In practice, there's a second, heating loop attached to this one that can take heat from the car's exhaust system and dump it in the passenger compartment. A couple of valves on both loops ensure the system is working either as a cooler or a heater, but not both. So, very simplified...
A kitchen or bathroom extractor fan (left) is designed to suck hot, moist air from your home and dump it outside. Since it takes one fluid (the hot air in your home) and mixes it with another one (the cold air outside), it's not a heat exchanger. It's just a heat extractor....