I've had great success with Pipe-Flo Lite for sizing pipes, piping networks, pumps and control valves. However this package will not size heat exchangers. I've found the accuracy of this software package to be around 98% by comparing the predicted results to actual measured pressure drops and associated flow rates. The pipe and fitting libraries are comprehensive and you can purchase the add-on fluids properties package for a low price adding a quite extensive fluids table. One problem with this package is that you can only model pumps with curves that decrease in flow rate as pressure increase therefore, positive displacement pumps can't be modeled.