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  ThermoFluidCalc — Offline Fortran Execution Guide
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Calculator : Double-Pipe Heat Exchanger Designer
Category   : Exchangers

Files Included:
  - double_pipe_design.f90 (Fortran Source Code)
  - input.txt (Pre-configured Sample Input)

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1. How to Compile
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Make sure you have a Fortran compiler installed (like gfortran).
Run the following compilation command in your terminal:

  gfortran -ffree-line-length-none double_pipe_design.f90 -o double_pipe_design

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2. How to Execute
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Run the compiled binary and redirect the input.txt file into stdin:

  double_pipe_design < input.txt

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3. Input File Details
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The input file 'input.txt' contains sequential parameters separated by
newlines. Here is the structure of the included 'input.txt':

  Line 1 (Hot Inlet Temp ($T_{hi}$) [°C]): 120.0
  Line 2 (Hot Outlet Temp ($T_{ho}$) [°C]): 80.0
  Line 3 (Hot Mass Flow Rate ($\dot{m}_h$) [kg/s]): 1.2
  Line 4 (Hot Specific Heat ($C_p$) [J/kg-K]): 4180.0
  Line 5 (Hot convective HTC ($h_i$) [W/m²-K]): 1500.0
  Line 6 (Inner Tube Fouling ($R_{fi}$) [m²-K/W]): 0.0001
  Line 7 (Cold Inlet Temp ($T_{ci}$) [°C]): 20.0
  Line 8 (Cold Outlet Temp ($T_{co}$) [°C]): 50.0
  Line 9 (Cold Mass Flow Rate ($\dot{m}_c$) [kg/s]): 1.8
  Line 10 (Cold convective HTC ($h_o$) [W/m²-K]): 1200.0
  Line 11 (Outer Tube Fouling ($R_{fo}$) [m²-K/W]): 0.0002
  Line 12 (Tube Wall Conductivity ($k_w$) [W/m-K]): 50.0
  Line 13 (Inner Tube ID ($D_{i}$) [m]): 0.025
  Line 14 (Inner Tube OD ($D_{o}$) [m]): 0.028
  Line 15 (Outer Shell ID ($D_{s}$) [m]): 0.05

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