Solving the heat exchanger equations using spatial finite differences

9 Solving the heat exchanger equations using spatial finite differences 

As was noted in Chapter 2, Section 2.6, and Chapter 19, the most accurate method of solving a partial differential equation of the form (20.9) or 

Assuming that the tube-side fluid is liquid, we may apply backward differencing for the x-variable to the liquid-flow equation (20.14) so that the ordinary time differential of temperature at the end of each section 

Assuming, for example, that the shell-side fluid is a gas flowing in counter-eurrent mode, the equation corresponding to (20.29) for the rate of change of temperature at the end of each section for the shell fluid is derived from equation (20.20)  

We take the specific volume at each point as a function of temperature at that point and the prevailing pressure in the heat exchanger  

---