two dryers on the same circuit
Ok here's the math. NEC Article 220 requires electricians to provide 5000W/240V circuit for each dwelling dryer. Most nameplates will give you a total demand of 4500W. So 4500+4500= (9000W/240V)= 37.5A. 37.5A won't work on a 30A breaker and it exceeds the rating of the #10 conductor that is usually feeding the circuit. Also you cannot wire appliances in series, that would give you 120V drop across both dryers so it would not work. You would have to run them in parallel. 

The normal method is to run a separate circuit for each dryer, which is what I would recommend. In other words don't try to reinvent the wheel. Just follow proven methods.