Develop a program that determines the entropy production inside a heat exchanger having two inlets and two outlets, when the mass flow rates, temperatures, and fluid properties of both of the flow stream fluids are known.
Assume the fluids do not mix inside the heat exchanger, and allow either flow stream to be an incompressible liquid or a constant specific heat ideal gas at the user's discretion.
Input all the variables with proper units. Allow the choice of working in either Engineering English or SI units.