No, you can't.
The point of using Transparent Data Encryption (TDE) is that the encryption is transparent. You'll never get back encrypted values. And it wouldn't make sense to run the database with the wallet closed.
Transparent Data Encryption is a solution that deny access to data in datafiles and backups (at rest) with tools like the cat command (UNIX) or dumping in hexadecimal.
It is very easy to get confuse with other security solutions that Oracle provides. If what you need is users not having access/permissions to certain data you can use Audit Vault or Data Masking depending on your needs.
On the other hand, it is possible to want a Database with the wallet closed, for example, when the database is in a period of no operation you must close the server wallet in order to leave it unusable from a TDE point of view.
In conclusion, TDE is not going to give you something like '&^$%@hs788' as a result in a query.