Can I schedule a process model to run twice a day at particular time?

Split the functionality into two separate Process Models. Create one as the 'Controller' and the other as the actual target Process Model (this is best practice anyway, even if you were only running once a day!). The controller can "fork" its flow and each fork can have it's own timer node. They can then both flow to the sub-process that contains the actual processing you want to execute. Something like this:

Note: if you want to switch off the execution in your target environment as it is currently designed you cannot do so without deploying a new version, so if that's a requirement (or you need an end-user to change the timings) then you will also need to re-design to handle this.

Split the functionality into two separate Process Models. Create one as the 'Controller' and the other as the actual target Process Model (this is best practice anyway, even if you were only running once a day!). The controller can "fork" its flow and each fork can have it's own timer node. They can then both flow to the sub-process that contains the actual processing you want to execute. Something like this:

Note: if you want to switch off the execution in your target environment as it is currently designed you cannot do so without deploying a new version, so if that's a requirement (or you need an end-user to change the timings) then you will also need to re-design to handle this.