Abstract: A coil heat exchanger is provided, comprising a closed vessel having an inlet for receiving heat transfer media and an outlet for discharging heat transfer media, a tubular conduit extending helically within said vessel from a lower part to an upper part of said vessel for transporting liquid products to be heated by said heat transfer media, and an inner housing enclosed by loops of said tubular conduit and sealed against the heat transfer media. The inner housing comprises an open passageway to the environment outside said coil heat exchanger.