  # EQUATRAN Tutorial 3: Heat Exchanger Calculation

This tutorial solves the heat balance equations for a simple heat exchanger as shown below. A hot process fluid flows into the heat exchanger with a flow Fh and a temperature Thin. The specific heat capacity is Cph. Cooling water flows through the other side of the exchanger with flow Fc, temperature Tcin and heat capacity Cpc. The two streams leave at temperatures of Thout and Tcout and the heat duty exchanged is Q.  The heat balance can be described by the 2 equations:

 Q = Fh.Cph.(Thin - Thout) Q = Fc.Cpc.(Tcout - Tcin)

If we know the heat capacities, the flow and required temperatures of the process fluid, and the inlet and outlet temperatures of the cooling water, the flow of the cooling water can be calculated. The other unknown variable Q (heat duty) will also be calculated.

Use the following input:

 // Heat Exchanger Calculation Q = Fh*Cph*(Thin-Thout) Q = Fc*Cpc*(Tcout-Tcin) Cph = 0.62;  Cpc = 1.0 // Input Fh = 1000              // Flow rate Thin = 60;  Thout = 30 // Temperatures Tcin = 18;  Tcout = 29 OUTPUT Q, Fc

Some points to note in the above source text:

• More than one equation can be added on a line of text, separated by a semi-colon(;).
• Comments can be added at the end of a line, preceded by //.
• The OUTPUT command lets us specify the variables to be reported in the results. This is useful as the problems become more complex as we do not necessarily want to see all the input values repeated in the output.

The results are as follows:

 // Heat Exchanger Calculation <<   results   >> Q               =  18600          Fc              =  1690.909

Save this problem as ‘Tutorial-3.eqs’. We will use it in the next tutorial.

Next: Tutorial 4 - Non-linear Simultaneous Equations