Dear student,
You should take up Mechanical Engineering to study about how air-conditioners & refrigerators work. Usually, to get admission at good Mechanical Engineering colleges, you will need to take B. Tech Engineering Entrance exams like JEE, BITSAT or GUJCET (since you have mentioned Gujarat as a preferred location).
Some good colleges include:
When the AP PGECET councelling for m pharmacy students
Mujhe admission mil sakta hai chemical engineering mai and fees kitni hai
Admition starting and closing date