We have SP2010 enterprise with Project server 2010. After setup multiple projects in development farm, we would like to migrate the projects to UAT. I thought it should have some "import/export" feature but I fail to find any article talk about it. Could you please advice?
There is no way in Project Server that you can perform import/export operation for few sets of Project Plan.
As mentioned by Tarun you can migrate entire Project Database along with all Project Plan. If you want to migrate few set of Project, in that case, you will need to save Project Plan as .mpp on the local system using Project Professional and then Publish to UAT. In this Process, you need to make sure you have exact same custom fields and resources in both environments in order to avoid unexpected errors.