Session related question - opening browser with multiple tabs
Per default, there is no way to have different sessions in the same browser window. The sessions are always shared trough all tabs. If two different Sessions are enough, you could use a privat/incognito browser window. 

A other solution could be to use HTML 5 SessionStorage for your variables. But this works only for your own variables: Craft CMS use normal sessions/cookies. You can find further informations about your topic here: https://stackoverflow.com/questions/368653/how-to-differ-sessions-in-browser-tabs.