Basically I wanted to test how fast my RPi will heat up under stress with or without heat sinks

How to perform stress test

It is easy with stress application.

Install:

sudo apt-get install stress 

Stress test:

sudo stress --cpu 4

it will span 4 processes that will execute on each of RPi core calculating sqrt function (source).

Constantly measure CPU temperature

Command:

watch -n 1 /opt/vc/bin/vcgencmd measure_temp

This command will print cpu temperature on console each 1 second.

CPU utilisation

You can observe how 4 stress processes are utilising cpu with command:

top

Radiator tests

Cheapest small aluminium radiators under 0.24$ per lot: link

No heat sinks:

• idle: around 50 C
• under stress: up to 82 C
• response on air flow: low decreases maximum temperature by 2-3 C

With heat sinks:

• idle: around 44 C
• under stress: up to 77 C
• response on air flow: good decreases maximum temperature by 7-8 C

Conclusion

I’m a bit disappointed with those small heat sinks, expecting that they’ll lower temperatures more drastically. Using fan that will blows air on them will give better results.