The most time, mac running the fan speed with a low level. If we play a video, then mbp will be hot and hot. So the best solution is change the fan speed automatically.
Here is my script to change fan speed: https://github.com/KiritoStudio/mbp_fan_control
It only test on my mbp 10.13.6. If your fan has more than one fan, you may change my script and send me the PR.