The air flows out from only one side of the bottom of macbook pro , is this normal

In general, the 15-in models have two fans, and the 13-in models have one fan.

Fan speeds are based on measured temperatures inside your Mac, so the fans go faster when higher heat is measured.

Fail-Safe hardware drives the fans to maximum if the System Management Controller does not come by to set then Lower several times a second.

If the processor get really hot, (near 100 C) it will do an emergency power-down to save itself.

The fan(s) exhaust the hot air out the back of the laptop. Some laptops have a single fan and others have two fans. Some laptops have vents along the bottom sides to bring cool air into the laptop.