You can select the FootInch units or Metric Units for the Design. All inputs will be in selected unit system. 
Type Name of txt file in which all process details will be written. 
Select Double Pipe or Tubular Exchanger. 
Flow in Kgs per hour or cubic meters per hour. 
Properites of liquids in two streams. 
Physical Properties of two Streams. 
Sizes of Pipes. 
Design Program for Tubular Heat Exchanger suggest which side Stream 1 should be, Annulus or Pipe. 
Enter Higher and Lower Values of Heat Transfer Coefficients and Dirt Factor. 
After Calculating Design Program for Tubular Heat Exchanger shows number of Double Pipes required. 
here to see Dialog Boxes in Imperial Units How the Design Program for Tubular Heat Exchanger Calculates?
Design Program for Tubular Heat Exchanger first picks up flow rates, and then inlet and outlet temperatures for two streams. Out of these six values, if one is not known, Design Program for Tubular Heat Exchanger calculates values based on other five. Design Program for Tubular Heat Exchanger also asks for permissible pressure drop on two streams. Design Program for Tubular Heat Exchanger then calculates LMTD and average temperatures of two streams. Based on these average temperatures, Design Program for Tubular Heat Exchanger asks for specific heat, viscocity and specific gravity of two streams. Design Program for Tubular Heat Exchanger then asks to select NB of two pipes, pipe schedules, and length of double pipes. Design Program for Tubular Heat Exchanger calculates cross sectional area of annulus and inner pipe. Stream with higher flow rate is placed where cross sectional area is higher. Design Program for Tubular Heat Exchanger then asks for expected Higher and Lower value of Overall Heat Transfer Coefficient and value of dirt factor. Based on these, calculation is done.
Calculation of number of Double Pipes:
For Annulus: Design Program for Tubular Heat Exchanger calculates Mass Velocity for annulus by dividing annulus mass flow rate by annulus cross sectional area. Design Program for Tubular Heat Exchanger then calculates equivalent diameter. Based on this Design Program for Tubular Heat Exchanger calcuates Reynold's number. Based on Reynold's number, Design Program for Tubular Heat Exchanger picks up value of j_{H} for annulus automatically. Design Program for Tubular Heat Exchanger then calculates Overall Heat Transfer Coefficient, h_{o} for outer side of inner pipe.
For Inner Pipe: Design Program for Tubular Heat Exchanger calculates Mass Velocity for inner pipe by dividing inner pipe mass flow rate by inner pipe cross sectional area. Based on this Design Program for Tubular Heat Exchanger calcuates Reynold's number based on inner diameter of inner pipe. Based on Reynold's number, Design Program for Tubular Heat Exchanger picks up value of j_{H} for inner pipe automatically. Design Program for Tubular Heat Exchanger then calculates Overall Heat Transfer Coefficient, h_{i} for inner side of inner pipe.
Design Program for Tubular Heat Exchanger then corrects the two values for viscocity of liquids at wall temperature. Overall Heat Transfer Coefficient is then calculated based on h_{o}, h_{i} and dirt factor. The heat transfer area required is calculated by dividing heat load by LMTD and value of Overall Heat Transfer Coefficient. Design Program for Tubular Heat Exchanger then picks up outer surface area of inner pipe per unit length. Dividing heat transfer area by area gives the number of Double Pipes required.
Calculation Pressure Drop:
For Annulus: Design Program for Tubular Heat Exchanger calculates Mass Velocity for annulus by dividing annulus mass flow rate by annulus cross sectional area. For pressure drop equivalent diameter is different. Based on this Design Program for Tubular Heat Exchanger calcuates Reynold's number. Based on Reynold's number, Design Program for Tubular Heat Exchanger picks up value of friction factor. Design Program for Tubular Heat Exchanger then calculates density of liquid. Design Program for Tubular Heat Exchanger calculates pressure drop due to friction. Design Program for Tubular Heat Exchanger then calculates pressure drop due to velocity of liquid. The sum of two gives Pressure Drop for Annulus.
For Inner Pipe: Based on Reynold's number calculated earlier, Design Program for Tubular Heat Exchanger picks up value of friction factor and calculates pressure drop.
If the two values are within limits, design is good. Otherwise new combination of NBs of two pipes is tried to get the result.
Report Generated by Design Program for Tubular Heat Exchanger
==============================================================
*Process Design
Units of Calculation : Imperial
Input Values in Metric system
==============================================================
Type : Double Pipe Heat Exchanger
==============================================================
*Pipes Data
Outer Pipe Diameter NB : 50 mm
Inner Pipe Diameter NB : 32 mm
Length of Double : 6000 mm
==============================================================
*Input Parameters
Annulus flow rate : 2869.10 kg/h
Annulus inlet Temp : 71.11 Deg C
Annulus outlet Temp : 37.78 Deg C
Annulus flow Allowable Pressure Drop : 0.70 Kg/sq.cm.
Annulus flow liquid Specific Heat : 0.4400 Btu/lbDeg F
Annulus flow liquid Viscosity : 0.41 cP
Annulus flow Specific Gravity : 0.8700

Inner Pipe flow rate : 4445.55 kg/h
Inner Pipe inlet Temp : 48.89 Deg C
Inner Pipe outlet Temp : 26.67 Deg C
Inner Pipe flow Allowable Pressure Drop : 0.70 Kg/sq.cm.
Inner Pipe flow liquid Specific Heat : 0.4250 Btu/lbDeg F
Inner Pipe flow liquid Viscosity : 0.50 cP
Inner Pipe flow Specific Gravity : 0.8800
==============================================================
Stream 1 on Inner Pipe side / Stream 2 on Anuulus side
Dirt Factor Rd : 0.0010
Heat Transfer Load : 166923.61 Btu/hr
==============================================================
*All Calculations done in Imperial Units
Annulus Flow Area : 0.0083 sq. ft.
Annulus Mass Velocity : 764321.51 ft/h
Annulus Reynold's Number : 58659
Annulus jH value : 160.00
Annulus c Value : 0.43
Annulus k Value : 0.09
Annulus Heat Transfer Coefficient h : 304.60 Btu/hsq. ft. Deg F
Annulus Heat Transfer Coefficient h (corrected for viscocity) : 299.81 Btu/hsq. ft. Deg F

Inner Pipe Flow Area : 0.0104 sq. ft.
Inner Pipe Mass Velocity : 943303.68 ft/h
Inner Pipe Reynold's Number : 89652
Inner Pipe jH value : 220.00
Inner Pipe c Value : 0.4400
Inner Pipe k Value : 0.0910
Inner Pipe Heat Transfer Coefficient h : 261 Btu/hsq. ft. Deg F
Inner Pipe Heat Transfer Coefficient h (corrected for viscocity) : 217 Btu/hsq. ft. Deg F
==============================================================
Number of Double Pipes : 6
==============================================================
*Pressure Drop Calculations in Imperial Units
Annulus side Pressure Drop
Annulus Side Reynold's Number : 58659
Annulus side Friction Factor : 0.0057
Annulus side Mass Velocity : 764321.51 ft/h
Annulus Liquid specific gravity : 0.8700
Equivalent Dia of Annulus Pipe : 30
Annulus Pressure Drop : 0.0248 kg/sq cm

Inner Pipe Pressure Drop
Inner Pipe Side Reynold's Number : 89652
Inner Pipe side Friction Factor : 0.0057
Inner Pipe Side Mass Velocity : 943303.68 ft/h
Inner Pipe Liquid specific gravity : 0.8800
Equivalent Dia of Inner Pipe : 0
Inner Pipe Pressure Drop : 0.0374 kg/sq cm
==============================================================
Summary
Type : Double Pipe Heat Exchanger
Outer Pipe Diameter NB : 50 mm
Outer Pipe Schedule : 40
Inner Pipe Diameter NB : 32 mm
Inner Pipe Schedule : 40
Length of Double Pipes : 6000 mm
Number of Double Pipes : 6
==============================================================

