/s]
1.2
! Hot Specific Heat ($C_p$) [J/kg-K]
4180.0
! Hot convective HTC ($h_i$) [W/m²-K]
1500.0
! Inner Tube Fouling ($R_{fi}$) [m²-K/W]
0.0001
! Cold Inlet Temp ($T_{ci}$) [°C]
20.0
! Cold Outlet Temp ($T_{co}$) [°C]
50.0
! Cold Mass Flow Rate ($\dot{m}_c$) [kg/s]
1.8
! Cold convective HTC ($h_o$) [W/m²-K]
1200.0
! Outer Tube Fouling ($R_{fo}$) [m²-K/W]
0.0002
! Tube Wall Conductivity ($k_w$) [W/m-K]
50.0
! Inner Tube ID ($D_{i}$) [m]
0.025
! Inner Tube OD ($D_{o}$) [m]
0.028
! Outer Shell ID ($D_{s}$) [m]
0.05
120.0
! Hot Outlet Temp ($T_{ho}$) [°C]
80.0
! Hot Mass Flow Rate ($\dot{m}_h$) [kg/s]
1.2
! Hot Specific Heat ($C_p$) [J/kg-K]
4180.0
! Hot convective HTC ($h_i$) [W/m²-K]
1500.0
! Inner Tube Fouling ($R_{fi}$) [m²-K/W]
0.0001
! Cold Inlet Temp ($T_{ci}$) [°C]
20.0
! Cold Outlet Temp ($T_{co}$) [°C]
50.0
! Cold Mass Flow Rate ($\dot{m}_c$) [kg/s]
1.8
! Cold convective HTC ($h_o$) [W/m²-K]
1200.0
! Outer Tube Fouling ($R_{fo}$) [m²-K/W]
0.0002
! Tube Wall Conductivity ($k_w$) [W/m-K]
50.0
! Inner Tube ID ($D_{i}$) [m]
0.025
! Inner Tube OD ($D_{o}$) [m]
0.028
! Outer Shell ID ($D_{s}$) [m]
0.05