Stopover in Guangzhou, both directions

Hi,

My girlfriend and i (both Australian passport) are travelling Melbourne to LA return via Guangzhou. On our outward journey we have a 15 hour stop in Guangzhou and inward we have a 39 hour stop. On both occasions we wish to leave the airport and explore the city of Guangzhou.

My question is, do we need a double entry tourist visa or are we able to get a transit visa for one or both of the stopovers?

Thanks very much