The best private college for b.tech(mech.) regarding placements is O.P.Jindal University. (http://www.opju.ac.in/soe_mech.php)

The Mechanical Engineering Department is well known for its quality of teaching and supportive environment provided to the students. The state-of-the-art laboratories, highly qualified, experienced and dedicated faculty members in all specializations of Mechanical Engineering, make this Department a vibrant place to study. Our programs provides flexible curriculum enabling the students to achieve their goals and make them industry ready. Presently department is active in various thrust areas of research in Mechanical Engineering and allied branches.

Industrial Training / Internship (http://www.opju.ac.in/soe_mech.php#collapse4)

Defence Research & Development Organisation

Adani power Limited

JSW Steel Ltd

Jindal Steel and Power Limited

Dear Kishu,

You can check the list of top private engineering colleges for Mechanical branch below

VIT University, Vellore

Birla Institute of Technology and Science, Pilani

SRM University, Chennai

Manipal Institute of Technology, Manipal

RV College of Engineering, Bangalore

Ramaiah Institute of Technology, Bangalore

Thapar University, Patiala

To check the complete list you can refer below link

https://engineering.careers360.com/colleges/list-of-engineering-colleges-in-India?f%5B0%5D=sm_college_course_level%3AUG&f%5B1%5D=sm_college_degree%3AB.E%20/Btech&f%5B2%5D=im_field_ownership%3A967&f%5B3%5D=sm_course_offered%3AMechanical%20Engineering

Good Luck!!