A CDA file is created when you add your audio files to an Audio CD. Once the procedure is finished, you can copy those CDA files, but they will not work unless the physical CD/DVD is inserted into the CD/DVD-ROM.
The correct process of converting FLAC to CDA is actually called burning to CD, the operation where you use an application that can transfer the files to a physical disc.
You can use Ashampoo Burning Studio Free: http://ashampoo-burning-studio-free-v-6-83.software.informer.com/
