That depends on your humidity. As I already said, if you're in a desert that's normally dry enough...

If you're not in a desert, though, you'll have to dry the desiccant for it to have an actually significant effect. Though that's true regardless of which desiccant.

Within the phone, general relative humidity is FAR more important than airflow.

Just remember that dessicant (including rice) should be dried out in the oven if you're going to expect it to drop humidity below normal ambient humidity. Obviously not baked, but a few hours at ~180F to ~220F will dry out most dessicants. Some are really hydrophillic, though, and might take even higher temps.

Usually the kinds that dry out at lower temps are labeled as reusable or similar terminology. (unless it's a disposable packet, then it's what ever the hell they decided to throw in there).

Thank goodness DE isn't electrically conductive. It would definitely still be awful - the final boss of getting sand in your phone charging port.