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 Pounds per hour or cubic feet per hour. 
Properites of liquids in two streams. 
Physical Properties of two Streams. 
Sizes of Pipes. 
It suggest which side Stream 1 should be, Annulus or Pipe. 
Enter Higher and Lower Values of Heat Transfer Coefficients and Dirt Factor. 
After Calculating it shows number of Double Pipes required. 
here to see Dialog Boxes in Metric Units
How the Program Calculates?
Program first picks up flow rates, and then inlet and outlet temperatures for two streams. Out of these six values, if one is not known, program calculates it based on other five. It also asks for permissible pressure drop on two streams. It then calculates LMTD and average temperatures of two streams. Based on these average temperatures, it asks for specific heat, viscocity and specific gravity of two streams. It then asks to select NB of two pipes, pipe schedules, and length of double pipes. It calculates cross sectional area of annulus and inner pipe. Stream with higher flow rate is placed where cross sectional area is higher. It 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: Program calculates Mass Velocity for annulus by dividing annulus mass flow rate by annulus cross sectional area. It then calculates equivalent diameter. Based on this it calcuates Reynold's number. Based on Reynold's number, it picks up value of j_{H} for annulus automatically. It then calculates Overall Heat Transfer Coefficient, h_{o} for outer side of inner pipe.
For Inner Pipe: Program calculates Mass Velocity for inner pipe by dividing inner pipe mass flow rate by inner pipe cross sectional area. Based on this it calcuates Reynold's number based on inner diameter of inner pipe. Based on Reynold's number, it picks up value of j_{H} for inner pipe automatically. It then calculates Overall Heat Transfer Coefficient, h_{i} for inner side of inner pipe.
It 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. It 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: Program 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 it calcuates Reynold's number. Based on Reynold's number, it picks up value of friction factor. It then calculates density of liquid. It calculates pressure drop due to friction. It 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, it 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 Program
==============================================================
*Process Design
Units of Calculation : Imperial
Input Values in Imperial system
==============================================================
Type : Double Pipe Heat Exchanger
==============================================================
*Pipes Data
Outer Pipe Diameter NB : 2"
Inner Pipe Diameter NB : 1 1/4"
Length of Double Pipes : 20'
==============================================================
*Input Parameters
Annulus flow rate : 6323.50 lb/h
Annulus inlet Temp : 160.00 Deg F
Annulus outlet Temp : 100.00 Deg F
Annulus flow Allowable Pressure Drop : 10.00 lb/sq.in.
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 : 9820.00 lb/h
Inner Pipe inlet Temp : 120.00 Deg F
Inner Pipe outlet Temp : 80.00 Deg F
Inner Pipe flow Allowable Pressure Drop : 10.00 lb/sq.in.
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 : 166940.40 Btu/hr
==============================================================
*All Calculations done in Inperial Units
Annulus Flow Area : 0.0083 sq. ft.
Annulus Mass Velocity : 764321.95 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 : 945422.48 ft/h
Inner Pipe Reynold's Number : 89854
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 : 764321.95 ft/h
Annulus Liquid specific gravity : 0.8700
Equivalent Dia of Annulus Pipe : 7/16"
Annulus Pressure Drop : 0.3523 psi

Inner Pipe Pressure Drop
Inner Pipe Side Reynold's Number : 89854
Inner Pipe side Friction Factor : 0.0057
Inner Pipe Side Mass Velocity : 945422.48 ft/h
Inner Pipe Liquid specific gravity : 0.8800
Equivalent Dia of Inner Pipe : 1/8"
Inner Pipe Pressure Drop : 0.5347 psi
==============================================================
Summary
Type : Double Pipe Heat Exchanger
Outer Pipe Diameter NB : 2"
Outer Pipe Schedule : 40
Inner Pipe Diameter NB : 1 1/4"
Inner Pipe Schedule : 40
Length of Double Pipes : 20'
Number of Double Pipes : 6
==============================================================

