HEAT PUMPS

Goal: heat a room.

Method

1. Pump some fluid into the room.
2. Compress the fluid, heating it up (it releases heat to the room).
3. Pump the compressed fluid out of the room.
4. Expand the fluid, cooling it down (it absorbs heat from the environment).
5. Repeat.

Recall that an object that feels hot is radiating heat, and an object that feels cold is absorbing heat.