空气能不能一开就热？

Air conditioning works by moving heat from one place to another. In order to cool down a room， it needs to remove hot air and replace it with cool air. Similarly， in order to heat up a room， it needs to remove cold air and replace it with warm air. This is where the concept of "heat pumps" comes in.

Heat pumps use a refrigerant (a substance that absorbs and releases heat) to move heat from one place to another. They can work in both heating and cooling modes. When in heating mode， the heat pump takes heat from the outside air and moves it into the room. This is why they are known as "air-to-air" heat pumps.

However， the effectiveness of a heat pump in heating a room depends on the temperature of the air outside. If the outside temperature is extremely cold， it may not be able to extract enough heat to warm up the room to a comfortable temperature. In such cases， traditional heaters may be needed.

It's also important to note that heat pumps take time to warm up a room. They cannot simply make the air warm instantly like a space heater. It takes time for the system to extract enough heat from the outside air and circulate it into the room. This is why it's recommended to keep the heat pump running continuously rather than turning it on and off frequently.

In conclusion， air can be heated up using heat pumps， but it will depend on the temperature of the air outside and the effectiveness of the heat pump in extracting heat. It will also take some time for the system to warm up the room.