I think it looks really great, the illustration is really crisp and the idea is cute and funny. It just needs a little zing I think, don't be afraid to use the whole shirt I would say, it's a little tiny, and hard to get from a distance.
Looks good and reads well. If you think it's missing something, have you tried incorporating a design element that is the end result of the flow or something connecting the flow to give it a double meaning or complete the thought somehow (the mechanical vs the organic, someone using the turbine), or I don't know really. I like what you have. If you weren't to change anything I would suggest seeing it on a different t-shirt color.