First an on campus interview, it was simple behavioral based interview not more than 30 mins. Will look at experiences, research and GPA more than anything else. Then if selected there is a functional interview over the phone. They asked pretty solid technical questions from thermodynamics and gives you problems to solve there and then. Revising before hand helps. And will ask you to interpret a concept by giving you a situation and example. Only bad thing about the process is they are very late in replying back, we have to catch up atleast twice to get to know whats going on.