💻 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.
Heat Exchanger ε-NTU Rater
Core Numerical Engine in Fortran 90 • 0 total downloads
heat_exchanger_ntu.f90
! =========================================================================
! Source File: heat_exchanger_ntu.f90
! =========================================================================
program heat_exchanger_ntu
implicit none
double precision :: T_hi, T_ho, T_ci, T_co
double precision :: m_h, m_c, Cp_h, Cp_c
double precision :: U, A
double precision :: Q_max, Q
double precision :: dT1, dT2, LMTD
double precision :: C_h, C_c, C_min, C_max, C_r
double precision :: eff
double precision :: NTU
integer :: config
integer :: i
character(len=40) :: config_name
double precision :: factor, term
! Read inputs from stdin
read(*,*) config ! 1=Parallel, 2=Counter, 3=Shell-and-Tube (1-2), 4=Cross flow (unmixed)
read(*,*) T_hi ! Hot fluid inlet temp [C]
read(*,*) T_ci ! Cold fluid inlet 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(*,*) U ! Overall heat transfer coefficient [W/m2.K]
read(*,*) A ! Heat transfer area [m2]
! Input validation
if (config < 1 .or. config > 4) 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 (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 (U <= 0.0d0 .or. A <= 0.0d0) then
write(*,'(A)') 'ERROR: Overall heat transfer coefficient and area must be positive.'
stop
end if
! Configuration name
select case (config)
case (1)
config_name = 'Parallel Flow'
case (2)
config_name = 'Counter Flow'
case (3)
config_name = 'Shell-and-Tube (1-2 Pass)'
case (4)
config_name = 'Cross Flow (Unmixed)'
end select
! Heat capacity rates
C_h = m_h * Cp_h
C_c = m_c * Cp_c
if (C_h < C_c) then
C_min = C_h
C_max = C_c
else
C_min = C_c
C_max = C_h
end if
C_r = C_min / C_max
! NTU
NTU = U * A / C_min
! ============================================
! EFFECTIVENESS CALCULATION
! ============================================
select case (config)
case (1)
! Parallel Flow
eff = (1.0d0 - exp(-NTU * (1.0d0 + C_r))) / (1.0d0 + C_r)
case (2)
! Counter Flow
if (C_r < 1.0d-6) then
eff = 1.0d0 - exp(-NTU)
else if (abs(C_r - 1.0d0) < 1.0d-6) then
eff = NTU / (1.0d0 + NTU)
else
eff = (1.0d0 - exp(-NTU * (1.0d0 - C_r))) / (1.0d0 - C_r * exp(-NTU * (1.0d0 - C_r)))
end if
case (3)
! Shell-and-Tube (1 shell pass, 2 tube passes)
factor = sqrt(1.0d0 + C_r**2)
term = exp(-NTU * factor)
if (abs(1.0d0 - term) < 1.0d-12) then
eff = 0.0d0
else
eff = 2.0d0 / (1.0d0 + C_r + factor * (1.0d0 + term) / (1.0d0 - term))
end if
case (4)
! Cross Flow (unmixed)
if (C_r < 1.0d-6) then
eff = 1.0d0 - exp(-NTU)
else
eff = 1.0d0 - exp( (NTU**0.22d0) / C_r * (exp(-C_r * (NTU**0.78d0)) - 1.0d0) )
end if
end select
! Limit effectiveness to physical bounds [0, 1]
if (eff < 0.0d0) eff = 0.0d0
if (eff > 1.0d0) eff = 1.0d0
! Heat transfer rates
Q_max = C_min * (T_hi - T_ci)
Q = eff * Q_max
! Outlet temperatures
T_ho = T_hi - Q / C_h
T_co = T_ci + Q / C_c
! 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
LMTD = 0.0d0
else if (abs(dT1 - dT2) < 1.0d-6) then
LMTD = dT1
else
LMTD = (dT1 - dT2) / log(dT1 / dT2)
end if
! ============================================
! OUTPUT
! ============================================
write(*,'(A)') '============================================================='
write(*,'(A)') ' HEAT EXCHANGER ANALYSIS - E-NTU METHOD'
write(*,'(A)') '============================================================='
write(*,*)
write(*,'(A)') '--- CONFIGURATION -------------------------------------------'
write(*,'(A,A)') ' Flow Arrangement = ', trim(config_name)
write(*,*)
write(*,'(A)') '--- INPUT PARAMETERS ----------------------------------------'
write(*,'(A)') ' Hot Fluid:'
write(*,'(A,F12.2,A)') ' Inlet Temperature = ', T_hi, ' C'
write(*,'(A,F12.4,A)') ' Mass Flow Rate = ', m_h, ' kg/s'
write(*,'(A,F12.2,A)') ' Specific Heat = ', Cp_h, ' J/kg.K'
write(*,*)
write(*,'(A)') ' Cold Fluid:'
write(*,'(A,F12.2,A)') ' Inlet Temperature = ', T_ci, ' C'
write(*,'(A,F12.4,A)') ' Mass Flow Rate = ', m_c, ' kg/s'
write(*,'(A,F12.2,A)') ' Specific Heat = ', Cp_c, ' J/kg.K'
write(*,*)
write(*,'(A,F12.2,A)') ' Overall U = ', U, ' W/m2.K'
write(*,'(A,F12.4,A)') ' Surface Area A = ', A, ' m2'
write(*,*)
write(*,'(A)') '--- HEAT CAPACITY RATES -------------------------------------'
write(*,'(A,F12.4,A)') ' C_hot = m_h x Cp_h = ', C_h, ' W/K'
write(*,'(A,F12.4,A)') ' C_cold = m_c x Cp_c = ', C_c, ' W/K'
write(*,'(A,F12.4,A)') ' C_min = ', C_min, ' W/K'
write(*,'(A,F12.4,A)') ' C_max = ', C_max, ' W/K'
write(*,'(A,F12.4)') ' C_r = C_min/C_max = ', C_r
write(*,*)
write(*,'(A)') '--- ANALYSIS RESULTS ----------------------------------------'
write(*,'(A,F12.4)') ' NTU = UA/C_min = ', NTU
write(*,'(A,F12.4,A)') ' Effectiveness (e) = ', eff*100.0d0, ' %'
write(*,'(A,F12.4,A)') ' Max Heat Transfer Qmax = ', Q_max, ' W'
write(*,'(A,F12.4,A)') ' Actual Heat Transfer Q = ', Q, ' W'
write(*,'(A,F12.2,A)') ' Hot Outlet Temperature = ', T_ho, ' C'
write(*,'(A,F12.2,A)') ' Cold Outlet Temperature = ', T_co, ' C'
write(*,'(A,F12.4,A)') ' LMTD = ', LMTD, ' deg-C'
write(*,*)
! Temperature profiles for chart
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: both fluids travel same direction
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/Shell/Cross flow: cold fluid travels opposite direction
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 = e x Q_max'
write(*,'(A)') ' Q_max = C_min x (T_hi - T_ci)'
write(*,'(A)') ' NTU = U x A / C_min'
write(*,'(A)') ' C_r = C_min / C_max'
end program heat_exchanger_ntu
Solver Description
Performs heat exchanger performance rating using the Effectiveness-NTU ($\varepsilon$-NTU) method. Computes capacity rates ($C_{min}$, $C_{max}$, $C_r$), solves Number of Transfer Units ($NTU = UA/C_{min}$), calculates effectiveness ($\varepsilon$) analytically based on configuration, and computes outlet temperatures.
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 heat_exchanger_ntu.f90 -o heat_exchanger_ntu
Execution Command:
Execute the program by feeding the sample input file into the program using stdin redirection:
heat_exchanger_ntu < input.txt
📥 Downloads & Local Files
Preview of the required input file (input.txt):
! Configuration (1=Parallel, 2=Counter, 3=Cross Unmixed, 4=Shell-Tube 1-2 Pass)
2
! Hot Inlet Temp ($T_{hi}$) [°C]
120.0
! Cold Inlet Temp ($T_{ci}$) [°C]
20.0
! Hot Mass Flow (m_h) [kg/s]
1.5
! Hot Fluid Specific Heat ($C_{p,h}$) [J/kg-K]
4180.0
! Cold Mass Flow (m_c) [kg/s]
2.0
! Cold Fluid Specific Heat ($C_{p,c}$) [J/kg-K]
4180.0
! Overall HTC ($U$) [W/m²-K]
800.0
! Heat Exchanger Surface Area ($A$) [m²]
8.5
2
! Hot Inlet Temp ($T_{hi}$) [°C]
120.0
! Cold Inlet Temp ($T_{ci}$) [°C]
20.0
! Hot Mass Flow (m_h) [kg/s]
1.5
! Hot Fluid Specific Heat ($C_{p,h}$) [J/kg-K]
4180.0
! Cold Mass Flow (m_c) [kg/s]
2.0
! Cold Fluid Specific Heat ($C_{p,c}$) [J/kg-K]
4180.0
! Overall HTC ($U$) [W/m²-K]
800.0
! Heat Exchanger Surface Area ($A$) [m²]
8.5