Cooling things

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Physical mechanics of cooling

Passive cooling

Passive cooling tends to mean 'what happens with no moving parts'. whatever amount of conduction, radiation, or convection would happen anyway.

Sometimes includes adding a fan. While technically that's active cooling (because you're adding work, and using energy), the same amount of convection would happen anyway, but now a little faster because you're stirring the air better. (If you're stirring in air that is colder essentially for free (e.g. if outside air is), great)

On the technical side

This tends to mean

  • conduction - a good conductor spreading heat throughout
  • radiation - thermal radiation means movement of charges in materials (anything above 0 K) is radiated as EM at the surface
(black-body radiation can be seen as a "thermal radiation's real-world math becomes easier if we make some assumptions like that it's not really interacting in other ways")
  • convection - fluid flow, in this context often
flow caused by heat changing temperatures and densities
that flow assisting better heat interchange with that fluid, because warmer air moving up tends to draws in colder air from the sides (which technically is an effect that needs gravity)

In practice there's more than one of these happening, but often one that counts for most exchange.

Evaporative cooling

Refrigeration cycle

Heat pumps

Free cooling

Dessicant based systems

Peltier effect and related effects


Peltier device behaviour and uses


On efficiency

Using the effects - practice and products

When passive cooling works

Windows and windcatchers

Convection in houses

Device cooling

Passive device cooling


Heat pipes and vapor chambers

Personal cooling


Why wind helps even when you're not sweating

Spray bottle

Misting systems

Some small tricks

Wrapped towel


Swamp coolers

Mini dehumidifier

Those small personal ACs

Air conditioning

single hose portable air conditioners

two-hose portable air conditioners

Car AC

"Eco coolers"

Passive effects


Parts of designs

Heat exchanger


Cold and hot drinks

Ice packs