Putting the two DEs in a list. This turns out not to be useful, but does demonstrate that dchange can handle multiple equations in a single call to it.
R is the ratio of the heat capacity of the tank to the coil.
F is the ratio of the heat transfer coef to the flow heat capacity. B is the ratio of the control action to the heat transfer coef. Note that Maple may oder the two equations in newlst differently on different occasions. It is very long. Inspection of eq.