In truth a auto radiator is a styring af varmepumpe In standard terms you are using a liquid or gasoline
A fridge is shifting heat from inside the box and pumping it to a radiator outside the box in which it goes into the air that is why there is heat around the outside the house of your fridge.So a swimming pool styring af varmepumpe will get warmth from the bordering air and shift it by means of refrigerant gas and a compressor to a warmth exchanger releasing the heat into the pool drinking water flowing around it.