A heat pump does what the name suggests. It pumps heat from one place to another.So a heat pump tumble dryer would use the waste /extracted heat to warm the house water or add to the central heating. A condenser dryer condenses the extracted water vapor back into liquid water. The condensed water is similar to distilled water and can be used in steam irons for example.
Eddie, no it doesn't! It dries the air and reuses it in the machine! basically its the next generation of condenser dryers as per Giz's link....Do you just have a happy guess before you answer I wonder :)
According to that link bednobs, heat pump technology has been used in Switzerland and Germany for over 13 years.
It's basically a more energy efficient method, as it recirculates and reheats the air, rather than releasing it; which is what the conventional condenser dryer does.
I had a condenser tumble dryer ,but it was a good few years ago. It had a tank to store the condensed water. You had to empty the tank when it got too full.
I have a condenser tumble drier and the condensate is NOT suitable to be used in a steam iron. If you put some into a glass and hold it up to the light you will observe that it contains a lot of fine fibres, this will clog a steam iron.