Enclosure electronic box heating +20°C/+70°F

[lem0nhead]

Hi
I made a simple electronic project using an ESP32 and some relays (rated for 30A) that switches 13A/230V. This is enclosed on a "project box" that's about 1 liter in volume.
When the switch is on, I noticed the box get pretty hot (the temperature increases about +20°C/+70°F).
The box is not completely closed since there's a non-sealed hole on the top for the wires to come in/off.

Some quick calculation (first time I'm doing it though) shows that 0.2Wh is enough to heat 1L of air to +20°C, so perhaps this is normal heat from resistance of the wires/components.

Does that sound reasonable? One thing that makes me not worry much is that the temperature increases quickly at first, but stabilizes (see graph below, ignore the values in the bottom, they're noise).



Thanks

[Kleinstein]

The heat capacity of air is pretty low. The main part it more the heat capacity of the relay, the board and the box itself.
Usually it is not so much the heat capacity, but the termal conduction to care about. So the final temperature rise and not how fast is rises.

The temperatures look pretty high to start with.  A 20 K temperature rise is not be big deal if it is starting at 20 C.

[lem0nhead]

The temperature is pretty high to start with because I'm cheating and using the ESP32 CPU temperature sensor. It rises because the surroundings get hot, not because it's doing more work (it's just keeping 2 relays on).