Coming to the TU Wien
There are direct flights from many cities to Vienna, and the city centre is accessible from the airport in less than 30 minutes.
Once at the airport, there are two connections to the city centre: either the CAT line (16 minutes non-stop, 12 € for one-way, 21 € for a two-way ticket), or the S7 line (25 minutes, 4,40 € for a one-way ticket including the public transport system in Vienna), or the usual railway to “Hauptbahnhof” (16 minutes non-stop (3,90 € for a one-way ticket). CAT and S7 go daily every 30 minutes to Wien Mitte, which is located in the heart of Vienna. There, you can easily reach the University via the subway line U4, at Karlsplatz (2 stops, direction Hütteldorf). From “Hauptbahnhof” you reach the TU Wien via the subway line U1, at Karlsplatz (2 stops, direction Leopoldau).
Taxis are quite expensive, however, there are companies with flat rates that you can prebook (for example € 33.- with http://www.airportdriver.at/en).